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1980 SP 400 - VM36 carb upgrade problems

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Tuley
Wisconsin

Tuley has no Avatar

USA
1 Posts

Topic started on 04/14/2012 at 12:10:01 PM

Hi, White Brothers used to sell a VM36 carb for this bike that they claimed would gain 5 horsepower. So I bought a VM36-4 with standard jetting and now need some help picking out some jets for a starting point. Here's what I have now.

Main:310
Pilot:35
Needle Jet:Q-5 159 series
Needle:6FJ6
Slide:2.5

with this jetting it idles OK, is flat 1/4 to 3/4, cuts out wide open, and pops and bangs when I let off on the throttle. It's a completely stock bike, except the K&N filter for the new carb. It runs great with the original BS36SS carb, which I have back on so I can ride it. But I want those five horses. Please help, on another forum I couldn't even get a response.

80 SP400

b_king
Oakville, ON

b_king's Avatar

Canada
4566 Posts

Posted on 06/24/2012 at 6:15:44 PM

When you say it idles ok, have you adjusted the fuel/air screw to set the mixture at idle?

Have you done a plug check at all at the various throttle openings, that might be a start? The only other thing I would suggest is bite the bullet and find a local shop with a dyno, and get it jetted there.

08 KLX450R

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