2011 EC250 - Need Some Jetting Advice
 

Hello all.

I recently acquired a very nice 2011 EC250. I rode it for a solid 4 hours this weekend in the terrain I typically ride (hilly, rocky, very technical enduro type). All in all, I am beyond pleased with how much of an improvement this bike is over my previous bike (CRF230F).

However, I've got an issue with jetting that I'd like some help with. First, a few facts.

Bike is stock except an RB Designs head mod and carb mod. I don't know the exact "model" of the carb, nor the extent of the mods performed, but it definitely has the divider plate and is bored out to 39 mm. Pictures below. 178 main, 42 pilot, CEK needle on 3rd clip, #7 slide, and the adjustment screw (not sure if it's fuel or air) was only 1/2 a turn from all the way in (I haven't adjusted anything, just ridden it as is). Supposedly, the carb is exactly as it was when returned from RB.

The previous owner put in a new BR8ES plug before I bought it, and when I test rode it, and rode it around the farm just a bit at Christmas, I was absolutely blown away at how much off-pipe torque it made. This is my first 2 stroke, and I've always been partial to the power delivery of a 4 stroke, but this bike has blown my world open. And the power it makes on the pipe is equally ridiculous.

So, back to the "real" riding I did this past weekend. Elevation was 1500'-2500', roughly 30-40 degrees F over the day. The bike started off strong, but as the day drew on, I could swear that it was losing some of that low end torque. It was still pretty good, and would easily lug WAY down low, and made plenty of power up top. But it didn't seem to have that blow-my-mind low end that I remembered when I first bought it. Being that we're mostly riding enduro-type stuff, the bike wasn't being wound out on the pipe 24/7, but we've got quite a few big hill climbs, so it certainly wasn't just lugged around all day either.

One other tid-bit to know: I don't know which is "rain" and "sunshine" because I don't see any logos on my switch, but on the larger button (which I assume to be the sunshine), it runs great. But on the smaller button, it starts breaking up in the higher rpm. Not sure if that has anything to do with anything, but it definitely doesn't seem right.

When we got back to the truck at the end of the day, one of my friends suggested that it was rich based on the spooge out of the tail pipe. I know that's not always a good indicator of the jetting, but between that, the amount dripping out of the powervalve drain, and the fact it's mixed only 50:1 with a very low flashpoint oil (Maxima Bio 2T), it's probably a little rich. Pulled the plug, and at least to me, it also shows it a good bit rich. Pictures of both the tailpipe and spark plug below.

Being a little rich on the pilot wouldn't surprise me, because even after sitting all night at ~15 degrees F, and it only being about 25 F in the morning, it fired right up on the choke on the first kick, and idled perfectly with the choke immediately turned off.

I had a spare plug, and swapped it in, and took it for a quick rip before loading up for the day. The difference was massive. The low end torque was completely back, and the bike was as awesome as I remember it being. The new plug completely fixed it, though I'm not sure for how long.

So I guess I've got 2 questions.

1. What are your thoughts on the jetting? Should I go a little smaller on the pilot? Different needle?

2. Is this a typical thing, for the torque to go away some as the plug gets gunked up, and a new plug restores this? I'd always been under the impression that plug was either fouled and wouldn't run at all, or it was fine. I didn't think there was an in-between.

Thanks in advance for the help!

http://i.imgur.com/EBlOguHl.jpg

http://i.imgur.com/QCAF0nal.jpg

http://i.imgur.com/NCyyEOYl.jpg

http://i.imgur.com/PVhX0JVl.jpg

You should be spot on I am running the same set up on all my bikes but we ride 5-9000 ft in colorado I did change my needle to a jd blue it pulls better in higher gears I do run the briex8 plug though klotz R50 40:1 100 octain race gas hope that helps

You run that same jetting at 5k-9k? That sure seems like it'd definitely be rich way up there.

Overall, yes, the jetting is probably quite close to what it should be. It cranks easily hot and cold, idles nicely, lugs very low, and is overall very smooth throughout the rev/throttle range. No weird hesitations or bogs or anything like that.

Only issues are:

1. Doesn't run right at high rpm in "rain" setting
2. Noticeable loss in low rpm torque after some time riding, which was completely regained with a fresh plug

I'm simply unsure if those are things to worry about and try to fix, or just forget it and live with them.

How much time on top end

Unsure. Previous owner stated a recent rebuild (<15 hours), but I don't have a way to verify that.

Based on how it runs, my guess is that it's not very much.

On my bike I wire it in the "sunshine" setting and discard the switch. The rain setting moves all the hit to the bottom and then as you have noticed signs off early, exacty opposite what you would want when it is slick ,imho.

In doing some reading about needles, jetting, etc., I came across something interesting. Check here:

http://www.gasgasrider.org/forum/sho...highlight=n3cj

Specifically, post #37. The poster says that he is seeing a noticeable power loss after the bike gets fully warmed up.

After thinking about it, this could actually be accurately describing my situation. It may not be the fresh spark plug that regained the power that I noticed had decreased, but instead could have been the fact that it was sitting in 30' F temps for over a half hour while we loaded all the other bikes up, and thus drastically cooled down. The head/plug was completely cool to the touch when I changed it. In addition, none of the previous riding I'd done on the bike prior to this weekend (test ride before buying, puttering around the farm a bit at Christmas) was really enough to get the bike nice and warmed up, so that may be the reason it always ran so well.

The other poster points out that this could be the result of a lean condition, which actually makes sense. A few posts later, the OP swaps in a richer needle and a richer pilot jet, and seems very happy with the results.

I'm actually beginning to think this is what's going on with my bike. I think the pilot / air screw may be a touch rich, based on how easily it starts and idles cold. The main is probably pretty close, based on how well and cleanly it runs. And the needle/clip is on the lean side. As the motor gets hot, it gets leaner, and with the needle/clip a little lean, it shows as a loss of torque in the 1/4-3/4 throttle range (where I ride at 90% of the time).

Upon a closer inspection of the plug with a magnifying glass, I actually don't think it's rich at all. The top of the threads and the ground strap are black from the oil, but looking far down inside at the insulator, it's a fairly light tan color, indicating that it's somewhat lean.

I think I'm going to order an NEDW needle to put in, and actually tune the pilot / air screw / idle, and go from there.

Do you know for sure if the big button or little button is the sunshine? My switch doesn't seem to have any kind of markings.

Thanks!

2011, small button = rain, large button = sun.

If the NEDW gets you close keep in mind that NECW is a half clip leaner.
So NECW clip#3 is in between NEDW #2/#3.
In my (limited)opinion these needles (NED #2/NEC#3) work pretty well 0degC to 35degC 70%humidity 0-3000ft.(New Zealand)'13 200
You look a little colder,humidity? Prob start with NED #3
The bottom is smooth and progressive/stepped rather than on/off up onto the pipe,good mid to top.Hope it works for you in your conditions!!

Thank you so much for confirming that!

I'm having 2nd thoughts about the NEDW. I know a lot of people are saying it's smooth, but I've seen it reported several times that it runs lean lower in the throttle position, and isn't really anything exceptional regarding low end torque. I'm not so convinced yet that it'll be better from the CEK I've got now.

I'm now considering just trying to tune the CEK. Overall, everything works pretty well other than the assumed lean condition at mid throttle. Raise the CEK needle a clip, which should just add a set amount more fuel across the mid-throttle range, without changing off-idle or WFO, and see how it does.