Bike won't idle, poor compression.

[Chuey]

Can't hurt. Good luck

Matt, it is heart warming to read these posts and see how much you have helped with this problem. A note from the sidelines to say "good job", your generosity is recognized.

Chuey

[mattcfish]

Can't hurt. Good luck

Matt, it is heart warming to read these posts and see how much you have helped with this problem. A note from the sidelines to say "good job", your generosity is recognized.

Chuey

Shucks Chuey, just can't stand to hear about a great bike that won't run, especially a special one like this. We're all kindred spirits here, no matter what our personalities.
I imagine with the improved flow of these heads that carburation adjustment,jetting, timing, and ignition are very sensitive.
I hope Krawser4valve can get things sorted out before the weather gets too nice. I hope I can get my bike back together before then. Of course, here in Bellingham Wa, it could be August before that happens.

[Krauser4valve]

My Norton-racing friend is convinced I have a bent valve and as I had a spare half hour after work I decided to pull the right cylinder head to take a look. Lots of soft carbon

[Krauser4valve]

The guy that built the engine knows what he is doing

So, we might ASSUME that "the guy" used components and techniques that resulted in a proper build.
We might as well also ASSUME the possible consequences of a period of running time
that allowed carbon to accumulate on the valves and piston dome
and the consequences of 15 years of sitting ...
Carbon indicates prior use. That, plus 15 years of sitting,
would be reason enough for me to pull both heads and cylinders
for measuring and inspection.

VERIFY the engine's current condition.

If I do need to re-hone it, do I need new rings?

I cannot presume to answer this question
without seeing the rings, measuring their fit to the piston,
and the fit of the piston assembly into a straight bore.
Same with honing –
Cylinders must be measured for taper and out of round
to understand if honing, boring and honing, or replacement is necessary.

Pulled the cylinder off and immediately noticed how loose the rings were. End gap on the top ring is .048, measured in the bore. You were saying something about assuming nothing....

[mattcfish]

Looks like you've got to the root of the problem. Now is it too big a bore or wrong size rings?

[Major Softie]

Looks like you've got to the root of the problem. Now is it too big a bore or wrong size rings?

Yep, time to check piston to bore clearance.

[Krauser4valve]

Bore is still within the "B" range stamped on the casting and the piston size is also, though I am sorta taking a guess on that, Krauser didn't list a diameter in the manual. There is "94,20" stamped into the piston top, which is close to the "94,25" rings listed on the dehobbyist.nl website that owns the Krauser spares these days.

[Krauser4valve]

Anyone out there know a good source for Krauser rings? Motobins doesn't have any and the source in the Netherlands wont sell me any without buying the pistons too, at somewhere around $350. As a cheap shot in the dark, I'm buying a set of these, the thickness is correct and so is the brand. http://www.jbugs.com/product/4578-45.html

[mattcfish]

Anyone out there know a good source for Krauser rings? Motobins doesn't have any and the source in the Netherlands wont sell me any without buying the pistons too, at somewhere around $350. As a cheap shot in the dark, I'm buying a set of these, the thickness is correct and so is the brand. http://www.jbugs.com/product/4578-45.html

Mahle products are top quality. You don't need Krauser specific rings, just the correct size. Make sure they fit the pistons and file the ends squarely to the correct gap. The middle ring should have a slightly larger gap than the top ring.

[Krauser4valve]

Anyone out there know a good source for Krauser rings? Motobins doesn't have any and the source in the Netherlands wont sell me any without buying the pistons too, at somewhere around $350. As a cheap shot in the dark, I'm buying a set of these, the thickness is correct and so is the brand. http://www.jbugs.com/product/4578-45.html

Mahle products are top quality. You don't need Krauser specific rings, just the correct size. Make sure they fit the pistons and file the ends squarely to the correct gap. The middle ring should have a slightly larger gap than the top ring.

It looks like Total Seal makes an oversize set or two that would work if these don't have enough meat to grind back. I know it's been 20 years, but now that I know what's wrong I can't wait til these rings show up.