yz400f please help


5 replies to this topic
  • maverick_26

Posted April 01, 2007 - 04:34 PM

#1

Hi everyone. I have a 1998 yz400f. Recently I've been putting my bike back together after the rebuild i've done to it. I had the head completely rebuilt, and now i'm this far and it wont start:foul: . I tried timing the cams the way the manual said to do with the l mark on the rotor. Lined up the cams with the head making sure that the e marks were on the exhaust side and the I marks were on intake side and also making sure that there were 12 pins between the 12:00 timing marks on the cam sprockets. I have a feeling there is something wrong with the cam timing even though its the right way. Theres air, fuel, and spark. The head was torqued to spec with an oem yamaha headgasket, valves were replaced, seats were cut and lapped so there are no leaks there. I'm pretty sure that the cam timing is right but it seems to kick over without the compression that it used to. The piston was also replaced with a new wiseco with piston rings. I dont even need to use the compression release to kick it over. It has a new spark plug and the valves were shimmed to spec also. What am I doing wrong? Any suggestions:excuseme: ? Please help. I just want to go ride:ride:.

  • SDBSKI

Posted April 02, 2007 - 07:09 PM

#2

Did the shop that rebuilt your head set the valve clearance or have you checked it after installing your cams?

  • Bikermice

Posted April 02, 2007 - 07:42 PM

#3

"Don't have to use the decompression lever to kick it over". Sounds like you've got one or more valves staying open....Check the valve shims that are under the valve spring cups. One or more of them could have slipped out of position when you were putting the cups back in place, happened to me. Use grease to hold them inplace in the cups. Check your valve clearance when you get the cams bolted down........Let us know what you figured out.

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  • maverick_26

Posted April 02, 2007 - 07:52 PM

#4

I found what the problem was. Turns out somehow my intake cam sprocket spun on the actual camshaft. I compared it to another and it was about 7 teeth off. Dont know how it happened. But i'm getting it fixed permanently by sending it to powroll and having them index it and weld the cam and sprocket together so it wont happen again.

  • SDBSKI

Posted April 02, 2007 - 08:00 PM

#5

I don't know the cost difference but if you bought a hotcams exhaust cam you can buy the matching intake. They are supposed to work better in unison but check with hotcams to be sure.

  • Bikermice

Posted April 02, 2007 - 08:12 PM

#6

I found what the problem was. Turns out somehow my intake cam sprocket spun on the actual camshaft. I compared it to another and it was about 7 teeth off. Dont know how it happened. But i'm getting it fixed permanently by sending it to powroll and having them index it and weld the cam and sprocket together so it wont happen again.

Well, I've heard of that but don't think it's all that common....Do you have a # for powroll incase I need them some time (hope not but you never know)?





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