2009 Wr 250 Jetting Question....

Hi all, new on here.
Just bought an 09 wr 250.

It is running rich. I have overhauled the carb so know all seals etc are new. Reed looks good. New spark plug. Final mixed at 50:1 as per manual.

Standard jetting according to book. Pilot 35, main 400 needle middle clip. I’ve set all this to standard and set float height to what it should be 20mm +- 2mm.

I have changed pilot to 30 and have same problem.

My question is is it strange that I am about 200 ft above sea level and it’s about 8 degrees c and I’m still rich even using smaller jets from recommendation?

I have oil dripping off pipe and bike won’t idle, will die without throttle and bogs on any inputs. Air screw wound out 5/6 turns doesn’t even help. Going to try a 25 pilot.

Any ideas?

It the mikuni tmx 38 with flat slide.

Cheers.

I had one with issues around the seating of the float needle - is that new?

Yes I tested the old one and it was leaking so new plunger and seat with o ring fitted. I then filled it with carb cleaner with the plunger closed, blew down the fuel feed and I couldn’t see any bubbles or leaks. Float moves freely too.

What was your float height? Mine is not level with the gasket surface, apparently it should be around 20mm.

I cant remember float height . Normaly lts measure when at around 45 degrees .
Are you sure its rich ? I wouldnt worry about spooge - oil .
Needle is easy to adjust . Try raising needle - putting the clip on the needle at bottom slot and see if it still bogs

It bogs on cracking throttle. Lots of smoke and lots of spooge down exhaust, won’t idle just dies, starts from cold without choke. Air screw doesn’t seem to do much.
Lowering needle will cause more fuel to enter the carb making it richer would it not?

Lowering the clip will raise needle and bring more fuel in . The needle normally cures a bog which is normally a lean bog.
If its crackly/stuttery above that bog its probably rich on the main jet .
I dont want to confuse you more but a 400 main jet is also quite rich for the older flat slide carb . You could try smaller.

So try needle clip at bottom or one up and I'd also go back to 35 pilot . Richer bottom end will always pull better down low.
Check air screw location is at 1 1/2 screws out

The JD jetting kits have a different Needle Jet an S-4 . I believe this is a big part of the JD jetting "fix"

I have a 2008 WR250 (been riding this one for 8 years now), and i am still working through some rich mixture issues (plug fouling) at the moment myself, here in Auckland NZ. I notice that my flat slide is a No. 3, whereas manual states this should be a No. 4 which will be leaner. What slide do you guys have in your TMX 38s?

In OZ they were 3.0 from memory . I dont think it makes a lot of difference

I do have a JD jetting kit that I am not using anymore

Thanks, Rockdancer. You have the similar WR 125? Just don't see any of those here in NZ now.
My 250 came with a JD kit fitted by the previous owner, and the set up at the moment is Red needle, clip at top (first position), S4 needle jet, 400 main, 32.5 pilot, mixture screw 2 1/4 turns out. NGK B7ES plug. Motul 710 oil, 35:1 ratio.
I have a Honda CR 250 reed cage and Boyesen Pro Series reeds in it for 5 years now, since I could not find any new reeds for sale anywhere for the original V-Force 2.

Just repacked the muffler, and surprisingly hardly any soggy spooge build-up like I used to get when running Motul 800 at 50:1.

I thought maybe with a No. 4 slide, I could get the needle clip back to more like a centre groove. Probably nothing to stop me filing a mm off it perhaps if I get really carried away.

The bike always runs well, but sometimes a bit hard to start from cold if not used for a few weeks. Never any performance issues at any throttle setting with the pine forest trail rides I do. Lots of fun 2nd gear stuff with mud, roots and ruts.

Checked the compression yesterday and it is now down to 150 psi, from more like 200 psi after a top end rebuild 5 years and 175 hours ago, so there are indications that this will be another job to do soon.
The Wossner piston I think has held up well, with no "death smile" on it yet so I will get another one again soon from MXParts NZ.

Have you tried the blue needle? I have a slide that was modified from a 4 to a 5 on the newer carb.
One of the best mods is an oversized air screw adjuster for changing during a ride . When it heats up adjust to suit
My 125s dont like to start when cold either . I reckon new top end is worth doing now for sure at 175 hours . I am going to check mine again as they just run better when fresh. Id say for a 125 every 50 hours max

Yes, i have certainly tried the blue one, but the red one is supposed to be the leaner of the 2 supplied in the JD kit.

Thanks for response.

I ordered a no.4 slide as mine had a 3 and book said it should be a 4 and I ordered a no.61 needle. To my surprise this has worked, I tried the slide first which improved things and then the needle on middle clip. The bike started east and idled straight away. No bog and air screw adjustments seemed to make a difference. No splurge.

From reading I thought the idle jet made the difference on idle and initial throttle but it didn’t. I now need to fine tune and may end up going back up to a 35 pilot from the 25 I’m at. The slide want cheap but now it’s running it’s worth it!

I’ll try factory jetting and see how it goes. 175 hours sounds amazing! Hope I can get even half that out of mine!

Thanks for the help.

Is that a richer needle? Anyway good to hear youve had some success

No it’s a leaner needle slightly fatter.
Took it out today and the revs seem to pick up when I’m about 4 turns out so that indicates I need an even smaller pilot, already at a 25 which is ten below recommended.
Didn’t get to try it properly so not sure what else I need to change but the oil dripping from end can has stopped and it not doesn’t bog anywhere near as much. Is it usual to need to go so lean on the pilots?

2 more things, I always keep an eye on:
Nice clean freshly lightly oiled air cleaner - helps avoid any rich running issues.
Spark plug: Which one are you using? A good check to see if a spark plug is stuffed or possibly needs rejuvenation with the old brake clean & tooth brush scrub trick is to use a multi meter on the highest ohm setting to check for absolutely infinite resistance from the plug lead connection point to the body.

Yeah good points, I made sure I corrected every other possibility before I narrowed it down to carb jetting. Brand new filter and oil and I tried the stock plug br8eg and now running the iridium version. Neither seemed to change much.

4 in mine; much better power

Hi steadydirt, in the TMX 38, did it previously have a "3" slide and you swapped it out for the "4"? I am really thinking that I need to try this mod.

yep.

cleans up the bottom