'81 carb issues

Bobman · Posted: August 9, 2007, 9:36 pm Post subject: '81 carb issues

tech tips from mike's and 650 central say the '81 carbs are notorious for running lean. the suggestion was to up the main jet and lower the air jet. I
have gone up one notch on the main and down two notches on the air. I am still getting a little hesitation at full or near full throttle. It seems like it is flooding out especially under load. Any input fellas?

jayel · Posted: August 9, 2007, 11:01 pm Post subject: Re: '81 carb issues

what do the plugs look like? do a plug chop, do a good run at speed and hit the kill switch pull in the clutch and coast to a stop and pull the plugs to look at them - what mm carbs are the 81's?

xsjohn · Posted: August 10, 2007, 7:14 am Post subject: Re: '81 carb issues

If you want to richen the mixtures try tuning to a Autolite 64......Works perfect for the richer mixtures I now run on my 80.......About like a BP6ES

Instead of going down on the air jet on my 80 I went up on the pilot....
Raising the main needles .032 thousands and using a 137.5 mj........No throttle issues or plug problems what so ever......Runs way better and cooler..............

Richening the Tin Tops is all in the main needle......They placed it low to please the EPA....Trying to tune arounda stock needle setting willwork but half ass but why bother since it is so easy to raise....Mikes also has the Canadian needles which I havn't tried....On mine I just removed the anodize on the first long slope so I didn't have to raise the needles so much and get them out of time coming and on the off the pilot........Floats to high or low will screw everything up.........Don't know the best plastic float settings...nine are brass floats........

Here is what I would try....Not ever owning 81 carbs though.......

Stock air jet
47.4 pilot jet...don't use them as a tune all....keep them in a bit.....Or bore them yourself using an .018 guitar string.......1 1/2.. better decel from high speed for sure.......

raise main needle (jet needle) + .032-.034 thousands-- 137.5 MJ.....

Autolite 64 Spark Plug.....Gap .032 thousands.....63 is a bit cooler for stock mixtures.....66 for extra hot cylinder syndrome.....I had one hot cylinder no explaination.........

ake sure float is not to high or low.....maybe 24-25 mm....?

One main problem I was having with the smaller pilot was when letting off the throttle slowly from high way speeds it would starve for gas and shutter some......very anoying and I am sure damaging to everything....I had to set my pilot at 3 1/2 plus turns....now it is 1 1/2 turns out with the larger pilot and the lean shutter is gone........Transition to main needle from pilot is much better also.......Never tried reducing the air jet though....

y 80 with the main needles in the stock position and the stock pilot jets set 3 1/3 turns out was totally fricken useless and terminally aggravating to say the least........The s*** heads suits and ties who tuned mine cost me a lot of time and I hope everyone who thinks Al Gore is cool can vote vor him so he can screw up everything else even worse and the highways will be clear for me to ride.....How much can a 650 polute.....Gerrrrrrrrr........

I went from a piece of s 60 miles a gallon to 52-53 pleasant riding mpg...guess my sanity and investment was not as important to those idoits.......Ranting again.....sorry........

John

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