Another PJ34 jetting thread

[royalt67]

Ok, guys, I know this has been beat to death a bit but I'm getting a bit frustrated with the PJ's choke/idle speed combo knob.

Standard jetting recommendations for this carb are genereally 50-55 pilot and about a 155 main. At this point I have a 35 and 155, idle mix about 1 1/4 turns out. I put in the 35 because it was the only pilot that i could get it to idle with, and then only with the idle speed all the way up, giving it basically no choke. That's ok for the moment because it will start without it.

The problem is that it has very little low end. No holeshot, a stocker can beat it off the line with the right rider. Won't pop a wheelie. This annoys me considerably, lol. BTW it screams on the top end and I just did a leakdown and fixed some leaks. Throttle response is improved but low end power still kinda sucks.

My gut says put in a fatter pilot, but idling is important. I see some guys adjust that with the cable, and I'm starting to lean that way, but obviously that isn't how honda did it, and they used them for years on CR125s and TRX250Rs. So PJ users, please weigh in on how you have dealt with this prob or whether it gave you a problem at all

 

[Kgibson]

I have the carb and had the same isues. I was at a 35 too and turning the idle all the way to the choke also. I called vito's and they sent me a needle that they send all the pj's out with. Big diff, I am now at a 42 and it idles perfect. I would check the # on your needle then call and see if there's is differant. Hope it helps.

 

[Vootie]

My Tecate 250 has a 36mm pj and it will not idle. I've tried slow jets from 42 all the way to 60 and no go. I really hate this carb and will be ditching it for a pwk soo. It really is a terrible idle adjust design.

 

[super noober]

i must of bought the nicest 34mm pj ever made lol I:I. mine idles like a champ and responds to twisting the idle/choke knob almost instantly. with my mods ive got a 55 pilot and a 162 main.

 

[super noober]

ok, here is a vid of my 34mm pj, first start of the day, no choke. i looked and i have a slide that has a 42 marked on it so mabey that is the key. i hear so many people hateing on the pj's but i really like mine..

 

[hotrodaj_2]

I've had no probslems with my pj34. It responds to idle adjustment and idles fine. I would try the needle change first. The PJ34 is a low end carb anyway. She should scream off the line when adjusted right. The only thing you havent tryed is the needle, try that dude.

 

[yb200]

I have the carb and had the same isues. I was at a 35 too and turning the idle all the way to the choke also. I called vito's and they sent me a needle that they send all the pj's out with. Big diff, I am now at a 42 and it idles perfect. I would check the # on your needle then call and see if there's is differant. Hope it helps.

what needle are you running gibson ?

 

[Kgibson]

The #DGH was like night and day on ours. Wouldn't idle no matter what I did with the pilot. Now the knob actually works.

 

[CC&Fabb]

I dont even mess with the idle/choke on the PJ's. I just adjust with the cable. Save yourself the headache.

 

[CC&Fabb]

Oh and its a 2 stroke, its not really suposed to idle.

 

[Blasterdude27]

Oh and its a 2 stroke, its not really suposed to idle.

What? Thats like saying a 4storke isn't supposed to rev high.........
You have to let them sit there and idle on a cold start to warm them up, otherwise you WILL lose lots of engine life.
If your bike can't idle its a air/fuel problem.

 

[musselman]

I have been messing around with mine for a while. Right now I have a 58 pilot and the idle tends to hang a bit (lean) but it does idle. I'm thinking I need to go to a 60 or 62 maybe.

 

[Awk08]

turn that piece of sh*t choke/idle knob the whole way down, hit yourself in the head with a big f 'in hammer so you get amnesia, and forget that silly sh*t
adjust the idle with the cable at the thumb throttle
next get the needle kgibson suggests, DGH <ftw , THANX GIBBY!!!!!!!
just put mine in last week, and my ken oconnor ported/f7 piped bike is now almost uncontrollaby wicked !!!!!!!!,
gave me back all my bottom end i lost when i first installed the 34
with the ??? klh needle???? < or sumthin like that,
and will pull the front end up, at will, and sometimes unexpectedly, in any gear< if your at that gears speed
oh and i'm running a 45 pilot, will not start without the choke when cold, but fires first kick everytime after warm up, airscrew somewhere under 2 turns, revs very cleanly with no hesitation at all like the old needle had
and 155 main, < may try 1 or 2 larger since the needle exchange, but plug looks good, and why mess with perfection
compression has been at solid 152 ft.lbs, since doing the heat cycles 2/3 months ago,
i check it weekly

