Take a look at my spark plug. What do you think?

[mayhem17]

216652

So, off idle if I hit the gas hard it tries to stall out. Seems a bit doggy also through the revs. Only thing not stock is the K&N air filter. Went from a 130 main jet to a 140. Seemed to help off idle a bit. Plug was much more white before changing jets. Ideas?

[oscarmayer]

i think it's a sparkplug!
:p


looks rich. drop 2 jet sizes i would have done a 132 or 132.5 (what ever the next size up is) main only. had the same issue with my son's race quad.

[mayhem17]

I thought rich at first also, but acting like its running lean. Bogs bad until I get the rev's up a bit. Also doesn't rev down as quick as I think it should. If it were rich though, would it be that white in the center like that?

[mayhem17]

Was thinking of dropping the main down a size, and maybe pilot up one?

[Jmoozy27]

It's rich, the arc is what makes it white. What you want to look at is the middle porcelain area, not so much your gap but all the way down into the plug. I run a 135 in my BR and it is still a tad rich. The BR motor is just hard to squeeze more power out of. I hate my following statement but: it is what it is.

Unless of course you go with a MD-BB kit.:naughty:

[phantomtracer]

I second or third that: Looks rich, lots of unburned fuel there.
If you jet too rich it can fool you into thinking its lean as it bogs.
quick unscientific check is to shut the fuel petcock off and as the float bowl starts to run down the mixture will lean out.
You should notice the throttle response improves as you blip the throttle when the fuel mixture leans out.
Could also remove the air filter to help lean it out a bit more for testing purposes.

[barnett468]

.
what is your elevation?


that is not just rich, it is filthy pig rich by a mile.

make sure your air filter is clean or try it without as phantomracer suggested

make sure you have the correct heat range . . a plug that is too cold will carbon up because it is not hot enough to burn it off.

put your needle clip in the center position

go down 3 sizes on the main to start.

leave your pilot as it is for now . . if it pull starts easily, then your pilot is pretty darn close.

install a new plug . . if you dont have one, clean the bejesus out of that one with carb cleaner and a tooth brush


if it spits and sputters when you first accelerate, it is rich . . if it simply hesitates like it is out of gas, it is lean but it can sometimes be hard to tell the difference so pay close attention.

PS - The good news is that it is a honda and it runs, and that it does NOT look like it is burning oil. :)

[mayhem17]

It doesn't sputter at all. It hesitates like it's out of fuel. Shutting fuel off makes it worse. It had this issue before I went up on jet size. Got much better after going up.

It starts up first kick no problem. You have to slowly roll on the throttle off idle or it just wants to quit. Feels just like when you forget to turn your fuel on when you go ride.

[Jmoozy27]

Have you checked your needle clip?

[oscarmayer]

it's rich!!!!! fixor it!! several of us told ya, drop in a 132 main then get back to us or go back to the stock for testing.

[250rRoostmaster]

If it bogs off idle your pilot is lean.... How old is the plug? Need to use a fresh plug and do a plug chop...

[mayhem17]

Plug is brand new. Put it in to check it actually. It doesn't so much big off idle as it completely falls on it's face like out of fuel. If I roll on it slower it's fine, but can tell it's also bogging throughout the revs. Hence why I thought lean. Then pulled it and saw black. Although bit wet.

[mayhem17]

And yes, will drop it down tonight once I'm home abd try that. Stock was definitely lean.

[oscarmayer]

ok. good luck and let us know. but I would say with a filter you probably need 1 size up only.

[barnett468]

.
ok we have no idea exactly what mods or changes you have so the following is what i would do . . you can NOT easily or even properly jet a bike if the float level is off very much so that is the first thing i would look at and fix if it is off very far.


how old is the gas?

put some gas in a clear glass and look at it . . if it is yellow, it is bad.

you can put an 8" long piece of clear plastic line on the float bowl drain fitting

tape it to the carburetor so the end of the line is near the top of the carb.

turn the gas on at the gas tank.

loosen the screw on the float bowl.

gas will enter the clear line.

the level of the gas should be around 1/8" - 3/16" below the main carb body where it meets the float bowl . . if it is above the bottom if the main body, it is definitely too high and might be flooding it.

if you don't have a clear line you can use a black one . . just lower the open end of the line until gas comes out and gets on your engine and your floor . . the point at which it starts to run out will be the gas level.

