Riddle me this carb idle circut Guru's

[TecateDan]

Okay so Jeff gave me a PJ38mm for my tecate 250 stock with DG pipe. trying to adjust the air idle screw and needle jet. INstructions say to warm up and get her idling then turn up rpm about 500 abve norm. Turn screw. If highest idle is less than 1 turn out put in bigger jet. If more than 2 turn out put in smaller jet. Pretty simple right???? So It likes a 62 pilot which is huge abour 1.5 turns out but it idles super fast and the idle adjustment screw is all the way down. The spring is fully closing the slide and the cable is loose??? What gives. IT's not lean cause if you pull the choke out it idles down and dies. Very confusing to me. I've tried every needle jet from 50-65 and it makes no diff when you get air screw set right it just revs to high at idle

[yaegerb]

Is there any air leaks around the intake boot? Crank case/cylinder free of air leaks?

[Dave8338]

I wouldn't rule out a lean idle condition, just yet. Even though it slows (hint #1) and then dies with the choke on, the fact that it slows suggest to me that you are still a little lean on the idle circuit. The choke on that carb, enriches the idle circuit via internal passages in the carb that draw fuel from the bowl and up into the venturi, correct? Meaning there is no choke plate that closes the venturi throat? The fact that applying the choke will momentarily drop the idle suggest to me that you are still lean. It may not be in the carb itself, however. Have you checked all the orings to see that they are sealing and not allowing un-metered air past? Crank seals good and tight? The DG pipe alone, will call for a rejet in most cases and especially so, on a two stroke. What was the stock jetting on the stock carb? Was the PJ carb new when you got it? They do "wear out" over time and make the fine tuning a PITA. Also, is the oil injection pump in good condition and adjustable?

[TecateDan]

All new seals and the problem is specific to this carb. Had a Mik on it and did not have high idle problem

Is there any air leaks around the intake boot? Crank case/cylinder free of air leaks?

[TecateDan]

Old carb. No oil injection. Carb was never stock to this bike but similar 250's had 55-58 pilots. Crank seals are all good!! It's specific to this carb it seems since motor did not have any problems with different carb. INtake boot is good

I wouldn't rule out a lean idle condition, just yet. Even though it slows (hint #1) and then dies with the choke on, the fact that it slows suggest to me that you are still a little lean on the idle circuit. The choke on that carb, enriches the idle circuit via internal passages in the carb that draw fuel from the bowl and up into the venturi, correct? Meaning there is no choke plate that closes the venturi throat? The fact that applying the choke will momentarily drop the idle suggest to me that you are still lean. It may not be in the carb itself, however. Have you checked all the orings to see that they are sealing and not allowing un-metered air past? Crank seals good and tight? The DG pipe alone, will call for a rejet in most cases and especially so, on a two stroke. What was the stock jetting on the stock carb? Was the PJ carb new when you got it? They do "wear out" over time and make the fine tuning a PITA. Also, is the oil injection pump in good condition and adjustable?

[shortline10]

Sounds like your needle and seat are worn or possibly the slide as well .

[Dave8338]

Gut feeling tells me the carb slide is worn. Are you using Keihin jets or DJ jets? The DJ jets run smaller than the same size Keihin jets do.

[TecateDan]

The carb slide does rattle around a lot. Well I have a brand new 40mm PWK air striker comming to my house friday for a 500. Maybe I'll try it on the tecate and see what the deal is..... they are knock of Keihin but said keihin when I bought them

Gut feeling tells me the carb slide is worn. Are you using Keihin jets or DJ jets? The DJ jets run smaller than the same size Keihin jets do.

[TecateDan]

Sounds like your needle and seat are worn or possibly the slide as well .

Brand new needle but the carb is older so may be the issue

[Dave8338]

The carb slide does rattle around a lot. Well I have a brand new 40mm PWK air striker comming to my house friday for a 500. Maybe I'll try it on the tecate and see what the deal is..... they are knock of Keihin but said keihin when I bought them

I'll bet she runs on that, right out of the box.

[JasonB]

x2 on it running perfect out of the box. nothing like ruling out EVERY ISSUE with a new part lol


and i see stuff about knock off jets being bad news bears since they usually are off and can cause you to have hell jetting a bike right with out burning it up

[fabiodriven]

Get that POS DG off of that fricken bike!

[TecateDan]

i'm doin that just to upset u. i like looking at the crf in my shop. It's also not causing the problem.

Get that POS DG off of that fricken bike!

[barnett468]

Okay so Jeff gave me a PJ38mm for my tecate 250 stock with DG pipe. trying to adjust the air idle screw and needle jet. INstructions say to warm up and get her idling then turn up rpm about 500 abve norm. Turn screw. If highest idle is less than 1 turn out put in bigger jet. If more than 2 turn out put in smaller jet. Pretty simple right???? So It likes a 62 pilot which is huge abour 1.5 turns out but it idles super fast and the idle adjustment screw is all the way down. The spring is fully closing the slide and the cable is loose??? What gives. IT's not lean cause if you pull the choke out it idles down and dies. Very confusing to me. I've tried every needle jet from 50-65 and it makes no diff when you get air screw set right it just revs to high at idle

Hello TecateDan


Sounds like you have your problem solved with your new Air Striker Carb so the following poat is just for general info.


