Float Level and Mixture on 81 - what are you running?

jimdi · 650Rider Supporter Joined: Oct 27, 2005 Posts: 512

I have heard a lot of different specs -
I have an 81 with stock Mik. 34 carbs.

What are you running for float level -

And what are you running for turns out on idle mixture screw?
(the hidden one under the plug in carbs)

Please let me know -
Jim

I am currently at 25mm on floats
and 2 turns out from seated on idle mixture.

xsjohn · Last edited by xsjohn on January 2, 2008, 7:55 am; edited 3 times in total

80 model...Float 27mm... Got tired of the stock carb.....Designed a kit to relieve the BS34 carbs.....

John Underwood

5twins · Full Member Joined: Aug 05, 2006 Posts: 1616

xsjohn · Last edited by xsjohn on January 2, 2008, 7:56 am; edited 3 times in total

Best seting so far is float at about 27mm. Have some kits that also fix the right hotter cylinder........

Old Yamaha Mechanic John Underwood

jimdi · 650Rider Supporter Joined: Oct 27, 2005 Posts: 512

Ok, after experimenting this weekend I discovered that:
1) the oil breather tube richens the mixture - So I took it off the airboxes and just put a "Breater Filter" on it.
2) The Richest I could go without it stubling from being over rich was two turns out. (that is what it was from the factory)
3) The float level set at 24-25mm still leavels the gas level low (lean) in the bowl as compared to what the Yamaha manual says it should be (using the clear tube test to see gas level). My gas level doesn't reach the top of the bowl -it sets about 3mm lower than the top of the bowl.

It seems to run smooth through the entire range from idle to 6k rpm.
Plugs still get a little rich fouling on them - but not as bad since I removed the oil breather tube from the carb intake.

I rebuilt the carbs ground up before doing all of this - new everything except diaphrams - they looked ok.

Even changed the coil - thinking I had weak spark.

the plug fouling just bugs me - they used to run very clean.
Jim

5twins · Full Member Joined: Aug 05, 2006 Posts: 1616

jimdi · 650Rider Supporter Joined: Oct 27, 2005 Posts: 512

The jets are factory - cleaned very throughly.
I replaced - gaskets, float valves, floats, needle valves, o rings.

Quite frankly - it runs great.

I just can't figure how all these other guys are richening up to 3 turns out
and claiming better performance.

Jim

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