After running with my Dynojet stage 1 installed for about 150 miles, I have decided it was running too rich. (I did mistakenly put in the 120 jet instead of the 116). This is a completey stock 09 KLX250s.
The bad:
It occasionly sputtered and missed fired at WOT, and it could be driven immedatly after starting with no choke.
The good:
No more sputtering and surging (like you were running out of gas) at 1/8 - 1/2 throttle steady cruising.
So,
Yesterday I removed the bowl to install a smaller main jet size. Since the reccommended 116 measured identical to the stock jet (.045"), and I already had WOT stats on the stock jet, I decided to play and put in the smallest Jet provided in the kit, the 112. (I'm sure they stuck it in there for a reason?)
My WOT up hill test with this jet was equal to the stock jet and I lost obout 3 mph in my top speed highway test.
I will leave this jet in and work on leaning out mid and low throttle positions.
What I will work on is getting as lean as possible, but not so lean as to get that mid range surging back.
I also beleive the bike should have to warm up before it can be ridden unchoked.
My question is:
Would reinstalling the origional diaphram spring make the bike run leaner or did DynoJet supply that spring for another reason?
I know lower the needle by moving the clip to the first or second notch should get me leaner, but I'm not sure what the shorter DynoJet spring is for.
P/S My pilot screw was at 2 3/8 turns before I pulled the plug and opened it to 3 turns.
Craig

 

That spring only makes it a tiny bit easier (faster) for the slide to move up. It won't make the bike run any more lean or rich at a steady throttle position. I guess instantaneously, the lighter duty spring could allow the mixture to be a bit more lean for a millisecond as you crank open the throttle, but, I'm not sure you could measure it on an AF Meter.

 

True, the light spring has no efffect on jetting. It is a throttle response item allowing more fuel sooner when you quickly open the throttle.

You put in the 112 eh? Actually smaller than stock. I suspect DJ put that in the kit for super high elevation riders with stock bikes.

I'm not a fan of the three turns out of the fuel screw. Mine has been at 2.25 turns out and seems just fine. The pilot is where your early choke release will be fixed for you. I never really thought three turns out was the right thing to do so in that one case I went away from the DJ instructions.

Don't you think that dynojet already did some thinking when they designed their kits and ran them on the dyno? Do you think that they purposely screwed it up?

 

If that angle was applied fully, there would only be one of each jet in a DJ kit. I don't think anyone said they screwed up - actually you said yourself that you went away from the DJ instructions, so maybe that's what you think?

Bikes vary, conditions vary, fuels vary, riding types & conditions vary, and rider preferences vary. All of which makes all this stuff even more fun. And great reading.

 

That's not what I said. You are the one that "applied that angle fully" to suit your own conclusion. I asked if the OP thought that DJ screwed something up.

If you actually read the directions you would find that there are reasons for the several different jets in the kit.

And yes, I did vary from the instructions. I think that this is allowed. Maybe that's why there are so many jets in the kit and why the fuel screw is meant to be adjusted.

What's your point ns503? All you did was try and twist someone else's words.

 

Here's a crazy idea. Have you called DynoJet and ask them?









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If you lost 3 mph on top end, then the main is too lean or leaner than what you had and it cost you. You proved it too.

Like Highbeam said, 3 turns out is not for everyone Just a starting point. I was around 2 1/2 with good luck. Removing the vacuum hose for the air injection changes where the mixture screw has to be.

Its like salt, season to taste. We want different things out of our bikes.

You get different jets because you can create different air flow. Intake and exhaust have all to do with it. On these bikes it seems intake has more to do with it.

I had the dynojet spring in the slide and I took it out. Just so you know the dynojet spring is .001" smaller wire. Its weaker, but Vacuum is what really moves the slide, the spring just puts it back. I thought the slide was hanging up ( I could feel it) so I put the stock one back in. Its a to each his own thing.

Your Mileage Will Vary
Yadda Yadda Yadda

 

Here is the best reading I have found on tuning a carb.

http://www.mikuni.com/pdf/hs40_manual.pdf

David

 

Thanks David.

Good info to have.



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