Carb slide modification
Posted March 08, 2011 - 11:58 AM
with a 412cc Big Bore kit from Powroll.
Working on a 1974 Honda xl 350 Carb is a 32mm CV Keihin (Piston Valve)
Posted March 08, 2011 - 12:20 PM
Posted March 08, 2011 - 12:37 PM
Also...are you sure you can't cure the rich condition with some jetting changes and air fuel screw adjustments?
Posted March 08, 2011 - 01:53 PM
Posted March 08, 2011 - 04:23 PM
In every case the component actually causing the rich condition turned out to be a worn needle jet - in your carb this is P/N 16012-356-004 - but the leaner slide further improved performance in the summer. It doesn't appear that Honda specified any leaner or richer slides for your carb.
Posted March 08, 2011 - 06:56 PM
Iv'e seen this more often in the high miles larger in-line fours,also sinking floats.
Years ago i had access to a machine shop and had lots of fun distroying carbs and motors:smirk: But i learned a lot:banana:
Posted March 09, 2011 - 11:15 PM
I finally talked to an old timer honda mechanic and he suggested finding some new old parts for my carb. He explained that with the big bore kit installed those bikes vibrated quite a bit. The needle jet and seat would oval out just enough to not meter fuel properly. I think Ray is on to somthing here. I found a keyster carb kit on ebay that I will try. If that don't work I may get an identical carb off a savage yard and try the slide milling. I don't really want to file my slide down if at all possible.
You guys rock with great info.
Posted March 10, 2011 - 03:48 PM
If the needle is sanded / cleaned up and a thin, even coat of solder applied to the straight section above the taper, then chucked into a drill and the solder turned down perfectly flat, it should work a lot like replacing the needle and jet. You'll probably start out super lean and have to turn it down a few times to get it right, and the solder will surely wear down after a while. A thinner, harder layer would be better - maybe epoxy paint or some kind of metallic coating, spun under a heat lamp to dry?
I've never tried this as I always lucked out and found a NOS needle/jet first, but if I absolutely couldn't find one, I would definitely give it a shot before cutting the slide. Apparently others have also had success with filling and redrilling the needle jet, but I'd need a small drill press and a set of jet drills to attempt this myself.