I've snapped a Power Valve!!

jonny1deck · Post by **jonny1deck** » Fri May 11, 2007 5:44 pm

I've just put new pistons, rings, put the barrels on, all good! But then I put the head on which was a bit tight going over the power valves, then snap!!! So has anybody got a spare one and what was I doing wrong??
Thanks

the-elf · Post by **the-elf** » Fri May 11, 2007 6:00 pm

The trick is to assemble the cylinders, power valves and the head on the bench and torque the head down. Make sure that the power valves can turn etc. Then once thats done put the complete top end onto the engine and torque down the bottom of the cylinders. The reason is that the cylinders may not be perfectly flat or the same height and if you put the cylinders onto the crankcases first you can twist the head when you put it on.

Don't forget to re toerque the cylinders to the crank case again after the first heat cycle.

Cliff · Post by **Cliff** » Fri May 11, 2007 6:06 pm

That's correct, i've done it. Only i was lucky not to damage anything.

jonny1deck · Post by **jonny1deck** » Fri May 11, 2007 6:14 pm

Its a bit of a pain in the ARS*!! I wanted to get it going this weekend!!
Also its really hard to get a spanner on the front barrel bolts? Is there anywhere in the south I can get a Power valve from?

mr_bungholeo · Post by **mr_bungholeo** » Fri May 11, 2007 6:43 pm

ive got a spare if you want it...little bit scored but ar'nt they all?...pm me...also did it so bought plenty of spares....

jonny1deck · Post by **jonny1deck** » Fri May 11, 2007 6:49 pm

PM sent!

mgtkr1 · Post by **mgtkr1** » Fri May 11, 2007 9:29 pm

this seems to be one of few faults with the kr. would it be wise to have cylinders machined flat as PB did this via v.p engineering to good effect! the bike was raced by steve marlow and prepped/fettled by the late J.R with which they gained a few nags just by improving tolerances. 57h.p was produced at some point with minimal tuning (ledar intake stacks etc). i believe this same bike only made 44hp initially although kips were assembled wrong. the reason i ask is because my bike is fitted with 26j pistons and need to know if machining would effect anything regarding squish/clearance. will also have head matched to suit new piston profile. cheers matt

mr_bungholeo · Post by **mr_bungholeo** » Sat May 12, 2007 10:30 pm

let us know if it all went well.....

jonny1deck · Post by **jonny1deck** » Sat May 19, 2007 3:58 pm

I've put it all back together, started first kick sounded not bad, done the heat cycle. Just taken it out round the block it won't pull away without dipping the clutch then seam to have the power of a 125!! Also the gearbox is very stiff, I've changed the oil but still the same!!

Also the power valves on one side vibrate alot more than the other side???

the-elf · Post by **the-elf** » Sat May 19, 2007 5:24 pm

Are both cylinders firing? check the HT leads etc. Are you sure you got the powervalves set up correct?

mr_bungholeo · Post by **mr_bungholeo** » Sat May 19, 2007 7:04 pm

sounds like u got them back to front!!!...n the clutch drag is the washer in the basket...behind the center...or the actuating arm.....any wear on the washer will screw up the clutch..changed mine on elf's findings even though wear was minimal..it turned a crap clutch into a perfect one....glad u never snapped another though...only got one left....

jonny1deck · Post by **jonny1deck** » Sat May 19, 2007 8:12 pm

It seams to be missing on 1 cylinder, but it was running on both, the power valves wouldn't make it miss?? I swapped the petrol lines but it still misses on the same side. I'll try some new plugs.

KR1 Man · Post by **KR1 Man** » Sat May 19, 2007 8:16 pm

KR1 Man calling Mr Bungholeo. Do you mean the main thrust washer?

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I've snapped a Power Valve!!

I've snapped a Power Valve!!

All running but not that well.