Bonneville America Forums Forums Technical Forums Performance Mods Problem..... Need help

I've just put my bike back together after a big cleanup, and she is now running like a pig! I had a leaking carb that came down to incorrect float level. I set the floats to 17mm put her back together and she stutters /misfires on small throttle openings like when trying to hold constant speed at say 2000 rpm. all is good on excelleration - pulls strong - but no good sitting on constant revs. I changed out the plugs and coils for no difference. I raised the float level 1mm, still no difference. Got me buggered. Any ideas?????

Hi I am having the same problem. The bike which is a friends was running ok and I cleaned the carbs for him. Now it is way rich accross the board and barely idles, kills plugs etc. I have had the carbs apart around twenty times looking for the obvious but had no luck. I race bikes with kiehins and have never had a problem like this. I have had the black box rebuilt, checked coils, checked wiring, rejeted carbs even, but it only runs ok with the fuel off and about to run out. The floats are as low as posible to still allow some fuel in.It is running 120 main 42 pilot 1 shim on needles no air pump I can see but where do I look. I have been at it for weeks and know its something simple but dont know where to go from here.

Link, Yours aint the same problem! Mine idles ok, it accellerates just fine. It is only when held at constant revs that it misfires and farts and carries on. This happena when riding or when stationary in my shed. There may be a similar strain to both problems. Are you sure you're moving the float level the correct way?

Birchr, So I assume you mean the pilot jet? Just thinking this through again you are probably correct. Seems to be happening in both cylinders though? It's night time in aussie right now so I will have to have another go in the morning.

No Im not sure on the floats and it accellerates really well but if it idles for a while it loads right up. open throttle is good but just off idle it surges and carries on as if majorly rich. heaps of black smoke. He bought it up running poorly but its now worse. I thought yours sounded a bit similar as you said after a good clean it played up so I was hoping for someone to have a miracle cure for us both.Does anyone have any carb settings or an idea on why its running bad after a clean. I have jetted lean tried pilots and mains etc, needles lowered .I have checked all plugs for the throttle positon sender etc. I am seriously running out of ideas. Slides are worn but not as bad as others I have tuned around.

Link, your problem sounds like float levels to me. The factory settings are as follows. Remove the bowls form the carb. invert the carbs and measure from the carb body to the outside edge of the float. this measurement should be 17mm + or - 1mm. Your problem is indicative of too higher float level. on accelleration you are using the fuel as quick as it enters the bowl or there abouts. At lower revs /idle the fuel level in the bowl builds up until it floods the pilot jet which causes the engine to bog down and eventually stall. check in the tech vault for better instructions regarding float levels, but I reckon thats your problem dude.

Now back to my problem.

Thanks I will check again but as I said if I run any less float no juice is gunna come out. I did have a similar problem to yours with dirt,junk in the airway between the air filter side passage that runs to the mixture screw. I m sure youll sort it out anyway.

There is an easier way to quick check the float levels. Put the bike on a stand or otherwise level it. Slide one end of a clear tube on the float bowl drain nipple and hold the other above the fuel tank (like, tie it off the the handlebar or just hold it). Crack the float bowl screw open. The fuel line should be +/- 1/8 inch from the gasket line between the carb bowl and carb body.

Did you mess with the throttle position switch? That can be a real problem for idle if you removed it and didn't put it back correctly. You're not suppose to remove it. It's set and sealed from the factory.

Have you checked the mini fuel filter is clean and that the carbie diaphram is seated correctly?

Hi guys I didnt mess with the throttle position sensor but someone has. This bike has been modded a bit but ran half ok before I cleaned the carbs it is now so rich I had to turn off the fuel when I took it for a ride to clear out then turn it back on. I have checked the two diaphrams countless times and the little diaphram around 5 times they all seem sitting well and seated.Needles are home and retained by the plastic holder. Where is the little filter as described and thanks for assistance from you all.

What do you have for exhaust and air filtration? If those have been changed you may have too small a main jet.Check the flaot levels again and set them where they are supposed to be don't modify that setting due to a problem but rather check for free movement,damaged float needle or seat, or gas inside the float itself. Any of those could allow too much fuel in no matter how you adjust the float.

Might also check for vacume leaks.

I have a couple more ideas but cover those first.

I know it sounds a little lame with all these excellent suggestions but have you tried draining the fuel and putting in some new. Worked for me once when bike started to run rough.
What ever hope you fix it

Blessings

Really sorry to baboon I have never used a forum before and seemed to have stolen his posting with my probs!!!!Link

link: check your air mix screws, sounds like they are way out of adjustment...like maybe the washers and o-ring might be reversed. Also, crud in the enrichener (choke) circuit can cause it not to seal properly and cause a mystery rich condition.

baboon: you might take a good look at the o-rings sealing the float bowls and the diaphragms on the slides as a slight leak at either will do exactly what you describe.

Check to make sure that the little four footed piece of plastic that retains your slide spring is not covering the vent hole in the slide. If this is the case it will exhibit the exact symptoms you are describing.

Problem solved. Ray (birchr) was correct I pulled the pilot jets and put a oxy tip ceeaner through them. the problem is now gone. I suppose it was a case of k.i.s.s. ( keep it simple stupid )
I was looking for some thing way more sinister when I should have stuck to the basics.Lesson well learned. Thanks Ray

Glad you found the problem. Here's a picture the in-line fuel filter described earlier.