'79 XS1100F Carb Issues; Poor Performance on the Main Jet.

[DEEBS11]

Emultion tube.

[DEEBS11]

..........

[banzaibob]

Here's what I think happened:

Some a-hole bought a really nice 1979 Yamaha XS1100....and instead of riding it during the colder weather or even storing it properly during the winter, he let it sit outside behind the garage. When they came back around the 1st of May to go for a spin, they found that it would'n start. There it sat for the next year or so. Finally they sold it to a kid up the block who took it to a bike mechanic who simply bought 4 K&L kits and installed them without making a determination as to whether the existing parts were actually worn. I replaced the original tank...which was re-lined with Kreem but NOT cleaned first (it was coming out in great chunks).

The emulsion tubes (or needle jets) are the original X-2s. I also have some genuine Mikuni #45 pilot jets coming. That may cure it's anemic performance off idle. I wish it had the stock exhaust of at least a decent, modern 4 into 1. I keep getting closer though.

[banzaibob]

Maybe the last update?

The NOS 5GZ6 needles arrived Wednesday. I installed them yesterday and took it for a spin without the air filter and without adjusting the fuel screws or doing a final synchronization. Ran great. So....I installed the stock air box, stock air filter, new Mike's XS breather, etc. I should take a moment to also describe my "test track": I live in a VERY rural area where there is a long 1.5-2 mile straightaway. Since it is so rural I have to take care not to go too fast for fear of colliding with deer. In fact, last year I was involved in a serious motorcycle accident which was a result of hitting a deer. I can go a little faster on the return trip because I've checked it out already.

On the way down I rode normally, like it would if I was trying to ride on the interstate. On the way back I was able to do a high speed pass. By this time I am sure that the engine is up to operating temperature. I did not want to go past 6000 rpm in top gear....around 90 mph...that's fast enough for my reflexes. I can report that it appears to run flawlessly. There is NO hint of misfiring or the "shudder" that I would feel previously. Throttle response appears to be very good from 2500 rpm, all the way to at least 6000 rpm in top gear. There is a sort of grabby "hit" of abrupt acceleration at around 4000 rpm that I'm sure many would love to have. I'm simply willing to tolerate it at this point.

I'm pretty sure that I have the very last set of stock 5GZ6 needles in existence since they appear to be exclusive for only '78-'79 XS1100s. Before I installed them I measured them with a known good set of calipers. I checked them mostly at the first taper. What I found was that the "Y265" K&L needles were remarkably the same as the 5GZ6 needles. Other than being made from aluminum, the "Y265" needles appear to be only about 0.003" smaller at the 1st taper and also about 0.004" smaller along the needles in other areas. That's not a lot. I would also have to assume the the shape of the profile is somewhat different considering that the Y265 needles only came close to working correctly at the highest (leanest) notch. The 5GZ6 needles are in the middle position.

There are other things that I'm going to have to deal with on the bike but none that appear too important right now. It seems to have developed a light "tick, tick, tick" at idle. In 2nd gear, 25 mph, just barely off idle it cannot be heard. I'm. not too worried at this point.

Anyway....I'd like to thank ALL of you for your help. I think we may have this one licked.

[bikerphil]

Glad it runs properly now. That is the problem with aftermarket needles, they could be copies of copies, which will not be accurate like the OEM. As for the ticking, you may have an exhaust leak at one of the headers at the cylinder head. Careful not to snap one of the studs if you attempt to tighten them.

[banzaibob]

Glad it runs properly now. That is the problem with aftermarket needles, they could be copies of copies, which will not be accurate like the OEM. As for the ticking, you may have an exhaust leak at one of the headers at the cylinder head. Careful not to snap one of the studs if you attempt to tighten them.

I discovered what the "tick, tick, tick" was. After syncing the carbs it went away. Sounds like a wobbly clutch basket.

[DiverRay]

To have fun with other bikes, do as I do. "let's race" he says. "OK" I said, but my way. High gear at 25mph and then full throttle. VERY few bikes can do that! you win without having to beat the other bike. The HD croud HATES me for doing this