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Romney1

Rmx250 1995 project

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How come on ebay when I look for needles it states suitable for pj and pwk carbs? 

Does that not mean they can be used for both ? 

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Well yes, and no

A PJ 38mm uses the same length needles (aftermarket F,G,H) as a PWK 36mm, but the PWK 38 calls for shorter length (aftermarket C,D) length needles.

So, it depends on the size of PJ or PWK your working with....

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How come iv seen people that swap the needle from there pj and all the same jets on other forums and use the pwk that way   Could i not swap my pj carb needle and give it a go before i remove the pwk and see what happens 

also you say you use the newer rm needle in your rmx short body pwk carb . Why do your you think it wouldnt work for me , im sure the issue is the needle As it doesnt look the best it doesnt have any markings i only know the spec from the listing on ebay so chances are it could be anything .

 

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Because I’m trying to “recommend” things that might work for you and are not foolish. If you want to replace a D length with a G, go for it. It’s your bike.... Then again, if the China clone needle was anything similar to a real DDJ needle, you wouldn’t be having carburetion issues you have now and be riding it. I can say that in a genuine Keihin, 45, DDJ, 180 would, and has, run well on my RMX. Only (minor) issues I had with that jetting setup was starting diameter, and slightly rich main, so I replaced the DDJ with a DDL and used a 178 main...

OEM needle, used in a OEM YZ carb, with a programmable CDI that works the Power Jet in a “tweaked”, but OEM type of way. Even though starting diameters differ, the NECJ provides the same off idle A/F ratio as the DDK did in the aftermarket PWK I was running which tells me the needles “jet” are different size between OEM and aftermarket carbs. 

Since you have neither OEM or aftermarket Keihin, and are working with a clone, maybe it will, maybe it won’t.

Without the CDI to operate my power jet, (which is providing about 20% of my fuel above 40% TPS and 4500RPM) my NECJ is VERY lean mid TPS position up, and runs like 💩... I’m not going to go disconnecting my Power Jet to see if I can run a clip lower to fudge a Power Jet type needle to run without one...

If you have micrometers and calipers, measure your clone needle and compare the measurements with real DDJ provided here;

https://jetsrus.com/a_jets_by_carburetor_type/needle_keihin_N427-48.html

Remember, I do not own a clone carb. You do. Like I said pages ago. If known genuine jetting does not work on your clone, and no one with a clone chimes in here, your pretty much on your own.... Testing, and reading your plug is the ONLY way to get it right....

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Found a company that will set my bike up on the dyno 40 mins away for £40 im not messing about and getting stressed over it ill leave it now and let someone who knows what there doing tune it to perfection :) he seemed extremely knowledgable and said he will 100% sort it 

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Thats what he said bring the pair , now i can sleep at night , cant do it till January now as i can only get there on weekends,

Im think i might buy one genuine needle to give it a fighting chance at tuning it do you thing a ddl ?

 

Edited by Romney1

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Can you also look on this site in the shop and tell me what section of needles is correct for the pj carb its all in numbers and im not sure also a needle close  to the standard needle or the one you used after 2 years ? 

Site might also be useful for uk people to find replacement parts for there carb and the prices and service is good 

http://www.allensperformance.co.uk/shop/

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Ok well went to town on cleaning the old pj carb and stripped it completely and checked everything with the manual i found that the rubber was missing from the idle screw so replace that with a new 1 and the small washer behind that and set the float hight to 16mm new 55 pilot and 180 main the needle in the middle clip  air strew at 1 and a half 

bolted it on first kick with choke on and the bike sounds like completely different bike more ting ting sounding and revs seem to fly up now .

i didnt mess to much  but i got it to idle aswell but I noticed if i turn the choke nob to far upwards the revs seem to hang when the throttle is blipped . I need to adjust the air screw correctly to make it not bog when snapping the throttle ino it’s possible as i did it but didnt count the turns so ill see at weekend result think I might be getting somewhere.

i also look down into the needle jet to check for anywear and ovaling but seems all good .

i also noticed the smoking of the bike has changed to nearly none even when cold 

Edited by Romney1

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Excellent. :thumbsup:

Sounds like a definite improvement. Take it for a ride and see how it does with the needle that’s in it. Wouldn’t be a bad idea to mark your throttle grip at 1/4, 1/2, and 3/4 positions so if you have an issue, you know which circuit needs adjustment. Since jetting is new to you, another thing that may help (or possibly improve performance) is to try different needle clip positions. That way you know what it feels like when your 1/2 throttle position is too rich, or too lean.... Once optimal clip position is found, then work on WOT with plug chop tests. Plug should be a nice mocha brown.

With those two things done, then we can look into your needle starting diameter. The goal here is to lean it out just enough to keep plug from getting excessively carboned up (black or wet looking), without feeling a loss of power at partial (steady cruising) throttle position. 

The Jetsrus link I provided above is the correct series needle you need. N427-48

As for a needles similar to OEM or optional RMX, that is covered in the conversation chart within above link. 

99B615A5-649E-47F9-863B-A9AC19703ED8.jpeg.30c6870b57610fd3fde751112c481623.jpeg

As you can see a 1470N is shown in the examples. Closest option is a DGL. To figure out which is closest to a 1471, or a 1473, simply look to the conversion table. A “71” is similar to a “M” and “73” to a “P”. Unfortunately there is no DGP available, so your closest options there are either a DGN, or a two steps leaner, DGQ.

Lets see how it goes with your current needle before ordering. If cruising is not all that smokey and taking awhile to carbon up plug you might try just two steps leaner (DGM), but if real smokey and plug is looking wet, then a DGN or DGQ might be best.

Oh, and on the hanging idle, that is a common characteristic of our US RMXs’ also. Many think it’s a carburetor issue, but in fact it is due to the timing curve of the CDI. Discovered this when I first installed the programmable Zeeltronic ignition on mine. Stock, RMX idles with absolutely no advance (0*) up to 1500RPM, then makes a pretty drastic ”all in” jump to 16* BTDC at 3000RPM. That’s why it hangs, and sounds like it’s laboring at idle. It is.... Not much can be done about that besides set idle speed just high enough to not stall, and low enough not to hang up at 3000RPM...

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Well today i was hopeful to get on the bike but started with the snapping the throttle when warm iv managed to get it to do so but the Air screw have to be 3 quarter turns out from closed if its above it bogs out when snapped and even dies if i roll the throttle slower it can rev up but not snap . 

I have marked the throttle like stated but it started to piss down so unable to hit the road soon as i get chance im looking forward to testing it out .

like you said if i adjust the idle up to much when i snap the throttle the revs hang higher than normal for about 5 seconds then drop slightly lower once more . Iv also noticed if you go higher on the choke nob rotation you need to adjust the air screw again to be able to snap the throttle 

cheers 

 

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