Jetting ?

[rootsnrocks]

Need some quick advice. I am pretty sure my main jet is too small. The bike runs great down low and mid-range is fine, but it just does not want to get on the bike and open up. I can sometimes get it to do it if I really try, i.e. today I held it WOT in a sand pit and after about 5 seconds it finally came alive... It's an 09 EC 250 and currently has a 180 main. I read the jetting post and I see other people with 180+ mains in the same elevation (sea level-1000ft) 80-95 F... I guess I will try to go leaner. How low can I go safely? I guess I am wondering if I should try a 175 or is that too big of a jump maybe I should try 178? Thanks for the help, really the first time I've had to play with jetting on a bike. It also has a ton of spooge out the exhaust prob from all the low speed riding in the tight stuff?

 

[noobi]

Need some quick advice. I am pretty sure my main jet is too small. The bike runs great down low and mid-range is fine, but it just does not want to get on the bike and open up. I can sometimes get it to do it if I really try, i.e. today I held it WOT in a sand pit and after about 5 seconds it finally came alive... It's an 09 EC 250 and currently has a 180 main. I read the jetting post and I see other people with 180+ mains in the same elevation (sea level-1000ft) 80-95 F... I guess I will try to go leaner. How low can I go safely? I guess I am wondering if I should try a 175 or is that too big of a jump maybe I should try 178? Thanks for the help, really the first time I've had to play with jetting on a bike. It also has a ton of spooge out the exhaust prob from all the low speed riding in the tight stuff?

Depends on the needle, and its position. You can run a rich needle with a small main and achieve similar results as a lean needle with a large main.
Although, it does sound like being rich.

 

[Jakobi]

Like Noobi said. The needle plays a large part as it overlaps with the main circuit. If its a rich needle providing extra fuel towards WOT then you can run a leaner main. If its a lean needle you may need a larger main.

Also you start your post also by saying you think your main jet is too small, but then state you want to go leaner. I'll assume you meant you think your main is too big.

I'm also going to take a stab here and suggest that its not all your main jet and quite possibly the needle involved too. If it was just the main that is rich, then no amount of open throttle at WOT will improve it. It will simply burble more. It sounds to me like you are too rich somewhere lower in the revs which is then loading the bike up and inhibiting its ability to rev out cleanly on demand.

As for making changes, I'd suggest 1 step at a time whichever way you do it. If its the stock needle (N1EF) then you should safely be able to run a 175/172 at those temps. If its a JD needle/yamaha you'd expect 178/180. Possibly 175 on a humid day or with some elevation.

 

[rootsnrocks]

Sorry, yes I meant to write I think it is too large.

 

[GMP]

Where are you located, and what are your complete jetting specs? '09 should have older PWK AS I carb with screw top, correct?

 

[rootsnrocks]

Located in MA (sea level, it's hot as hell here and humid 90F 90% RH). Yes the cap screws onto the top of the carb. I am going to try a 178 main, and I guess I would agree that perhaps it is loading up in the mid-range, would explain all of the spooge, and also why it is taking a very long time to clean it out when I am WOT on the main. I will try the CCK needle and maybe also the NEDW needle at some point. It has never ran right since I got it which I find very strange, got it from a "AA" rider, figured the jetting would be spot on... What is the exact model of my carb? Bike is 09EC250Race.

 

[Jakobi]

Stock carb should be a 38mm PWK AS1. I'd still suggest pulling the carb to double check the needle you have in there currently too.

 

[wasp4banger]

Located in MA (sea level, it's hot as hell here and humid 90F 90% RH). Yes the cap screws onto the top of the carb. I am going to try a 178 main, and I guess I would agree that perhaps it is loading up in the mid-range, would explain all of the spooge, and also why it is taking a very long time to clean it out when I am WOT on the main. I will try the CCK needle and maybe also the NEDW needle at some point. It has never ran right since I got it which I find very strange, got it from a "AA" rider, figured the jetting would be spot on... What is the exact model of my carb? Bike is 09EC250Race.

Fuel to oil mix also affects the fuel to air mixture, so if the AA rider was running more oil than you it would have been leaner

 

[rootsnrocks]

Good point but I doubt he ran more oil than 40:1 which is what I'm running...

