Passion Motor Won't Pull In Midrange

[Blue Duece]

bigger carbs.......

[PassionRE]

Ultimately, my 12 port strokers benefit tremendously from the use of larger carbs in general. Many of these engines are sporting 34,35,and 36mm carbs and maintain great bottom end and throttle response. I also understand that many owners cant for whatever reason, mount the larger carbs on these engines initially. I have found that the use of the larger carbs minimizes mid-range jetting problems.

Jetting 101......pilot jet selection should be based on cold idle characteristics almost exclusivly. A engine that idles with the choke off immediately when cold is rich on the pilot and a engine that will idle with the choke on after warm is lean...pure and simple. The engine should idle on its own with stock carbs after approx 45 seconds of warm up and is generally close enough for jetting puropuses on bottom end if it will do so. Anything after 1/3 throttle doesn't use the pilot jet at all.

Main jet selection...no other part of the jetting process is more important. As a rule, for reliability purpouses, your engine should be jetted as rich as possible and still maintain crisp all out runs on a hot engine.I have also found that if you jet the main like this that mid-range transitional jetting becomes easier on ported engines, not to mention a engine that will flow as much air as my 12 port strokers.

 

I also understand that extra HP can be obtained with leaner main jet selection but its the risk that many of you are not willing to take, including myself except for closely monitored race day only applications.

In NO circumstance should mid range jetting be adjusted with main jets unless you are willing to take the above mentioned risk. Final main jet selection should be obtained with proper plug chops, adjusted to the point of YOUR comfort level, and mid-range jetting adjusted from that point with the main jet as a constant.

 

Reded, warm your engine up, plug chop the main to your comfort level and then run the bike at approx 45 mph in 6th(depending on gearing, approx 4500 rpm cruising speed), twist the throttle wide open. If it bogs out lift the choke momentarely at WOT and see if it gains power or loses it. If it gains, you need a thinner needle if youve already adjusted it to its richest setting.If it loses power, your rich and need a thicker less agressive tapered needle.

 

I would love to be able to give dead on jetting specs on all my engines, it would make my life much easier. But with all the variables, and they are infinate, this is just not the case although I do get luckier with the larger carbs....Jim

Edited May 23, 2004 by PassionRE

[cb67rs1]

I might give that a try, good thinking man. Did you do plug test to see if its too lean that way?

yeah we did, it seems to be just right, they were slightly brown, we might go a little larger on the mains though, do to the fact that the plugs look good but there is alot of heat we can tell from the pipes turning blue, like i said try some 310's and work your way up, running a little rich is always better do to the fact of your not over heating and you have great lubrication, less chance of tearing up the top end. good luck.

[PlaynSand]

Wll when I finally listened to Jim , I got mine right.

I am not worth a crap at reading plugs , so I just started going up on the mains until it would nose over or fall off the pipe real early, then backed off a couple of sizes .

Well it ran good but not real good , so I started playing with the needles when I finally hit on a combination that worked and it changed the whole power band,

You will shit yourself when you get the needles right and one clip on the needle makes a lot... of difference.

 

I got me a torque monster that revs like a drag bike .. What more could you ask for .

[Blue Duece]

I got me a torque monster that revs like a drag bike .. What more could you ask for .

ill second that, life is good with a fine tuned passion motor

[Banchetta]

Stroker motors usually run leaner on the needles than stock cranks. SEt the clip at the 1st or 2nd clip from the blunt end...One clip position makes a HUGE difference...DON'T lower the main jet, I almost melted a piston on trials w/ a 300 main....ended up w/ a 380 main.....You have to also go w/ larger intakes, v-force or pyramids, along w/ larger carbs....HUGE GAINS!!!! 9hp on the dyno. The stroker isn't much w/o the other intake mods.....

[PlaynSand]

Banchetta,

Mine is just a stock stroke ,

 

I am running stock carbs and intakes with V-force , do you think I would make any gains by changing to aftermarket intake or carbs ?? But don't want to kill my torque , Heck when running in 6th gear now I catch myself trying to grab another gear , I know I need to gear up ,I am going to get a 15tooth front sproket and try it . I do realize I won't be able to pull the higher gearing you stroker guys do .

