Scored a 4-1 for my 79sf...

[TopCatGr58]

Hey John,

That's interesting about the bypass bolt being 19mm, cause when I measured mine and was creating the replacement mounting pipe for the spin on adapters(and they've all fit), I used a 20mm x1.5mm thread, and die for cutting the pipe to those parameters!?!?

So....I think the thread size is 20mm diam. by 1.5mm pitch.
T.C.

[John]

I should have been more specific... the hex on the bypass bolt is 19mm. I have no idea what the diameter or thread pitch is.

[Shuriken]

I swapped vacuum diaphragms. My 79sf had some crappy ones in it. I had tried the rubber spray fix on the top side but inspection showed that they were very sticky - gas was eating it. Wonder if napa changed their rubber spray?

Anyway, I had a spare set of 78e carbs with fair diaphragms. I installed those with the clip position 1 notch leaner than stock. Both changes resulted in much better performance.

I had thought that the mains were fine since when I got the bike on the WOT circuit it pulled really hard. The midrange circuit sucked. It just flubbed until it got onto the mains. The idle circuit was fine but flubbed in transition to the midrange.

Swapping carb diaphragms with a better set and changing the jet needle position made all the circuits overlap, which is what I wanted. The throttle is smooth but midrange still needs a bit of tweak.

With the previous diaphragms, I tried 1 notch rich and 2 notches rich. Neither worked. I also tried 1 notch lean. That didn't work. All resulted in decreased performance. So I think the main difference was in the diaphragms. But since I changed 2 variables at once (diaphragms and needles), I can't say for sure. One should always change only one variable at a time.

Anyhow, perhaps next weekend or something I'll have a chance to just change the needle positions. I really think I only have 2 other tests to make - I'll try the stock needle position and 2 notches lean.

I DID go to a higher flow 4-1, but kept the stock airbox and the bike is at nearly 7,000 feet elevation.

Also, my brother in-law and his wife hopped on to my 80g and my girlfriend and I hopped on to the 79sf. We ran them up a hill. He was just cruising along at 65 or so on the uphill. I dropped the 79sf down a gear, perhaps 3rd or 4th and put it on the WOT circuit. We just flew by my 80g.

I have been riding on worn engines for a long time. It's nice to feel some new pull. I would like to do a complete bore kit rebuild sometime if I don't sell both XS's for an FZ1.

Ben