Boring out cylinders: Questions, comments, concerns
 

OK, so the new rings came in so I went to hone the cylinders out. Turn out they are marred up. I'm surprised I did not see that before. Well I tried to hone best I could, but still the scar remains in the rear cylinder. Which would explain the little-bit low compression. Here's what I need to know:

1. Boring out the cylinder. Who's done it, any advice would be greatly appreciated.
2. What size do you suggest I go up? The cylinder is just slightly scarred, so that's not an issue. I'm kinda thinking to go balls out, but don't know for sure.
3. What jet size do I need to go up to?
4. Holy shit, this bike is getting really expensive. Looks like 200 bucks wasn't the bargain I thought it was. Damn!

might be easier to source another rear cylinder head???

Personally, I think a 1200 Superhawk would be really cool! :)

The cylinders don't split.

Superchickenmoster, did you ever get the PM I sent? Was interested in those fairings if they were available?
Thanks

And just to make you aware you have to order 4 pistons from je if you want oversize

Can you re-sleeve the cylinders?

Hey, bud. Yes, I got the PM. The distribution of my free parts is dependent on weather or not I can get this bike running. I'll let you know.

OK, here's an update. I checked the depth of the mar in the cylinder. It's extremely shallow. So, about 30 minutes of honing took the scar out. Or rather, I removed enough material from the cylinder. I put the new rings on and got the engine back together. Without starting the bike, I checked the compression. 145 in the front and 150 in the rear. I know the book says 164, but this is with new rings that are not set in to the cylinders, on a cold engine. I think I may have fixed the issue. I should have the bike up and running before the end of the day, I'll let you all know.

I've bored my engine. Take it to a good race-car engine builder and they should fix you up. Be prepared to take the bore dimension and tolerance with you - they won't "figure it out" for you.

Good luck!

Pistons are going to be very loose in the bores. Piston to cyl. wall clearances are going to be off, and I am willing to bet that the bore is probably tapered now.

As long as the bores measure within service limits it should be ok. Maybe not ideal, but workable at least.

When I had SuperChicken II rebuilt and tweaked, a very well-respected race engine builder told me that it is usually a bad idea to go anywhere too far beyond 20% outside of OEM specs when it comes to modifying engine bore, compression, and horsepower. Motorcycle engine design is quite complex these days, and there are physics involved relative to engine-casing size, effective heat dissipation, and engine-life. For example, a twenty-five percent increase in horsepower might shorten the life-expectancy of the engine to the point that you find yourself going through another engine rebuild, in far too short an interval. It's kind of like the devil's bargain: get too greedy for power, and the engine might have a very short life-span. :(

It's freakin' expensive to tweak an engine with forged pistons, tricked-out cams, light-weight valves, and the whole sha-bang, and it's my understanding that this is one of the reasons why the 20% rule makes good sense (in the long-run).

The day it was stolen, SuperChicken II made several dyno-runs at 120 h.p. (with gobs-and-gobs of torque). A SuperHawk with aggressive street cams, light-weight valves, and 120 h.p. is a nasty beast indeed--so much fun to ride.

:wheelie:

cheers,
--Professor Chaos