Starting issues (I can't seem to win!)

[MikeC23]

The culprit was the exhaust valves. The tappets were so tight that those valves never could have fully closed. I'm not sure how they got that way. I adjusted them to spec this winter. Gremlins... it must have been gremlins. She runs like a boss now

 

[DaveO]

Thanks for letting us know. I hate not knowing.

 

[peanut]

common thinking these days seems to be to run your valves looser like the XS1 and XS2 were .006" and .012" .
There is an old saying apparently 'A loose tappet is a happy tappet '

Seriously though Yamaha apparently specified the tighter clearances in an effort to reduce engine noise but tight tappets mean less time for the exhaust valves to dissapate heat to the head so hotter running engines and more chance of burnt valves /seats due to the valves not seating properly.

Howard at Smedspeed explains it very well and his site is a really good read when you have a bit of time to put your feet up with a coffee

http://www.smedspeed.co.uk/tech.html

 

[MikeC23]

That was a great read. Thanks!

 

[XS650D]

I run my valves at .025 intake .005 exhaust on my 77, I have tried many settings and find thats were it runs pretty quiet and runs good.In my manual it states .002 intake and .006 Ex.

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