7 replies to this topic

[Neo]

Hi all,

I have a question for all you Keihin PWK Professionals.

I fitted a PWK28 to my 02 Sherco 290 a few months back. I selected the setup based on what I read on these forum pages. And after some messing around I had it purring like a kitten and as controllable as a guide dog….I love it!

Only problem is after I’ve been riding for half an hour or so. Or after I've given the engine two or three hard things to do. The idling starts to pant. As if it’s out of breath. And sometimes stalls, if left to idle. Most times I can rev it up (gently at first) to stop it stalling. But if I it does stall it takes quite a few kicks to get her going again. The other odd thing is that most times when I rev it up, or just keep riding, everything returns to normal again. And then it might come back a few minuets later. At its worst, it flattens the low down pull of the bike…but not often.

Setup is:-
48 pilot
120 main
Float level checked at 20mm
JJH needle, This was in middle clip position, but now it’s in forth position (on the advice of a friend). But this didn’t cure the problem.

I also have two tubes on the overflows running down to the back end of the bash plate.
And I’ve seen petrol moving down the float bowl tube at about the same time the engine was panting.

Howard I noticed you are using 38 pilot 110 main and a float level of 19 mm. Could my setup above cause my problem?


Best of balance.

Neo

Edited by Neo, 31 August 2006 - 09:58 AM.

[copemech]

The bowl vent tube on the right side may be pinched or blocked. I had to drill through the left(blank) nipple to let it vent properly as the hose was pinched shut on mine due to close quarters with muffler. Fuel cannot flow properly if this happens. ( Yes, remove it again so you can clean and air dry bowl after drilling passage)It creates a negative pressure in the bowl that cannot be overcome.

Be sure these tubes are short as fuel in them acts to block air pressure equalization in the bowl as well. That is what happens to the stock Dellorto as well and why the tubes are most often removed. However I will tell you that I prefer the short hoses even on the dellorto to prevent contamination.

As there is no "L" outlet on these Keihin vents, hoses are neccessary to prevent dirt and water entry into the bowl area. Otherwise you would contaminate it every time you wash the bike!

Many folks wonder how dirt gets into the carbs, past the fuel filters to block their pilot jets, now you know!

Hope that helps!

Edited by copemech, 01 September 2006 - 03:13 AM.

[Neo]

Thanks Copemech,

That information put me right on track. I had already drilled out the bowl vent tube, on the right side. Because I read that there was little to no clearance in previous post. But I put two long tubes down the back of the engine, to the delta link. The one coming for the bowl vent must have not been breathing properly. So I’ve replaced it now with a short tube that runs down to the front sprocket, behind the chain. I rode her all day today and she was fine. Such a simple fix to what seemed like such a weird problem!!

I’m quite happy with the way she’s running now, but would she be even better with Howard’s jet set-up? Or is it best to let sleeping dogs lie?

Best of balance.

Neo

[Howard Wallace]

Neo,
Ran that combination on the 4T.
What you have is fine, except for needle clip position ????

[Neo]

Thanks for the reminder Howard,

You never miss a trick, do you my friend....Spot-on every flipping time!


Best of Balance

Neo

[Howard Wallace]

Neo,
the symptom you describe, sounds lean on the pilot. Air screw should be 1/2 to 1 1/2 turns out. Anything outside this range requires a jet change. But your running a 48, which should be plenty of fuel, so don`t understand ????

[Neo]

Howard Wallace, on Sep 4 2006, 08:58 AM, said:

Neo,
What you have is fine, except for needle clip position ????

Sorry Howard,

I've confused things a bit.
I was just commending you on the fact, you remembered that I had moved the needle clip.


Many thanks again.

Neo

Edited by Neo, 04 September 2006 - 04:33 AM.

[copemech]

Howard, have you tried the VHST with the proper workings?