.
...........................................i think it should be at or just below the solid black line in your case.

.................................http://ww2.justanswer.com/uploads/motoforge/2010-08-01_013312_Float_level_adjustment.jpg


.................................................h ere's another and you can see the is level way too low.

........................................http://www.bbburma.net/FujiFotos/FloatHeight/DSCF2434.jpg
.

[yaegerb]

So apparently I am the only one without a crystal ball.....what motor is this out of? At least for me, it would make it a lot easier to diagnose if we know whether it's 2 or 4 stroke and what CC it is.

[mayhem17]

I actually have no drain tube on this carb at the moment, will get that tomorrow and see what happens. I went back to a foam filter tonight with closed air box and stock jet size with a new plug. Did a plug chop abd got this. I'm still having the same issue off idle though, although seemed to be smoother after that. Forgot to say this is an 85 250sx also.

[barnett468]

.
why didn't you put the 132 jet was suggested? . . i would have been better based upon your description of the plug being white with the 130 jet

we need a photo of the plug.

try it several times with the needle all the way up and then all the way down.

from a dead stop, just push the throttle around 1/3rd of the way and no farther and drive it around 50 feet at the most . . do this several times to get a feel for it.

tell us what is better

.

[barnett468]

.

imo, this plug is a little rich but not extremely rich . . i would go down 1 on the main jet if the plug looked like this after 30 minutes or more.

.................................................. ..........https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcSNCmSDDREQ9FBer6cgSK0i-FF6RxdrnJS9tC5iw3wrkYb2rvHP


although the porcelain on this plug is nearly pure white, the end of the threads have a light black coating of carbon which means that this is not necessarily screamin lean but i would still go up 1 on the jets if the plug looked .like this after maybe 30 minutes.

......................http://i.istockimg.com/file_thumbview_approve/5218968/6/stock-photo-5218968-used-auto-spark-plug-.jpg

[mayhem17]

I didn't put in the 132 because I had already planned on going back to this filter type, and the fact that I didn't have access to one. Smallest I had was a 136. The K&N was temporary and was what I had at the moment. I thought I attached a pic of the new plug last night, but didn't attach. So here it is.216769

[oscarmayer]

The 136 is better but still rich. 134 max.


Sent from my iPhone using Tapatalk

[yaegerb]

I did a quick search and it seems this is pervasive problem with your model of carburetor. I would do a search and see if you can glean any wisdom from others carb related issues. Another avenue is to contact FlyingW (Jim). He's probably the most knowledgable with the 250sx and 350x carbs. I am surprised he hasn't replied yet.

[Jmoozy27]

That doesn't look too bad, I'm no expert but I would say it's a hair idle rich, mid range looks good, and I can't see far enough into the plug to see WOT but usually if the mid is good WOT is too. Maybe tighten your mixture screw 1/8 of a turn or just leave it the way it is. How does it run currently?

[barnett468]

.
ok, please answer the following questions one at a time.


1. exactly what main jet and pilot jet are in there?

2. does it now have some type of horrible problem when you accelerate or is it minor?

3. In other words, if it never ran better than it currently does, is it acceptable or not?

4. does it run better than it was with the 140 jet?


as you can easily see, that basically falls right in the middle of the two photos I posted for you to compare to, which means that you are very, very close, ESPECIALLY, if that plus has less than an hour on it because it will likely darken up just a hair more.

You really need to do the tests I suggested just the way you described . . if you have a slight hill to do them on it would be a little better but it’s not that important at the time.

Also, don’t forget the fuel level test I suggested . . this is very important.

There is not a huge difference in air flow between a foam filter and a k and n especially at low speed so unless your k and n was extremely dirty, changing the filter basically had no affect on your jetting.

