Engine re-built - need help with tuning.

[fuzzy]

From idle (throttle closed..cable slack), slow walk speed and at least 2nd, maybe 3rd gear, to WOT as-fast-as-you-can-flick-it

Doesn't everybody anally adjust this before leaving camp?

RE: Sled carbs....Sure that wasn't a butterfly carb with integrated fuel pump? Like this:



These have been popular at one time or another on things like sleds and jet skis...Basically a huge weedeater carb. They suck for low end-mid response, but jet ski=WOT, and sled has high-stahl variable clutch. We use then on karts....sigh. Been wanting to get a PWK w/ external fuel pump working on mine. These do work great with methanol, even in cold weather, as they won't ice up like a slide carb....Which would be exciting on a vehicle with 1:3 power:weight on a 10th mile bullring in the winter

[jc7622]

Ok, it runs like a scalded dog now. This is more power than I will need for a while. I can tell that there is a tiny bit more room for improvement on the jetting, mainly in the midrange, but it is running really good.

I started at 155 - 45 and the needle in the middle position.

I wound up at 160 - 45 with the needle raised all the way up. The airscrew is 1.25 turns out. I didn't mess with the air screw mainly because I'm not totally sure what it does. Any additional suggestions on raising the main/lowering the needle or playing with the air screw?

[canyncarvr]

Needle of choice in a lot of 'oem' (not modified) carbs is the CEL./DEL.

Did I miss it, or you DO have an OEM carb?

Mess with the air screw and find out! (..what it does).

It's not as critical an adjustment as it is in a modified carb, but it does make a difference.

A cut-away plug chop would be interesting to see with that 160.

[fuzzy]

My first KDX, 94, came from GA with a 165 main in it. It fired on the 2nd kick when I arrived to pick it up, and he said "This plug's been in here for two years...Should probably change it out" It ran great, but plug didn't look the greatest when I changed it. I threw in the Canadian Dave/FRP 'jet kit' as a baseline and the difference was amazing. Saved me some fiddling (especially since Fredette is in our state). Anyway, I've always been amazed at how that bike ran with such a fat main in it...Can't believe anyone fouls plugs in these things. However, I think the E might have a bit more powerful ignition.

[jc7622]

Needle of choice in a lot of 'oem' (not modified) carbs is the CEL./DEL.

Did I miss it, or you DO have an OEM carb?

Mess with the air screw and find out! (..what it does).

It's not as critical an adjustment as it is in a modified carb, but it does make a difference.

A cut-away plug chop would be interesting to see with that 160.

I think my needle had 1174 on the side of it. I might have to try a CEL or DEL needle. Which one is the smoothest?

Yes, the carb is stock.

I'll mess with the air screw when I get back out to fine tune the carb a little more. I have a new plug ready to do a plug chop.

[m0rie]

DEL should be a smoother more linear power delivery vs the MX style hit the CEL will deliver. Its worth picking up both to give them a try.

[jc7622]

Where's a good place to get one of these needles?

[canyncarvr]

Sudco.

Get an e-clip or two..too. You won't likely find a replacement at your local hardware store when the one you had goes z-i-n-g to a corner of the netherworld.

Might as well order a #7 slide while you're at it! It's an air striker slide in the OEM PWK, btw.

Spread the wealth!! Spend some $$. Keep the 'ol economy moving!!

[jc7622]

#7 slide? I ahven't heard of that upgrade. What will that do?

I'm all about spreading the wealth...voluntarily and when I get something back in return (like goods or services). It's this forced BS that I don't like. I think it may also be time to buy some cosmoline and go out to the farm with a shovel.

[canyncarvr]

RB's modification includes a #7 slide. He cuts slides, too (will cut your OEM #5 to a #7)...for a lot less money than the cost of a new slide, but then you can't change it back if you decide you don't like it.

The slide is one of the mixture 'circuits' in the carb. You've seen the chart I'm sure with the different circuits, how/where they overlap? The slide effects the bottom end of the throttle range. The #5 slide in the OEM carb is generally considered one of the parts that don't work as good as it could.

The numbers (5/7) are mm measurements that define the slope of the slide cut..how much metal is removed.



The farther up the back side of the slide the cut is made, the more 'lean' the slide's function is in the carb.

I was really just kidding about the 'As long as you're buying stuff....' comment. Before you sink $70 (or so) into what a new slide costs, put those $$s toward RB's modification.