82 XJ 750 pops

Rebuilt carbs, I used a cheap amazon rebuild kit, all brass. But the shaft seals came from xj4ever. new coils, wires, caps and plugs. Carbs synchronized several times using two sets of gauges. (YICS blanking tool used) runs great starts well good performance. No vacuum leaks, all idle mixture screws turned out to where I found them, exhaust does not smell like the machine is burning rich. No Gas in the oil. BUT.. Between 3000 and 3900 RPM the bike pops a bit through the carbs. Not extreme blowouts. Just annoying enough to concern me and avoid this RPM range. Should I be looking at an adjustable main jet needle? I hear that works on some machines. Or should I just use an xj4ever rebuild kit and be done with it. Any other suggestions welcome. Thanks!!

 

Keeferhydude, sounds like you did a good job on them carbs, but with carbs that have been sitting for a long time, supper hard to get them clean the first time. My first XJ even though I thought I had the carbs cleaned, well took me six times to clean them right and then the bike ran very well.

In the bottom of each float bowl there is a small jet that is pressed into the bottom. Taking a very small wire, compressed air and carb cleaner, that has to be very clean for the bike to run. That means all four of them have to be supper clean for the bike to not pop and idle they was she should.

Have you checked to make sure the boots going from the carbs to the engine don't have any air leaks or visible cracks in them? That would also cause some of the pops you have.

Good luck and tell us what you find.

 

Those cheap kits come with jets, pilots and main needles. Unless your old ones are damaged, I would try to reuse them.

Not saying that's the issue....I've put $12 Chinese carbs on mowers, tillers and such and they've worked fine. But small changes in dimensions can mean a lot on the brass parts.

 

Thanks so much.

 

Ok good to know. Thanks.

 

What kind of numbers are those? With new jets and older engine they have likely changed so a color tune would be nice, or try the lean drop method if you have good ears - I never could do it.

Or, set them to the suggested 2 1/2 to 3 turns out as a starting point

 

Thanks

 

Thanks