[mayhem17]

Main and pilot are stock again with the last plug pic. The only time I have the problem is when I stab the throttle from idle-low rpm. Once I'm in the mid range or higher I don't have the issue, runs fine. Starts first kick and idles fine. I'm about to test my float level in about 5 minutes.

[barnett468]

Main and pilot are stock again with the last plug pic.

i have seen over 1,000 jets and have never seen the word "stock" written on any of them . . honda made 50 different atv's with 50 different jet settings and i dont haven't memorized the actual size of every jet for every year and every model . . some jets have no number . . if your current jets have no number, i would install a 130 or 132 so we know exactly what is in there.
.

[barnett468]

The only time I have the problem is when I stab the throttle from idle-low rpm.

that did not answer all of my questions . . after you answer them all, it will be much easier to help you, otherwise i for one am still guessing to some degree.

if it has a flat spot right off idle, your ignition timing and/or cam timing might also be retarded.

do the tests i suggested, it may fix your problem.

do you have a stock exhaust pipe or an aftermarket one?
.

[barnett468]

Starts first kick and idles fine. I'm about to test my float level in about 5 minutes.

if you dont answer all of these, i for one cant help you . . please answer them one at a time.


what is your approximate elevation?

what is the outdoor temp when you first try to start the bike for the day?

EXACTLY how much choke do you give it?

how long do you let it run before you turn the choke off?

does it stay idling immediately after you take the choke off?

AFTER it is warm, does it idle smoothly and at the same rpm?


when you do the acceleration test exactly the way i described it, also try it with the choke 1/2 way closed a few times then fully closed a few times . . I would do this choke test BEFORE i did the needle test . . if it runs better of the bottom with the choke on, it suggests that it is lean off the bottom.

its sounding like your pilot jet is perfect or within one size of perfect /. . changing it one size will NOT get rid of a fairly big hesitation off the bottom which suggests to me that you could fix this with a needle adjustment as i suggested . . a different needle is sometimes required.

[mayhem17]

Main jet is 130, pilot 38. Elevation is 1900 feet. Has the same issue from 50 degrees to 90 degrees. I don't choke it to start it. When it was cooler I had to choke it once, left it on for about 30 seconds and turned it off. Idles fine after turning it off. If I try to turn the choke back on to do the acceleration test it dies.

Guess I'll try adjusting the needle clip. I have never done this before though. What does moving the clip up and down do for it? Will give me an idea of which way to go when testing.

[yaegerb]

This thread is pretty choppy for a diagnosis, but if you are bogging off idle (0-1/4 thumb throttle position) that is NOT your needle, it's your pilot. I think something is wrong with your pilot/choke circuit. Have you thought about cleaning and rebuilding the carburetor?

[mayhem17]

This thread is pretty choppy for a diagnosis, but if you are bogging off idle (0-1/4 thumb throttle position) that is NOT your needle, it's your pilot. I think something is wrong with your pilot/choke circuit. Have you thought about cleaning and rebuilding the carburetor?

Has been rebuilt and cleaned. It only happens when I stab the throttle though. If I roll into it, it does fine

[barnett468]

what were the results of the gas level test? . . . your latest description suggests that you may not have a problem because in fact if you took most of these atvs in stock form and instantly mashed the throttle they will die or hesitate . . this is why i asked you if the problem was minor or huge etc . . if you are rolling along at maybe 10 mph or more in first gear and it has a problem then it is not normal . . i will telll you how to change the clip on the needle in a little while if no one else does and you should certainly do this test but based on my interpretation of your last comment it will not affect your particular problem . . also the choke test needed to be done at 1/2 as well as full . . i would also do a compression test with a good gauge if you have one and i would advance the timing a little if it is adjustable . . .i would also post all the mods done to the engine . . if you want it to accelerate quicker you can also change the gearing . . this will reduce a bogging problem a littleb in many cases .. . . . . . . bthrottle as well as but or

[barnett468]

also if your problem is only when you push the throttle to near full throttle or more quickly your poblem is not from 0 to 1/4 throttle .. . . . n or

[barnett468]

i would try opening the throttle quickly to around 1/3 and not more than half . . do this in both neutral and also in first gear from a full stop and post results.

