K30/K35 vs Modern Open Reeds

My previous big bore engine ran good for a few years. Then started to give trouble and wouldn't turn over 12,000 rpms. We replaced everything, checked everything, rebuilt everything, from ignition to piston, rod, coil, whatever, and never found out why it would never turn rpms again like it used to. last time I was checking it broke the piston and messed the crank cases too. That was a big bore engine with normal stroke. When it was running good it would be OK, but nothing compared to the stroker. It was slower and way harder on the clutch. Tended to be very violent when getting into the power band compared to the stroker Sudam I have. At least on dirt ovals I'll take a stroker. Might be a different story on sprint asphalt tracks. In fact in these tracks I would take a good 100cc rotary valve or a reed on gas and on a small carb. More "reliable" if there is something reliable over 18,000 rpms and very fast on top end.
 
I've heard others say they have piston issues with anything over 56.5mm. I didn't have any problems in years past running the 58mm wiseco's from the 125's that I re-pinned in my K35 and Dap T62, 14,500 and up all day long, maybe I was just lucky.
That might depend on what you call 14,500 and up. Take it to 18,000 and up like the small 100cc engines...
 
Derek woodbury few yrs back ran a tkm 150 he use to kick ass on it at duqouin indoor.but 3 port exh stuff is way to go.i had bought a k35 yrs back and it had alot of work to cylinder but the crankshaft was split where someone pressed it back together,so i wrote that off project list pretty quick when came time to buy a crank.these hoarders are hoarding cranks,motors old and new,buried away in garages going to waste.sad thing they will never do anything with it but talk about it.😂if they do sell it they want 2500 for it,when they probgave 500 for it,guess the 2000 is the fee for digging all the stuff off top of it😂

Fwiw: I recently have rebuilt a couple of K35 cranks for VKA/Vintage racing, and also had one show up with split pin bore on the PTO side. I ended up with a few K35 cranks halves here, and found them all to be too tight on the c-pin bores, and every one of them I checked was .0002"-.0003" out of round as well. I just set up and honed 3 crank halves the other day -- made them round again, and dropped them down to .0032" interference. .0030"-.0032" is the number I always would shoot for on 18mm crankpin bore way back when I was building a lot of engines. Always worked for me.

Having a very round and VERY polished radius on the end of the crank pin, as well as a polished corner-entry on the crank half also makes a big difference in how they "feel" going together.

With the B-Limited and C-Open turnout at New Castle last year, it's no wonder the 135/150 engine parts are getting expensive!

PM
 
when I was building engines, I machined a crank alignment fixture for pressing the cranks together... I always had crankwerks move pin holes, they always did a perfect job.. there are a couple of my fixtures still out there..
 
I run an open 100cc K11 , it will hold its own on a 1/8 or smaller bull ring
I have a couple of K11s. Good motors but there are plenty of newer 100cc engines that make more power. That said I'm sure you are right especially when the track goes dry slick and everything but max power matters more.
 
Back
Top