Cold Cylinder #2, '81 KZ750 LTD

Injected wrote:

You need a minimum of around 100 PSI for combustion to occur. I would also check valve lash while your running thru all the rest of a basic checks.

I've already done the valve clearance checks and re-shimmed. The valve clearances are in spec.

Have you tried setting the petcock to "prime" and blanking the vacum port on #2 carb ?

Wookie58 wrote:

Have you tried setting the petcock to "prime" and blanking the vacum port on #2 carb ?

Thought I had done that when my test/secondary fuel tank was connected. I usually hook that up to the fuel line in and then block the vacuum connection on cylinder #2. When doing that got the same result.

Wookie58 wrote:

Have you tried setting the petcock to "prime" and blanking the vacum port on #2 carb ?

I was mistaken. With the test tank connected and the vacuum connection blocked on cylinder 2 it fires up and cylinder #2 exhaust pipe is hot as expected. Though I am now also getting a runaway RPM issue. Blip the throttle and the RPMs climb to about 4k and just stay there. 

Progress then, looks like a vacum leak through the petcock. Sounds like you also have other air leaks given the "hanging revs"

Wookie58 wrote:

Progress then, looks like a vacum leak through the petcock. Sounds like you also have other air leaks given the "hanging revs"

I already have new carb intake boots as well as new airbox boots. Do I need to start spraying WD-40 or starter fluid in places? 

SnyperX wrote:

Wookie58 wrote:

Progress then, looks like a vacum leak through the petcock. Sounds like you also have other air leaks given the "hanging revs"

I already have new carb intake boots as well as new airbox boots. Do I need to start spraying WD-40 or starter fluid in places? 

You can try WD40 but it tends to be inconclusive unless the leak is huge. Have you tried slackening the throttle cables then operate the throttle linage by hand (this will rule out a mechanical or cable adjustment issue)

Wookie58 wrote:

SnyperX wrote:

Wookie58 wrote:

Progress then, looks like a vacum leak through the petcock. Sounds like you also have other air leaks given the "hanging revs"

I already have new carb intake boots as well as new airbox boots. Do I need to start spraying WD-40 or starter fluid in places? 

You can try WD40 but it tends to be inconclusive unless the leak is huge. Have you tried slackening the throttle cables then operate the throttle linage by hand (this will rule out a mechanical or cable adjustment issue)

Wookie, I did try this and it seemed to operate fine. If I pushed the throttle more closed using my hand it made the engine sound like it wanted to die. So in my mind throttle linkage is not an issue. The bigger issue that is now scaring me at the moment is that all 4 cylinders are showing a cold compression level of only about 100 psi for all 4 cylinders. I did re-shim the valves and hoping that's not impacting anything. Terrified the top end if going to need to come off and if machining is needed I don't know what I will do. No real good machine shops around.

SnyperX wrote:

Wookie58 wrote:

SnyperX wrote:

Wookie58 wrote:

Progress then, looks like a vacum leak through the petcock. Sounds like you also have other air leaks given the "hanging revs"

I already have new carb intake boots as well as new airbox boots. Do I need to start spraying WD-40 or starter fluid in places? 

You can try WD40 but it tends to be inconclusive unless the leak is huge. Have you tried slackening the throttle cables then operate the throttle linage by hand (this will rule out a mechanical or cable adjustment issue)

Wookie, I did try this and it seemed to operate fine. If I pushed the throttle more closed using my hand it made the engine sound like it wanted to die. So in my mind throttle linkage is not an issue. The bigger issue that is now scaring me at the moment is that all 4 cylinders are showing a cold compression level of only about 100 psi for all 4 cylinders. I did re-shim the valves and hoping that's not impacting anything. Terrified the top end if going to need to come off and if machining is needed I don't know what I will do. No real good machine shops around.

Did the revs still hang with the cables slackened off ? forget the compression for now (should be checked "hot" with the throttle wide open)

I'm saddened to hear about your continual problems.  You have put forth a truly honest effort.

If you want to take a pause on this project, and send me your carbs, I'll go through them for you for free.  Just pay the shipping.  I can't assure you that this will solve your bikes problems, but I can assure you that the carbs will NOT be the problem, when we are done.

You already have my contact info, since you bought O-rings from me.  Send another email if you want to move forward...

Ed