Vintage Dirt Bike Q & A

Tired of messing around with the Keihin. No rebuild kits available so I think I'm going to throw a Mik on it. Any suggestions on which model/jetting and best source? I'm at sea level and temps are moderate year round.

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osu_cowboy

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bump to see if anyone has replaced the stock Keihin with a Mikuni and if so, which one and what jetting?

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osu_cowboy

I have a Mikuni with stock pipe on my 79 cr250. I also am using a twin air filter and 32 to 1 BelRay MC1. Boyesen Reeds
400 main, needle fill rich, 70 pilot. I may try a little richer on the pilot like a 75
I started a little leaner on the needle and then changed one slot at a time at a practice track

Thanks Vonspor! I have a stock pipe w/DG silencer. Boyesen reeds. Dumonde Tech Castor oils @ 32:1. Which Mikuni are you running?

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osu_cowboy

I also have a DG Silencer. I couldn't get the bike to work with a DG Pipe. These setting are pretty close to what Thor Lawson is also running. The Mikuni is a 36. I also use a B9ES. With each needle change I made, the plug got a little darker. We will see how a 75 pilot does. The plug is not quite chocolate colored with the 70 pilot. The tracks I run on have a lot of low speed corners.
The original carbs. are getting pretty worn out and going to a Mikuni has worked well for me.
Also, I don't use any exotic fuel blends - just 93 octane Sunoco Premium. I also have two Maicos (76 and 81). They run on the same fuel and oil mix.

I have never owned a Honda before and after a season of racing, I am very impressed with how it works for me.

Mikuni VM36 Round Slide
Pilot 35
Air screw 1.75 out
Slide 2.5
Needle Jet 159-P8
Needle 6FJ6
Clip #2
Main 360-380
Float height 19mm

ProForm pipe and silencer
Moto Tassarini V-Force reed valve
40:1 Maxima

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Michael Stiles
1979 Honda CR250R Elsinore | 2006 Husqvarna SM510R | 2007 Service Honda CR500R-AF

Thanks for the replies guys. Exactly what I needed. I will look for a 36 Mik and start with the recommended jetting and let you know what happens.
Happy Holidays,
sj

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osu_cowboy