pistons

[jwhughes3]

I got stop light smoking...

But am pretty sure its worn valve seals - If I have to tear into anything up top then I will address it - otherwise its the guy behind me's problem not mine so I ain't worried about it!

It isn't smoking visibly when on the go - and it takes a minute or two for it to start once warm...

John

[TopCatGr58]

Power is as Power Does!

Hey there Gump,

I did the same mod to the same bike, 81SH some 10 years ago. It's been discussed that due to the larger/deeper recesses of the pistons due to the larger diameter valves, that the actual compression ratio increase is less than the 10.5:1 stated by Wiseco. 78-79 stock ratio is 9.2:1, 80-81 ratio is 9.0:1 Part of the stock ratio drop was also the cam specs/lobe heights and timing/durations changed for tighter EPA standards.

However, stock compression values are listed at 142 psi at sea level. I'm at sea level. After my rebuild and break in, I got over 180 psi across the board. I did a valve lapping job with the rebuild, would expect your shop to do that at least also if not actually regrinding the valves/seats!? I still have stock cams. I do have aftermarket 4-1 pipes and Indy filters. I also put on aftermarket hi output coils from MikesXS.

It had been 10 years before the rebuild that I had last been able to ride the bike, so the seat of the pants memory was a bit faded. The resultant power feels stronger, Not scary uncontrollable, but definitely more than the stock PULL as best as I could remember! My Dyno run numbers weren't as impressive, but it's more than enough power for me! YMMV!

T.C.