gt750, pull cylinder in frame?

[smoketriples]

Hey folks, one of my 750's has low compression all cyls (90 each cyl), bike runs and rides great, no apparent seal issues, no trans oil in cyls or drains.

Bike sat for close to 20 years and I've put about 250 miles on it since 'resurrection', total of 12k on engine.

My assumption is that with the cyls dead even on compression, it's unlikely this is sticky rings and more likely it's just worn and needs rings and possibly pistons.

Getting back to main question....is there room to pull cylinder block in situ or does engine need to come out of frame?

Thanks!

Eric

[oldjapanesebikes]

There is room to pull the barrels off with the engine in the frame, but if they have never been off previously then the likelihood of being successful is slim. You could be lucky. On the other hand, if its running well and if you are just pottering about rather than burning up the freeways, why bother ? If it were me, I'd leave it till I was ready to do a full over haul (crank seals, water pump rebuild etc.).

[smoketriples]

This one doesn't have a lot of power, but it's also the one with the carb issues. I *know* middle cylinder carb has an issue so that may be my power problem, but I got curious last night and ran the compression test. My other GT has 120 per cyl, (well, 122, 120, 124), so figgered 90 was flat out dead...

Maybe I'm just buyin trouble, I guess I'll fix my carb issue first and see if I'm happy with it....

[tz375]

90 is a little low to be sure, but I agree with Ian that if it hasn't died yet, keep it running for a while.

You could drain the water and lift the head off for a look see in the barrels but I'd clean the exhausts first because if they are choked the CR will stay low.

[smoketriples]

Well, of all things, after a bit more riding this week, did the test today and all three are bout 120. I *guess* after sitting 15 years 250 miles of riding wasn't enough to break everything loose, or maybe the waterpump drive gear shattering and me hitting high temps actually helped .

Middle cylinder still doesn't play. Messed around a bit and made sure timing was good, did that new compression test, put on my 'known' good carbs from another GT and middle still kicks in when it wants to, which isn't that often. Thinking condenser or coil at this point. Battery is flat in my digital vom so cant' test condenser. Maybe tomorrow.