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Krauser4valve wrote:I will try the clay clearance test, I think the shim is messing up my valve clearance adjustment range anyway. Someone in the past had added lash caps to make for the added gap, they seem too loose on the valve stem.

mattcfish wrote:
http://www.aircooled.net/gnrlsite/resou ... /calcs.htm
Using this compression calculator, 1mm shims would drop you to about 9.2:1 compression in case you're curious.

mattcfish wrote:I thought he was just a legend?

the quinner wrote:Hi. It looks like you found the major problem...but a few things come to mind:

One...Krauser pistons use regular old BMW rings...all three rings. Get the proper size and type for your cylinders. IF the builder used Krauser pistons actually intended for the iron bores, they are probably first or second oversize (you must measure to be certain...a lot of uncertainties here). The iron bore Krauser pistons only came in oversize...think about that a little bit; Krauser did not offer a "drop in" piston for the iron bores...they were supposed to be installed in properly cut oversized cylinders...because the piston fit and cylinder/ring fit is VERY IMPORTANT...as you are learning. How was the gap on the other two rings? I.e., do all three rigns have the huge gap? or, just the top ring?


I'm holding the stock R100 piston, the Krauser piston I am using and the spare Krauser piston (for a Nikasil bore, low compression, which I found in a box the other day. Now I know where the too-small rings came from) in my hands. The Krauser piston has smaller top ring land, .055 inches versus .068 for the stocker. I also have the stocker top ring and the Krauser is 1.5mm thick versus the 1.75mm for the BMW part.

All three rings had the same .048 inch gap. New rings, a sweet .015
I
Next...were the heads modified to use the NGK plugs? Heat range and thread diameter are only part of using a cross-referenced spark plug. The sealing surface and metal "body" of the NGKs are different than the Champions and some machining is required for the NGKs to seat and seal properly. Remove the spark plug and look down the tunnel with a flashlight...any signs of combustion blow-by in there? It's hard to tell in your photo, but this issue might partially shroud the spark plug tip...not your major issue, but it might be a contributing factor. G63 spark plugs are hard to find and don't last long, but they are the plugs the heads were designed around. Ferrari F40s use those plugs and some vintage British race cars use them...find a Sunbeam/Triumph/MG/etc. race shop

That's interesting info about the plugs, need to definitely check that out. I got the last few sets from a guy on Ebay and I still have a few spares. The Triumph TSS used them too. The NGK plugs don't look shrouded, maybe I'll upload a picture so that you guys can take a look.

I'm surprised there's a lash cap on the valves. What was done during the "valve job" at CC Products? If they cut the seats at all, we're talking even less than the 1mm (added by the base shim). What size are the lash caps (how much clearance do they remove)? Valve geometry is very important...the 2-piece pushrod set-up requires some considerations above and beyond the standard, straight pushrod set-up.

IIRC, they were .30 thick, have to dig them out, maybe they were there to correct what seems to me to be a very offset contact point on the valve stem. The valves don't seem to have been touched on the tip, but I don't have any specs for them to be matched to. CC did some port matching on the castings, nothing too crazy.

Since you have one head off the bike, if you can, I strongly recommend disassembling them for a thorough inspection. Krauser heads are known for going through guides...based on the piston ring, I would want to double and triple check everything that was done or that could be a problem. I sure don't have all the information, but the story, as told, doesn't give me a lot of confidence that the job was done correctly the first time. If it were me, I'd want to strip both sides for a thorough inspection and careful reassembly.

Read everything Vanzen says. There's significantly more bad information than good information about Krauser heads...he has been researching for quite some time and has a very good grasp on which is which.

Krauser heads are a VERY big performance upgrade for an airhead. Doing it right is time consuming and can be expensive, but is very rewarding...doing it wrong is a waste of time, even more expensive and no damn fun. In other words, I suggest that you take a comprehensive approach to make everything correct...as opposed to looking for one issue that might allow the bike to run. Good luck!

woof!