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Power jets - to use or not to use
http://www.kawi2strokes.com/forum/viewtopic.php?f=14&t=2332		 Page 1 of 1
Author:  smoff83 [ Sat Feb 04, 2012 12:23 pm ]
Post subject:  Power jets - to use or not to use
I'm interested in upgrading my stock H2 carbs. The mikuni tm34 carb kit from Niche Cycle seems like a good, comprehensive package. Anyone know how a power jet would affect the tuning and performance of these? I understand the concept. Some sources say it's highly recommended for 2 stroke applications. I guess my confusion is this: why would this improve the tuning characteristics if the proper main jet is installed? Wouldn't it over-richen the main fuel circuit towards WOT when the power jet kicks in? Or are 2 strokes really that thirsty when run at WOT? Or is it a way to lean out the main jet while not risking detonation to improve 1/2 to 3/4 throttle opening? Seems like a redundancy to someone like me with no experience with them
Author:  Ja-Moo [ Sat Feb 04, 2012 12:47 pm ]
Post subject:  Re: Power jets - to use or not to use
They just complicate tuning. If you take time to tune the carbs properly, then they do get redundant. (on the street)
Author:  ZERO [ Sat Feb 04, 2012 3:53 pm ]
Post subject:  Re: Power jets - to use or not to use
Im currently running PUMPERS on my non stock H2A. My thought is that at ultra wide open throttle settings there would never be a lean burn condition. However if you're 100% sure that you are in perfect tune........ The plusses are #1 You can use the tube as a float level indicator..HANDY! (You can see at a glance if a carb has run dry or is too high.) And almost as important #2 People always ask "What is that?" Then there's the fact that they turn off, too. :thumbup: More fuel. Cool, and potentialy a safety feature. Its a WIN, WIN to me!
Author:  smoff83 [ Mon Feb 06, 2012 5:27 pm ]
Post subject:  Re: Power jets - to use or not to use
Ja-Moo wrote:
They just complicate tuning. If you take time to tune the carbs properly, then they do get redundant. (on the street)


Are they more useful in race applications? Obviously I couldn't run WOT or near WOT for very long on the street, or keep my license for very long while doing it.

ZERO wrote:
Im currently running PUMPERS on my non stock H2A. My thought is that at ultra wide open throttle settings there would never be a lean burn condition. However if you're 100% sure that you are in perfect tune........ The plusses are #1 You can use the tube as a float level indicator..HANDY! (You can see at a glance if a carb has run dry or is too high.) And almost as important #2 People always ask "What is that?" Then there's the fact that they turn off, too. :thumbup: More fuel. Cool, and potentialy a safety feature. Its a WIN, WIN to me!


Interesting, what type of carbs do you have installed?
Author:  Ja-Moo [ Mon Feb 06, 2012 6:01 pm ]
Post subject:  Re: Power jets - to use or not to use
smoff83 wrote:

Are they more useful in race applications? Obviously I couldn't run WOT or near WOT for very long on the street, or keep my license for very long while doing it.



They are more for racing applications. Hot porting can cause a lot of reversion in the intake, so you get a rich midrange. You can lean out the needle, and add extra fuel with the power jet at WFO.
Author:  H2RTuner [ Mon Feb 06, 2012 6:37 pm ]
Post subject:  Re: Power jets - to use or not to use
The better power jet systems use an electronic valve to cut and open the jet, at certain levels of acceleration/sustained rpms. The latest TZ250 Yamaha's use a part of the timing computer to do a two section valve opening.
Author:  smoff83 [ Mon Feb 06, 2012 7:32 pm ]
Post subject:  Re: Power jets - to use or not to use
Thanks guys. Makes more sense to me now
Author:  ZERO [ Tue Feb 07, 2012 4:50 am ]
Post subject:  Re: Power jets - to use or not to use
Smoff83, Currently 34mm Mikuni pumpers. However my engine is not even close to stock and is reed valved. I was just mentioning the features that I like personally.(Like that they hook up to the original throttle and choke cables) I am seldom at full throttle...if ever. I've got a ZX14 for that. I need to also ad that there will be more effort at the throttle due to the stiffer slide springs. I don't notice it anymore.
Author:  rickman [ Tue Apr 17, 2012 10:05 am ]
Post subject:  Re: Power jets - to use or not to use
I've had the thought that the power jetted carbs allow fuel to be mixed with air better, because of the two points that fuel enters the airflow into each cylinder. Almost opposite each other.

Instead of one point low down in the air flow.

A valid thought, or izzit useless at these air speeds?
Brett

P.S. I've got 3 power jet equipped Mikuni carbs, new, never used. Bought from someone years ago, who had some triple project, and failed to utilize them... Think his was a kettle?
I put one onto a TM/TS 400 Suzuki projeckt... Haven't finished playing with that one yet...
I think another one went onto my Rickman 250 road racer...
The other one still sits in top of the tool box....
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