Topic: strange problems with jumpy idle speed, points sparking too often

[patpollin]

Greetings, I have been picking away at a jumpy idle speed issue and have decided to pose a question or two here after not being able to decide for myself answers to them.  For one, my points act a little strange, the 1-4 points spark at the 1-4 mark And at the 2-3 mark.  The 2-3 points fire also at the 2-3 mark.  Is this a common occurence?  The 1-4 points are new, the 2-3 are not but look new.  That might be the problem.  On a different note, the jumpy idle is a terrible pain, it will die if I do not give it a little bit of gas, but sometimes jumps on its own to 3,000 rpm or is slow to react to throttle changes, and will sometimes hold at 3,000 if I rev it above that and release.  I am assuming that my carbs need syncing, but in order to do that I need the bike to stay at one engine speed because I only have one vacuum guage to share between the carbs.  I've been through everything, timing is on, point gap is spot on at about .39 mm, I have checked for vacuum leaks and found none.  my float levels may be slightly differing, which I am going to correct tomorrow with a drain tube, and I am replacing the slow jets thinking that maybe I gouged them during cleaning.  thanks to those still reading for your patience and thoughts on these issues, I'll check back in with any progress tomorrow.  Thanks again, Pat

[750goes]

not returning to idle and sticking a bit - lubricate your throttle cable/s and look for any binding or tight anngles and lubricate all the carburretor linkages may help a bit

[patpollin]

does anyone know where the fuel level should sit normally?  I've been adjusting my floats to not overflow which they all are now safe from, but I know that they are not uniform, and since they're a bit bent up the clymer's 22 mm adjustment doesn't apply.  I've only done the level check on one carb which was sitting above the top of the bowlby a cm or so.  is this about right?  I lubed up the throttle cables very slick and the idle still is crazy.   From doing plug chops I know that three cylinders are running very rich and one comes out wet.   This has to be contributing to the sluggish response,  Is there a way to lean the mixture out?  My air screws are at the book's spec of 2 turns out from fully in, and the air filter is clean.   Thanks again, Pat

[TwoTired]

From the data given, we know that you might have a 350F, 400F, 500, 550K, 550F, 650, 650SC , 750K, or 750F.
The year model could be from 1969 to 1978.
Some of the above bikes no longer have stock equipment, like air filters and exhaust, and stock carburetor settings then no longer apply.

Pretty sure these models vary in float height specifications, too.  And, some of the models Clymer is unaware of and provide no specifications.

Here are some generic causes for erratic idle.
Leaking carb rubber couplers.
Carbs out of vacuum synchronization.
Sticking mechanical timing advance.
Routine tune up items not properly addressed, (valves, cam chain tension, spark plugs (deposit removal, numbers, and gap), points (gap and timing), air filter (as new)
Fuel contamination

I believe it is an unrealistic expectation to vacuum synch four carbs using one vacuum gauge, as changing the slide height will almost certainly change the idle speed and the vacuum level.

good luck!