'83 185s - Acceleration problem

[webbch]

My 185s didn't run when I got it. I cleaned out the carb (soaked in carb cleaner, blew out jets, etc), cleaned the fuel tank and added fresh gas and was able to get it running. After getting it warmed up and adjusting the carb, it idles very well. However, it falls on it's face when you try to accelerate. Even in neutral, if you goose the throttle, it either hesitates for several seconds or dies, depending on how quickly you apply the throttle. A couple of key points:
1) Not the OEM carb - I'm guessing it's some kind of chinese carb - other than not having Keihin stamped on it, it otherwise LOOKS like the stock carb.
2) Previously had a #86 main jet and #35 slow jet. When I rebuilt the carb, I installed a #98 (Update: actually a #95) main jet and #38 slow jet per the contents of the rebuild kit for it.
3) A little difficult to start when cold (below 60 deg) on half choke. I haven't operated it enough to know if it needs full choke when cold or not.
4) I hear some valve noise - like I need to adjust the valves, which I haven't done yet.

Since the engine dies if I quickly goose the throttle (i.e. before RPM's have increased), it makes me suspect that the valves are NOT the likely culprit. It would almost appear to me that I need to go bigger on the main jet to supply more fuel, but I'm not sure if that's the right approach.

Any tips? Thanks

[trike savior]

move the needle on the carb slide. that controls your mid-range. Move the spring on the top of the slide and you will see how to get at it. there is an e-clip on the needle. Moving the e clip down a notch, moves the needle up and richens the mixture.
also could be restriction in fuel coming from tank. Check filters and sediment bowl on petcock.

this is assuming you are on the lean side. easiest way to test for lean condition is open the air box and hold a few fingers over the intake to the carb. if it runs right taking away some of the air you are definately lean

[tri again]

Most would say adjust hard stuff first.
No real reason to fool with carb mix if valves aren't right .
Will it rev if you apply a little choke?

[dougspcs]

Just as probably is your spark advance..this machine has a centrifugal weight system designed to advance the timing as RPM and not electronic timing control like some of the other trikes. If the weights are jammed then no advance. As the revs go up..it will fall on it's face!

Grab a copy of the manual from any that are available online and dig in to the ignition section to find out how to set your base ignition timing and check the operation of the timing advance.

Also, I feel the need to correct you about your assumption that the valves may not be the issue.

Since you said there is noise it stands to reason that you should be looking there too..improper valve adjustment will definitely cause power issues or if there is a broken valve spring you may have a valve floating open when the RPMs go up..

Stop wasting time on random jet changes, consider re&re your carb again and put the stock jets back..get the thing as close to factory design then you can start dialing in.

Also here is a great video for a way to check the timing chain adjustment since the adjuster often sticks and doesn't always adjust according to the book..

While your at the rest of this do a compression test too. Basic engine fitness info is also a good start point.



I suggest you get back on the trike and check everything..since you just got the trike and don't know anything of it's history you can't ignore anything as possible cause..

That should keep you busy for a while and most likely in there is the solution to your issue.

[webbch]

OK, adjusted the valves tonight. I also pulled the carb and re-cleaned the main jet real good, using those carb cleaner wires and blew it out real good. I was mistaken about the main jet: it's a #95, not the #98 that's recommended in the manual for this year's model. After getting it all done, it seems to be doing SLIGHTLY better. Tomorrow night I'll try moving the needle down a notch or 2 (Correction: moving the CLIP down, needle UP) (after doing the airbox test to verify it's running lean) and see if that cleans it up. I'm aware of the timing chain adjustment as I've done it on my 200s before (I've seen all those D-Ray videos and they're very good), but I'll definitely do that tomorrow as well. I checked cylinder pressure a couple months ago and it was at 150 psi.

It WILL rev with the choke on, which I think supports the argument of a lean mixture at mid range. Is moving the clip down a notch more effective at richening up the mixture than moving up a size on the main jet or do they kind of do the same thing? Thanks for all the help

I already set the timing at 1300 RPM with my timing light....it was right on the F mark. I didn't check the advance at higher RPM's though, so I'll double check that tomorrow, but given the fact that I could easily kill the motor by quickly goosing the throttle (i.e. dies before the RPM's increase), I figured I could rule that out.

Kind of ironic that my 185s idles just fine, but can't rev, while my 200s can't idle, but revs great. I'll get 'em working right one of these days

[Iceracer1]

The main jet effects 3/4 to WOT and the needle effects between 1/4 and 3/4 throttle. You might want to find out if that carb is the right size and not one someone just threw on it to get it running.

