WR250 tuning

[Kurlon]

Ok, so it needs a bit more than simple tuning, especially after I put a fist sized dent in the pipe Sunday. : )

I've no idea what the carb is setup with right now, and have a pathetic selection of jets on hand, anyone got a suggestion for places to order jet assortments cheaper than Sudco?

(360 main standard, serious? Biggest main I have for anything is a 125 Mikuni long hex. I think I can replicate a 360 with a McDonalds soda straw.)

[Rambunctous]

If need be. Maybe this http://www.rockler.com/product.cfm?p...urce=googlelps

[Kurlon]

I have a friend that will be so happy when I ask to tag along on a trip to Rockler to get tools to fix my dirtbike, awesome find Mike!

Edit: Found one way to update the suspension, and cosmetics in one shot... 2008 YZ250 rolling chassis for $1000. Other than exhaust mounts my motor should drop in. Now if I only had the cash.

[breakdirt916]

how much were they on sudco?

and not sure if it's the same for mikuni, but I found that rockymountainatv.com had competitive pricing for keihin jets

[Kurlon]

I think Sudco is around $2 a jet, but you have to order in packs of 4. Min order of $20 also.

[Fast_Eddie]

I'm running a 400 main in my YZ125, so a 360 might not be too far off.

[Kurlon]

Looks like back in the day Eric Gorr was suggesting a needle change and 400 main for this bike too. Guess I have a range to start with now. Still seems HUGE.

We have to get together and ride some time btw, been too long.

[Fast_Eddie]

Kurlon, I'll be ready to ride a lot in the spring. Flu season hit me hard this week, so I'm going to end my season early.

We will definitely be riding together next season. I am planning on doing some track days with Black Squirrel and Paul ED. I'm sure that will take me up to MX101 a few times.
I ride in the woods every week when it's warm.

I heard that the spark plug cap can get funky on the old YZ's. If that was my bike, I'd start by changing to an NGK cap and a fresh B7ES plug and a 390 or 400 main jet.

[Kurlon]

Sounds like a safe plan to me.

[seth399]

Edit: Found one way to update the suspension, and cosmetics in one shot... 2008 YZ250 rolling chassis for $1000. Other than exhaust mounts my motor should drop in. Now if I only had the cash.

whaaat, where you find this?? gimme!

[Kurlon]

whaaat, where you find this?? gimme!

http://www.thumpertalk.com/forum/sho...346&highlight=

You get the 2008 chassis, I want yours! : )

[Kurlon]

Clutch cable and pilot jets on their way from Thumpertalk along with a new clutch cover gasket. Still haven't found a source for individual Mikuni mains. I'm going to pickup a new plug and cap Saturday too.

[Kurlon]

Bah, TT Fail... pilots are not available individually.

[typeone]

you contact JD Jetting at all? may be an option, but i've only bought a full kit from them...

[KB]

Clutch cable and pilot jets on their way from Thumpertalk along with a new clutch cover gasket. Still haven't found a source for individual Mikuni mains. I'm going to pickup a new plug and cap Saturday too.

I have always had great luch with jets at the local mc shops in manch naults especially. Doesn't and even when they do need to order them I usually have them in 3 days tops.

KB

[Kurlon]

Pilot located, mains on order, new plug and cap in hand.

On the gearing front the bike came stock with a 15/52 (3.466) setup. It's currently 14/50 (3.571). I'm thinking 13/51 (3.923) should shorten it up decently without going too far, or should I go right to 12/51 (4.25)? (How fast did Yam want this thing to go stock, it already feels crazy tall out of the crate?)

[TheIglu]

I'd go big in the back instead of going 13 up front. That is a pretty tight little corner to have your chain be making.

[Fast_Eddie]

I've tried several gearing setups both on my current YZ125 and the YZ250 I had before that. The 13/50 combo seemed to be the sweet spot on my YZ250. I run 13/52 on the 125.

Any lower than 3.9:1 tightens up the gear spacing too much on a YZ. The WR should be better. I still wouldn't go to 4:1 on a 250.

Most Yamaha chain guides will have to be modded to fit a 52T or 53T sprocket.

[Paul_E_D]

I was gonna suggest 13/50, but the fast one beat me to it...

[Kurlon]

Plug cap pulled, rusted all to hell and rattling, that can't be helping any so it's replaced. Plug was new but black, running pig rich at least in the throttle ranges I've been using... replaced with an irridium fine wire unit just 'cause.

Got into the carb. Stock jetting is a 40 pilot, 360 main. I found the stock pilot (and it only took 15 mins of cleaning/scraping at the patina to identify it...) and a 350 main. I can only assume someone was trying to correct for it running rich at light throttle with the main? 35 pilot has been swapped in as that seems to be the go to pilot for that carb/bike combo. 350 main left for now while I wait for my 380 to 400 assortment to arrive. (Theoretically the 'right' mains for this setup). Can't test 'cause it's already dark.

Swapped clutch perch and lever for my folding ASV setup I used to use on the GS. (It's a dirt lever, got a good deal on it, crashed well.) I have a new cable on standby but did some testing and it looks like I'm going to have to either replace or shim my push rod to get the clutch back to it's happy place. So making progress there too.

Edit: Plug/plug cap/pilot change seems to have helped, I can fire it up (requiring choke when cold like it's supposed to), stall it, and fire it right back up with one kick. Now if it'd just stop raining so I could play a bit...

[Kurlon]

Got most of my mains, 410s are on back order through PU at the moment though. Swapped the 350 for a 400, haven't had a chance to test yet. Clutch pull arm and push rod are on order from Yam along with a new seal and roller bearing for the pull arm just to make sure everything is right.

New clutch cable installed as well, and verified clutch is assembled correctly, no notching/etc, problem is definitely the pull arm itself.

[Paul_E_D]

If you're already rich and going up on mains, its important that you are going leaner on the needle. Stock needle is likely gurgly to begin with, which is why your plug is soaked and black. The pilot is not likely the sole culprit. You can drop the stock needle, but might need to go leaner.

Fat main, lean pilot and needle usually make for a smooth running two-stroke that won't foul.

[netra709]

Does this bike have the round slide Mikuni? I have a 36mm and a 38mm keihin pwk, that I have been swapping back and forth on the KX. If you don't get what you want with the mikuni, you can try one of these. I have a shit load of keihin jets and needles. Tim

[Paul_E_D]

a 36 pwk would prolly work great on this bike.

[netra709]

a 36 pwk would prolly work great on this bike.

I picked that up because I was really curious how it would change the power delivery on my KX250 I have setup for netra.
It hasn't been a huge difference from the 38, but with the 36 and the gnarly pipe it is abrupt enough on the lowend that I need to go back to my other setup for the hare scramble in 2 weeks.