Boy Racer

By "Sirius Online" do you mean these guys? I'll check the condenser, but as I thought about it more and more today, I think (I hope) it's a jetting issue. It ran fine on Sunday afternoon and Monday afternoon; as both days warmed up, the bike ran fine. Both afternoons were in the 60s. The only real trouble I had was when the temperature was below 50. I think that can be traced to the mains being too lean. They may be 42.5, I might want to try 45 in the cold weather, then swap back as the days warm up. We'll see. I remembered today that the headlight does dim each time the blinker lights up. It kind of oscillated in kind with the cadence of the blinkers. Again, we'll see what that's all about. It's not bad, just a slight dimming I noticed. I'll bet it's normal. Thanks for reading this and all the suggestions. I get frustrated sometimes, but it'll all be worth it when it runs well. 60 MPG (Yamaha) will beat the hell out of 13 MPG (Ford F-150), especially what with gas being consistently over $3.00 now. This summer it's supposed to be mid- to high- $3.XX. I can't wait.

No, I have not replaced the needle valves or the seats. That's the last thing, I guess. I hadn't figured they would have been a problem (they passed visual inspection), but since I've cleaned and replaced every other component of the fuel system from the petcock filter to the air/idle screws, it must be the jet needles/needle jet. That site you posted is awesome, it's got some great stuff. Between that and Mike's XS, I should have a complete resto done on this thing in the next few weeks. I did get it running yesterday pretty good. I test rode it for about 6 miles around the neighborhood in 58 degree weather and it ran fine, didn't even leak. Well, I opened up the garage door this morning (39 degrees) and I could smell it before I saw it. Gas was leaking again. I dried it off, started it up and it ran like crap! All the way to work it ran progressively worse. 12.5 miles, mostly neighborhood streets, stop & go, between 30 and 55 MPH, and cold this morning. But at lunch it had warmed up to around 55 degrees and it ran better but not perfect. On the way home tonight in 63 degree weather it ran flawless. I can't figure it out, other than it likes warm weather. The biggest problem this morning was it wouldn't hold an idle (had to run on 1/2 choke the whole time) and it had no throttle response. It would rev up to 6K and go no further. It wouldn't pull hills unless a lot of down shifting was involved, and it would occasionally buck & surge at level throttle.

In all fairness, your experience isn't the same for all persons everywhere. My petcock, after rebuild, flows just slightly less fuel on 'ON' as it does on 'PRIME'. That's a problem for which I have found no solution. When the bike sits on it's sidestand, it leaks from the right side carb onto the engine then onto the floor. On the centerstand it leaks from both carbs, just not as badly as the one carb when on its sidestand. I've rebuilt the carbs three times now. If I move the float bowls any lower, it starves the engine and it won't rev over 4k. If I move them any higher, it leaks all over the place. My best bet (based on vehicle value and my tolerance for rebuilding this bike every weekend) is to replace the petcock with an 'ON-OFF-RES' version. I'd rather have a petcock that works and an engine that revs where I need it to so I can ride it, than have the gas spill all over the place. Anyway: The '81 XS400H petcock part number is 3X8-24500-00-00. The '81 XS650H petcock part number is 3G1-24500-03-00. Can anyone decode these numbers? Are the first three the model and the next 5 the part? I hope? The '24500' part looks promising.

You're using an FZR600 wiring harness to run the 400 motor. They will interchange by fit alone (pins and receptacles), but the 600 CDI box will not properly fire the 400 motor. It won't rev past X,000 RPMs (I can't remember the actual number). We run into this every once in a while on the club racing circuit I run. I have one spare 400 box that I know of, and they're pretty rare. The 600 boxes are far more common and may people sell them claiming interchangeability. They aren't.

Spray the insides of the boots with WD-40, they'll slide on easier that way. You can also use aerosol hairspray, it's slippery when wet, but dries tacky and helps them stay on. Works on grips, too.

Can anyone tell me if the vacuum petcocks on XS650's will fit on an XS400? I see Mike's XS has a kit that will retrofit a standard petcock in place of the vacuum disaster that was fitted as stock to the XS650's. I want to retrofit the vacuum petcock on my 81 XS400H with a standard on-off-reserve unit like what he's offering, but don't know if they'll interchange. Can anyone research the two Yamaha part numbers and see if they're one and the same?