Killing the bike

S

singletracker

New member
In the last two enduro's that I've been in I've killed the bike several times. It's usually either when going down hill or into a tight corner.

I try not to lock the back wheel up, and if I have to I use the clutch to avoid killing it, yet I kill this bike more than my previous two stroke bikes (KTM 250's). I also try to focus on giving it a little gas when braking hard into corners to avoid killing it. It usually happens when I'm pushing hard in race mode, so some of it could be rider error, but it is easier to stall than what I am accustomed to. Maybe I'm not pulling the clutch in far enough at times? The clutch is a little touchy.

2011 250xc Race +- 35 hours, compression 190 psi
MJ 175
PJ 40
NECW#1
A.S 1.5
Temps: 80's-90's
Elev. +- 700ft

Rider: +40A hare scrambles, +40B enduro

What would you adjust first to improve this? Does the Race version have a lighter flywheel than other models?
 
You can check the flywheel by looking where the ignnition harness comes out from the stator cover. If its ten o'clock then its a 2k2 (lighter). Two o'clock is 2k3. You can still get fly wheel weights for the 2k3 if you think it would help.

Does the clutch drag? Does the bike idle well on its own in gear clutch in?? Try bumping the idle speed up a touch?
 
As Jakobi said about the idle, and set it so that in gear, with the clutch just biting, it is high enough to keep turning itself over.
Also check the clutch for bite point. if it is too switch like it can lead to stalling. A little free play in the lever may help.
Have an experiment with the lever positions and such. :D
 
This clutch fix takes a lot of time and patience (and maybe a small dose of OCD), but is otherwise free and should make your clutch work well:

Clutch Fix pdf

I found adjusting the rear brake pedal biting point quite far into the downward stroke of the pedal, so that dragging is within comfortable reach, but locking the brake is quite a stretch, is a help on steep descents where it is easy to hit the brake too hard and lock up the wheel.

[Edit: The original thread for the clutch fix is here Credit is due to the writer - he clearly put a lot of time into producing the article]
 
I'd guess its your idle/low speed jetting thats a little off, causing it to stall when you chop the throttle. My '12 250 has a light flywheel setup and never stalls. That NECW #1 sounds super lean to me even with the new carb.
 
A little more info and a couple of more questions.

I have the idle set so the bike will idle with the clutch in while in gear, but it is a slow idle. The clutch seems more on and off than what I am used to, so it is a very fine line when slipping the clutch. However, the clutch pull is very light, which I like.

I am not 100% my jetting is as good as it can be even though I spent about 5 or 6 hours experimenting with it about a 1.5 weeks ago. I like a smooth strong power with very little hit.....any further suggestions here? I was thinking about upping the PJ to a 42 and using a NEDJ needle. During my latest jetting session I was convinced that the 42 was a little rich, but with temps dropping a little it might be the ticket.

I like the article on the clutch work Caravan Monster provided, but I think I will try changing oils before going to that much trouble. I'm using Motul 5100 10w-40 synthetic blend. I may try ATF next since it's cheap and I had good luck with it in other bikes.
 
I have a similar problem, but haven't done anything about it. I wind up stalling my bike more than I like. It's always with the throttle closed and probably due to the low idle speed I have set. I do this to help reduce knacking as I'm mostly a slow speed rider.

Once in a while I stall it from being too aggressive on the brake before I've pulled the clutch in. I might go to a 42 pilot to improve things. I believe lean jetting contributes to this issue since I added a flywheel weight and noticed only slight improvement. The bike can lug right down and pull great as long as I keep the throttle slightly open.
 
A couple of other things to think about are tire choice and front suspension. Some tires don't provide much braking so are pretty easy to lock up i.e. trials, Metzler MC5. If the forks dive too much when braking you will unload the back tire making it easier to lock up.
 
Neil E. said:
I have a similar problem, but haven't done anything about it. I wind up stalling my bike more than I like. It's always with the throttle closed and probably due to the low idle speed I have set. I do this to help reduce knacking as I'm mostly a slow speed rider.

Once in a while I stall it from being too aggressive on the brake before I've pulled the clutch in. I might go to a 42 pilot to improve things. I believe lean jetting contributes to this issue since I added a flywheel weight and noticed only slight improvement. The bike can lug right down and pull great as long as I keep the throttle slightly open.
Click to expand...

It sounds like we are experiencing about the same thing. I'm glad you brought up the flywheel weight. I was thinking about that option, but I really don't want to add more inertia if I don't have to.
 
Dave said:
A couple of other things to think about are tire choice and front suspension. Some tires don't provide much braking so are pretty easy to lock up i.e. trials, Metzler MC5. If the forks dive too much when braking you will unload the back tire making it easier to lock up.
Click to expand...

Dave, you might really be onto something here. I'm going to pay more attention to that the next time I ride. I'm about 170 lb naked, so probably about 195 lb ready to race, and I'm using stock springs.
 
That bike has more than enough inertia now, there is a big weight under the primary pinion gear in addition to the ignition. I think if you dial in your idle/low end jetting you will be in good shape.
 
Glenn, the OP's bike is a 2011. Did these get the same primary gear crank weight as your 12? Does this only apply to the Race models?
 
Not sure, but it will have at least an 8 oz, mine is more like a 10 - 12 from the size of it. But add that to the 2k-3 and its A LOT of weight on a 250 for an A class harescrambles racer. I wouldn't be looking there for the problem.
 
One interesting thing in this discussion is that the pinion gear weight possibly could be used to replace the pinion gear spacer for those few people with estart bikes who want even more flywheel effect.

This assumes that the 2K3 bikes have a spacer that is the same width as the gear weight. Adding weight on the primary drive side is the best way to add inertia (less stress on the flywheel key).
 
Neil,

Yes, absolutely. The pinion originally had the CB drive gear behind it. then they went to a 10 oz round weighjt, 8 oz eccentric, and now what I have. The old MC motocross models just had a small spacer. Does your estart bike just have a spacer?
 
I agree with Glenn that thats some lean jetting. I have run similar temps and put in a stint on my 300 with NEDW#1 which I thought was too lean. The pilot and main both sound good.

I have my idle set up low to stop the knacking and tanging on decel as well. I occassionally muff it up and stall the bike as well. I put it down to rider error. The bike will fire up again first kick and take off.

One thing that pops to mind, my bike needed really really lean jetting with the stock engine or else it ran rough as a dog right up to half throttle. It was also hard to set the idle and have it ru consistantly. If you haven't done it yet, I'd strongly consider a head mod to help make things more stable. Then if you want to throw money after it, I hear those recluse things make the bike all but unstallable.
 
I haven't done the head mod yet. Is RB the only option in the U.S.?

So do you guys think I should just raise the needle a clip or two or try a different one. I actually have a bunch of needles. Fuel economy is important, but not the most important factor. A little more bottom end would be good.

Here is my list of needles: NEDW, NECW, NEDJ, N1EF, N3EW, N8RH, N8RJ, N8RW, NOZI, R1366N, CEJ, CGJ, CEK, CGH, CGL, DGH and CHN
 
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