38mm PWK needle?

[3wheelrider]

Does anyone run the needle(DDJ) that the 38mm PWK carb comes with-on their stock 85-86 250R cyl. with no porting or mild porting? Or is this needle usually too lean/or too long/short,taper off? for a 85-86 250R? I know what the digits are for and have the needle chart. Just want to know if anyone runs it and what their mods are. Never had a problem-just wondering:wondering------------

[RIDE-RED 250r]

I haven't yet memorized the letter system for the needles other than lower in the alphabet is leaner.

But based on advice from many whose opinions I trust, I have DGH needles in the big bore and the stock cylinder. I am told the DGH is a good safe needle that is usually adequate to dial in for performance.

I find that I can drop the needle on both of my engines to the point there is a lean stumble, so I can't imagine they are overly rich. I have had good results with the DGH needle profile.

But looking at the chart, it appears you are just a tiny bit leaner than a DGH. And if I am understanding it correctly, It looks as though your needle will have you beginning the transition from the pilot circuit to midrange a tad sooner.

[TecateDan]

I run the stock needle on my kxt500 and have a special needle for the kxt250, I'll look for it tomorrow

[85250r313]

i have ddj in a 38 pwk as. the top end is esr 72 mm. makes so much power on top i just recently realized how terribly lean in the middle it was. i just got an envelope from jetsrus with 4 richer needles. problem really showed up flat track racing, hold throttle at half and sounded almost like a diesel. I also have the digital cr250 ign, dont know if that affects jetting much but it might. ya might fish around internet, there are some good websites out there for two stroke tuning and theory.

[3wheelrider]

So from DDJ to DGH (taper/length/diam.) the greatest difference is the length of the needle- (over 3mm diff.)!!! The taper is the same and the diam. is not really much different- one size down-but very minor diff. But why would I use a "G" length that is over 3mm. longer? -I realize many people run that DGH but not sure if I should change it or leave it. Seems fine tho? Odd tho because with the shorter needle my main is still on the big side. I just went down to 172. Needle was in the middle but now on 4th pos. -Main is still on the big side but runs great. Never had any sputtering anywhere.:wondering . -Just leave it?

[Mosh]

I just went through this whole fiasco 2 weeks ago on one of My 250R's with a moderately ported top end, shaved head, PWK 38 carb, and ESR pipe.

I had one hell of a time getting it dialed in. No matter what I did starting with a 45 pilot and 172 main this thing had the must disgusting mid range, burble coming onto the pipe, that I chased for a week.(Most probably would have rode something like that and felt it was fine, but I like my stuff CRISP)...

I went down to a 168 leaned the DDJ needle all the way out, did not help..Dropped to a 42 pilot and needle in middle, not much better. I won't go through the whole gammet but after various mains, pilots, and needle movements, etc..... In the end, I was down to a 40 pilot and a 165 main needle all the way lean to get it liveable. After talking to my engine porter, he said that he never had good luck tuning anything other than the DGH. That DDJ offers virtually no tuning curve to it IMO, and as soon as I can I will be switching that DDJ out for the DGH. I would like to have some adjustment in the needle setting for finer tuning and that DDJ won't allow it. The only way I can get it not to burble coming up on the pipe, is if I lean the needle all the way. DDJ stands for "dirty dam jetting" IMO...At least that is how I will remember it from now on...

If you end up keeping it that way with the DDJ, I will buy the DGH from you.

[3wheelrider]

Mosh-I dont have the DGH needle-just wondering if I should tho since ive seen it mentioned alot on another site. Isnt it
easily avail. on ebay?-etc.? Ive wanted to try it but a 3mm+ difference is what Im amazed about..... gonna change
jetting alot I assume.

[RIDE-RED 250r]

PJ Motorsports, Jetsrus are the 2 places I get most of my carb stuff from. The needles are pretty cheap.

http://www.jetsrus.com/individual_parts/017_033_su.html

[Mosh]

Mosh-I dont have the DGH needle-just wondering if I should tho since ive seen it mentioned alot on another site. Isnt it
easily avail. on ebay?-etc.? Ive wanted to try it but a 3mm+ difference is what Im amazed about..... gonna change
jetting alot I assume.

Oh I am sure you will have to re-jet if you change the needle. I run 2 very similar engines on PWK carbs. One is a air striker 38, and the other a quad vent PWK 38. (That is the one with the DDJ I had issues with) I run a 42 pilot and 172 main with the DGH in the middle posistion in the 38 air striker, but as I said earlier I am down to a 40 and 165 and the DDJ needle is all the way lean on the quad vent PWK.

I see some are saying that in theory the DDJ is a leaner needle, but according to this chart, the DGH is a leaner needle. Some guys were describing "lean" stumbles or symptoms, but mine was exhibiting a rich stumble coming onto the main and needle transfer that would eventually clear out at WOT. If I rode it at 1/4- 1/2 throttle long enough it would start to foul the plug. I pulled the plug when it acted that way at those throttles and it was wet. The 3mm shorter DDJ will be coming out of the main quicker in the slide opening allowing more fuel through the main the way I understand it, which were in line with my symptoms of being too rich transferring to the main jet. Of course I have been known to confuse myself with over thinking it. I had no idea the 3mm difference until you posted this thread, so I learned something that explains the problem I was having.

http://i6.photobucket.com/albums/y210/Supertrunk/03%20KTM%20200SX/BasicKehinNeedle.jpg

[3wheelrider]

If I put that needle in -then I Imagine its gonna want bout a 200 main jet if it ran fine with a 180-lol and a 60 pilot -ran
fine with a 55?- not sure why it accepts so much fuel already with no symptoms of sputtering. I love this
QV/AS as is because seems to be real forgiving & runs great regardless -compared to the stock 86 carb I had-but if I can improve tuning/perf. even more then-I will...

[El Camexican]

Maybe this link will help with figuring out which way to go
http://www.jetsrus.com/a_jets_by_carburetor_type/needle_keihin_N427-48.html

I (on a different 2 stroke engine) was having the same issues in that I was having to go too lean on my pilot in order to get crisp acceleration using my stock needle at any setting and most troubling of all was that if held at a constant RPM just below the “hit” the engine would knock and rattle like it was full of marbles unless I raised the needle to the point of making it too fat. I ended up ordering a JD kit for my engine and of the two needles (red/black) the red needle seemed to improve things a lot, but not 100%. I drove like this for almost 2 years. FYI the jets they send are just standard sizes to get you close, I don’t even know why they include them. The money you spend is for the needles.

Fast forward to getting a head modified (shave and reshaped combustion chamber) last year and I was able to use the stock needle again, drop a pilot size and eliminate the knocking sound completely, it absolutely rips from the bottom to the power band now with the only complaint being that if I lock the rear brake up going downhill it won’t fire back up in loose rocks due to the added compression, but it still runs on pump gas.

Again, not a 250R engine, but if there is a reputable builder out there offering a reshaped dome for your engine you may want to consider it before you get too far into your tuning. For $60 it was the best bang for the buck I’ve ever gotten.