[mayhem17]

It's not how far I press the throttle per say. It's more about how quickly I do it. Does it in neutral also.

[barnett468]

.
ok well, you still haven't told us what the gas level is in the carb or what modifications your engine has.

i will post how to change the needle clip in a few minutes.

after you do all the tests exactly as described, you might have a better idea what might help reduce the problem, but as i mentioned, if you push the throttle too quickly, it can cause this hesitation, however, without being there, we really have no idea just how fast you're pushing it so we cant say for certain if it really is as problem or not.

[yaegerb]

Still say it's your pilot circuit.....probably junk in your pilot. Also have you checked for air leaks around the intake manifold?

[barnett468]

.
if you want, you can certainly try to go up on the pilot jet first, especially since you have already done this so you are familiar with the process, however, everything you say in regards to how it starts, suggests that it is perfect and in fact, it might be just a hair on the rich side for starting anyway.

your bike probably starts easier than most peoples and it does it without a choke, however, as yaegerb mentioned, the pilot also affects the carburetion right off the bottom, so i would maybe remove the pilot then spray carb cleaner in the pilot hole in the carb by sticking the end of the long nozzle that comes in the can right up against the hole then spraying for a few seconds.

the bikes are jetted for seal level up to around 1000 feet . . since you are at 1900 feet, it means that your bike is now a little richer than the factory setting even though you have the factory jets in it.

since you have a 38 pilot jet now, i would go up 2 sizes and see what happens because one size is a pretty small jump and possibly too small for you to notice.

jeep in mind, if it burbles and sputters, even the tiniest bit, it is rich.

[Mosh]

To the original poster...
The thread is going too many different directions IMO.

A member here that has tons of real world experience on these carbs, versus armchair engineer evalutions, has written the most acurate tutorial one ever could find on your model carb, with many tips and trouble shooting tips. My advice would be to read it 2 times....and have at it.
take a break from the trike for a day, clear your head and start from scratch. I would lookat post 31 especially compared to your carb and rule it out, but the tutorial as a whole is a wealth of info.

Here is the link.
http://www.3wheelerworld.com/showthread.php/161746-ES-SX-350X-Carb-rebuild-Tutoral

[mayhem17]

.
ok well, you still haven't told us what the gas level is in the carb or what modifications your engine has.

i will post how to change the needle clip in a few minutes.

after you do all the tests exactly as described, you might have a better idea what might help reduce the problem, but as i mentioned, if you push the throttle too quickly, it can cause this hesitation, however, without being there, we really have no idea just how fast you're pushing it so we cant say for certain if it really is as problem or not.

I posted my gas level several posts ago. As stated, my fuel level was exactly like it showed in the diagram posted, right at the top of the bowl.

I know how to change the needle clip, just need to know going which way does what. If I raise the clip higher on the needle, if I drop it down?

[barnett468]

ok no prob . lowering the clip raises the needle which will make it slightly richer and vise versa.

[barnett468]

.

I posted my gas level several posts ago.

Sorry but I must have missed it . . please give me the number of the post it is in so I can see what the level was.

[RIDE-RED 250r]

I don't mean to possibly further sidetrack you, BUT:

Carb cleaning means alot of different things to alot of different people. A true, thorough carb cleaning involves COMPLETELY disassembling the carb and cleaning every single fuel and air circuit in the carb body itself, vent circuits (I once had mud bugs plug a carb vent line causing all sorts of issues I thought was jetting/dirty carb), jets, and emulsion tube. Due to the tiny size of the idle air and fuel passages in the carb body, they are the easiest to get plugged up with stale fuel varnish or other debris and are often overlooked on a "carb cleaning".

Might I suggest getting yourself a 1 gallon can of carb cleaner that is for soaking the carb and individual parts overnight? I have had great results getting stubborn areas cleared out on carbs with this method. It's very easy to use and is designed to eat that junk out of every passage and port, even the ones you can't clean by conventional means as you can do with main and pilot jet circuits. Just be careful to use proper PPE (personal protective equipment) as that stuff can be pretty toxic.

