Vacuum leak has me stumped

[chacal]

Hello all.  I've been lurking on this forum since the beginning of the year while I have been slowly bringing an '85 FJ1100 back to life.  I have been able to solve most of the problems thanks to your information on this board, but I'm now chasing a vacuum leak that has me completely stumped. 

Situation:
'85 FJ1100 that was sitting outside at least 2 years before I bought it late last year.  Approximately 8900 miles.

Compression test results:
1: 128psi
2: 130psi
3: 127psi
4: 149psi

The bike is currently running using a remote fuel take with all 4 intake manifold ports attached to vacuum gauges.  The idle RPMs are anywhere between 1000 and 1500.

Symptoms:
1) The vacuum gauges on all 4 intakes read approximately 10 cmHg (there is 1-2 cmHg difference between the cylinders) when the choke is closed.
2) The engine will start to overheat fairly quickly when sitting at idle (lack of airflow isn't helping, although I am using a fan to help)
3) After the engine is sufficiently warm, the RPMs will climb to around 5000 and stay there until I hit the kill switch.

My response:
I cleaned and rebuilt the carbs following David Raforth's guide and using Randy's carb kits (big thanks to both of them since this was my first foray into carbs).  This was a complete tear-down and cleaning using a dip-type carb parts cleaner.  I checked the results by flipping the carbs upside down and blowing into the main fuel line; there was no noticeable leaks.  I tested blowing into the oval port at the top of each carb; the diaphragms did not show any noticeable leaks.  I replaced the seals on all 4 intake manifolds and inspected the manifolds; there was no visible cracking.  Spraying starter fluid all around the intakes has no noticeable effect now.  I removed the head, cleaned and lapped the valves, replaced the valve oil seals with new seals from Randy, and corrected the valve clearances.  Finally, I checked the vacuum gauges by using a vacuum pump.

Now:
I am not sure where else to go.  The vacuum readings have not changed since I started this process.  The compression numbers on cylinders 1-3 suggest potentially more work on the head and work on the compression rings, but cylinder 4 doesn't seem to support that theory.  I also find it odd that all 4 cylinders have almost the same vacuum readings after only a bench synchronization.  Is there any possible leak source that could affect all 4?  Suggestions as to where else to look?
Thank you very much for all your help (and Randy for all the parts).

[giantkiller]

Do the 1100 have the vacuum advance? If they do unplug the vacuum line to it and see if the idle drops. If it does it could be the intake o rings. I had the same problem. I tried the spraying starter fluid no effect. Even tried spraying water to see if it would have opposite effect. Still nothing. I had the o rings from Randy's kit. So I installed them and the problem went away.

[giantkiller]

Sorry intake o rings

[FJmonkey]

Welcome chacal, might you be located near any members that can help you? How certain are you that you have a vacuum leak? Sounds like you covered the bases. Was this your bike that sat for 2 years? Some history might help. Was it running fine before sitting in storage? Over heating is frequently a lean issue and not a vacuum leak. How do the plugs look? What condition is the air filter?

[chacal]

I believe there is a vacuum advance (off the second intake boot).  Per your suggestion, I disconnected and capped that line and didn't see a drop in idle.  With regards to the intake o-rings, I replaced those with the ones from Randy's kit (when I said intake seals earlier, I meant o-rings – sorry for the confusion). 

I am located in southwest Fort Worth, Texas.  The bike was not mine when it was sitting for 2 years; I have never seen it run other than my current tests.  It was not stored properly; it looked as though it had been ridden to the storage location, placed under a tarp, and left there.  I've spent time over the last year completely disassembling, cleaning, and reassembling the rear 3rd of the bike; redoing both brake systems; redoing the clutch release; working on the front forks; and cleaning and fixing the carbs.  I wanted to get a bike that wasn't in running condition in order to learn how to service it without worrying about breaking something that is working well.  I may have gotten more than that for which I bargained, but it has been a fun journey.

I agree that it seems to be running lean; I was trying to figure out what would be causing the lean condition.  All idle mixture screws are set at 3 turns, all jets are stock, and I modified the main needle jet on Randy's kit by 1 notch to enrich the mixture (which shouldn't affect idle).  According to the Haynes manual, the vacuum at idle should be 25 cmHg.  When I found that all cylinders were at 10 cmHg, I assumed there was a vacuum leak that was causing the lean condition; that may not be correct.  The plugs on cylinders 1 and 2 are more white than on cylinders 3 and 4, and the 1 and 2 plugs appear to be more white that the pictures I have found online for good plugs.  I also notice that cylinders 1 and 2 tend to get hot more quickly.  None of the plugs appear to be oily or wet (cylinder 4 was before I replaced the oil seals on the valve stems).  I have been running the bike at idle and then also revving it up while in neutral to see the affect on the plugs.  I replaced the air filter with a K&N, still using the stock airbox.  The old air filter had crumbled nearly into oblivion.

Thank you very much.

[FJmonkey]

Once the bike is warm have you tried to adjusted the idle speed? Maybe it is just set too high.

[SlowOldGuy]

I might have some time over Thanksgiving week to stop by and take a look.

Did you do the compression test with the throttle held wide open?
Have the valves been adjusted?

Who did you buy it from?  (Rich Simmons by chance?)
Where abouts in SW Ft. Worth?  I'm over near Allen.

DavidR.

[racerrad8]

Cam timing...

