Tuning the Mikuni Carbs

[Tom Cole]

I have NO idea how to tune the mikuni carbs on these cars.  I'm sure I could understand it if I took it apart, but I don't want to do that without a little knowledge first.

Anyone have any links about tuning these carbs? 

How about links to parts and rebuild kits?

[T48]

Tom, I went through all of my links and found this on legendsforce.com:
"The carburetors are Mikuni BS36 x 4 constant vaccum.  Re-jetting is permitted.  The engines are mounted 90 degrees counter to the way Yamaha designed them to be cooled by air flow.  The #3 cyl. is a common problem area on these engines due to heat and the restricted air flow to the back cylinders.  Have the carbs tuned to keep #3 and #4 from running lean.  Venting fenders and hoods, while staying within rules, is recommended.  See the FACTORY Professional Tuning Components website for good information on performance carburation setup."

It's not an answer to your question, but it brought up another question for me - we got a vented hood as an extra with the T48, but I never see anyone using one, so we didn't.  Does the above suggest that we should?

Also found this, if  it's of any help:
http://www.carbparts.com/mikuni/mikuni_tuning_info.htm

[T48]

AHA!  The tuning manual for the Mikuni Carbs is online here in .pdf format!

http://www.nightrider.com/biketech/download/Mikuni_manuals/tune_mikuni_carbs.pdf

[Tom Cole]

Great links!

The vent hood is not a bad idea.  A good oil cooler with a fan and top end oiling system seems to do pretty good for me.  The fan only helps when you are not moving fast enough for good airflow.

Something else.  I put a digital head temp guage on the other day and found that it really does help to not shut off the engine right away when you get back to the pits.  Get plenty of fans blowing on the engine and let it idle a bit.  The peak temp will drop quickly.

[DARK AGE 53]

Hell, I can't even find the idle adjusment knob the 600 Racing Manual says to use when adjusting the idle...anyone have a pic of where this puppy is?

Thanks,
Al

[gramps05]

If you look under the carbs you will see the cam chain tensioner in the center of the engine, the idle adjuster is slightly to the right and slightly higher, it is a round knob which can be hard to turn, may have to use two hands. Careful you don't burn your hands if the motor is hot.

[gramps05]

T48, the web site you gave is for a different model carb not the B36. try this site http://web.telia.com/~u14114695/Mikuni_BS36_carbs_function.htm

[Tom Cole]

Great link gramps

[T48]

Yes, thanks!  I've changed my bookmark. 

[DARK AGE 53]

If you look under the carbs you will see the cam chain tensioner in the center of the engine, the idle adjuster is slightly to the right and slightly higher, it is a round knob which can be hard to turn, may have to use two hands. Careful you don't burn your hands if the motor is hot.

Thanks for the info, I now know why I couldn't find it....there's no pilot screw knob on this car. These carbs have been redone by the dealer who sold the car to my son, I'll be calling him this morning asking why there no pilot screw.

[gramps05]

Here is another good site for carbs and tuning, you have to look around but there is a wealth of info there.   http://www.factorypro.com and look under Product Support.

[6th Geer]

This may be to late.... but there is a small piece of metal that covers the pilot screw. You will need to drill these out without ruiningh the screw beneath it. It is on top of the carbs.

[Tom Cole]

A friend of mine recommended a jet kit from Ray Scott at Redline Pro Motorsports 706-367-1524.

I installed the kit per his instructions and it really woke that sucker up!  Especially on the second half of the straight.  He has a very unique needle design that is the trick.  That is the best money I've spent on a performance part yet.  Tell him Tom Cole sent you!

[qweedqwag]

If your near Texas I recommend Ron Scrimma at Racing Engine Services. His kit rocks and is 150.00 good money spent .

[6th Geer]

Yes, know that the secret is out!
Redline has some of the best jets and needles you can buy. He hand grinds the needles himself.
I swear buy them, heck half the other people rebuilding these carbs are using his jets and needles as well.
They are 160 for the set and he will go through and rebuild them for another 150. Money well spent if you like to run up front.