Here is a link: http://www.napaonline.com/Catalog/CatalogItemDetail.aspx/Carburetor-Choke-Cleaner-1-GAL/_/R-MCR6402_0410678710

Use as directed, carb and parts will come out looking almost new after soaking overnight then rinsing in hot soapy water and blown out with compressed air.

[barnett468]

.
.
Here's a partial chronology of what has transpired.

Post 25

The only time I have the problem is when I stab the throttle from idle-low rpm. Once I'm in the mid range or higher I don't have the issue, runs fine. Starts first kick and idles fine.


Post 29

Main jet is 130, pilot 38. Elevation is 1900 feet. I don't choke it to start it. When it was cooler I had to choke it once, left it on for about 30 seconds and turned it off. Idles fine after turning it off. If I try to turn the choke back on to do the acceleration test it dies.


Post 31

Has been rebuilt and cleaned. It only happens when I stab the throttle though. If I roll into it, it does fine


Post 32

your latest description suggests that you may not have a problem because in fact if you took most of these atvs in stock form and instantly mashed the throttle they will die or hesitate . . this is why i asked you if the problem was minor or huge etc . . if you are rolling along at maybe 10 mph or more in first gear and it has a problem then it is not normal


Post 34

i would try opening the throttle quickly to around 1/3 and not more than half . . do this in both neutral and also in first gear from a full stop and post results.


Post 35

It's not how far I press the throttle per say. It's more about how quickly I do it. Does it in neutral also.




From today on flywingw’s sx carb tutorial thread,


This is a great thread that was linked to me today because I am having issues with my 85 250sx carb. The issue I'm having is off idle, if I stab the throttle quickly, it falls on its face and sometimes dies. If I roll onto it, I do not have the issue. Starts and idles great. It seems to run great once I get about 1/4 through the revs.



This is a common problem with these carbs. . I'd say more than 75% of the carbs I've rebuilt including my own does this. …I'm at a total loss as to the cause. Don't stab the throttle like you would on a 250R.

I saw your post on flyingw’s thread, and unfortunately, after 8 pages and 110 posts, neither he nor any of the other posters had an answer for the specific type of problem you are having other than generally the same answer I already gave you, however, I additionally mentioned that this problem is not uncommon with other ATV’s so it is not only on the 350X although it may be more pronounced on this model in the cases where it occurs.




One of the main causes of this is low engine vacuum which is one reason it's good to check for vacuum leaks as was suggested.

Carburetors are complicated, and very people few fully understand them . . I know enough to do what I need, but I’m not the worlds foremost authority on them by far, however, while i worked a kawi, I was solely in charge of determining what the factory jetting should be for every single model of ATV Kawi produced during that time . . I also do this for a few motorcycles . . I had also jetted all my own race bikes and street bikes for years before that . . at Kawi I was limited to the parts they supplied me with which in most cases were enough . . The main thing they did not supply was jet needles with different emulsion holes, which would have been nice to try in some cases.

Anyway, a fuel injection engine has the fuel forced into it . This fuel is also "atomized" into almost a mist, which helps it burn which also basically eliminates stumbling caused by fuel that is not sufficiently atomized/mixed with the air.

A carburetor only forces fuel into an engine when the accelerator pump is active . . The rest of the time the fuel is drawn into the engine via “vacuum”, and it takes a certain amount of “vacuum” to draw/suck the fuel in . . Different carb designs draw it in at slightly different vacuum ratings, but in general, there is not a huge difference between them . . This process applies to all siphon type carbs which includes automotive ones whether they are stock or aftermarket like a Holley or Edelbrock etc.

One way to visualize this process is to imagine sticking the tip of a straw around 1/4” into the center of a toilet paper roll then sticking the other end into a glass of water and then trying to get the water to come up the straw by simply sucking on one end of the tube . . Well it simply won’t happen whether the tube has emulsion holes or not, so you can see how difficult it is for an engine to do the same thing at low vacuum.