[barnett468]

My 185s didn't run when I got it. I cleaned out the carb, cleaned the fuel tank and added fresh gas and was able to get it running. After getting it warmed up and adjusting the carb, it idles very well. However, it falls on it's face when you try to accelerate. Even in neutral, if you goose the throttle, it either hesitates for several seconds or dies, depending on how quickly you apply the throttle. A couple of key points:

1) Not the OEM carb - I'm guessing it's some kind of chinese carb - other than not having Keihin stamped on it, it otherwise LOOKS like the stock carb.
2) Previously had a #86 main jet and #35 slow jet. When I rebuilt the carb, I installed a #98 main jet and #38 slow jet per the contents of the rebuild kit for it.
3) A little difficult to start when cold (below 60 deg) on half choke. I haven't operated it enough to know if it needs full choke when cold or not.
4) I hear some valve noise - like I need to adjust the valves, which I haven't done yet.

adjusted the valves tonight. I also pulled the carb and re-cleaned the main jet real good, using those carb cleaner wires and blew it out real good.

I was mistaken about the main jet: it's a #95, not the #98 that's recommended in the manual for this year's model. After getting it all done, it seems to be doing SLIGHTLY better.

I checked cylinder pressure a couple months ago and it was at 150 psi.

It WILL rev with the choke on, which I think supports the argument of a lean mixture at mid range.

Is moving the needle down a notch more effective at richening up the mixture than moving up a size on the main jet or do they kind of do the same thing?

I already set the timing at 1300 RPM with my timing light....it was right on the F mark. I didn't check the advance at higher RPM's though, so I'll double check that tomorrow, but given the fact that I could easily kill the motor by quickly goosing the throttle, I figured I could rule that out.

Thanks for the help.

TIMING - You cannot rule out the advance not advancing as part if your prob. If you have no advance it will cause a hesitation. I’m guessing that this is why dougspcs suggested you check it. The advance needs to work properly for the bike to run properly. I would not try to jet it until I was sure it worked because timing affects jetting.


JETTING

a. Trike savior suggested to move the clip on the needle down to richen it up. Moving the clip down will raise the needle. One position will likely not make any difference, I’d go 2 or 3.

b. The results of the choke test you did that Tri Again implied you do, strongly suggests it is lean imo.

c. As Iceracer1 implied, moving the clip a few positions on the needle will affect low to mid.

d, Your latest info suggests to me that IF, your ignition advance is working properly, you are close or perfect on the pilot jet, but I might try 1 step bigger.



You are lean on the needle AND main jet imo.

I’d raise the needle as suggested and if you get to the last clip position and the problem is still significant, but not worse, but a 98, 100 and 102 main and install the 98 first. I'm guessing it might take at least a 100 to cure it.

There's a small chance you might need a larger needle jet.



CARB SIZE – This is often on the side of the carb and is denoted by a 2 letters followed by 2 numbers like VM28 or VM32. The number is the carb bore size in mm. If there are no numbers you can simply measure the id of the bore from the intake side.



MODIFICATIONS AND JETTING - The bikes are jetted for sea level to 1000 ft. Installing less restrictive exhaust, higher compression piston, boring it out and/or installing a larger cam can make a bike leaner than it was prior to these modifications.

If your bike has these, it will likely require a bigger main jet than stock, richer needle position or richer needle jet.

If it has a cam that is much bigger than stock it can cause a big flat spot/bog off the bottom. aT THE VERY LEAST, higher compression and lower gearing are required for cams that are much bigger than stock.

This being said, your 150 compression is good but even with good compression, a large cam can still cause a flat spot off the bottom.

[dougspcs]

Well is sounds like you've been applying a bit more logic than other new members..this is good. Many just fixate on the issue they think is causing their problem and ignore all else..

Anyway, once you've been thru the entire list if your issue is still there you may consider buying one of those ebay chinese carbs..I've run into carbs that just didn't work right, no matter how many time I cleaned it.

[webbch]

OK, good news. I've got it idling great and I'm about 95% happy with the off-idle throttle response.

I started out by checking that the timing advance mechanism was operating smoothly, then I started up the bike and verified that I was still getting poor throttle response.

With the engine running, I removed the airbox cover and suddenly I could rev the motor. Remove the air cleaner and it revs even better. So I'm thinking it must be running too rich if extra airflow makes it run better (I double checked the airbox-to-frame boot to ensure it wasn't clogged with debris and restricting airflow further). So I put the air cleaner back together and move on. The needle clip position was right in the middle, so I moved the clip to the top position (needle lowered) to lean it out, and the throttle response got worse...I couldn't even inch the throttle up past about 1/4 of the way before the engine would just plain die.

After all this, against my better judgement (I was certain it was too rich after the airbox test), I moved the clip to the BOTTOM position which should've further richened what I thought was an already overly rich mixture. Sure enough the throttle response got _much_ better than it's ever been thus far. I can now actually ride it around and accelerate.

