Bog...usually lean condition?

[Micahdawg]

I've got a 2001 Rm250 that I've been sorting out for quite some time. I've got it running just about as well as it ever has, but have one final area that still bugs me.

Long story short, the head has been milled significantly. Stock compression is 10.5 low and 9.0 high, my compression is 12.2 low and 10.2 high. And it shows up on the compression gauge with 235-240 psi.

Only other mods include carbon reeds, stock cage, ps pipe and silencer, uni filter with no air lid. Jetting is stock. (a/s is out 1.5).

I run Klotz 32:1 with VP C12 and a BR8ES plug. The bike runs pretty well, responds great down low and pulls good up high, but there is some hesitation in the mid range. As the circuits transition I can HEAR the exhaust note get lighter (a more "tinny" sound) and it seems like it takes a little longer to responds. If you mash it, it will never stall out or fall on its face, but it just doesn't respond as quick as the bottom/top do.

I always chalked it up to the characteristics of this engine, but last weekend when going up a sweeping hill, I felt like it needed improved. This hill has a burm carved into it and you can usually pin 3rd gear as you get in the groove and ride it allt he way up (while turning right). This weekend, 3rd never seemed to rev. It just kinda sat there in a bog that wouldn't accelerated.

Sorry for the novel, but does this sound like a lean condition? I guess my next step is to adjust the clip.

Micah

 

[Vic]

Lower the clip a notch and see what happens.

 

[2-strokes-4-life]

not trying to hijack your thread,but my last post went unanswered and i'm curious about this to. is a bog a lean only condition or can it also be caused by rich jetting?and by bog i mean if you dont let off the throttle the engine will die.at least thats what my bike is doing off the bottom.

 

[Micahdawg]

Well, in my case I can't see it being a rich condition. My jetting is stock, yet I have a pipe, silencer, filter, no airbox lid and a lot higher compression (milled head). I know factory jetting is fat, but at this point, I might be right around the limits of the stock jetting. At least I can't see it still being too rich.

And my premix isn't THAT rich either. 32:1. The VP C12 should make things a little richer, but I don't know that it would have this much of an impact. I've got some wiggle room with the clip position so I might go full rich and see what symptoms the bike has when I DEFINITELY add more fuel.

Micah

 

[2-strokes-4-life]

from what i have read,race fuel actually makes your jetting leaner which could be whats causing my confusion as i just switched to running it full time.my bike also has the head milled for higher compression so maybe thats why running a larger than stock pilot still wasnt enough.im gonna try a bigger pilot tomorrow and see if that fixes it.with the pilot thats in it,if if i left the choke on and had the air screw at about a turn from closed i could accelerate from almost a dead stop without any hesitation.so hopefully thats telling me a one size larger pilot will fix my problem

 

[KDX CRAZY]

I agree with Vic Lower the clip as that will richen up your mid throttle .

 

[Micahdawg]

Haven't had the bike out yet, but my clip was in the 3rd spot. So my jetting is SPOT on stock. 48 pilot, 162 main, stock needle in stock position. Power jet I THINK is 50 and stock...at least I haven't messed with it. I just moved the clip down (2nd from bottom) to richen up the midrange, but it bugs me that the stock jetting is fine everywhere except for the midrange. Unless I should maybe go up a size on the main and see if I pick up any top end?

If it doesn't rain I'll ride this weekend.

Micah