Now, because the vacuum from many engines is too low to immediately draw fuel in when you open the throttle quickly, the accelerator pump forces a small amount of fuel into the engine as soon as the throttle moves . . When properly set, this gives the engine enough fuel to run on and build enough rpms so it has enough vacuum to suck the fuel out of the carb on its own . . So, one of the questions this brings up is this: If this is the case, then why don’t motorcycles have an accelerator pump like an automotive carb does?

These are just a few of the answers:

Most motorcycle engines do in fact run “well enough” without one . . This is not to say that they run perfectly, but accelerator pumps are expensive and add to the cost of the vehicle which is usually a concern for most mfg’s, and if a bike works “well enough” without one for its intended target market, they deem it an unnecessary item that will unnecessarily add to the cost of the vehicle . . In other words…if it ain’t completely broke…don’t fix it, lol.

Another reason is that since most bikes run well enough without one, even though adding one would improve its performance, the increase in performance is not big enough to justify the additional cost.

Another reason is that from what I remember, there wasn’t any motorcycle carburetors that had an accelerator pump back when many of these atv’s were built . . The concept obviously existed for automobile engines, but for reasons unknown, there just weren’t any for bikes.

There have been motorcycle carbs around for a while now that have an accelerator pump which was added to cure this exact problem, but these were “invented” much later than when most of these atv’s and other older bikes were produced . . Once they began to appear on bikes, they began to appear on lots of them . . They are not only on some of the biggest bike engines made, they are also on bikes as small as a 125.


ACCELERATOR PUMP TEST

If you have a car with a standard carb or a motorcycle with an accelerator pump on it, and what to actually experience the affects of it, you can simply warm your engine up, then disable the pump, then try to drive it.


WHERE TO FIND CARBURETORS WITH ACCELERATOR PUMP

If you find that you can not fix the problem to your satisfaction, one option is to buy a carb with an accelerator pump and try it . . The one below is a 30 mm and could be adapted without a lot of trouble . . I don’t know if it will fix your problem because I don’t know what your problem is yet but it’s a fairly cheap and easy test . . Of course it too will have to be properly jetted etc.

...............................http://www.ebay.com/itm/KEIHIN-30mm-Hand-Chock-Carburetor-with-Acceleration-Pump-for-200cc-250cc-ATV-/191194550872

.............................. http://thumbs2.picclick.com/d/l400/pict/251763598509_/HONDA-CG125-CARBURETOR-WITH-ACCELERATOR-PUMP-BRAND-NEW.jpg



Heres a video of how it works in place on an FCR carb.

https://www.youtube.com/watch?v=I319vj9ktSw



Here’s a picture of an accelerator pump on a motorcycle carb.

http://www.dansmc.com/carbs_accelpumpcarb.jpg


This is what happens when you open the throttle on a motorcycle carb with an accelerator pump . . once the fuel is injected into the air stream, even the slightest amount of vacuum will draw it into the engine.

...........http://www.dansmc.com/carbs_pumpercarb.JPG

[barnett468]

.
Post correction because I have no edit button.


“…and very people few fully understand them.”

Should read

“…and very few people fully understand them.”


“The main thing they did not supply was jet needles…”

Should read

“The main thing they did not supply was needle jets…”


“Here's a video of how it works in place on an FCR carb.”

Should read

“Here's a video of how the accelerator pump works on an FCR with it in place.”
.

[mayhem17]

Anyone have a few suggestions to carbs with accelerator pumps built in? This was actually my original thought after re-jetting with no luck, but wanted to try this first. I've seen a hundred different brands listed on ebay and other sites. Anyone have some personal experience with one for the 85 250sx?

[barnett468]

Anyone have a few suggestions to carbs with accelerator pumps built in? This was actually my original thought after re-jetting with no luck, but wanted to try this first. I've seen a hundred different brands listed on ebay and other sites. Anyone have some personal experience with one for the 85 250sx?

Well, I already posted one suggestion and it’s one of the cheapest you will find but the mount is different which is no big deal . . there certainly are better carbs out there and an accelerator pump carb certainly will work on any atc if properly set up so if it doesn’t work properly, it’s definitely not the carb or the concept.

