250-500cc WR300 jetting and tuning thread

[WoodsChick]

Good day all.
I am new to the forum, have posted an introduction on another thread.
If I hijack this post, I am sorry,

I need some advice please.............I own and race a 2006 WR 250 with a FMF Gnarly pipe on.
It is time to replace the piston and rings again. I was looking at somehow putting a big bore 300cc kit on.
A few questions
where will I find the big bore kit, everybody seems to only keep the 4T stuff?
Will the FMF still fit or will I have to replace the pipe as well?
Will the standard 250 Mikuni carburetor be good enough (I will play with the jetting to get it right)

The problem in South Africa is that there is only one dealer / importer so the availability and prices leaves a lot to wonder about.

Again, sorry for the hijack but I cauld not find the right place to start a new thread.

Johnnym

Hi, Johnnym! Welcome to CafeHusky! A new thread in the 2stroke forum would be the perfect place for your questions next time



WoodsChick

 

[zilly]

The needle from the so called "full power kit" has the clip in second slot, main is down to 400, pilot down to 30, air screw out two turns. We'll roll the dice with that as the starting point for 7300-8500 feet, but what will be unusually high humidity for CO (it's been raining a lot lately). I have about 3 more gallons of 32:1 to burn as it has an hour on it.

So, would you do the full power kit again?

I am thinking of going that route.

I am having trouble getting the jetting right on my bike. I am at 500 to 1000 feet in Eastern WA state (the dry side) and just installed a 450 main, 2nd clip on the needle and 30 pilot on what is essentially a brand new 09. I have a huge hesitation(almost a miss) coming off of 1/4 throttle to half and full throttle. The bike is clearly not running right and what's worse is that its clearly my fault.

Before I jetted my bike it didn't idle and so I adjusted the idle screw as per the manual but I had to turn it nearly all the way in (its flush to a little past the lock nut) and am wondering if maybe somehow that is messing up how the carb runs.

I am new to two strokes and while I have played with carbs a little I obviously still have a lot to learn.

Any advice?

 

[BikeSDP]

The WR is my first smoker and the first time I've ever jetted anything. I had been riding FI bikes for a number of years. I would buy the kit again, especially since Hall's substituted leaner jets for me. So, 5 jets and a needle for $50 doesn't seem outrageous.

So it sounds like you've jetted your carb almost the same as mine with the exception of a fatter main. At 32.5, for my elevation, clearly I'm too rich in the pilot. I'm going back to 30 when I get my bike back. What did you do with the air screw? I know there are some PNW's out here who can hook you up with some recommendations.

 

[zilly]

Cool. Yes 50 bucks isn't bad at all. Unfortunately when I talked to Halls the kits are on back order from Husky. I'm on the list but am hopeful that I have my bike running better before that.

I know my jetting is in the ball park based on stuff I have read on here and some good advice I've gotten from other members so I am thinking that it might have everything to do with how I adjusted the pilot circuit.

I adjusted the fuel screw after I set the idle-trying my best to get the idle to smooth out, but I think that is where I need to start over and see if I can get a better baseline.

One word of warning for anyone out there don't ride off (even a short distance) without locking the idle nut back down. I went maybe a hundred yards with the nut just on there and not tight and the idle screw had nearly vibrated all the way out. Probably obvious but just thought I'd share.

 

[krieg]

The needle from the so called "full power kit" has the clip in second slot, main is down to 400, pilot down to 30, air screw out two turns. We'll roll the dice with that as the starting point for 7300-8500 feet, but what will be unusually high humidity for CO (it's been raining a lot lately). I have about 3 more gallons of 32:1 to burn as it has an hour on it.

So, would you do the full power kit again?

I am thinking of going that route.

I am having trouble getting the jetting right on my bike. I am at 500 to 1000 feet in Eastern WA state (the dry side) and just installed a 450 main, 2nd clip on the needle and 30 pilot on what is essentially a brand new 09. I have a huge hesitation(almost a miss) coming off of 1/4 throttle to half and full throttle. The bike is clearly not running right and what's worse is that its clearly my fault.

Before I jetted my bike it didn't idle and so I adjusted the idle screw as per the manual but I had to turn it nearly all the way in (its flush to a little past the lock nut) and am wondering if maybe somehow that is messing up how the carb runs.

I am new to two strokes and while I have played with carbs a little I obviously still have a lot to learn.

Any advice?

