78 GS 1000 top end rebuild (rings/valve job)

[Guest]

OK .... getting ready to dig into my winter project - '78 GS 1000. The "bolt on stuff" (brakes, cables. R/R etc) is no problem.

However with the compression at 100/105 on all four cylinders I'm thinking top end rebuild. So ... first a few questions:

1. Can I take the top end off (head/jugs) with the motor still in the bike?
2. Has anyone else done this?
3. What are the potential dissassemble/assembly problems?

Thanks
Dom

 

[doctorgonzo]

Absolutely you can remove the jugs and leave the bottom end on the bike. I did. However, by the time I was putting it all back together the bottom end was off as well (for frame powdercoat), so how much harder assembly is with it on the frame, I couldn't tell you.

 

[Nessism]

Hi Dom,

1) yes, you can service the top end with the crankcase still in the chassis.
2) yes, lots of us have done engine rebuilds like this. If you search the archives you will turn up lots of different threads.
3) One problem we often hear about is people snapping off exhaust bolts in the head. PB Blaster, heat as necessary, and most importantly a delicate touch is required to avoid this pitfall. Upon reassembly the biggest headache is getting the rings into the cylinders. Also, have the head and cylinder checked for flatness and get them surfaced as necessary so you don't get any leaks.

Good luck and hope this helps.

 

[waterman]

Many here have repaired/rebuilt topend without removing engine from frame with only a few actual problems that potentially could give you trouble.

Low compression doesn't always mean a topend rebuild is necessary. How does it run? Does it use/leak any oil? Do you wish to modify motor?

Many of these engines have sat unused for many years, often they will initially show low compression on startup. Get the carbs cleaned and then run them for some miles. See how it runs before risking exhaust bolts, rings, and gaskets in a topend rebuild. Obviously, if there are other issues like leaks or upgrading motor parts, tear into it.

 

[Spyderman]

OK .... getting ready to dig into my winter project - '78 GS 1000. The "bolt on stuff" (brakes, cables. R/R etc) is no problem.

However with the compression at 100/105 on all four cylinders I'm thinking top end rebuild. So ... first a few questions:

1. Can I take the top end off (head/jugs) with the motor still in the bike? yes it can be done with the engine still in the bike no problems
2. Has anyone else done this? again yes i just did it this summer on my 78 1000
3. What are the potential dissassemble/assembly problems? none really as long as you havea manuel and the right tools the 3 most important things are 1 make sure you clamp the cams in place with a pair of vice grips when removing & installing the cam caps or you'll strip the the holes that hold the cams inplace 2 make sure you lock the the cam chain tensioner before you unbolt it or it'll go down into the crankcase 3 be sure to have a wire or rope through the cam chain so you don't loose it down into the crankcase

Thanks
Dom

my answers are in red hope that helps you

 

[doctorgonzo]

To Nessism's point on exhaust bolts. I just brought home a "new" 1100E. As I removed the exhaust I heated EVERY bolt at the base (actually the head where the bolt enters it) for about 10 seconds with a propane torch before I tried to remove it. This is after a 1 week soak in daily applications of PB Blaster. They all came out easy as pie. They might have come out that easy if I had done nothing, but with unknown condition, and snapping one off sucking SO bad. It's well worth the extra effort.

 

[Nessism]

To Nessism's point on exhaust bolts. I just brought home a "new" 1100E. As I removed the exhaust I heated EVERY bolt at the base (actually the head where the bolt enters it) for about 10 seconds with a propane torch before I tried to remove it. This is after a 1 week soak in daily applications of PB Blaster. They all came out easy as pie. They might have come out that easy if I had done nothing, but with unknown condition, and snapping one off sucking SO bad. It's well worth the extra effort.

Good work there!

The key thing is to calibrate your hand to understand when you are over torquing the bolts and putting them at risk to snap. Sometimes you need to flirt with the break point but never go over the line.

 

[doctorgonzo]

Good work there!

The key thing is to calibrate your hand to understand when you are over torquing the bolts and putting them at risk to snap. Sometimes you need to flirt with the break point but never go over the line.

Hey, I may be slow, but I'm learning!

Just before one breaks you usually "feel" it about to happen, and fail to stop. I'm doing the same method (torch) on all the cam cap bolts. I started taking them off, and got that exact feeling we are discussing on one of them, and stopped myself. I decided to return to it when I had a chance to take a deep breathe and use the torch method to heat each one before I tried to remove.

 

[Guest]

It can be done ... so a new set of rings is in the plan.

Looks like the key tips are:

• preheat exhaust bolts before removal
• Pre-load (clamp) camshaft retainers before installing fasteners
• and don't drop anything associated with the chain tensioner into the engine

Thanks again
Happy new Year to All
Dom

 

[Guest]

I just run the engine a few minutes then i remove the bolts. i wear the "ove-glove" to keep from getting burned.

 

[Suzuki_Don]

Pre-load (clamp) camshaft retainers before installing fasteners. Dom

Also clamp the camshaft when removing the cam caps, if not the threads can be stripped.

A big tip here is to replace all the cam cap threads with 6mm recoil threads. I also did the exhaust threads (8mm) and the cam cover threads as well while the head was off.

Then no probs in the future, ever.

Big plus for me is that I get the Recoil kits from work at no cost to me. There are some advantages of working for a living.