yz450 really hard to start

ive got a yz426 that has been bored out to a 450 have a look in my garage for full spec my bikes far from standard so this could be a long shot :)

the prob is my bikes really hard to start now its been rebuilt with the new parts added :o never had a prob with starting it in over 3 years that ive owned it ??? ive had the bike running a couple of times and have now run the hotcams in etc , the bike rides really well and theres no probs in the runing of it or the power it goes as it should :D but its dam hard to start its as if theres loads and loads of comprshion i cant kick it up :D could it be that its not run in yet everythin is tight etc :) or could it be the timing ?? as i now have a auto-decomp im just after an idea where to start looking :p sorry for the long post ;)

I would bet that it is your valves clearance. Make sure they are in specs

But then again, I have never kicked a yz426 that has been bored out to a 450 :)

pull the valve cover off and see if the arms on the exhaust cam are moving apart check your cam timing too

Probably something to do with your valves, check the clearances.


ive cheacked all the valve clearences and there all as they should be , i put the old de-comp leaver back on and the bike started first time really easy :) so my prob must be with the auto de-comp on the exhaust hotcam but it all seems to be working fine ?? what could be the prob :) the valve lash on the hotcams is more than on the standard cams so could that be anythin to do with it ?

Make sure the valve lash is in spec with what HotCams recommends. Also double check your timing. I'm going to venture that if you're off by one tooth it may be enough to make starting difficult. I really don't know for sure but it's easy enough to check. My next stop would be HotCams tech support line.

has anyone got any info and pics of timing up the hotcams :) before i ring them ?

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