Valve adjustment & hard starting

3 replies to this topic
  • 450high

Posted February 27, 2005 - 03:07 AM


Can valves being to tight cause a bike to be very hard to start when hot ?.When my bike gets hot ( tight slow riding )it appears the battery is flat when i try to use the starter, although it kicks over and starts 1 st kick.Except once when it got very hot and appeared not to be able to kick ( jamed up ) until it cooled a bit.When it cools down ( long open tracks )it cranks no worries.Oil is o.k and plenty of coolant and not appearing to boil just hotter than usual.I'm wondering if thight valve and a higher temp makes them close up and increase compression so much the starter won't turn it over.
thanks dave

  • 5valve

Posted February 27, 2005 - 03:56 AM


in any case, if you have tight valves, correct this issue soon, before too late
tight valves are bad, much more than loose, you can burn your valves and seats
tight valve means it is pushed more into the chamber by the cam and overall does more travelling up&down, making an open route for the explosion to expand during slower closing of the valve because of the greater travel
its minimal but in time it does damage

its strange that very hot bike blocked, but still the coolant didnt spurt into the expansion...check radiator cap

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  • ddialogue

Posted February 27, 2005 - 07:16 AM


I recently checked and adjusted every valve on my 03 WR450 and before the adjustment, the bike was getting hard to start. I've got two rides on it now since the valve adjustment and everything is back to normal. :)

  • Frostbite

Posted February 27, 2005 - 10:46 AM


I popped in a new set of cams and had a couple of valves on the tight side. I ordered shims but went for a ride anyway. After an hour break in I went for a little high speed run and the engine gradually lost power and then died like a 2 smoke melting. When I tried the kickstart lever there was zero compression and then it brought up solid. I though the worst, a bent valve. I rolled the bike back in gear and tried the kick lever again, same thing. No compression and then a definite solid stop. I was a ways out of town and it was either walk or wait for someone to come along so I waited. After a while the compression started coming back and a sledder came along and gave me a tow and I bumpstarted. It ran rough for a few minutes, then cleared up and I rode taking it easy for another couple of hours. I changed shims and now it seems fine.
It could've been the cold froze a valve open but most likely it was the heat expanding things. A tight hot valve will stay open and lose compression. Maybe your starter was turning slow since it was hot too.


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