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1982 GS750T....Soon to be 1981/1982 GS1100T

  • Thread starter Thread starter bikemtn
  • Start date Start date
The spark plug will tell you...it should be rather dark. Hopefully it's not ring related!
 
80GS850GBob said:
The spark plug will tell you...it should be rather dark. Hopefully it's not ring related!
Click to expand...

After I got the carbs back on I started it up and ran with a box fan for a bit. It does not smoke on idle, but blip the throttle and smoke galore. Pulled the plug and it was dark with oil residue. The main build up was right on the end of the plug (ground electrode). With a flashlight I looked at the piston and I can see fluid on the top of the piston. I dabbed the fluid and it seems like oil and an aroma of oil resonates from that plug hole.
I do not know the history of this motor, but the guy I got it from said that compression was 125# on all 4. Once I find a 12mm adapter for the compression tester I can do that test!! In the meantime I have Marvel Mystery Oil soaking the piston in case it is a stuck ring. The one thing that does stand out is that this piston is clean compared the the carbon build up on the other 3 pistons.
 
Around here, most local parts places loan out tools and the like - a compression tester should be one of those items {would have to leave your drivers license as collateral or pay a deposit which would be returned on return of the tool}....could that be an option for you?
It could be a bad valve guide seal....but if it's a bad/broken ring you'll be letting gas into the oil every time you run it.
 
Was thinking about it...that is awfully odd that "that" one piston top is dead clean when compared to the others - might make me think the PO swapped a piston or something, which then makes me wonder if it's sized correctly as well. You might want to consider a leak down test as well.
 
Did a compression test today. Cylinders 1,2,4 were 141 to 143. 3 was at 121. That does not seem to be a huge deal as I think the motor sat for awhile and needs to be run. I'm charging the battery so I can check 3 again since I did it last. Going to do leak down next. I suspect bad guide seals at this point. We will see.

#4 was the piston that was clean. But good compression on it so I don't know ...
 
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Charged and another try. Still at 121. Added a bit of oil and it went to 175. Now I'm not sure. Dang.
 
Soaked the questionable cylinder in Marvel mystery oil for several days. Cleaned it out and started up. I let it run for a while and it is not smoking like it once was. Pretty sure at this point is fuel related. Which is good news. I have a creeping idle likes to go up to about 2000 and hang. Exhaust is really gassy. Besides the obvious air leak from boots which are new by the way I am tempted to tear these carbs off again. It is vacuum synched. I sprayed WD-40 all around the boots and it does nothing to the idle.
 
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bikemtn said:
Soaked the questionable cylinder in Marvel mystery oil for several days. Cleaned it out and started up. I let it run for a while and it is not smoking like it once was. Pretty sure at this point is fuel related. Which is good news. I have a creeping idle likes to go up to about 2000 and hang. Exhaust is really gassy. Besides the obvious air leak from boots which are new by the way I am tempted to tear these carbs off again. It is vacuum synched. I sprayed WD-40 all around the boots and it does nothing to the idle.
Click to expand...

You check the vacuum diaphragms? If you installed new boots {and o-rings I'd hope} and that's all good, I'd look to the 4 diaphragms as a possible reason for the slow raise up in idle.....floats good?...height and not full of fuel?
 
80GS850GBob said:
You check the vacuum diaphragms? If you installed new boots {and o-rings I'd hope} and that's all good, I'd look to the 4 diaphragms as a possible reason for the slow raise up in idle.....floats good?...height and not full of fuel?
Click to expand...

Diaphragms are all brand new, boots are new, new o-rings in all the carbs, 22.4 mm float height at the shoulders of the floats, no fuel in the floats. I am stumped to be honest. My valve cover leaks and I have a new OEM one to put on. So while I have it off I am going to check my valves, even though they were all in spec, and re-torque the head.
I bought all new diaphragms from http://jbmindustries.com/Dimensions.html.
 
The one thing Suzis do is increase the idle when adding choke...we sure the choke circuit isn't being slowly activated...aside from the obvious telltale choke knob being up, I was thinking of leaks in the circuit.....with everything being new that seems the place to look - to me.

Your compression test came up a lot from adding oil...maybe the rings are sticking {or worn}. I'd suggest adding enough marvel mystery oil to a cylinder, on it's compression stroke, to cover the top of the piston with a decent amount of oil. Slowly turn the crank via wrench, to mildly compress it....slowly, as in till it pushes back and then leave it and try again later. Do this a couple of times to try pushing the oil thru the rings where gravity just doesn't like doing that sometimes. You don't want to push so hard to blow a gasket. I've seen a few old engines release the rings that way...some not, but its worth a shot. Pop the plug and let it come out when done...next time it's run under power will be a tad smokey till the rest burns off/out. Try this on all four cylinders...but your compression reads aren't that bad...100psi is min. Some folks find that driving a bike for a while will loosen the rings up.
 