I'm at the same alt. and conditions as you. I tried a 30 pilot but it was too lean, ended up with a 32.5. You may want to go with the 3rd clip position to get things a little richer as you transition to the needle. You didn't mention where your air screw was set, but it should be between 1.5 and 2 out. Then start messing with the idle screw. I ran a 450 main for about a week then ended up going back to the stock 460.

 

[zilly]

So are you thinking keep the pilot at 30 and try the 3rd clip?
No shops in town here have a 32.5 apparently its kind of an off size.
I am going to order one but would like to get the bike running decently in the mean time.

I am thinking about going back to the stock jetting, keeping the needle raised and messing with the pilot circuit just to see where I need to go from there.

The bike idled and idles fine its just under load that I am getting the hesitation and what I assume is called blubbering.

 

[PC.]

I had a hard time tracking down a 32.5pj myself, but a local Honda/Kawi dealer had one in stock.

The 32.5 is the pilot for my bike at my ride spots, which should be of relatively similar temp, elevation and humidity levels as yours.

Read this jetting thread on TT: http://www.thumpertalk.com/forum/showthread.php?t=412662

It may not make much sense now, but once you begin going through the steps to get things dialed in it will start to come together.

My float height is set to 8mm using the method described in that thread. It was at approx. 6mm stock and the bike would puke fuel if sitting at a slight angle. FYI...Going to 8mm decreased the amount of fuel being held in the bowl at any given moment.

You said it acted the same with the stock jetting, correct? Did the problem get better or worse after changing the pilot and needle? 1/4 throttle is affected by both the pilot and needle as those circuits overlap at that throttle position, so either (or both) can be a contributing factor.

This diagram is a nice tool. It shows what circuits are in use at a particular throttle opening. Be sure to use throttle opening and not RPM to determine jetting.

I'd start my measuring float height. If it checks out then put the 35pj back in and see if it improves or not. If no change then its not the pilot and then change the needle back to stock and check for improvement.

 

[krieg]

So are you thinking keep the pilot at 30 and try the 3rd clip?
No shops in town here have a 32.5 apparently its kind of an off size.
I am going to order one but would like to get the bike running decently in the mean time.

I am thinking about going back to the stock jetting, keeping the needle raised and messing with the pilot circuit just to see where I need to go from there.

The bike idled and idles fine its just under load that I am getting the hesitation and what I assume is called blubbering.

I definitely think the 30 is too small and making the hesitation off-idle worse. My 300 did not like the 30 at all. My thoughts are that a bigger pilot combined with a richer needle may help. But you also need to make sure the air screw is right to get the pilot circuit dialed in.

Also, I'm assuming when you say 2nd clip, you mean second from the top so going to the 3rd will be one step richer (raises the needle).

 

[zilly]

Okay, I'll check the float height tonight.
Change if need to and see how it runs.
If no improvement back to stock pilot(35).
If still no improvement back to stock on the needle (3rd clip).
My main will still be one size leaner and if need to I'll bring that back to stock too.

I feel like maybe I jumped into too many changes at once and needed to go step by step instead. I know patience, patience...Its just that its such a cool bike and I'm ready for it too be running right.

I had to order the 32.5 pj since there are none in town.

thanks for the help and the patience.

 

[TROFFER88]

G-A-Y Needle

Just installed needle from power up kit, middle clip, 460 main, stock pilot, air screw out 2 1/4 turns. All i can say is wow , this thing rips from right off idle to going way faster than needed. Jetting seems really close.Also installed 51 in the back with 13 in front , gearing seeems really good too.

 

[zilly]

So yesterday and today were my first days to ride my bike with the 32.5 pilot jet. Just ran it at a buddies track and some local hill climbs but it was still a pretty good test. Bike is running very well. No bog, no miss and just flat rips. Thanks for everyone's input on this.

I am hoping to get some real single track time in this up coming weekend. Didn't want to mess with elk hunters too much this weekend but Sunday next week they should mostly be gone...

Snow is coming so time is running out.

 

[MARK WOOLARD]

I have a PC pipe on my 07 WR250 with the stock Husky spark arrestor. I bought it like this, the silencer pipe might have been cut to fit, but it works and no spooge leaks.

 

[ray_ray]

A new pipe for a 2T is always a joyous time ...

I always gotta say the C2 racing pipe I put on my 02 CR250 was one bad a$$ pipe ... Whatever the power curve was on paper from the PC pipe it had on it, this pipe totally superseded that entire line ... The beast was released!