81-550T, compression & rings

[Buffalo Bill]

I'm considering the compression in my 81-550T, it reads 110psi in #2, and 100psi in the others after a 5 minute warm up.
Questions:
1-Can I get the block off without removing the engine from the frame?
2-Good source for gaskets and piston rings?
3-Are the head bolts reusable?
4-I put a new starter O-ring in, but I still see an oil drip-(only after running the engine and only from near the starter drain hole).
Thanks! Bill

[Nessism]

Did you adjust the valves before performing the compression check and add some oil to the cylinder to confirm the rings are leaking instead of the valves?

Regarding your questions...

1) Yes, the head and cylinder can be serviced with the engine in the frame

2) OE parts are highly recommended, in fact I doubt you will find any other source for rings

3) Yes, all the bolts are reusable although you should replace the copper washers under the outer head nuts

4) I have no idea what is leaking on your engine. Any oil that drips down the back side of the engine will work it's way toward that drain so check the cam chain tensioner and valve cover before you order parts.

Good luck

[brveagle]

I would HIGHLY recommend pulling the engine. It's a couple of motor mounts. Makes the process so much easier.

[Buffalo Bill]

Did you adjust the valves before performing the compression check and add some oil to the cylinder to confirm the rings are leaking instead of the valves?
Good luck

The cam to tappet clearances are within spec.
I did the oil comp. test last fall when I got the bike, all showed a pressure increase with oil. However I expect to service the valves too.
Know a good source for a valve cutting kit? [Forget it, I just saw some prices ($750) I'll find a machine shop.]
Know a good machine shop to do a valve job?
Thanks! Bill

[tkent02]

Just curious, how many miles has this engine run in the last ten years or so?

[Buffalo Bill]

Me too!

Just curious, how many miles has this engine run in the last ten years or so?

Who knows. The odometer reads 20,000.
What's on your mind?

[tkent02]

No I mean how much in the last few years?
If it has sat much lately the compression will always be low.
Run it a few thousand miles and the numbers may come out perfect, especially since they are not that low, and fairly close together.

[Nessism]

With only 20k miles on the engine, the valves and guides should be okay unless somebody never adjusted the clearances and there are some burned valves. A simple lapping job with new valve guide seals should be all you need. As for the cylinder, a bottle brush hone job and new rings should do it. Of course, Tkents advice is good; go run the engine good and hard and see if the compression comes up. Running some MMO in the tank is good to help free up the rings if they are sticking in the pistons.

[Suzuki_Don]

I'm considering the compression in my 81-550T, it reads 110psi in #2, and 100psi in the others after a 5 minute warm up.
Questions:
3-Are the head bolts reusable?

There are only two head bolts on this engine and they are 6mm on the very outer ends of the head. The main retention of the head onto the block (barrel) are the through studs that screw into the crankcase. These are really long studs that pass though the cylinders and head with special washers and nuts on top to hold it all together. These studs are definitely reusable. As ED says just replace the washers with new ones and everything else will be Ok for a good engine for plenty of miles to come after the job is finished.

[Buffalo Bill]

Can it get stronger?

With only 20k miles on the engine, the valves and guides should be okay unless somebody never adjusted the clearances and there are some burned valves. A simple lapping job with new valve guide seals should be all you need. As for the cylinder, a bottle brush hone job and new rings should do it. Of course, Tkents advice is good; go run the engine good and hard and see if the compression comes up. Running some MMO in the tank is good to help free up the rings if they are sticking in the pistons.

I have put 700 miles on it since March, and it was running (barely) when I rescued it from the second idiot PO. It just seems to be “not living up to it's potential”, as I used to hear about myself.
What is MMO?
Thanks! Bill
P.S. Just curious, I have an old Clymer manual from 1978, it has a chapter on performance upgrades including big bore piston kits from Yashimura R&D. I suppose all that performance stuff's been discontinued for this bike right?

[tkent02]

I have put 700 miles on it since March, and it was running (barely) when I rescued it from the second idiot PO.
What is MMO?
Thanks! Bill
P.S. Just curious, I have an old Clymer manual from 1978, it has a chapter on performance upgrades including big bore piston kits from Yashimura R&D. I suppose all that performance stuff's been discontinued for this bike right?

You can put GS 650 cylinders on it, and they can be bored to fit 750 pistons...
Do a search on this forum. Someone here did it a couple years ago.
MMO is marvel Mystery Oil, it is magical and getting old stuck rings and things moving again.

[Buffalo Bill]

Dream big.

You can put GS 650 cylinders on it, and they can be bored to fit 750 pistons...
Do a search on this forum. Someone here did it a couple years ago.
MMO is marvel Mystery Oil, it is magical and getting old stuck rings and things moving again.

650 cylinders on a 550 engine with the 550 head, or with the 650 head and carbs, sounds magical!
Thanks for the clue!
Bill

[tkent02]

650 cylinders on a 550 engine with the 550 head, or with the 650 head and carbs, sounds magical!
Thanks for the clue!
Bill

Can't remember which head they used, do the research. I've been looking for a 550 for a while now, I want to try it out.
I think it ends up being 725ccs or something like that.

[Buffalo Bill]

I found this thread:

Suzuki GS 6/550 Yes, 672 block and pistons on a 550 cases..
It sounds like a difficult project, but their work shows the way. I wonder how long their engine lasted? Would the transmission stand up to the greater power?
Next question: Would a 650 engine fit into a 550 frame?
Bill

[tkent02]

Suzuki GS 6/550 Yes, 672 block and pistons on a 550 cases..
It sounds like a difficult project, but their work shows the way. I wonder how long their engine lasted? Would the transmission stand up to the greater power?
Next question: Would a 650 engine fit into a 550 frame?
Bill

Well whether or not it fits, you lose the advantage of having a six speed, alas, the 650 has only five.
I can send pics of my 650E if it will help you see if it fits.