One of the problems is that to my knowledge, no one here has done this including flyingw, otherwise I think you would have seen it mentioned by him or another on his 8 page sx carb thread somewhere which it is obviously not . . as I mentioned, very few know fully how a carb really works or how these engines work in general, otherwise they would have thought of this incredibly simple idea long ago . . this is certainly not to suggest in any way that flying doesn’t know his stuff, especially since he said his own bike has the exact same problem, because I think he does know his stuff, and I have in fact suggested to others on this site that they send their carbs to him for rebuilding and/or coloring etc and he appears to do an excellent job.

it's also certainly possible that flyingw may have in fact thought of doing this before but just never got around to it, I just don’t know, however, I would think that he certainly might know of a carb of similar size that might be easy to adapt . . i asked my friend Damon if he might know of one because he knows the different honda models far better than i do and he suggested looking into a 250 trx one and gave me the link below, so my thanks to him for his help . . this may be a Chinese carb but the Chinese carbs seem to work ok . . I would make sure it is close to the factory size . . if it is much larger, it might cause a similar problem when you stab the throttle . . I would also suggest you ask flyingw if he knows how to adapt a carb like this because he has done several of the sx carbs etc.

http://www.ebay.com/itm/Carb-Carburetor-Honda-TRX-250X-TRX250X-1987-1988-NEW-/121670697523?hash=item1c54238233&vxp=mtr

[barnett468]

.
ok, since they both have thumb throttles, i figuered that if your orig cable didn't work on the trx carb, a trx cable might . . yes brilliant thinking i know, lol . . any way . . here's the deal . . if the only problem you have is that the length of the inner cable is incorrect, you can simply get one made to fit your outer cable . . i have both made my own over the years and had some made . . it shouldn't cost much to get this done . . damon gave me the link below to a trx cable after i mentioned the idea to him.

as a worst case scenario, you could simply buy a trx throttle too . . it should fit and work just fine on a 350 and im guessing the overall cable length would be long enough.

another thing to consider is that the trx may require a different intake boot but flyingw may know about that.

http://www.ebay.com/itm/Honda-TRX-250X-1987-1988-1989-1991-1991-1992-Throttle-Cable-NEW-TRX250X-/380903455352?hash=item58af9d7a78&vxp=mtr

[barnett468]

.
ok, i had a minute to look into this a bit more and the 250sx carb is a 27 mm and the trx250x carb is a 36 so this would be a bad choice for a box stock 250sx . . i will have a little more time shortly to look into this further for you . . the interesting thing is that the 36 mm trx250x carb has the exact same jetting as the 27 mm 250sx one does.

[Jmoozy27]

http://www.ebay.com/itm/Keihin-32mm-Carburetor-With-Primer-Pump-/200950531300?hash=item2ec995c4e4&vxp=mtr

This may fit with minimal mods

[barnett468]

http://www.ebay.com/itm/Keihin-32mm-Carburetor-With-Primer-Pump-/200950531300?hash=item2ec995c4e4&vxp=mtr

This may fit with minimal mods

unfortunately, that carb does not have an accelerator pump.

[barnett468]

.
I found a few things today in my search to adapt the 30 mm carb I posted to the 250sx.

This adapter may bolt right on to the 30 mm carb I posted which may actually be a 27 mm instead . . The other end has a 61 mm bolt hole spacing and 30 mm bore size . . unfortunately I can’t tell if either set of mounting holes is offset but this should be able to be made to work . . from the othr hotos i hve seen, it also looks like it is clocked correctly, however, I am still looking for others . . I started off with the old Honda cb 175 and cb 200 ones unfortunately the 175 ones were for 20 mm carbs and the 200 ones where clocked incorrectly so the carb would be rotated too much.

...............................http://i01.i.aliimg.com/wsphoto/v0/32249875141_1/Motorcycle-Dirt-Bike-Racing-Carburetor-font-b-Carb-b-font-Aluminum-Adapter-Inlet-Intake-font-b.jpg


1983 - 1985 atc200x throttle cable should thread into the atc250sx throttle housing and be long enough to reach carb . . inner length may need to be adjusted.

