GS750 running hot

[hannibal]

I'm convinced that something is not right with my motor. I just got the bike running this summer (May 30) and have since done about 1100 miles. I dipped and cleaned the carbs (did this twice since I didn't get them clean the first time), replaced petcock, adjusted valves, and bench and vacuum synced carbs. New head gasket and cleaned and reinstalled the cam chain tensioner. All work was done having only idled the bike in the yard.

Since I've been riding a few miles a week, I've noticed the bike is running hotter than it did at the beginning of the summer. It used to send a lot of oil smoke out the breather cover, but has improved as I've been adding more miles. I've had to top off the oil a few times, but never found it less than half way between Full and Low. I did have a leak appear so I'm planning to replace the two seals on the tach drive and the half moons on the cam shaft ends.

Now it's running so hot that my clutch engagement changes as I ride. If I adjust the clutch to disengage when cold, it will not disengage when hot. I thought I broke the clutch cable one night and limped the bike home. Once I opened the clutch cover, I was shocked to find the cable intact. I adjusted at the clutch helix as shown in the manual. Test rode it a few miles and everything was great. Later that night, I went on a 10 mile round trip ride through stop and go city traffic. By the time I got home, the clutch would no longer disengage. It's also getting harder to start. At first, it would fire up with a sec or two of cranking. Now if I let it sit for a day or two, it always wants some choke and 5+ seconds of cranking. The bike has seen the redline maybe twice in that 1100 miles (and it scared me). I usually don't take it past 7000 rpm.

I have not done plug chops at higher rpms, but the plugs look good after idling. I suspect the motor is running lean at higher rpms which is causing it to run hotter than it should be. My question is where to begin. I plan to check valve clearances again to make sure nothing's changed in the last 1100 miles (the hard starting makes me think they tightened up since it's been running). Also need to recheck the cam shaft caps. I didn't understand how to properly torque them down earlier this year. Then I think I should do plug chops.

Any advice??

[cowboyup3371]

How many miles has it been since your last oil change and what are you using?

[hannibal]

I had fuel leaking into the oil and a stripped oil drain plug. Changed the oil maybe 3 times in the first 100 miles so probably 1000 miles since the last change. Using Rotella 15W-40 once everything got sorted out.

[John Park]

Sounds like blowby to me. Smoke, or any great amount of flow out the breather means the combustion gas is getting past the rings. This may not result in high oil consumption depending upon the wear pattern of the cylinder and rings.

Air cooled engines are highly dependent upon not having the crankcase continually heated by the exhaust. It's normal to have the clutch adjustment change as the block heats up on these old style clutch mechanisms, but yours sounds like the block is doubling as an auxiliary exhaust pipe.

Do a compression test, but by the sound of it you will find the problem in the cylinder/piston/rings area. Running lean will not cause this sort of overheating.

[tkent02]

It's normal to have the clutch adjustment change as the block heats up on these old style clutch mechanisms,

None of mine do. The 750s, 550s, 450, all with the same helix mechanism. Adjust the clutch correctly and it works fine hot or cold.

[TxGSrider]

Just a thought, but if you have a clutch problem (as indicated in the original post) it can sure heat up the oil in a hurry. Slipping plates get hot. Pull the plates out and check for signs of slipping/burning.

If it is a jetting problem, and if its really lean, then while youre driving down the road at a steady speed (on a level road) slowly put the choke back on and see if the engine picks up speed. If it does, then you're really lean... if it runs allot worse, youre pretty close or a little rich.

[hannibal]

None of mine do. The 750s, 550s, 450, all with the same helix mechanism. Adjust the clutch correctly and it works fine hot or cold.

How do you adjust the clutch? Fully loosen the adjusters at the lever and on the engine case, then adjust at the helix as shown in the manual? Dumb question, loosening the adjusters means adding slack correct?

I will try to adnust the clutch and go for a ride so I can try adding choke. Think I tried this below and it made it stumble.

I'll also do a compression test.

[John Park]

None of mine do. The 750s, 550s, 450, all with the same helix mechanism. Adjust the clutch correctly and it works fine hot or cold.

You've never noticed? Check the cold slack at the lever and then again when hot. Magazine tests noticed. The early 750s did it.

Yes, it works fine hot or cold , but it changes. There's a lot of aluminum between the helix and the pressure plate.

[jprice90]

it is an old bike, it might just need to be looked over better.
i'm wondering if it could be a topend/head gasket? you're saying you have to keep topping the oil off.
no engine leaks?

[gs11ezrydr]

I would make sure the ignition advancer springs are not fatigued Or the advancer is stuck. Make sure it opens and closes easily. and the springs aren't sagging. If they are worn you will be running in the advanced position all the time. Shoot it with a timing light if you have access to one.Could cause overheating.

[tkent02]

You've never noticed? Check the cold slack at the lever and then again when hot. Magazine tests noticed. The early 750s did it.

Yes, it works fine hot or cold , but it changes. There's a lot of aluminum between the helix and the pressure plate.

A slight bit of change you can notice if you are paying attention is different from this:

"If I adjust the clutch to disengage when cold, it will not disengage when hot."

This is NOT what the magazine writers were talking about.

[John Park]

A slight bit of change you can notice if you are paying attention is different from this:

"If I adjust the clutch to disengage when cold, it will not disengage when hot."

This is NOT what the magazine writers were talking about.

True, but a buddy had a badly pooched same model that was also using the crankcase as an auxiliary exhaust system, and it had a rather widely variable clutch adjustment/temp gauge. The magazine guys had fresh and tight ones.

My super tight 450 hardly changes; my old wheezy 400 moved a lot more.

[hannibal]

Thanks for the replies. I should have some time this week to look little closer.

[hannibal]

Two questions: tkent suggests it's easy to adjust the clutch if you do it right. I haven't been able to find the correct procedure (other than what's written in the manual). Based on the order of items in the manual, I believe the clutch should be adjusted after the engine is fully warmed up. Is this correct?

Secondly, I believe the advance governor is located behind the points plate. I only see one pic in the manual. Is this where the governor is located? Will I need to reset points after removing the points plate to inspect the advance governor?

[JTGS850GL]

I've adjusted the clutch cold and warm. Doesn't seem to really make much of a difference.

Yes, the advance is located behind the points plate. If you mark the plate before you remove it, then you should be able to reset it without having to adjust the points.