Rings N Things

[wera racer]

So I'm deep into the '78 GS1000 rebuild. All the whirly bits are fascinating. One of the piston tops where the recess is for the exhaust valve is bright while the rest of the piston top is the usual grunge. The valves are heavily carboned, so do you think the valve was hitting the piston? Another piston is lightly "burnished" at the same spot. What now?

Also, the manual shows different top and middle rings (rounded and beveled), but my stock rings are square at the edges. What's up with that?

 

[headsbikesmopars]

Absolutely..clipping the piston.

 

[Guest]

So I'm deep into the '78 GS1000 rebuild. All the whirly bits are fascinating... <snip>

Also, the manual shows different top and middle rings (rounded and beveled), but my stock rings are square at the edges. What's up with that?

Agreed, the whirly bits are definitely fascinating! Was definitely an enjoyable educational experience putting my 450 back together.

I also noticed the manual mentioning different rings top and bottom, but my stock replacements were the same shape like yours, and the ones in there were also the same shape, so I just continued on...

 

[TeamDar]

If only one piston is showing that valve to piston contact and the others look good, then I would suspect that the crankshaft is twisted. Just a guess....

 

[Larry D]

The rings should be shaped like that. It's very difficult to see with the naked eye. Try a magnifying glass.

 

[wera racer]

Dropped off the head, cylinders and pistons at the machinest today. He suspects weak springs and/or over-reving is what caused the valve to piston contact, creating a couple dings in the #3 piston recess. He's going to price stronger springs to close the valves faster. The excess carbon on the valves is probably what "polished" the same areas on the #3 and #4 pistons.

Just for grins, here is the Cooley/Yosh-inspired vintage racer rolling chassis, complete with period-correct frame bracing, traxxion front racing springs and emulators, 18" aluminum front wheel, Tarozzi fork brace, aluminum swing, and salty monk brake conversion. Ikon rear shocks to come and Tarozzi rear sets are on the shelf to be installed. Aluminum rear wheel to be added later in the year (need to decide if it's going to be 17 or 18 inch). First race is Nashville in April!

 

[Guest]

Mate that looks great for just a rolling frame! Can't wait to see those Ikons on, they're what I'm eyeing off for my 450 once I get the engine and electrics sorted.

 

[wera racer]

A last quick question before I assemble the cases. Everything is clean as a whistle and I have all new OEM seals, o-rings, etc.

I'm going to use ThreeBond on the cases. Please confirm that I only want to use it on the flat aluminum cases surfaces that touch, not on the bearings or seals themselves. The presumption being that they seal themselves when the cases are tightened up.

First race April 15!

 

[Guest]

Yup, you got it! At least for the 450 that's the case, and I assume the same for everything else... I expect someone will be along shortly to confirm