.................................................. ...............http://i.ebayimg.com/00/s/MTYwMFgxNTU5/$%28KGrHqV,!n0E-v2loRWhBPutmd4IRw~~60_35.JPG

[barnett468]

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I would also try these tests.


THROTTLE RESPONSE TEST

This is something I have done myself many times for various and it is a little tricky, but when done well enough, it can usually help determine if an engine is lean or not when stabbing the throttle . . Use aerosol WD40 only for this test, don’t use starting fluid or flammable brake cleaner.

Remove the carb to air cleaner boot.

Take an aerosol can of wd40 and stick the long nozzle on it.

Hold the end of the nozzle at the opening of the carb . . Don’t stick it inside the carb.

Spray a short burst of WD40 into the carb at the exact same time you stab the throttle.

Do this a few times by stabbing the throttle around half way and again by stabbing it to the stop or close to it and see what happens.

If the hesitation is reduced by a significant amount, the engine will definitely benefit from either richening the carb in the appropriate circuits or by using a carb with an accelerator pump that is properly set up.


LEAN CONDITION TEST

I have done this test also many times for various reasons and it can help determine if a carb is lean in a particular throttle position . . I mainly use it to test automotive carbs from 1/8th to 1/4 throttle because this is where they transition from the idle circuit to the primary circuit and is where they have the most problems because if they are lean here and you turn the fuel mix screws out to correct the problem, it will often be too rich at idle in which case adjustments in other areas must be tried.

With the fuel or air mix screw for best idle, open the carb slowly with the idle set screw maybe 4 turns and listen to the engine to see it reaches a point where it either barely or completely stops gaining rpm as you turn the screw . . If it does, it is most likely lean in this position . . Just take some WD40 with the long nozzle and gently spray a tiny continuous amount into the carb . . If the rpm increases, it is definitely lean.

[Thorpe]

Just gonna add my $.02 here... But I ran into an issue either on my Big Red or SX, when it came time to rebuild the carb, I tore it down, fully cleaned it and installed a new aftermarket "stock rebuild kit" and it ran like dookie... Rich didn't even begin to describe my issue. After tearing into it a couple times, (to no success) I finally compared the new aftermarket parts to the originals, and discovered that the jets, even though stamped the same numbers, were drastically different in the calibration of hole size... Cleaned old jets very well, reassembled, and ran perfect after that. (Ymmv)

[oscarmayer]

i think accelerator pump carbs have their place. not every trike needs them and they are not best for all types if riding. i prefer not having one. i usually swap out to a normal kien or miki carb and jet appropriately. makes my life so much easier down the road. but then again i don;t do tons of trailing.

[barnett468]

.
interestingly enough, there are no non cv or non fuel injection type automotive carbs that do not have an accelerator pump, even if they have cams with a more sedate profile and the engine has higher vacuum levels than the atc200sx.

the old 70's bikes with cv type carbs like the 750 honda's didn't have accelerator pumps either which caused them to have throttle lag, which is far different from the hesitation being discussed here . . in fact, every vehicle i have ridden or driven that has not had an accelerator pump on a cv type carb has had throttle lag.

although there are still many bikes that do not have accelerator pumps, nowadays they are installed by the mfg's on far more bikes than ever before, including some models that are under 250 cc.

if an engine has insufficient vacuum to draw enough fuel from the fuel bowl to prevent a hesitation, it will have a hesitation and will benefit from an accelerator pump.

although the improvement might be small in some cases. most vehicles that do not have fuel injection or an accelerator pump will benefit from having one . . just because a bike seems to run well enough without one doesn't mean it wont run better with one . . its more of a matter of whether it's worth the time, effort and money it would cost to get one and set it up properly for the amount of improvement in performance it will provide.

[oscarmayer]

my problem is running a track bike with one is much harder. We like to remove the idle circuit anyway, so there is not a lot needed at that point. change the needle to what you need, set the jets up right and your good to go. (2strokes mainly)