After all this, I still had some valve train noise, so I adjusted the timing chain using that slick trick with an M3 x 0.5 x 50mm screw I learned from the D-Ray videos. That cleared up the valve train noise.

I'm pretty happy with it now, but still think I could do just a little bit better. From idle, quickly goosing the throttle results in a momentary hesitation (but it doesn't die at least). When I had the needle out, I compared it against the needle from my carb rebuild kit (keep in mind this appears to be a Chinese carb, and my rebuild kit was for the stock carb. That's the only reason I didn't replace the needle right off the bat). Upon close inspection of the needles, the one in my rebuild kit was the same length, but had slightly less taper to it (slightly smaller diameter). Now that I have a working baseline, I may try installing the new needle and play with the position to see if I can fine tune the throttle response just a little bit better.

If anyone could explain the flaw in my logic about the airbox test, I'd appreciate it. Thanks again for all your help! And thank you dougspcs for the encouraging words.

[barnett468]

If anyone could explain the flaw in my logic about the airbox test, I'd appreciate it. Thanks again for all your help! And thank you dougspcs for the encouraging words.

Without more info it would be almost impossible to make a reasonable guess as to the reason for this imo.

There are many questions you have not answered. The answers to those questions would help myself and others to make a more informed “guess”.

We still don’t even know what mods your bike has or if you are below sea level, at sea level or in Benson Az as you location says, which is around 3600 feet.


NEEDLE COMPARISON

Does your new needle have less taper AND is smaller in diameter throughout.

The taper controls the fuel “curve”, the diameter controls the amount of fuel allowed within that curve.

The following is an example providing the top of the effective part of both needles are the same diameter.

Steep taper = Rich on bottom leaner on top.

Shallow taper = Leaner on bottom and same on top as needle above.


Needles often [but not always] have very tiny id numbers/letters on them just below the bottom clip position. One can often look these numbers up on a chart to see the differences. If your needles do not have these numbers you can do the following if you want:

Put the needles side by and line up the clip grooves

Use a fine tip felt pen and put a mark at around 1/4”, 1/2”, 3/4” and 1” up from the bottom.

Measure the diameter of the needles at these marks using a mic or dial/digital caliper.

Smaller numbers indicate richer, larger indicate leaner.


PILOT JET AND FUEL MIX SCREW - In addition to affecting starting, these can also significantly affect up to around 1/8 throttle.

[trike savior]

Glad the airbox test worked for you. I never thought about mentioning reving it with no lid and filter on but I am glad you figured it out yourself. You are right on with it being too rich. the hesitation is more than likely because it is still rich. I would say you need to step down 1 size on the main jet and you should be all good. Might need to play with needle a bit more after to get it just right.

[barnett468]

With the engine running, I removed the airbox cover and suddenly I could rev the motor. Remove the air cleaner and it revs even better. So I'm thinking it must be running too rich if extra airflow makes it run better (I double checked the airbox-to-frame boot to ensure it wasn't clogged with debris and restricting airflow further). So I put the air cleaner back together and move on.

Did you reinstall the air box lid?

[webbch]

Glad the airbox test worked for you. I never thought about mentioning reving it with no lid and filter on but I am glad you figured it out yourself. You are right on with it being too rich. the hesitation is more than likely because it is still rich. I would say you need to step down 1 size on the main jet and you should be all good. Might need to play with needle a bit more after to get it just right.

So you agree that the airbox test pointed out that I was running too rich at mid-range. Yet the corrective action (moving the clip down, which moves the needle UP, and hence further richens the mixture...or so I thought) that resulted in desirable behavior is counter-intuitive and what I don't understand.

yes, I did re-install the airbox lid before making any adjustments.

[barnett468]

So you agree that the airbox test pointed out that I was running too rich at mid-range. Yet the corrective action (moving the clip down, which moves the needle UP, and hence further richens the mixture...or so I thought) that resulted in desirable behavior is counter-intuitive and what I don't understand.

yes, I did re-install the airbox lid before making any adjustments.

Still not enough info for me to make an informed guess yet at least, perhaps others might try.


Did you ride it with the air cleaner lid off or did you just reinstall it after doing the rev test?

From what you could tell, was there less hesitation everywhere when you revved it?

Was the hesitation the same at any point in the rpm range?

Did the hesitation get better in one place but worse in another?


The fact that removing the lid significantly reduced the hesitation suggests that it was starved for air and/or too rich. No way to tell for sure based on the limited info provided imo.

Since you say it revved much better without the air box lid, logic would dictate that it would have more hp/power if you left it off. In your case, I might either leave it off, drill some holes in it, put a vent in it or space it up a little so it does not seal which will allow more air inside.

I would ride the bike and jet it after doing that.

[barnett468]

After you reinstalled the lid, did the same level of hesitation reappear?