Throttle hesitation

jwe2 wrote:

...serious hesitation when I gave it a small amount of throttle. It hesitated to the point where it would have shut off had I not let off the throttle. I was however able to rev the engine high, it just seemed that under 4k or so rpm it wanted to hesitate/bog down and die....

Imperfect pilot circuits could result in the issue as reported.

Good Fortune!

[Click on image to enlarge view.]

I'm going to compile a quick checklist of things suggested by all of you and start going over them tomorrow to see what I find. Forgive me for being so naive when it comes to carburetors, but this is the first engine other than a lawn mower that I've done significant work on that has carbs rather than throttle bodies and fuel injectors. That being said I didn't even check the air mixture screws, nor do I know what the factory settings are... I have an old service manual so hopefully that is in there somewhere..

As far as I know, both breaker-point and magnetic-pulse are both transistorized ignition. My bike has magnetic pulse coils or 'pickups', rather than points.

Yes the bottle I was using for fuel was vented, and I had the other line plugged. Unplugged it would just pull air and the rpms would skyrocket. It's a poor setup, I know. I just did it that way so that I could play with the carbs easier while the engine was running. Instead I will just buy longer fuel hose and hook the tank up properly while leaving it sit on the shelf so I can play with the carbs.


I have a compression tester, not sure if I have the correct size fitting for my bike yet tho.
I apologize for using the word "rebuild" what I should have said was "put back together"
The bike was non-functional and in pieces so I replaced gaskets and pieced it back together. I "rebuilt" the carbs using kits with jets, gaskets, o-rings, etc. Like I said before I'm a bit of a carb novice but they seemed clean to me. I'll have to look into those things you guys said tho about the pilot circuits and what not. Maybe they weren't as clean as I thought.

I've been so sure it was an electrical issue for the longest time, I'm going to kick myself if it turns out to be carburetor related hahah

.

I pulled the carbs out again to clean them as you instructed in the diagram. Hopefully this is the last time I have to remove/install these for a while lol. Any suggestions for removing the idle mixture screw plug? I would think it is set correctly since it looks like the plug has never been removed, but maybe it's clogged or dirty?

Small drill bit for the Idle screw plug, then a small screw pulled with a pair of pliers. If those are still in there then the circuit will be dirty/ plugged up. Complete disassemble and cleaning with new kits is best.

and lots of compressed air it is your friend, when your cleaning carbs

great, I brought the carbs with me to work where we happen to have a myriad of tools and the biggest air compressor I've ever seen, so they should be clean by the end of the night haha

Well, I don't think the carbs could be any cleaner if they were brand new. Used carb cleaner on all the orifices so that I could tell it was definitely making it all the way through each passage. Before I put them back together I shot each little hole with 120psi of air so there is definitely nothing blocking jets. I made sure the pilot circuit was clear on each carb. I guess the only thing to do now is reinstall them and make sure the idle air screw are set properly. Does anyone know off hand what these are set at?

while putting new carb kits in today I noticed that the idle air mix screw in the kit is quite a bit longer than the original one. Is that normal? The threads and diameter are the same, it is just much longer.

Been following this thread and I am trying to check my float levels but all the relief screws on my bowls are siezed. Dont know how long its been since anyone turned them. Anyone have a clever way of breaking them? I have applied so much pressure that the brass screws are chipping with the screwdriver.

djcody wrote:

Been following this thread and I am trying to check my float levels but all the relief screws on my bowls are siezed. Dont know how long its been since anyone turned them. Anyone have a clever way of breaking them? I have applied so much pressure that the brass screws are chipping with the screwdriver.

relief screws :huh: ??

Good Fortune!

Relief screws....drain screws....whatever u call them. I just need to get them loose so I can check my bowl levels.