Put the ignition rotor on TDC, are both of the camshaft indicator holes centered in the #3 cam cap?

Randy - RPM

[chacal]

Yup, looks like the cam timing is a little ahead of where it should be; the indicator holes are about half visible in the #3 cam cap.  I'll fix that and then try adjusting the idle speed.  It starts up right now without requiring much choke, so the idle speed may be too high.

I ran the compression test with the throttle held wide open.  The valves are adjusted, and all are within the correct clearances now, except one (I must have measured that one incorrectly since it is still a bit tight).  I bought the FJ from Michael McCarrell in Arlington.  Since you're familiar with the DFW area, I live in Benbrook on 377 just south of 820 (across from Benbrook Lake).

I'll adjust the cam timing and let you know the results.  Thanks for the suggestions!

[Bozo]

Just a quick thought (yes us Ozy's can fink). It sounds like one of the cylinders is trying to do more work when hot.
I know you mentioned the cleaning and setting of the carbies but is there something you missed? i.e.
When you adjust the carbies did you make sure the throttle slides are exactly the same height? and only adjust the idle mixture screws.

If it was a leak in the manifold it would be idling bad all the time.

[chacal]

Update: after adjusting the cam timing, my compression test results are (1 to 4) 134, 135, 145, 145.  The cam timing adjustment did help (thank you Randy!).  I also adjusted the idle speed per FJmonkey's suggestion.  It takes a bit longer to warm the bike sufficiently to close the choke now (which makes sense), and the vacuum went up to 20cmHg in each cylinder, so that appears to be the issue instead of a vaccuum leak (thank you FJmonkey!).  I probably need to lower the idle speed a bit further to get the vaccuum to the Hayne's manual spec, but the bike still is getting hot while idling (after a few minutes, steam will start to rise off the engine if I don't shut the bike off), and the bike doesn't want to idle at 1000 RPMs with the idle screw pulled further out.  I'm wondering if the bike is still running lean at idle.  I currently have the idle mixture screws set at 3 turns each.  Is it normal to have to back them out further?  How do I tell where they should be set?

Bozo, when you say ensure that the throttle slides are exactly the same height, what do you mean by throttle slides?  I'm synchronizing the carbs using a set of vaccuum gauges.  Would that have the same effect?  If so, then you were right.  Once the vaccuum increased and I was able to sync the carbs better, the cylinder temperatures are more consistent with each other, based on my IR thermometer.

It looks like I need to focus on getting the carbs adjusted correctly now.

It is getting close to ready.  Thank you!

[Pat Conlon]

Steam? 

You can not leave a air cooled engine idling (for long) with no air flow across the cooling fins...
....that's why we call them air cooled engines, they need air flow.... If you let your engine idle for long... you *will* cook your motor

If it's happening while riding, could the steam actually be oil smoke from oil getting onto the hot engine from the leaking bolt grommets on your valve cover?

[Bozo]

Update: after adjusting the cam timing, my compression test results are (1 to 4) 134, 135, 145, 145.  The cam timing adjustment did help (thank you Randy!).  I also adjusted the idle speed per FJmonkey's suggestion.  It takes a bit longer to warm the bike sufficiently to close the choke now (which makes sense), and the vacuum went up to 20cmHg in each cylinder, so that appears to be the issue instead of a vaccuum leak (thank you FJmonkey!).  I probably need to lower the idle speed a bit further to get the vaccuum to the Hayne's manual spec, but the bike still is getting hot while idling (after a few minutes, steam will start to rise off the engine if I don't shut the bike off), and the bike doesn't want to idle at 1000 RPMs with the idle screw pulled further out.  I'm wondering if the bike is still running lean at idle.  I currently have the idle mixture screws set at 3 turns each.  Is it normal to have to back them out further?  How do I tell where they should be set?

Bozo, when you say ensure that the throttle slides are exactly the same height, what do you mean by throttle slides?  I'm synchronizing the carbs using a set of vaccuum gauges.  Would that have the same effect?  If so, then you were right.  Once the vaccuum increased and I was able to sync the carbs better, the cylinder temperatures are more consistent with each other, based on my IR thermometer.

It looks like I need to focus on getting the carbs adjusted correctly now.

It is getting close to ready.  Thank you!

my wording was incorrect I meant the butterflies, when you have the carbies out look at the butterflies open and close them slowly they should shut evenly (this is critical), these butterflies should always be even, and the vacuum on idle is set by the idle screws. Three turns out sounds high (depends on your pipe and filter arrangement), sometimes vacuum carbies can be a pain to set using vacuum gauges, my brother sets mine  by listening to each carby separately and his setup is always spot-on

[RichBaker]

A long. long time ago, when I was a tech at an MG dealer, I was given a MGB to synch the carbs. Pulled out the factory manual and it instructed to use a piece of heater hose and listen to the carbs with the hose in each carb throat and adjust the linkage so they sounded the same.....

[chacal]

I have been using a fan in front of the bike when idling to give it some airflow (obviously not enough, but helps a bit).  I was shutting it off before it idled for too long to make sure I didn't cook it.  I just wasn't sure whether the engine heat was due to having it sit still or whether the engine was still running lean.  I could try riding it and seeing whether, with normal airflow, it still gives me the same issue.  There is still a little oil on the head from when I was putting the head back on; so it probably is oil smoke.

I'll try listening to the carbs to sync them.  Apparently I have to do this quickly to make sure I don't overheat the engine. 

Thank you!