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Slabbie 7/11 thunderbike racer


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  • 2 weeks later...

Post mortem.

IMG-20210501-WA0010.thumb.jpeg.cd3ef2850ff095d34747a8ad8e715ff2.jpeg

Source of the smoke, heads bolts weren't very tight. Ho hum. Head needs a very light skim to clean it up.

There's more.

Hmmm20210501_145220.thumb.jpg.61e16a06df954892cf52cf3979cd220f.jpg

20210501_145212.thumb.jpg.56066e0013850cd81dba6862b063a93d.jpg

Well we cocked that up.

Stock exhaust cam and timing. Need to figure out what gone wrong here. Not enough valve clearance, or am I revving it too hard.

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21 hours ago, dupersunc said:

Post mortem.

IMG-20210501-WA0010.thumb.jpeg.cd3ef2850ff095d34747a8ad8e715ff2.jpeg

Source of the smoke, heads bolts weren't very tight. Ho hum. Head needs a very light skim to clean it up.

There's more.

Hmmm20210501_145220.thumb.jpg.61e16a06df954892cf52cf3979cd220f.jpg

20210501_145212.thumb.jpg.56066e0013850cd81dba6862b063a93d.jpg

Well we cocked that up.

Stock exhaust cam and timing. Need to figure out what gone wrong here. Not enough valve clearance, or am I revving it too hard.

Have you checked yet to see if the head or barrels have been previously skimmed 

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3 hours ago, Markz9 said:

Have you checked yet to see if the head or barrels have been previously skimmed 

No. The motor was originally built as a side car motor reputedly by Mistral racing. Who ever did it originally knew what they were doing as there is some nice work been done. I gave it a quick once over, and kept the came timing it was originally built with.

Need to do some carefully dummy builds to check cam timing and piston to valve clearance. I suspect it's just been over revved.

Some 750 valve springs may be in order, as well as more regular checks on head torque and valve clearances.

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