 

[royalt67]

Thanks, guys. Lots of good, useful responses. Although adjusting with the cable seems to work for many people, I think I will try the "right" way first. My PJ is off a 250R (I think) and obviously there are some differences in the experiences that people are having. It makes me wonder if the guys that have better luck with this carb are people who bought the aftermarket versions, as opposed to used off dirt bikes or quads. It wouldn't surprise me if there were differences between the bike and quad versions as well. I will look and see what needle mine has and go from there. Slide could be an issue too, since the cutaway would be the only passage for air at idle.

Here are the specs that Carb Parts Warehouse uses for their aftermarket versions.

Size Main Jet Slow Jet Jet Needle Throttle Valve
PJ 34MM 67R #152 #55 48CEG #6.0
PJ 38MM 67R #168 #62 48DGJ #6.0

Comparison between this and my carb to come soon. Feel free to add your own info if you haven't already. I went with this carb because it was supposed to have really good low end, but it doesn't yet. It can't just be a junk carb, there are too many of them out there. Hopefully I can figure out the perfect combo to chew up those Rappy 250s we race against.

 

[Erwin8r]

IMO, the PJ was a good carb... but it has been surpassed by the PWK. I hated the PJ's on my Banshee. They were a hassle to get "just right." When they worked, they worked just fine--but life is so much simpler with the PWK's (or Mikuni TM's...)

 

[royalt67]

Probably, so. I was just told that the PJ34 was the way to go for low-mid, while the PWK35 is the ticket for mid-high. With that in mind, the PJ should be a good choice for the budget as well, being stock on several popular models. (but yeah, I like my PWK better too)

 

[Awk08]

someone explain to me how adjusting that choke knob, which supposedly adds more fuel, makes it idle higher without adding more air, the only way i see to add more air/fuel is to pull the slide up in the bore
just adding fuel should not make it idle higher??????

 

[royalt67]

Yeah thats why I want to look at slides as well. The choke/idle is actually a mixture of fuel and air, thats where the air screw sends air, but it seems like the cutout of the slide would provide needed air too, without raising the slide with the cable.

 

[royalt67]

Just checked my carb. the slide is a 6.0 and the needle has no number. Guess I will order a new DGH and try it out.

 

[royalt67]

Update

So, the "stock" settings for an aftermarket PJ34 from either Sudco or CPW are:

Size Main Jet Slow Jet Jet Needle Throttle Valve
PJ 34MM 67R #152 #55 48CEG #6.0

KGIBSON says Vito sold him a DGH needle.
Duncan Racing's recommendation to me was 6.0 slide, 52-58 pilot, 165-170 main, 1 1/2 turns, CGJ needle. (just found my notes, i forgot they specified the needle)

I am going to buy a CEG (stock), DGH, and CGJ from Sudco. I was able to find what I think is a CGJ at my local shop and will try it this weekend. It has OEM style numbers that I have learned to decode with info from the Sudco catalog. (BTW their catalog rocks with good info, mikuni or keihin)

So far, I've come to the conclusion that the needle is a critical component that many of us are leaving out of the equation when jetting our carbs. Sure, changing the Main jet sets the ultimate upper end of the powerband, but the needle controls how you get there. Just as important, although many people feel that the main and needle only affect off-idle and upper end performance, this is obviously untrue. Because the Main jet tube is located directly under the slide in the path of airflow, fuel will be pulled up this tube even at idle. The amount is controlled by the diameter and depth of the needle, and the strength of the vacuum signal. This is why you must determine a main jet first, it affects everything else. (Sorry if I am repeating something you know but it helps me think) Really, the needle is the brain/controller of the whole works, with taper controlling how fast the transition occurs.