Powerjets while jetting... confused

[project_Tecate]

I figured i would put this here since many bikes these days have powerjets in their carbs, i'm just a little confused on what they do exactly and heres why:

I have a 99 rm250 and i am normally pretty good with dialing in a bike but I have never really encountered anything with a powerjet. First my bike started running really rich and fouling plugs left and right, looked at the jetting and I had the stockers in there, totally forgot about it because i used them over the winter time for a short period so the bike wouldnt lean out. Changed the jetting and was still fouling a lot and even spooging and smoking more than ever. Thought i needed a RH crank seal but ended up my floats were way to low. Floats are pretty much set i believe. Now I have it where it is crisp and pulls great but i am still getting some spooge and smoke from 1/4 around WOT. Now with the powerjet I understand it richens up the fuel from basically that area 1/4-3/4 throttle to make sure it doesnt lean out. How does it actually work? Stock main was a 158, I put a 152 in there, now is the powerjet compensating for the 152 and adding more fuel to the mix richening it up? If there was a 155 main in there instead would that change things up with the powerjet? Or am i way off and should prob still mess with the floats since thats what was causing most of the fouling in the end? Oh and my stock pilot is a 45, recommended was a 42 with needle on the second clip, i'm running a 40 with needle on the 3rd clip and that seems to have the best reaction yet all while running 32:1 Mobile 2t oil, been running for a while and never any problems. I just know on my 96 RM250 I had no spooge and it barely smoked so i am confused if the powerjet is throwing me off. Thanks

[flotek]

IMO your problem wil l not be solved by running a power jet ,you want to fine tune the needle and may need tot ry several differnt needles to accomadate the jetting and remove the bog yo u have .i wouldnt even run the powerjet if your using just gas . basicly it effectivly splits your mainjet and delivers additional fuel when the incoming charge draws it through the carb body according to the engiens needs ,this and i n theory adds more fuel to lean spots i n the powerband ,if your enigne bogs it is already experiancing too much fue l and may actaully get worse IMO .just my 2 cents

[project_Tecate]

I dont have a bog anywhere when riding but when i seem to hit the main circuit that when it seems to get rich which i am assuming is from the powerjet. What I am thinking is possibly my main is a tad to lean which is causing the powerjet to put to much fuel in to counteract the lean condition so I was more curious if i put a little richer of a main in will that compensate for the excessive fuel the powerjet is putting in? Almost like because of the lean condtion it is trying to level it out to much giving me to much fuel?

[tecateboy]

from what iv heard is they are used so that you can use a leaner main jet for better response but the powerjet will still feel enough gas to keep it from running lean.

[project_Tecate]

Originally Posted by tecateboy

from what iv heard is they are used so that you can use a leaner main jet for better response but the powerjet will still feel enough gas to keep it from running lean.

yeah thats the impression i'm under but my manual says the powerjet feeds extra fuel when the circuit is at certain RPMs to compensate for a lean condition when present so thats why i was thinking maybe i'm to lean on the main so it compansating to much if it is lean so if i richen the main a little it wont allow as much fuel to come in and richen it up as drastically. But i keep reading different things on how powerjets actually work so that is why I am confused out of my mind

[tecateboy]

i was thinking just try to lean it out a little more, it seems that the powerjet can only feed a certain amount of fuel and the higher rpm would draw more fuel through it, so i would try one or two sizes smaller and see what that does, you could also try to but a bigger main in it too. i know these powerjets are on the stock mikunis on my 340 and 440 invaders and they have pretty small main jets in them if i remember correctly.

[project_Tecate]

I guess its back to the drawing board again, I think I have pulled my carb out about 20 times now, also i was looking at my manual and its saying from a little after 1/4 to a tad past 3/4 thats when the powerjet compansates for the rich condition but at WOT it shuts off so you get full power of the main so that is why I am a lil sketchy with going any leaner on the main but i guess we'll see what happens. i think i am going to try the richer main first just to be safe then go from there

[project_Tecate]

anyone else have insite on how the powerjet actually works, will it the same amount of fuel to richen the mixture up no matter what main jet is in there? I wanted to work on the bike today but practically cut the tip of my finger off so stayin away from that till tomorrow, just would like more insight