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

[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-Carbure...238233&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-25...9d7a78&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-...95c4e4&vxp=mtr

This may fit with minimal mods

[barnett468]

http://www.ebay.com/itm/Keihin-32mm-...95c4e4&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.

...............................


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.

.................................................. ...............

[barnett468]

.
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)