Tri-z PowerValve

[nstyle73]

Glad you could get the triples set up, they look great.

[NeverLift]

I rode it last night before dark. The shortened intake made it feel different like its breaking up not just flattening out. Next chance I get I'll do a plug chop and play with the jetting. Its about 40° warmer now than last time I rode.
I went from a br8es to a br9es and it was worse. Do you think its from being to rich?

[NeverLift]

This is the br8es 5 gear full throttle while its breaking up. 178 main. Before I cut the threads off I would have thought it was lean but down at the base its black. What y'all think?

[onformula1]

Too lean for me, especially at WOT.

The plug trick was meant for a normal head, stock head 180 PSI MAX, not a Fuelie.

[NeverLift]

Too lean for me, especially at WOT.

The plug trick was meant for a normal head, stock head 180 PSI MAX, not a Fuelie.

If the plug trick isn't meant for high compression how do i go about jetting? Harry Klemm talks about using a tachometer. When the highest RPM is reached the jetting is correct. Whats your preferred method?

[yaegerb]

^^I think a few missed this.

110 octane is not an issue for 15-16:1 UCCR on a two stroke.. 100 usually works from my experience.. Powervalved bikes can also trap a higher PSI for a given UCCR.. My kx250 trapped 245 with a thin base & stock dome lightly skimmed for .040 clearance.. They are around 220 stock. Cranking pressure only tells half the story unless comparing engines with fixed ports of similar duration.



All my modded 250's have been over 15:1... I have never used a dome smaller than 21cc with a domed piston. Even with a flattop piston you would have likely been over 17:1 with that 15cc dome.. that engine might have trapped 250-260psi on my gauge.. If your gauge doesn't have two functioning valves, and an adapter with 3/4" thread length it's gonna read low on a small engine.

To each his own. I like running my R's around 185PSI, .080 squish, which puts me median 13:1 and using 93 at the pump.

[yaegerb]

I rode it last night before dark. The shortened intake made it feel different like its breaking up not just flattening out. Next chance I get I'll do a plug chop and play with the jetting. Its about 40° warmer now than last time I rode.
I went from a br8es to a br9es and it was worse. Do you think its from being to rich?

Got the CC's off that head yet?

[NeverLift]

Not yet I should have time this weekend.

[averysdad]

The plug is too lean? looks black to me.

I would also be interested in a way to check the jetting without cutting the plug?

How did you cut your.

[NeverLift]

Dremel and a cut off wheel.

[cr480r]

I like to measure the true volume at tdc with the head on the engine. The flat plate method of measuring the head is really only useful for comparing heads or measuring changes. Measuring the assembled engine tells the true story of what the engine really sees. The chamber, piston dome, squish, and gasket volumes are measured all at once.

[NeverLift]

I like to measure the true volume at tdc with the head on the engine. The flat plate method of measuring the head is really only useful for comparing heads or measuring changes. Measuring the assembled engine tells the true story of what the engine really sees. The chamber, piston dome, squish, and gasket volumes are measured all at once.

What method do you use to do this?

[yaegerb]

I like to measure the true volume at tdc with the head on the engine. The flat plate method of measuring the head is really only useful for comparing heads or measuring changes. Measuring the assembled engine tells the true story of what the engine really sees. The chamber, piston dome, squish, and gasket volumes are measured all at once.

So do I, but I can't do that with Neverlifts engine, unless he wants to ship it to me, thus the "ballpark" figure I mentioned earlier.

[yaegerb]

What method do you use to do this?

uncorrected compression ratio test, UCCR.

[cr480r]

What method do you use to do this?

I usually do it on the bench during assembly, but I am sure it could be done in the bike if you tore it down enough. I remove the head and rotate the piston to tdc. Usually it will stay put, but sometimes you might need to wedge the flywheel with something so crank doesn't rotate. Smear a layer of grease around the edge of piston to seal the ring lands. Install head and gasket and level engine. Pour known amount of liquid into spark plug hole from a graduated burrette and fill to bottom spark plug thread. Measure remaining liquid and subtract from initial quantity for the volume of cylinder. Add 1.2cc for spark plug and calculate compression. Example: 249+19/19=13.89