Carbs? Synch? Or Throttle Cable?

[dontlikeoc]

When the engine is hot, the idle is very unstable and hovers around 2,500RPM. When I rev it at a stop light to see, it doesn't drop right away. It sticks around 4000RPM.

I first cleaned the tank rust by electrolysis. Was never sure if the tiniest rust particles had been completely washed out. After that, carbs were cleaned and synched by a mechanic, at the time, I trusted. Right after that, it had been running fine for a few weeks. They took the bike back for one month for redoing a warranty fork seal work...(they failed the first time). It looks like that they had gone back into the carbs and did a very shoddy job this time as I noticed that even intake manifolds are rather loose. (I tightened them.) They also replaced the throttle cable with a custome made one. The cable feels slacky to me too.

At this point, I don't feel like trusting the bike to any mechanic again. I would rather do all works myself(despite the lack of a proper workshop space at my apartment).

- What is the reasonable order of things to checK? Does re-synching carbs first makes sense? (That is the easiest thing to do.)

- The idle may have been tampered with. Is it alright to just re-synch first without worrying about it?

- Where do you get a new throttle cable? Partsnmore doesnt list it.

[psycoreefer]

Check your synch -> it can cause lots of strange symptoms. Doesn't mater what RPM, should stay close to the same at all RPM's anyways.

Make sure you've got a fan blowing on the engine while your working, don't want things to get to hot.

If the synch is off you'll have to adjust your idle, the closer you get to perfect synch the higher your idle will go.

Next thing I'd do if the synch checks out ok is look for vacuum leaks, if you do a search you'll find plenty of methods.

[DenyP]

If the ball or barrel at the end of the cable isn't centered in the carb linkage, it will hang and not allow the carbs to close properly. I would check this first. I would recommend you purchase a cable luber and a can of lubricant before replacing the cable. Chances are if it is the cable, it is just hung up on some dried up lube or gunk which will clean out nicely. Lubing the cables is part of regular maintenance so your not buying something you don't already need anyway. IMHO there is no future in messing with carb sync or mixture settings till you get the rpms down.

Deny

[TomRodgers]

does it idle high even at cold temps? or only hot? If at cold, it could be the throttle cable isnt allowing the carbs to return all the way to idle set. i had that issue with mine. the little steel cable end wasnt sitting down in the correct spot, and the idle was WAY high. who woulda thought that 1/4th of an inch would cause it to rev 2000-3000 over what its supposed to!!!

My concern is why they were jacking with the carbs again when supposed to be fixing fork seals??

Sounds morelike you will have to sync and verify your fuel mix..... Check your plugs. good indicator of something not right if the sync is okay...

[DenyP]

I should have added that I have had this problem and screwed away a weekend chasing it down. Disconnect the cable from the carbs and fire her up. If it is related to the cable, you will know right away.

Deny

[dontlikeoc]

Thanks for all the input.

Soon after it came back from the mechanic, the throttle cable end disconnected from the carbs. I rehooked it.

The high RPM is only when it gets hot. Right after cold start, it revs around 1,500RPM - which per se is only a little too high. So, does that mean more likely synch is the problem?

About the mechanics that messed things up, when they did the forks they messed up the tank. I made them fix the paint and the fork seals. I think they stripped and painted(including the hardnening) with the tank on the bike.

[cywelchjr]

Thanks for all the input.

Soon after it came back from the mechanic, the throttle cable end disconnected from the carbs. I rehooked it.

The high RPM is only when it gets hot. Right after cold start, it revs around 1,500RPM - which per se is only a little too high. So, does that mean more likely synch is the problem?

About the mechanics that messed things up, when they did the forks they messed up the tank. I made them fix the paint and the fork seals. I think they stripped and painted(including the hardnening) with the tank on the bike.

I would say it's more likely that the idle mixture is too lean. Every time I have run into that condition that is what caused it. Get the idle mixture right, and it will not to that, especially not the hanging high when coming down. As a matter of fact, with proper idle mixture it should actually drop slightly low momentarily when the throttle is twisted and released quickly when hot. If it hangs up, it's still too lean.

[Ivan]

Something just doesn't sit right with me about this whole mess. Like boobbies, er Tom, said they had no reason to dick with the carbs on a fork seal redo. Being a former mechanic, I know it burns a guys ass to have to redo something. The signs are pointing to someone ripping the carbs out of the scoot in a heated fuss, thereby breaking the throttle cable (which you said they cobbled together a new one) and in the process probably screwed up the linkage between # 2 and # 3. So, they had to take them apart to bend the linkage back into place and now your sync is no good any more. AQdd that to the sticky throttle cable and you are stuck with a high fluctuating idle.

My advice, find a GOOD mechanic. Might even be someone on this board that lives near. Have them make out an estimate for fixing it RIGHT, then sue the other guy for restitution and throw in some extra bucks for lost riding time. Check out the small claims process in your area, take lots of pictures and have lots of paperwork, play the victim role and get them for what ever the max in small claims is. I think in KS its $4500 dollars. The fee is nominal, and can be charged back to the defendant as collection costs.

[Ken Talbot]

It looks like that they had gone back into the carbs and did a very shoddy job this time as I noticed that even intake manifolds are rather loose. (I tightened them.)

Look a bit closer at those manifolds. Sounds to me like you've still got a vacuum leak.

[motoman]

Dead on what Ivan said!

[dontlikeoc]

Thanks for all the comments.

The sad thing is that this is the second mechanic that screwed up the carbs. (The first "shop" made up the need for the carb job I am sure the bike didnt need. And that they didnt do. I got the money back through a credit card.) My guess is that they tried to strip and repaint the tank they damaged during the fork job with the tank on to minimize the time they spend. That got onto the carb, which made it necessary for them to redo the carbs.

- As for making sure of the manifolds tightness, what tool do you use? The clearance for the hex wrench is impossible for most screws.
- About fixing the lean mixture, excuse me a dumb question, do I start by adjusting the idle - assuming the incompetent mechanic that cut the corner probably had tampered with it already?

[mro]

Carb adjustments

Set the idle at 1000/1100 rpm (main idle screw)
Synk carbs (reset idle as needed to maintane 1000/1100 rpm)

Adjust pilot screws. If you get NO responce (idle rpm does not change) check if that cylinder is fireing. If yes, then you may have a dirty carb problem. If no, then that needs to be resolved before going any further.

reSynk after pilot screw adjustment.


When I'm working on carbs (someone elses bike) I check the pilot screws to see where there set to before I do a synk. ( ie: how many turns out) If I find one much different than the others or there out more than I think they should be ... there may be a problem. Fouled plug, plug cap or wire problem, coil, vac leak, carb needs cleaning etc..

mro

[psycoreefer]

I know your looking to get your bike on the road, trust me I understand, but if you don't understand what your doing you may end up making things worse. Take an evening off working on the bike and spend some time reading here. Look at the maintenance tech tips and read about cleaning, syncing, and adjust the carbs. Do a search for "carbs" and browse the threads that sound interesting, or like they might be the same problems you've got. Arm yourself with knowledge. We can point you in the right direction but no one wants to re-type the whole step by step process, which is what it sounds like you need. That's already been done and is in those tech tips, there are even pictures there to help you understand what parts are what. Good luck and keep asking questions.