Air/Fuel mix measurement in the muffler

[Alphamazing]

I got my bike dynoed this past Saturday (41.7 HP and 27.6 FT-LB), but no one could get the air/fuel measurement tube past the middle of the muffler. There was a weird bend in it, and then it wouldn't go past that. Can't explain it any better than that right now.

Anyways, what sort of effects would that have on the jetting mixture measurements taken from that point, rather than further up the midpipe? Would it make it appear to be leaner than normal, or would the effects be negligable?

At idle the bike was off the charts lean, as in well over 18.0.

[makenzie71]

...I remember having 40hp dynos...makes me feel all naustalgic...lol

Really wouldn't matter there...the mix isn't going to be that much cooler at that point.  You need to liven her up a bit, though...

ninja edit...Idle isn't all to detrimental.  What'd it read at peak power?

[Alphamazing]

...I remember having 40hp dynos...makes me feel all naustalgic...lol

Really wouldn't matter there...the mix isn't going to be that much cooler at that point.  You need to liven her up a bit, though...

ninja edit...Idle isn't all to detrimental.  What'd it read at peak power?

It was off the charts until 4.5k where it dipped down to about 14 at 5k. At 6k it is at 12.5ish, and climbs steadily to about 14.3 at 9k, dipping back to about 14 until redline. Yeah. I need to richen her up a bit. I'm thinking bump the mains a size, and possibly bump the pilots a size.

[makenzie71]

Seems like the only real problem area is idle and low range...

[Alphamazing]

Seems like the only real problem area is idle and low range...

Shouldn't the jetting be around 12.5 to 13? So wouldn't 14+ be quite a bit lean?

[makenzie71]

depends on how much cushion you're looking for.  I kept my FZ600 between 14 and 15...but it didn't really run right anywhere else.

All in all, what you've got isn't going to be damaging if you just tweak the low end a bit...as to whether it's ideal or not depends on how the bike runs.  I'd probably up the mains a size and devote some attention to the idle and low range settings and then see how she dynos.

[Alphamazing]

depends on how much cushion you're looking for.  I kept my FZ600 between 14 and 15...but it didn't really run right anywhere else.

All in all, what you've got isn't going to be damaging if you just tweak the low end a bit...as to whether it's ideal or not depends on how the bike runs.  I'd probably up the mains a size and devote some attention to the idle and low range settings and then see how she dynos.

Well, seeing as how it's air cooled I don't want to run it too hot and burn anything up. I'll change the jetting this Thursday and see how it does. Thankfully I found a place that does dyno runs for only $40 so I can get them done without worrying about a serious cash drainage. Unfortunately I'[ll have to wait for my refund to come in before I go get any more dynos done.

[makenzie71]

shaZam! I wish some place out here would do dyno runs that cheap...

Oh, and the FZ600 is liquid cooled...just like the GS500.

[LimaXray]

I think you're picking up a little open air.  I don't think the engine would idle 18.0 AFR.  In my experience, its a Buddha Loves You to get an inline 4 to idle at stoch, and the fewer the cylinders you have the richer you need to be to keep it idling.  Although, as the engine revs higher, it probably becomes more accurate because less free air will be mixing with the exhaust gasses.  It's probably close enough where it really counts.  If you're worried about running too lean, all that matters is that it runs and its not detonating.

If dynoing is something you plan on regularly, have a O2 sensor bung welded into your collector.

[Alphamazing]

I don't plan on dynoing regularly as I don't have the money for it.

It is running lean, as the plugs are pretty white, so I'll just bump it up and see how it does.

[budget speed demon]

your running a stock exhaust with a lunch box filter right?

[Alphamazing]

your running a stock exhaust with a lunch box filter right?

Bingo. My rejet right now is 20 pilots, 62.5 mid main, and 135 mains.

[melloGS]

nice...i dynoed mine stock at 36.8hp