to teardown or swap...

[KPac]

My '77 gs750 is leaking/burning oil pretty damn profusely out the #3 cylinder. I'm thinkin probably bad rings or possibly valves/seat. Otherwise it still starts idles and even revs fine.
I'm trying to decide if i'd be better off attemptign my first rebuild, or just swapping in a "ran fine when we started parting it out" engine off fleaBay.
Im just looking for a little input from some of you experienced Gsers.
Thanks in advance for the advice.

Also... if I do end up rebuilding does anyone here have any experience with boring the 750 over?

[katoranger]

If you do a rebuild you know what you got. Buying a used engine can be questionable, but also cheap.

Also rebuilding can give you a chance to do some performance work if wanted.

Allen

[qslim]

I'd go with the rebuild. Like Ranger said, you already know what you're starting with. You may very well inherit as many or more problems with the used engine route. As far as engine overhauls go, you can't get much simpler than an air cooled carb bike engine. Grab a manual and go step by step, and if you get stuck, come here. That's what I did, and I love my bike even more now since I took it apart and put it back together.

[Ludeykrus]

Do you have the tools? Are you mechanically inclined?

If so, I strongly vote that you rebuild it. There is no better time to learn than now.

[KGB]

How do you know it's only #3?
Plug reading?
If so the cylinder may be out of round or the head can become warped due to overheating.

Wouldn't hurt to bite the bullet and do a rebuild instead of buying someone else's problems.This way you know what you've got and should have no worries.
Also any mods you want to do, do them now.

[flyingace]

I did a 'swap'. I bought an engine on EBay the guy said had only 10,000 miles. Of course that was hogwash. When I measured the parts, it was clear it had more wear than my current motor.

Rebuild it yourself. Look around and see if you can find the components for cheap. Read the articles here and other sites on engine rebuilds. You can almost alway get away with the top-end only, as the low-end is nearly indestructable.

[KPac]

Do you have the tools? Are you mechanically inclined?

If so, I strongly vote that you rebuild it. There is no better time to learn than now.

Yes, I am resonably mechanically inclined. No i don't have all the tools needed YET, but I do have Harbor Frieght, and a few good cycle shops in town.