Keihin Pwk Idle Jets Keeps Blocking

[kurt]

On My Gas Gas Raga 300 2007, I have the standard Keihin PWK carb.

Since a year or more now I'm always having a blocked pilot jet after about a 2h ride.

The throttle then starts to return slowly, well not the throttle actually but the revvings itself. When the engine start doing like that I know it's time to clean the carb again.

I clean the air filter about each ride in filtercleaner, and oilspray it again. I have new one now installed.

I checked the fuel and installed a fuel filter.

But still the jet keeps blocking, if I hold again the light, nothing. After a pressure blow and even a poke with a copper wire it's clear again and I can look trough it. I think I see then not a straight clear hole like at the main jet but more like an effect view, is it a light prism effect or so? Maybe that's just because it's so small, size 40 I thought.

Wat can be the reason of this frequent blocking?

[tankygsy]

is it moisture? Water can enter your fuel tank from the filler neck if the seal isnt good.

[jse]

is it moisture? Water can enter your fuel tank from the filler neck if the seal isnt good.

Blow out jets from the opposite way the fuel flows through them. Jets are usually cut and

drilled with a funnel-like bevel and blowing air through them in the direction fuel flows would

be like trying to push a golf ball through a funnel.

Make sure that there are lines on the vent(s) as dust is easily ingested through the short spigots

on the carb body if lines are not attached to them.

Flush out your fuel cans, you'll be amazed at how much junk collects in them over time and we usually

use them over a few years time before replacement.

Jon

[sting32]

I have had that problem with my 08 Raga pro 300. Turns out ANYTIME I used fuel that had ALCOHOL in it, it would glob up the premix, as you said in a ride or 2 it would be enough to cause a problem. I luckily, have a station near me that prides itself to 100% non alcohol gas, that I buy, and no more problems... it affects my 10, 11 & 12, raga's too by the way...

[doctorchopper]

I feal your pain, my enduro bike does the same(PWK carb too). I found that using a funnel with a fine mesh screen helps, but every ride my jet is plugged too. Like to know the solution to this.

[baldilocks]

On an early pro I had the air filter box wasnt sealed properly next to the boot that fits on the carb. During the trial loads of mud was getting in the filter box and some was getting past the element into the carb. Later models are sealed as part of the PDI process but I gess the glue could fail over time. How much muck is on the filter when you change it ?

[jse]

On an early pro I had the air filter box wasnt sealed properly next to the boot that fits on the carb. During the trial loads of mud was getting in the filter box and some was getting past the element into the carb. Later models are sealed as part of the PDI process but I gess the glue could fail over time. How much muck is on the filter when you change it ?

Good point. Usually you can look inside the bell (front) of the carb and if there is any fine grit on the lower part of the bell you have an airbox/filter problem.

Jon

[mr neutron]

It's always a good idea to seal up an airbox to keep junk from getting past the filter. But my experiences with various Kehin carbs goes right with what Sting32 said. I'd bet a bucket of donuts the fuel is the culprit. I don't know if you have ethanol or alcohol added to your fuel there in the UK, but fuel like that has always been a problem for my Keihin equipped bikes. it tends to plug up the pilot jets really quickly.....

If possible, try some non-ethanol/alcohol fuel. Regardless of the fuel used, I would turn the gas off on your bike, and drain the float bowl after any ride where the bike will sit for more than a day. The crummy stuff that the petroleum companies try to pass for fuel nowadays causes multitudes of problems, and it actually does it fairly quickly......

Jimmie

[bogwheeler]

Break the entire fuel system down, Flush everything,Gas can, fuel tank, clean fuel line or even replace with new, disassemble the carb and soak in a good carb cleaner. Then find a good non alcohol race fuel. I use VP fuel in all my bikes. Its always consistent in quality, does not get stale when stored in a metal can. And no odd looking scum laying in the bottom of your float bowl.Here in the states the pump gas can be crap (depending on where you buy it) for motorcycle carbs. I always use a screened funnel when mixing and filling the tank. You can never be too clean with your fuel.

Contamination, stale gas and ethanol/alcohol in the fuel system is the biggest problem I find when working on any small engine.

[kurt]

thanks for allthe usefull tips guys:

@JSE: I do blow my jets the opposite way, I have lines on the vents, but I was not thinking they may be a cause, you've got a point there, I gonna have an extra look at it.

@Sting32: I'm not aware if fuel here in Belgium has alcohol/methanol in it or not. We can choose Oct 95 or 98, but non-alcohol..? I've never saw it avertising or hear people talking about it... so I guess it is always with?

@baldilocks: Maybe I need to try to loosen the airfilterhose between the carb and filterbox to see if it has a good and close fitting there. I thought there 4 small screws there to undo together with a metal plate? The filter almost has now muck on it when cleaning after each day out. there is also the square transparant cover inside the airbox, which takes most of the muck leaking through the badly designed cover. But mostly I have to remove (4 screws) and waterjet clean the complete rear section to get it proper.

When I clean the carb/jet I don't see any dirt or water in the bowl.