1981 GS850G maintaining

[Guest]

Hi all

The bike in question has been presented in 2 threads before: getting it roadworthy after purchase, and making a Scandinavian road trip in aug/sep 2021.
https://www.thegsresources.com/_foru...-for-road-trip
https://www.thegsresources.com/_foru...on-a-81-gs850g

On the road trip the engine leaked oil from the head gasket about 1l every 1000km, so in the shed (in the background) with it, where I started taking it apart in the winter. This thread starts from there, no major goal in mind, Just trying to keep the bike on the road and enjoying it.

 

[Guest]

It wasn't until March when I finally built up the motivation and arranged time to start taking it apart. I don't know if it has ever been opened up before, but there was a thick layer of carbon residue everywhere as you could expect. Removing it was really really hard. I tried cleaner meant for ovens and grills, acetone, isopropanol, etc. but nothing made much difference.

 

[Guest]

In the end the best tool turned out to be a piece of soft aluminium sheet about 1mm thick. It was hard enough to remove the carbon but didn't make a mark on the pistons or cylinder head. In the end it was scraping with the soft aluminium, oven cleaner, brush, rag, over and over until everything was clean.

 

[Guest]

My goal for the engine work was not entirely clear. At least the head gasket had to be replaced, but I read somewhere that if you remove the cylinder head, you have to replace also the gasket between the cylinder block and crankcase. Cylinder surfaces looked really good, and I could not find piston rings for sale from any of my normal places. So, I thought I'd just replace the gasket and reuse the pistons as they were. The gasket had fossilized on the cylinder block so bad that it took many evenings to remove it. Nothing worked. In the end I had a rough nylon brush on a cordless drill and I used that to remove the gasket. I thought it would be safe, but ended up damaging the sealing surface on the cylinder block. Rookie mistake! This was really annoying, but I figured I'd be ok if I assembled it with some silicone sealant on both sides of the gasket.

 

[1978GS750E]

DO NOT PUT SILICONE ON THAT SURFACE!

Unless you want to do it again!

 

[Grimly]

If you've actually deeply gouged the surface, fill it with some JB Weld or Abrosteel, or whatever expoxy metal repair is available in your place.
After that, rub the filled area flat.
I'd use a light coating of spray Hylomar on the base gasket, but other folks wouldn't. That's up to them, I know what works for me time after time on many engines.

 

[93Bandit]

Maybe it's just the angle or an illusion, but that shed looks tiny, barely enough room for the bike to fit! Hopefully you have a heater, looks cold!