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Mikuni BS34 carb high revving

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GPRD
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Posts: 227
Joined: 11th Jul 2011
Location: York

Mikuni BS34 carb high revving

#1 PostAuthor: GPRD » Sat Jul 18, 2015 6:29 pm

I've had a set of BS34 carbs running on a GPZ750 with an 810 kit on it with no problem.
I've just fitted a new head that has been overhauled and gas flowed, it starts and ticks over but when I start raising the revs to about 2500, it takes off and starts revving up to 5 or 6 K before I have to switch it off.
It does seem to get very hot if that's helps.
Any ideas please?
Cheers
What we got here, is failure to comunicate.

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Al
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Joined: 21st Oct 2007
Location: Farnbronx Sin City N.E. Hants

#2 PostAuthor: Al » Sat Jul 18, 2015 9:32 pm

Had this happen twice. Once after US cleaning the carbs i set the fuel metering screws too lean and once having softened the pre-load of the butterfly springs to make the throttle twist grip easier to work with.
Have you changed anything other than the head?
Pod filters for example.
You could try excessively richening the pilot mixture screws one turn each anticlockwise when viewed from above. Just to see if this calms it down a bit!
There is a mistake in the factory manual with reference to the operation of those screws.

AL
1981 J1

GPRD
100Club
100Club
Posts: 227
Joined: 11th Jul 2011
Location: York

#3 PostAuthor: GPRD » Sat Jul 18, 2015 10:11 pm

Not changed anything else, but I'll try richening it up like you say, hopefully that will sort it.
Thanks for the reply.
What we got here, is failure to comunicate.


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