[cb67rs1]

Stroker motors usually run leaner on the needles than stock cranks. SEt the clip at the 1st or 2nd clip from the blunt end...One clip position makes a HUGE difference...DON'T lower the main jet, I almost melted a piston on trials w/ a 300 main....ended up w/ a 380 main.....You have to also go w/ larger intakes, v-force or pyramids, along w/ larger carbs....HUGE GAINS!!!! 9hp on the dyno. The stroker isn't much w/o the other intake mods.....

that also depends on where you are and what main you need to bee running.

[Oilsmoke]

I am in the process of getting mine dialed in.

I changed pipes too. I went up 7 mains from my old setup and it wasn't enough so i went up 3 more too 400's on my Mikuni 34 mm round slides it's little fat on top but good for break in. i try a 390 next.

But it was flat on the 3rd clip so i moved it to 5th clip postion ( richer) and it got worse so i move it to 1st clip and it running pretty good but still a little rich But so are my mains. SO i am thinking the 390's will bring it all together. Oh even though i am little fat on jetting i can cruise in 6th gear and roll on the gas a scare the shit out of my self with This Passion 12 port Long rod engine. I am 45 year old man I been on fast bikes before and This is One Fast F*cker of a Engine. Those who think there Passion Engine Won't pull or Not run hard Better Learn to jet a bike. Spend the time and Learn beacuse there is a lot of power in any 2 cycle engine with spot on jetting.

 

Ps 26mm mikuni's on a Passion 12port is a Total Waste of Money. GET Bigger carbs, Plan and simple.

[Banchetta]

Banchetta,

Mine is just a stock stroke ,

 

I am running stock carbs and intakes with V-force , do you think I would make any gains by changing to aftermarket intake or carbs ?? But don't want to kill my torque , Heck when running in 6th gear now I catch myself trying to grab another gear , I know I need to gear up ,I am going to get a 15tooth front sproket and try it . I do realize I won't be able to pull the higher gearing you stroker guys do .

I've only dealt w/ testing stock crank/stock port and also testing the 4mil stroker w/ low end porting...I've never tested a stock crank w/ porting so I can't answer you there.....Jim would have a better idea than me on that.....I do know that stock porting hates larger carbs, the 4mil stroker gets larger hp and torque # w/ larger carbs across the whole curve......thats w/ low end porting!!!!

[rebelbanshee2]

I am running Mikuni 28mm flat slides right now with 380 mains and 30 on the pilots with the needle in the middle. And it really runs strong deffinately pulls stronger than my ported stock stroke. However it did run absolutely terrible untill i got my jetting on, jetting is huge on a 2 stroke. So i think you should be able to get it to run properly with the stock carbs, just not to potential. However, as soon as i can afford a set of 34s those 28s are gone! I cant stand having engine not to potential!

[Blue Duece]

i am little fat on jetting i can cruise in 6th gear and roll on the gas a scare the shit out of my self with This Passion 12 port Long rod engine.

i run mine like that too, just a pinch rich,that way if i wanna pin it for any length of time im ok....i think the 34's are a good combo on jims motor with a decent intake and reeds and some air flow......... mine rips right off an idle, even geared real tall it pulls hard .......i cant see running stock carbs or anything under a 32 with this motor, just doesnt make sense.....follow jims recipe and im certain your motor will run well, some of his last post was a polite way of saying i told you so...........pj 34's will wake that motor right up.....and with the 34's jetting is not a pain in the ass........

[Schizo]

I had that same dead spot before the powerband and for 4 months of trying to get rid of it now it is finally gone! I jetted and re-jetted till I was blue in the face, went up and down on the pilots, tried different needle positions and different needles and still could get rid of that flat spot Finally I went to K&N clamp ons and lightend the flywheel and after 4 months of tweaking with it I'm finally happy My jetting now is 178 mains and 48 pilots and it runs like a raped ape ALL throughout the powerband.