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[Mike of Woking]

My Bullet has an open exhaust, pancake air filter and the Micarb carb has been re-jetted. Used to run okay, but now it runs on after you throttle back. No kinks in the cable. It is annoying as it is intermittent. When cold it is good, when it is hot it is lousy and I have to use the clutch drag to slow down the revs when stationary.

Any thoughts would be useful. Maybe I should change the cable or lubricate it - but it is intermittent and there are no obvious kinks in the inner cable. I don't think it is overfueling - but does anyone have experience if this, as I have increased the level of fuel in the float chamber to maximum.

Regards,

Mike

[Mark M]

Mike, running on is usually a sign of weak mixture so not overfueling. As you've been in the carb to rejet (?) I'd look for an air leak, in the inlet rubber, at the flanges or even if the top of the carb has been over tightened, slightly distorting it.
REgards, Mark

[John J]

Hi Mike, Check that you can always hear a click as the slide touches the throttle stop.You should hear it from any throttle opening from full to just off the stop. My guess is that this is the problem. Routing the cable is difficult where it goes from the tank to the carb.

[Norm]

Try rolling the carby away from the frame, it will work fine over on a slight angle, this allows the cable a better flow

[stinkwheel]

Did you replace the throttle slide too when you rejetted it?

The reason I ask is that when I did this on my 350 classic, the replacement throttle slide would occasionally stick in the throttle body. It turned out not to have a chamfer round the top of the slide like the original one did. Carefully making one with a fine hand file solved the problem.

In the following picture, the one on the right is the original, the one on the left is the replacement with a chamfer filed into it:
http://i48.photobucket.com/albums/f216/ ... slides.png

So I'd suggest making absolutely sure the throttle slide is free to move up and down inside the carb.

As luck would have it, you can easily do this by removing the pancake filter and watching the throttle slide move up and down as you open and close the throttle. You could even do this with the engine running and see if it's sticking open for some reason. I have seen excessively worn throttle slides on other makes of bike stick at an angle across the carb under high air flow rates. I've also seen people slightly oval the throttle body on carbs by overtightening the top and twisting the whole thing.

As has been said, an air leak somewhere between the inlet manifold and the carb could cause similar symptoms. A simple test for this is to get the bike at a steady idle then spray EZ start onto the inlet manifold area. If the revs increase when you do so, there is a leak.

[stinkwheel]

I really wish this board didn't erase my carriage returns, destroying the paragraph formatting, it makes posts hell of a difficult to read.

[Roy]

I assume by "running on" you mean that after you throttle back the revs take a long time to drop back to an idle. I had this on a Micarb and found that the air screw was incorrectly adjusted. They seem to be very sensitive to the air mixture settings and once I had corrected this it was back to normal.

[Alan R]

Hello STINKWHEEL, try using the arrowheads>>>>>>>>>>>> or the dots............ to create the spaces instead. It's a bummer I know. Also, as some of us have found out the hard way recently, if you do create a long posting, OR you take a long time actually writing your reply, you might loose the whole lot by a timed lock-out it seems and you find yourself back at the log-in. Just get in the habit of "copy" then --if needed--log.in again and "paste", Your efforts will not have been in vain !!

[Mike of Woking]

Thnaks to all of you for your comments. Stinkwheel was absolutely right. The replacement slider for the open exhaust and air filter mod is made of very soft alloy material. It does have chamfer, but over time the action of the slide hitting the throttle stop screw has caused a slight dent / ridge in the chamfer, which then catches on the screw and pushes the slider sidways in the bore causing it to stick.

How I over came this was to use the cable length as the primary means of setting the tick over, with the throttle stop set just below this point at a very low tickover. Result perfect return to the throttle cable and tick over position every time. Also because the throttle slide barely touches the throttle stop screw there is no more wear taking place.

If only Mikuni had designed the carb with a near vertical adjustment screw (like on the Amal Monobloc) rather than one that come in from the side, which is prone to pusing the slide sideways.

Regards,


Mike

[another Allan]

Mike, if you've set the tickover speed on throttle wire tension, be careful that it does not either stall or race as you turn the bars from lock to lock.......
Allan.