The New Kawasaki ZXRR125GP

[k14]

I think the PJ only really works well with unleaded anyway? The theory is magnificent but I found it didnt make too much difference with avgas. Best to put the cutoff down lower, 12250 should be a better bet than 12750

Agree with RG100, setting up the needle and pilot pays dividends. Problem is that the taper on the PJ needles is only really for unleaded fuel anyway and there is only one clip postion that works anyway. At least (if you are runing avgas), the earlier models offer more flexibility.

Yeah I was going to say that too. But with Ivan its in one ear out the other so I couldn't be bothered. The reason for the powerjet as far as I know is to richen up the mid range to prevent detonation and siezure. It may also help get a little more over rev but I would be surprised if it equated to any noticeable gain in power.

What are your reasons behind leaving the cutoff as low as possible?

[Dodgy]

Yeah I was going to say that too. But with Ivan its in one ear out the other so I couldn't be bothered. T

What are your reasons behind leaving the cutoff as low as possible?

Haha, I gathered that too with Ivan

The rationale behind the PJ is to lean out the top end and extend over rev. Due to the pipe, port timings and all that crap, the bike runs rich past peak power, so the PJ shuts off to lean it off.

If you read the HRC manual (which RG has my old copy), it nicely illustrates how you need to reduce the cutoff on tighter tracks, where the gearing is lower and where you spend less duration going thru this phase. HRC get all tech with an explanation about the time to drain out the PJ circuit as well.

My igniton is fully adjustable (well, in fact, far too adjustable), and had full data logging built into it. We found the bike responded better with the PJ cutoff right down around 11800 with avgas. It is a BPS unit, which was great for tuning, but crap for support.

[Ivan]

haha
Kinda sucks I listen just dont know what to type I have this issue,
Its not a mental thing just a Ginga thing I think.

[F5 Dave]

As the pipe is past peak power frequency & especially with a steep diffuser (which is good for peak power) the effective suction is greatly reduced thus power tends to fall off dramatically.

Any trick to increase pipe temperature, adjust ignition timing, lean off jetting may reduce this & give some more tasty over-rev.

. . . Meaning that you may be tempted to, say increase the angle on the diffuser for some more power & starting the whole ugly process over again.

Time to drain the PJ tube? That makes sense, -cool the things they think of.

Suppose this would change relative to the gear the bike was in & relative overall gearing; as in the shorter gears it would take longer to drain in relation to the revs rising, so you’d want to turn the PJ off earlier in early gears than higher gears, esp for long ccts.