Wr430 pwk 39 jetting

[jo360]

Hi guys got a niggling problem with relation to my jetting, bike is a mildly ported wr430 ac running a pwk 39mm n1ed needle, 40 pilot, 180 main ,8 slide, clip in second position, going to go to a 35 pilot.
Runs nice upto half throttle then a flat spot just before powerband then spins the back wheel til i change up a gear.
Next change will be 35 pilot 172 main and raise the needle 2 stages.looking for linear transition, any suggestions.

 

[Nikel]

I have a PWK39 on my 500LC and i have this setup.

Main
180-190

Needle
DGL
Leaner at first then richer.
Stock was to rich on first half.

Pilot
35-45

 

[disonny]

sounds like your issue is a lean condition with the needle or the main. When you adjust the jetting do it one step at a time. Only change the needle or the main. if you change everything then you may correct the problem but get another and not know what part made it better or worse. One step at a time you can see or feel what it did and you will know if your going in the right direction.
It always amazes me how different bikes can be. I'm at 1100 feet above sea level and my 430 has a 50 pilot and a 440 main.

 

[fran...k.]

Dgl sounds about right on the needle. I think 6 on the slide though they were about one third the cost of what I got the carb for so I didn't experiment. I tried to search up an old post. Picklito at one point stated a good starting point and it is about where I usually end up. I do not have my jet box and associated literature and notes near by. One thing I find is that the starting lever on the one I got (supposedly from sudco set up for 500cc husky) hardly makes a difference where pretty much the same carb on a ktm 200 makes a significatn difference. There are few positions on the needle. There is pretty good literature out there about what the needles and their position do.

 

[jo360]

Got a dgh needle that i will try with the 40 pilot and 180 main, least access to the carb is way easier than the modern stuff.will post up the results.

 

[jo360]

Found oil coming out from under the flywheel cover (blown stator side seal) rmoved flywheel and sorted new seal c/w hi temp silicon to hold in place, started it and ran up and down the driveway runs way better just before blowing off the slip on muffler.

 

[jo360]

Ok here is where iam at the moment pwk 39, dgh needle clip one up from bottom,50 pilot, number 8 slide,185 main.
Altitude about 500ft, absolutely no air leaks to bike when cold, cylinder ported by paul rooney in 1984 on its last overbore.
Tried 180 main with 40 pilot and needle in clip position centre, ran ok but had abit of a lull just before powerband then hit hard.
Once the engine was hot developed an intermittent surge when chopping the throttle from full revs, the set up at the moment gives a smoother transition into powerband but will have to do some more riding in the heat to see if the hot engine surge has been fixed, the surge is a couple of blips before settling down again.
Also tried a 35 pilot but this surged at idle once upto temperature.

 

[suprize]

still lean on the needle if your starving into the main jet giving the hit. be carefull, that surging is a lean condition as per needle seize. drop that clip, up the main!

 

[jo360]

still lean on the needle if your starving into the main jet giving the hit. be carefull, that surging is a lean condition as per needle seize. drop that clip, up the main!

Still got to check the heat run with the new settings but certainly smoother transition, also found one of the inlet manifold bolts threaded and too short to tighten properly so this may be contributing to the lean at high temperatures.the engine was totally air tight when cold pressurised it upto 30psi and maintained 6 psi without change.

 

[suprize]

your onto it!

 

[jo360]

2 hours riding yesterday using 95 octane fuel mixed with castor race oil at 30 to 1, current settings dgh needle at three from bottom, 40 pilot 185 main, number 8 slide, worked really well smooth transition all the way upto about 6000 rpm then levels off slightly then hits the powerband meat.torques up rocky hills unstoppable as long as throttle is held just adove idle, just chirps its way through.
Starts easily plug colour dark grey brown, throttle cam needs changing to a quarter turn currently about a 3rd turn.
Good news the bike was way easier to live with than the ktm520 which has too much torque and is too heavy, no back pain after 2 hours and less energy to ride, changed my style to a more seated style which is really easy with such a plush seat.

 

[suprize]

6000 then hits the powerband? its 430 not a 125??? how much 'mild porting" has been done?

 

[jo360]

Guesstimate no science involved what so ever, i will take a go pro to clarify.might try different needle position but very happy to fine tune from this starting point.

 

[suprize]

that makes sense as think these 400 - 430 peak out about 8000 or so.