New member 1979 GS1000: introduction, pics, and leaky cylinders!

[tkent02]

Can't see your pics, can you fix it so we don't need permission to see them?

 

[ecirmo]

Oops, fixing the problem...standby

Ok, here's an album link instead!

That oughta work.

 

[tkent02]

I didn't see anything that a little bit of lapping wouldn't fix. No obvious burnt spots, don't look too worn. Everything looks oily though.

 

[ecirmo]

Any advice for removing the thick carbon deposits from the valves and domes to clean things up before taking it to the machine shiop? I've been reading that apparently lacquer thinner does a good job, as well as chem-dip.

 

[Nessism]

The guides are bronze guides. The head looks to have been serviced before.

Lapping may get it, but some light cutting on the seats and valves would be better.

 

[ecirmo]

I think my plan at this point is to get it cleaned up as much as possible and have the shop lap the valves, valve seats, and the cylinder head surface as well. More than I was hoping needed done, but alas. The rest of the top end seems to be in quite good repair. Hopefully the shop won't tell me I need a new head.

 

[tkent02]

Well as long as it's apart, might as well do it all. The cylinders looking like a mirror might be why the compression is low.

 

[ecirmo]

Interesting! I figured that was a good thing. I was going to forgo honing; would you recommend I have the cylinders honed as well then?

 

[tkent02]

Interesting! I figured that was a good thing. I was going to forgo honing; would you recommend I have the cylinders honed as well then?

Yes! Absolutely hone the cylinders! See if the rings are still in spec, or just replace them. Pistons too, measure them and the bores but they are probably going to be fine with only 53,000 miles. Then break it in properly, which means opening and closing the throttle. NO GENTLE CRUISING!!!


Whatever you do, read this first:
http://www.mototuneusa.com/break_in_secrets.htm

 

[ecirmo]

Alrighty all,

Just heard from the machine shop. My heads overall are fairly good, some pitting in a few of the exhaust seats, but otherwise fine. The main problem is that apparently my valves are "cupping." My options at this point are to either throw everything back together or to get all new valves, guides, and machine new seats. I am inclined to take that route, since it would be a proper long-term fix. That said, it would push me into the $1200 area.

The guy doing the work was fairly straight ahead, and said that if we just lap everything and put it back together, it would run fine, and might even run a long time still, at which point I could just pull the head again when the time comes and do the new valves/seats etc. The question is, how long will that be?

I'm sure it's a crap shoot, but I am interested in your opinions on whether I should do the whole shebang up front and not have to worry again, or if the cheaper and shorter term route sounds reasonable.

 

[tkent02]

A used head with near zero miles might be easy to find.

 

[ecirmo]

Well folks, the rebuild is done!

Motor:

• head lapped
• new black diamond valves machined
• valve seats machined
• cylinders honed
• new rings
• new o-rings
• new gaskets
• new exhaust cam
• valves shimmed in spec

Carbs:

• new needle valves and seats
• gaskets

Coming up:

• carb sync
• progressive fork springs

New rings broken in using the mototune.com method, using Driven BR30 break in oil, changed to non-synthetic 10w40 after 150 miles.

Check out the pics here! https://goo.gl/photos/majXEzQGsqrEJPoB6