 

[Jakobi]

Good point but I doubt he ran more oil than 40:1 which is what I'm running...

Yeah jetting depends on a lot of variables. Its possible he ran at 32:1, but more likely would be that it was jetted for winter. You'll also find people who are harder on the throttle will also require a richer mix than someone who puts around mostly putting little load on the engine for any period of time.

The best approach is to do as you are. Have a look and see what you have in there to start with. Make one change at a time and see how you go towards making it better. Down the track you can experiment with different needles if you want to improve economy/change the power delivery.

 

[GMP]

OK, I'm in NJ, and have jetted several of my 250s with AS1 carbs, including my new '12. First make sure the bike is sound. Good reeds, seals, PV opening correctly, compression, etc. Float level is correct. Slide should be #7, if by chance it is not, get one, a #6 will make things difficult. Next, forget about spooge, especially if you run a spark arrestor and double that if its a Stealth spooge trap. We jet the 250 by feel for torque, period. They like to be on the rich side for max torque, and WILL spooge. Also, much of the information here is relative to the newer AS2 carbs that tend to prefer much leaner jetting. IMO, the NEDW will be too lean, so don't rush out and order one. My experience with needles of the same straight diameter tell me this. Even the CCK is borderline in some 250s, and from my experience the AS1 equipped 250s prefer the richer D taper needles like a DDK or DEK. For the main, 180 should not be too rich with a fat tip needle like these. You could be flat on top from being slightly lean, not rich. I have gone as high as a 185 main and still had good top end. The best needle I have found for the 250 for our conditions is the JD Blue. Expensive kit but it really works well and makes great power throughout the range. You can start with a DDK and DEK (one half clip range apart) and get it very close.

Try this:
45 pilot
DDK #3
182 main
air screw 1.5 turns

DEK #3 is a half clip leaner, DEK #4 a half clip richer for fine tuning.
Go up on the main until it obviously rich and back down two sizes and you should be there. If you can get it pretty good like this, the JD Blue will drop in in clip #3 or #4 and it will be perfect.

 

[rootsnrocks]

Okay thanks Glenn. I will try that set up. It could very well be lean I really wouldn't know the difference at this point. The only reason I was leaning towards rich was because it does get on the pipe and start screaming if I hold it WOT long enough (happened in sand pit, there is no trail that I have found where I could hold it WOT long enough to get it to clear out... that's how long it takes not to mention it sounds so awful I felt bad holding it WOT...)

 

[Diggs345]

Glenn , is the jd blue needle the same in all the kits ,Or was it the red, i have one left over from a ktm a few years ago .

Rgds
Chris

 

[Jakobi]

Glenn , is the jd blue needle the same in all the kits ,Or was it the red, i have one left over from a ktm a few years ago .

Rgds
Chris

Glenn emailed JD regarding this a while back. How I read it I believe the 2T needles are the same across the kits and the supporting pilots and mains are what are swapped out along with his setup info.

The kits come with both blue and red needles (rich and lean).

 

[GMP]

Its the same in the old generic PWK kit as the new GG kits, thats for sure. It could be the same as the KTM kit needle, likely is, but only JD could tell you that. I emailed and asked, they told me, ask them.

Measure the straight diameter, it should be the same as a **K needle.

 

[Jakobi]

Even if they are slightly different I'd be willing to give them a go. I have found just about all the other needles the pumpkin patches are running have swapped over into the Gasser with good results.

 

[Diggs345]

I shoul be home this weekend , ill be sure to check

 

[Diggs345]

The needle is a jd red , side by side with the n1ef they are the same to about just under half way from the top down then the n1ef tapers off much slimmer

 

[Jakobi]

The JD red is many sizes smaller in the diameter than the N1EF. Not visible to the eye though The last taper on the JD is much leaner though which is why you see people running large mains with it (178/180), while the stock bikes generally have around 172/175 mains.

From memory the Red needle is either a H/W diameter.

 

[GMP]

If its a JD Red I'd put $$ down that its lean, because I have tried this needle in two different 250s. I had lean issues off the bottom as well from the lean straight dia. The needle has a large tip which controls fueling even wide open. Stay out of the sand WFO with this jetting!