powervalve question

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Aug 20, 2007
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#1
I know this is probably a really dumb question but here goes. For the past two weekends The yz has been running really crappy. Last weekend I found out my V3 reeds were wore out so I put my old reed block in with an old set of boyesens.

I got the new V3 replacement reeds and put them in just in time to head off to the track. This weekend the bike ran like crap again and after pulling everything apart several times and trying different stuff I discovered the powervalve lever had broke and the powervalves were not working.

I went everywhere looking for a lever but no one had one so we traveled 500 miles for nothing.

Someone at the track suggested to wire the valves open and run it that way which we tried but to no value. It sounded like a fairly good idea but it would cut out everytime in the long straights of when we needed power on the large hills we had to climb. Last week the track was really tight and not as wide open as this track which is probably why I didn't notice it as much there.

The bike had great power in the low to mid but just died on the long straights. I guess my question is what would happen if you did hold the valves all the way open and not let them close? I couldn't get it to stay open because the wire I used was to light to hold them open.

I mean, I'm getting it fixed I just wanted to ask in case this ever happened again.
 

Jasle

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Nov 27, 2001
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#2
wiring them open usually takes away bottom end power and leaves topend alone. if they are not open all the way at max rpm then you don't have the right exh port timing for the rpm your at.
 
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Aug 20, 2007
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#3
Jasle said:
wiring them open usually takes away bottom end power and leaves topend alone. if they are not open all the way at max rpm then you don't have the right exh port timing for the rpm your at.
Thanks, that is what I thought should happen. I really didn't see much difference in the bottom, but with the 144 there is plenty of that to go around. It still had no power on top at all and it seemed like the longer into the moto it went the worst it got. I could hear it when he came by sometimes like it had a bad bog and a miss when he came up to a jump.

I took the carb off about a million times and checked and there was no water in the fuel and the jet's were clean. I am running the same jets as I have always run, 430MJ and a 42.5 pilot, stock needle in the third clip.

I took the jug off yesterday and looked at the piston. It looked clean, only there was the marks embedded where the exhaust bridge is. They seem rather deep to me and this time I took off the jug the ring had a flat spot on it. The first ring I took off looked brand new but the piston was marked. I have less hours on this piston than I did the frist time so something is diffenitly going on.

I think I'm going to send this cylinder back to Eric and get him to check it over before I pull much more of my hair out. LOL There has to be something wrong somewhere that I just can't put my finger on. At least if he checks it out and it's ok then I'll know I have to keep digging. I have aother ignition system I'm going to take this weekend. I'm going to put the stock cylinder back on for the race this upcomming weekend and hopefully that will eliminate that possibility.