Idle hangs on KZ 750 R1 (GPz750) 1982

[JudgeHawk]

I have a problem with my '82 KZ750R1.

After having made an overhaul on the carburrators on this bike
(changed a membrane++), I experience the following problem:

I have adjusted the idle to approx 1100 rpm, but when I go up to 6-7000
I often experience that the speed gets stuck at 2-3000 and won't come down to 1100.

This puzzles me a bit, and I am suspection out of sync carburrators or problems with the speed wire?

Any suggestions?

thx in advance

[Gosling1]

take the carbies off again, take all the tops off, and check that all the springs are fitted, and correctly fitted. It sounds like a slide is 'hanging up' in the bore and allowing the engine to rev higher than it should.

While you have the tops off, check the condition of all the other diaphrams as well.......if one has been replaced, its possible that the others may be a cause of an air leak and need replacement as well....

Make sure all the hose clamps on the carbie manifold rubbers are tightened properly, and no cracks in the rubber manifolds either. Sometimes the problem you have described is as a result of air leaks.

Thats where I would start anyway.

[Neka79]

I have a problem with my '82 KZ750R1.


Any suggestions?

thx in advance

buy a bike with EFI ??

sorry mate its way past my years..surely Gos or Smitty can be of use tho...

[JudgeHawk]

I've had all the carb tops off and checked the diaphrams and springs and have also checked that the slides run smoothly, so I doubt that is the problem.

I will check the manifold rubbers for leaks with some soap water to see if I have any leaks and let you know if that helps.

I've also oiled up the speed wire and the balance adjustment screws and springs in case one of the butterfly valves don't close properly,
but haven't had the chance to test it again.

[Gosling1]

Cool, if all the springs and diaphragms check out, then the air leak is probably in the rubber intake manifolds.........

this problem is generally not a balance issue, or float level, that sort of thing, its an air-leak problem somewhere.

[Smitty]

take the carbies off again, take all the tops off, and check that all the springs are fitted, and correctly fitted. It sounds like a slide is 'hanging up' in the bore and allowing the engine to rev higher than it should.

While you have the tops off, check the condition of all the other diaphrams as well.......if one has been replaced, its possible that the others may be a cause of an air leak and need replacement as well....

Make sure all the hose clamps on the carbie manifold rubbers are tightened properly, and no cracks in the rubber manifolds either. Sometimes the problem you have described is as a result of air leaks.

Thats where I would start anyway.

as Gos sez

the other thing to check is..your cables
Are they free to let the carbs get back to idle?

have you re-routed them or pulled them out when you did the carbs?
it is essential they follow the correct path...from handle bar
to carb coz otherwise they bind
and will not let the bike idle

I also assume you drained the carbs? when you worked on them
grit or shit in 'em with prevent the bike idling at normal revs


hth


Smitty

[Smitty]

I have a problem with my '82 KZ750R1.


Any suggestions?

thx in advance

buy a bike with EFI ??

sorry mate its way past my years..surely Gos or Smitty can be of use tho...

hmmm..us older (more experienced )blokes to the rescue

Nath
you in nappies in '82?

[mike-s]

c'mon, not even a clue JH? weak!! WEAK!!!!!

Another thing is, did you mix'n'match the diaphragms/sliders around when you replaced one? it just that it sounds a bit like that may have happened. the other possibility is an air leak. I had very similar symptoms before i melted a hole in my cb250 piston.

[JudgeHawk]

he..he.. to sum up what's been done, what's tested, and what's to try next

I have done the following:
Checking springs and diaphragms... NOT WORKING
Cleaned and drained carbs... NOT WORKING
Oiled speed cable and balance adjustment screws and springs... NOT TESTED

To do:
Check for air leaks
Synchronize carbs (in case of mixed diaphragms/sliders)

Thx for all suggestions, I'll keep you posted on the progress,
but unfortunately it's going to take a few days cause
I've removed both wheels to change the tires.

Fortunately I'm quite early with the bike overhaul... yesterday we had snow

[Neka79]

I have a problem with my '82 KZ750R1.


Any suggestions?

thx in advance

buy a bike with EFI ??

sorry mate its way past my years..surely Gos or Smitty can be of use tho...

hmmm..us older (more experienced )blokes to the rescue

Nath
you in nappies in '82?

nah mate i woulda been just outta nappies and probably shitting in me pants.... woulda been 2...

[Rossi]

To do:
Check for air leaks
Synchronize carbs (in case of mixed diaphragms/sliders)

Forget the Soapy water.......spray WD40 or EZ Start at the rubbers with the engine running............if you have an intake leak the revs will rise

[Rossi]

buy a bike with EFI ??

sorry mate its way past my years..surely Gos or Smitty can be of use tho...

hmmm..us older (more experienced )blokes to the rescue

Nath
you in nappies in '82?

nah mate i woulda been just outta nappies and probably shitting in me pants.... woulda been 2...

What 2 weeks ago Nate ?

[JudgeHawk]

first of all... thx again for all help

thought I should let you in on the solution to the problem...

After checking a lot of the suggestions above, I accidentialy
bumped into some of the plug cables, and suddenly the rpm jumped up to approx. 4000,
so here is what I did:
changed all plug cables... no luck
then I examined the ignitor coils and the wires connecting to it, and
discovered that there was a bad wire..

so now I don't have the "rpm hang"-problem..

but I suddenly have another problem:
cyl 1 and 4 burns ok, with no carbon fouling on the spark plugs, but
cyl 2 and 3 don't burn all the fuel (on inspection the spark plugs are wet) and gives me carbon fouling...

any ideas?
I thought about adjusting the pilot screw, but some friends of mine wouldn't recommend that...

[Neka79]

first of all... thx again for all help

thought I should let you in on the solution to the problem...

After checking a lot of the suggestions above, I accidentialy
bumped into some of the plug cables, and suddenly the rpm jumped up to approx. 4000,
so here is what I did:
changed all plug cables... no luck
then I examined the ignitor coils and the wires connecting to it, and
discovered that there was a bad wire..

so now I don't have the "rpm hang"-problem..

but I suddenly have another problem:
cyl 1 and 4 burns ok, with no carbon fouling on the spark plugs, but
cyl 2 and 3 don't burn all the fuel (on inspection the spark plugs are wet) and gives me carbon fouling...

any ideas?
I thought about adjusting the pilot screw, but some friends of mine wouldn't recommend that...

do the carbs need a balance/sync??

[JudgeHawk]

They might... but I thought that couldn't be the reason behind carbon fouling?
beeing a noob, I ofcourse have little experience in this..

I also thought about ignition timing...