Monday, October 21, 2013

Honing Bing Carburetor slides

Sticking carburetor slides are often a problem on /2's.  Before you go about attempting to hone your carb slides and bores, check your cables, cable routing, and throttle grip mechanism. Often times a sticky carb can be linked to a bad cable that otherwise looks fine or cable routing that pinches the cable.

If you cables look old, replace them.  If you have teflon lined cables, do not lube them.

Typical Situation of Pinched Throttle cables
A good rule of thumb for pinched cables is to check to see if the problem is worse when the bars are turned to the left or right. If moving the bars seems to affect the problem, it is probably a pinched cable.

Another area to check is the twist grip mechanism itself.  Check out this other article about that.

Ok, now let's have a look at those carbs.

I use a sharpie to mark up the slide like this:

So when I slide it inside the bore, I can see where it is rubbing.  Then I can take a piece of 1000 grit sand paper and take down that area a bit.

Sometimes you find that the slide is tight in the bore all the way around. This is often the case when replacing parts or when fitting a carburetor together from parts.

Before going this route, be absolutely certain your slide is good. Check to be sure it is a true cylinder by measuring at different points up and down the cylinder using a micrometer or caliper. All measurements should be equal.

If your slide is worn, replace it.

Once you are certain your slide is good, then you can bore the carburetor body to fit the slide.

Using a brake cylinder hone, hone the carburetor body. Use plenty of WD40 as a lubricant so that particles will not scratch the new surface. Measure at frequent intervals by cleaning the debris out of the bore and inserting your slide. Ensure that the new slide is as tight as possible while still allowing easy movement in the bore.