jet size thread

[adam79]

The float needle height I dont know how to measure

[adam79]

and here is a better picture of my exhaust. I think it might be stock.


Further down toward the back wheel is a cross over pipe

[egsols]

Sounds like the carbs probably needed a good cleaning.

The factory setting for the float height is 25.7 mm +/- from the base of the carb to the top of the float, that is with the floats upside down, measure from the base (where the bowl gasket goes) without the gasket in place, to the top of the floats, with no pressure on the floats.

Lightly seat all of your idle screws then back them out about 1 1/4 turns. Depending on how much you took apart, the carbs may be close to sync. If they aren't search for the bread tie sync on this forum. If you didn't really touch the adjusters between carbs, set your floats and idle screws and re-install on the bike. You will have to find some guages so you can sync the carbs. Make sure the bike is fully warmed up before doing the sync.

Make sure the vacuum line running to the advance is hooked back up to the port on the number 2 carb.

Yes, those look like stock pipes with after market mufflers. I take it you mean the XS and not your daily ride in the background

[psycoreefer]

It seems as if a PO was into your carbs who may or may not have known what they were doing.

Have you tried starting the bike after the rebuild? I think everyone has been going on the assumption that after the rebuild the bike still won't start. definitely replace those plugs before you try, they have way to much carbon build up and could be half the problem.

Float height - do a search, its really easy as long as take your time, I use a little metal ruler I got at harbor freight for like 50 cents, so it shouldn't cost you much.

It's not clear to me, did you put the 140 main jets back after the rebuild or did you use the 137.5's? I personally would go back to the 137.5's for now, as it looks like you have stock intake and exhaust. Although the wrong main jet shouldn't prevent the bike from starting.

If you used the new idle jets did they look exactly like the old ones? There are two different types of idle jets, the ones for our bikes have the little hole for metering the fuel at the end opposite the screw head, the other type will screw in and look very close but have the metering hole much closer to the other end. If you do a search for pilot jet you may be able to find some pictures.

Did you take the tops off the carbs? Do you remember which position the clip on the needle was in? If that clip has been moved it would make the bike run very bad.

Backfiring when trying to start isn't that big a surprise when you think about how these bikes work, its a wasted spark system which means that the spark plugs fire on the compression stroke and on the exhaust stroke so if the bike isn't starting then there is a bunch of gas still in the cylinder and it could ignite from the spark on the exhaust stroke.

Another thing to check if you haven't yet is the vacuum advance wires, if they are broken - which is common - then your spark would be irregular. If you have a multimeter its easy to check them.

[planedick]

Exhaust

Your exhaust looks like you have Jardine slip-ons with stock headers. I had put them on a '79 I had and the only adjustments I madt to the carbs was raising the floats a little and placing the clip on the main jet needle in the bottom position to make it run right. All jets were stock.

[adam79]

sorry for the delayed response, but prometheus came up to help me sort it out, and it was a little pointless to keep responding. But, it turns out that the PO had removed the vacuum advance line completely, and the middle drive vent hose was hooked up to the carbs instead! all of my needle seats in the carb were no good, so 4 new needles, 20 Qtips, and a bit of simichrome polish (that stuff works WONDERS) and no leaks whatsoever. The plugs were fouled and fired intermittently, and the carbs were out of synch. We got here all fixed up, a few new valve shims, and some adjusting, and she ran GREAT, for about 100ft, then she died..... well...turns out the PO also removed the fuse box and just connected the fuses to the wires, which worked, but it was all haphazard and shorting out. Dont have the new box yet, but until then, I replaced the the connectors and crimps, and set it up as clean and orderly as possible. Vroooom. The bike is in great shape now. NO backfire, stumble or shorts. Almost like new. The 140 jets dont make any noticeable differance either. Thanks for the help.

[XSPastor]

Exhaust looks stock to me...

That exhaust looks stock all the way back. The Jardine crossover pipe didn't have a clamp in the middle of the crossover pipe like that. I'd need a better picture of the mufflers to be sure. If there's no clamp between the headers (which are most certainly stock) and the mufflers, there's a good chance that it's all stock as the Jardines came with clamps to attach them to the stock headers. Even if it is Jardine slip-ons, there should be no need to rejet unless someone drilled them out or removed the baffles - and even then maybe not.