80GS850GBob said:
The one thing Suzis do is increase the idle when adding choke...we sure the choke circuit isn't being slowly activated...aside from the obvious telltale choke knob being up, I was thinking of leaks in the circuit.....with everything being new that seems the place to look - to me.

Your compression test came up a lot from adding oil...maybe the rings are sticking {or worn}. I'd suggest adding enough marvel mystery oil to a cylinder, on it's compression stroke, to cover the top of the piston with a decent amount of oil. Slowly turn the crank via wrench, to mildly compress it....slowly, as in till it pushes back and then leave it and try again later. Do this a couple of times to try pushing the oil thru the rings where gravity just doesn't like doing that sometimes. You don't want to push so hard to blow a gasket. I've seen a few old engines release the rings that way...some not, but its worth a shot. Pop the plug and let it come out when done...next time it's run under power will be a tad smokey till the rest burns off/out. Try this on all four cylinders...but your compression reads aren't that bad...100psi is min. Some folks find that driving a bike for a while will loosen the rings up.
Click to expand...

Thanks! My buddy suggested checking the choke circuit as well.
I did exactly what you outlined when I did the marvel mystery soak and it seems to have worked to loosen up those rings as it does not smoke at all now. The motor sat for several years.
Like I said the exhaust is pretty gassy and there is an occasional small, quiet pop.
 
Your choke circuit comment has me thinking. On the 750 motor I do not recall ever having issues with the choke. On this 1100 if you fully choke....it will start immediately and the RPMs are huge...like 4000. I have to bring it down to about 1/4 choked then shut the choke off once the motor heats up a bit.
 
Got the carbs back on and it runs pretty nice....the idle does not hang anymore, but it does tend to creep just a bit.
The funny thing is that if I put the bike on it's kickstand it idles perfect. So I am guessing there is an issue with the floats/float valves.
It is smoking, but the motor sat for awhile and I need to put some miles on it. Saturday morning I plan to take her for a hard ride.....and kill some mosquitoes. I am sure an Italian Tune up would do it some good.
 
Right before I sold her, my H-2 developed a extra smokey pipe...found out the clutch seal was just starting to let go...plug read a tad darker. I did a leak down test like I did for the snowmobiles - 10psi with intake and exhaust plugged...if it held for 10min it was ok...said H-2 cylinder was a tad off {lost 2psi in 10min if I recall correctly}.
 
80GS850GBob said:
Right before I sold her, my H-2 developed a extra smokey pipe...found out the clutch seal was just starting to let go...plug read a tad darker. I did a leak down test like I did for the snowmobiles - 10psi with intake and exhaust plugged...if it held for 10min it was ok...said H-2 cylinder was a tad off {lost 2psi in 10min if I recall correctly}.
Click to expand...

I think my rings in one cylinder are a bit stuck from sitting so long. Hoping some miles help.....I am optimistic. :)
 
Went for a 100 mile ride Saturday morning. Man does this 1100 have some power. Rode up to a quaint little town north of me about 35 miles....and then I extended the ride a bit to get some miles on this motor. It is still smoking, but hopefully it will subside with some miles. If not I will have to do a leakdown to see what the culprit is.


But even cooler is that I picked up a nice 2002 XR50 for my son for his 7th birthday....and he has been ripping! Loves his bike!!
 
bikemtn said:
Got the carbs back on and it runs pretty nice....the idle does not hang anymore, but it does tend to creep just a bit.
Click to expand...

So what do you think happened so the idle does not hang anymore? I ask because I am having idle hanging troubles also. Got the carbs off now and re-dipping them.
Thanks,

Larry
 
alke46 said:
So what do you think happened so the idle does not hang anymore? I ask because I am having idle hanging troubles also. Got the carbs off now and re-dipping them.
Thanks,

Larry
Click to expand...

Larry,
I pulled off the carbs and checked all the boots for proper seal and did the same when I put the airbox back on to be assured that there was no air leak.
I also checked that I had proper flow in the choke circuit.
Thtottle snaps right back now.

I am not 100% sure, but I do not think I had the airbox boots to carb on good enough on the first install.
It was rather difficult to get on and I used an old broom stick and wedged it between the box and the frame to be able to push the box closer to the carbs.

Derek
 
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