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Everything Dirt Bike
Make / Model Specific
Yamaha
1999 YZ400F NO START??
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<blockquote data-quote="Trfsrfr" data-source="post: 218366" data-attributes="member: 3959"><p>I love no-starts.</p><p>If it were mine, here is what I would do;</p><p>1 - remove valve cover, put piston at TDC, line up the timing marks on the cams and crank, ensure tensioner & guides are installed and working properly</p><p>2 - hand spin the engine over a bunch and make sure timing marks come back to TDC correctly, every time</p><p>3 - check valve clearances while you're here, if out, they're a PITA stupid design IMO. Caution, measure shims with a micrometer, not a caliper. NOTE- 99 WR400 valve specs are .15-.20mm int, .25-.30mm exh, measured cold, yours should be similar if not the same</p><p>4 - get a baseline compression reading</p><p>5 - do whatever is necessary to ensure fuel is good, clean, and available. make sure cap breather tube is clear</p><p>6 - Ensure the carb float-valve is functioning properly and float height is correct. Ensure correct jets installed for elevation/temp, write it all down. check, double-check, triple-check. Check TPS and enrichener/choke. </p><p>7 - ensure clamped surfaces like airbox and filter, and carb boot are air-tight</p><p>8 - ensure adequate spark - check stator, CDI, coil, neutral switch, etc</p><p>9 - take lots of pictures of it all</p><p></p><p>Provided you have good compression and all of the above checks out, it should fire.</p></blockquote><p></p>
[QUOTE="Trfsrfr, post: 218366, member: 3959"] I love no-starts. If it were mine, here is what I would do; 1 - remove valve cover, put piston at TDC, line up the timing marks on the cams and crank, ensure tensioner & guides are installed and working properly 2 - hand spin the engine over a bunch and make sure timing marks come back to TDC correctly, every time 3 - check valve clearances while you're here, if out, they're a PITA stupid design IMO. Caution, measure shims with a micrometer, not a caliper. NOTE- 99 WR400 valve specs are .15-.20mm int, .25-.30mm exh, measured cold, yours should be similar if not the same 4 - get a baseline compression reading 5 - do whatever is necessary to ensure fuel is good, clean, and available. make sure cap breather tube is clear 6 - Ensure the carb float-valve is functioning properly and float height is correct. Ensure correct jets installed for elevation/temp, write it all down. check, double-check, triple-check. Check TPS and enrichener/choke. 7 - ensure clamped surfaces like airbox and filter, and carb boot are air-tight 8 - ensure adequate spark - check stator, CDI, coil, neutral switch, etc 9 - take lots of pictures of it all Provided you have good compression and all of the above checks out, it should fire. [/QUOTE]
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Everything Dirt Bike
Make / Model Specific
Yamaha
1999 YZ400F NO START??
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