QuestionHello Bill. What is the best way to tune the two carbs on these bikes. I think the air is 1 1/4 + or -. How do yopu adjust the idle with 2 carbs. Is it by setting one then doing the other or by doing a little at a time on each? Bike seems to want to run when the choke is closed. When open it wants to stall. It was sitting for a few years so I took the carbs off, pulled the jets and cleaned everything that I saw. Ran a pin through all holes in jets and carb. Thanks in advance for your help. Stephen.
AnswerStephen, You really got to establish a baseline before you start doing troubleshooting on the lean condition.
1) Do a compression check on both sides... should be above 150 psi
2) Check valve adjustment (002" COLD at TDC compression stroke), if compression was low, then check compression readings again, after adjustment, to see if it improved.
If still low, fix the problem (valves, rings) before you try to make it do something that it can't.
3) Carefully check the ignition timing. First remove the point plate and check function of the spark advancer. Reinstall plate, set gap to .014" on high spot of point cam, then move the plate until the points just open at the F mark alignment on the rotor/stator.
4) Make sure that the carb slides are in the right positions... cutaways towards the air filters. There are LEFT and RIGHT side slides.
5) Drop the float bowls and main jet holders. Observe the carb needle tips moving up and down and adjust until the both move at the same time. Do this after you have backed off the idle speed screws to where the slides are bottomed on the carb body floors. Then, turn speed screws in so the slides just barely lift on each side. Put the carbs back together and start it up. Start with the idle mixture screws out about 1 to 1 1/4 turn.
There is a certain art to listening and adjusting the idle speed screws, so you get the same sound on both sides of the engine, listening at the mufflers. Some people will remove a plug wire, put a spare plug into the plug cap and ground the plug against the motor. This makes the engine run on one side, temporarily. If it will idle like that, set the mixture screw to where it runs the best, then turn in about 1/8 turn. Reverse the spark plug caps and leads and check the other side. If both cyls are even compression and both carbs are clean and the float levels are correct and there are no air leaks, then you should be able to do the same adjustment on the opposite side.
Connect both plugs up, let it idle, you may have to lower the idle speed a bit and then you should have it running well, with just a few tiny adjustments. Note that any fuel/air passageways that are restricted, any float levels that are incorrect or any air leaks at the manifolds will alter the carburetion settings and how well the engine will eventually run.
Bill Silver
