2008 Yamaha YZ450


11 replies to this topic
  • mx566

Posted August 08, 2009 - 11:25 AM

#1

I have a 08 YZ450 that is one year old this month and just recently lost compression when trying to start the bike. I last rode the bike on 6/27 and let it sit for about 6 weeks and when i tried to start it there was no resistance when trying to kick start it, it would kick right thru so easy in fact i could push the kick start thru with my hand. I put the bike in gear pulled the clutch in, messed with it a little bit and that seemed to fix it. I've ridden the bike once since then and now its doing it again. Any suggestions on what the trouble could be?

  • mjw1

Posted August 08, 2009 - 02:18 PM

#2

It could be the kick start gear not engaging.

  • grayracer513

Posted August 08, 2009 - 07:26 PM

#3

Check your valve clearance and cam timing. If the timing is off, replace the chain and tensioner.

Normally, the valves wear their faces and loose clearance, and eventually compression, but this normally takes much longer than one year. What you would be more likely to find is an excess of clearance which would indicate a valve held open by carbon on the stem or seat.

  • yz007f

Posted August 09, 2009 - 07:09 AM

#4

I would check your decompression lever on your exhaust cam. If you can kick it with your hand then there's no compression there at all. It's a good point what grey said but it started for him then I wouldn't think it was the valve clearance because it shouldn't of started at all then. It sounds like your decompression lever is sticking or something like that.

  • grayracer513

Posted August 09, 2009 - 08:54 AM

#5

It sounds like your decompression lever is sticking or something like that.

The YZ450 (any year) doesn't have one.

  • jim598

Posted August 09, 2009 - 05:38 PM

#6

Gray, I think yz007f is talking about the cam counter weight that works the decompression

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  • TheHarp

Posted August 09, 2009 - 07:12 PM

#7

Sorry to threadjack (sort of) but why does my 08 YZ450 kick over easier when I pull the hot start? If all its doing is leaning out the carb, that doesn't make sense....right?

  • grayracer513

Posted August 09, 2009 - 08:01 PM

#8

Gray, I think yz007f is talking about the cam counter weight that works the decompression

I doubt it, but even if it were to stick, it would have at least the normal cranking compression.

Sorry to threadjack (sort of) but why does my 08 YZ450 kick over easier when I pull the hot start? If all its doing is leaning out the carb, that doesn't make sense....right?

It might make it more willing to start, but there isn't any possibility of it making the engine easier to crank.

  • yamaha908h

Posted August 10, 2009 - 04:00 AM

#9

Im glad I found this post! I was riding yesterday. It was in the mid 90s and I was putting through the woods following my girlfriend and If I would stall the bike It would take me 10 or so kicks to get it to start. Just the wieght of my foot was making the kick starter go through. I probably could of with my hand. I have also noticed with the hot start lever engaged it kicks way to easy. I was getting pretty frustrated with the bike to say the least. At one time I had to lay the bike down to help the girlfriend get through a creek. It had to take 50 kicks to get it fired and probably 20 of them were the no compression kicks. Its a 2008 with only 30-40 hrs. What do I do??? Check the valves and timing? Thanks

  • mx566

Posted August 10, 2009 - 10:18 AM

#10

So far the only way to get the bike to start is put the bike in gear and then try to kick it through. After that I have compression again and the bike runs fine. Even later that night went to the races and not one trouble starting the bike

  • yamaha908h

Posted August 10, 2009 - 10:49 AM

#11

So far the only way to get the bike to start is put the bike in gear and then try to kick it through. After that I have compression again and the bike runs fine. Even later that night went to the races and not one trouble starting the bike


I know exactly what your saying! It just does it when it wants. Mine will also start better in gear when it happens. I dont race I just play ride so I know my bike isnt ridden to hard. Im clueless with 4 strokes!!!! I hope it is nothing major.

  • HONDA NO MORE

Posted August 11, 2009 - 03:45 PM

#12

I've owned 3 450's 04 05 06, they have all done this and I have three friends with 08's that pull the same trick, I think it is just a YZ thing. My did behave a little better with a new timing chain in it, but I never had any problems from the "no compression" kick starts, I just wished they would happen more towards the end of a long ride when I get tired:smirk: :thumbsup:





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