The spring is fully closing the slide and the cable is loose??? What gives. IT's not lean cause if you pull the choke out it idles down and dies. Very confusing to me. I've tried every needle jet from 50-65 and it makes no diff when you get air screw set right it just revs to high at idle


All new seals and the problem is specific to this carb. Had a Mik on it and did not have high idle problem

You can only eliminate a seal leak if the seals are the same ones that were in there with the previous carb.

Xxxxx

Old carb.

Could be worn out slide bore.

xxxxx

Crank seals are all good!

Only a leak down test can determine that with 100% accuracy. Never assume anything.

Xxxxx

From dave8338

Gut feeling tells me the carb slide is worn. Are you using Keihin jets or DJ jets? The DJ jets run smaller than the same size Keihin jets do.

Xxxxx

The carb slide does rattle around a lot.

Most likely cause as dave8338 suggested. All carb slides should have minimal play. A round one shouls have around .002 clearance between the slide and carb bore.

xxxxx

Well I have a brand new 40mm PWK air striker comming to my house friday for a 500. Maybe I'll try it on the tecate and see what the deal is.....

Good this will most likely fix your problem but it may need jetting, it may also have a slight “bog” due to it’s increased size.

xxxxx

they are knock of Keihin but said keihin when I bought them

They are not a knock off of a Keihin, that's why it said KEIHIN on it. If it says Keihin it is a Keihin. Keihin owns the name and it is illegal for anyone other than Keihin to use the Keihin name unless Keihin licenses someone to do that which they never ever will. I’m pretty sure if someone did this it would annoy Keihin greatly and they would bury the ,fg of the copy” in paperwork and lawsuits since they have a bazillion dollars.

JD Jetting buys the std PWK Keihin carb from either CPW [carbparts.com] who is the East coast distributor for Keihin and Mikuni etc. or from Sudco International. Then they simply install their own jets and needle. I do not know if they do their slide/slide bore modification to them. Their jets do not flow fuel any better, worse or differently ie increased atomization of fuel etc. than the std Keihin jets. The ONLY thing jdjetting does to their "Airstryker" carb that is different than Keihin is supply a jet needle with a different taper/diameter than the original Keihin and possibly do their slide/bore modification.


Fuel screw #JDFM040-

The JDJetting fuel screw is more accurately machined and maintains the same tolerance as a Keihin fuel screw from the factory

To what tolerance is the fuel screw more accurately machined to? They do not say. This statement makes no sense, they can’t be more accurately machined than the original Kehin if they are machined to ”the same tolerance as a Keihin fuel screw from the factory” as they claim.


NEEDLES

JD Jetting has a red and blue needle in their carb kits. Keihin has 24 different needles available for the Keihin PWK carb alone. I doubt that the 2 needles that come in the jdjetting jet kit are any different than the ones that are sold by Keihin. One could think that perhaps jdjetting did some extensive dyno testing to determine EXACTLY what needles would work best in each style carb for each particular bike etc. I don’t know but that sounds like a lot of stock bikes to gather up to dyno but then how did they account for bikes that had porting, cam and pipe mods etc?


KEIHIN NEEDLES FOR PWK CARB.

http://carbparts.com/keihin/needles_..._34_39_jn.html
.

KEIHIN MIKUNI DISTRIBUTORS

http://www.carbparts.com/

http://www.sudco.com/

[El Camexican]

Okay so Jeff gave me a PJ38mm for my tecate 250 stock with DG pipe. trying to adjust the air idle screw and needle jet. INstructions say to warm up and get her idling then turn up rpm about 500 abve norm. Turn screw. If highest idle is less than 1 turn out put in bigger jet. If more than 2 turn out put in smaller jet. Pretty simple right???? So It likes a 62 pilot which is huge abour 1.5 turns out but it idles super fast and the idle adjustment screw is all the way down. The spring is fully closing the slide and the cable is loose??? What gives. IT's not lean cause if you pull the choke out it idles down and dies. Very confusing to me. I've tried every needle jet from 50-65 and it makes no diff when you get air screw set right it just revs to high at idle

I had exactly the same problem with my PJ38 on my 250. I replaced the choke/idle gizmo, the float needle, set the float height, etc. The slide has no wear. I think I bought every piece of brass they sell for that fr&Ekin thing. Finally I gave up bought a new 38 AS. Immediately my idle problems were solved. Like you I was putting in up #70 slow jets in the PJ. The AS runs fine with much smaller slow jets and it actually idles. One day I will look at that PJ again and see if I can’t get it to work and if not I will give it away to someone I hate.