mugello 225 pwk jetting???

[paulski]

just trying to set up my mugello 225, with mec60mm crank,sterling pipe and sx200 gears with 15/47 primary. carb is a pwk/oko 30mm with remote air filter. has anyone got similar setup to advise on correct jetting cos its doin me nut in. engine case not been opened up to match barrel just bolted kit on with crank. jetting at moment is 128main/50pilot/jjh needle on second clip from top. runs well but when i thrash it it tends to want to hold the revs for a bit and not settle to idle very happily? engine fully rebuilt so confident no airleaks. has fast flow tap and does rev out when full throttled but dont no wether to modify float needle seat to 3mm as sugested in another post on here???will that make a difference to my symptoms?pretty sure pilot jet is more than enoughbig enough??? have adjusted float height so plenty fuel in bowl. any ideas, or where is best to take for dyno setup, i live in manchester. cheers

[Wayne Miller]

Hi,

I dont know wether this is any good but I have a kEIHIN 35MM carb that was set up for a TS1 . . . .

35MM PWK set up as below for TS1

Needle : CGL on Top clip position (1 of 5)
Slide : 6
Main : 140
Pilot : 52

[Adspeed]

I have a 30mm OKO on my TS1. Took a bit of fettling to get right but now spot on.

Chiselspeed have all the needles and jets needed to set it up. Both mine and a Honda 205 with the same carb required a little mod to the slide to really get it spot on. So IMO I'd give'm a bell.

[scar]

i think your idle is too high
try 42 you may need to go as low as a 36 though

[storkfoot]

Is it a proper Keihin needle that is marked JJH or has someone just told you it's a JJH? In my experience the neither the bgm or ScootRS "standard" needles are JJH.

As I think you know the taking time to settle down when you release the throttle is a sign of a weak mixture. Are you absolutely sure you haven't got an air leak?

On this subject, do have have a diaphragm valve that's not been blocked off? As you look at the carb from the front, if you crane you neck and look behind the throttle cable adjuster, is there a brass tube sticking up? There is on bgm PWKs and this needs blanking off.

The pilot maybe a bit big but I wouldn't have thought you need to go as low as 36. I take it it runs Ok at tickover and if you're just tickling the throttle up to, say, 1/4?

I wouldn't have thought your jetting is that far off from my knowledge of these carbs so an air leak or, as you say, the float needle seat may need opening out.

You've raised your float. It should be about 21 or 22mm. Just check it and that both floats are level.

Having said all that, given that Chisels aren't that far from you, it may be worth a trip to stop you pulling all your hair out_____believe me I've been there

[a.lo]

i have had the same problem on mine same settings but 42 pilot (i do think yours is too big,) i do think mine needs a bigger main jet as it can pink under load( i just ease off)but every time i try it the other settings get thrown out i find it hard to belive main jets can be sorted in isolation with these carbs. the thing is i have ridden like this for about 5/6000 miles with no ill effects. i keep meaning to follow storkfoots recomendation on the float level but cannot get my head round 22mm being raising from 19mm surely if the floats sit lower the fuel will cut off quicker? mr storkfoot any advice appreciated.

i know these carbs are often knocked and are not supported by many dealers(germans seem to like them)but my experiance even my poorly set up is better i.e response and economy than the phbh i had before.
must try to get genuine needles, i have three different ranges jjh , n80f , pw28 which cant help.

[storkfoot]

I was told by a bloke who races 2 stroke bikes on the IOM, and had used Keihins, to set the float at 21 or 22 and not 19 which is what the Americans tend to use. He was quite emphatic when he said this______less humid and colder over here.

Now I know his bikes aren't directly comparable to my scoots, but it did help sort my boggyness issues in mid range and I stuck with his guidance.

The level of petrol in the float chamber is controlled by the float but the speed at which it gets into the float chamber is another thing which is where opening out the float needle seat comes in. I never had to do this on my bgm PWK but I did on a previous oval bore PWK which may have been the ScootRS one (not sure about that as it was bought second hand).

There was a good post on here a few days back (Soosh?). He made the point that Keihins maybe are made to work with fuel pumps and not atmospheric pressure which is why they restrict the fuel getting into the fuel chamber. Got no idea whether this is right, but it seems reasonable to me

I've directly compared the SCK pw28 needle to the proper JJH. They are definitely not the same. I can't remember the differences now though

[paulski]

cheers for all the info guys, im starting to think maybe storkfoot has a point about fuel pump?? is there a better carb i should look for that is easy to set up?? ive tried a 28phbh but low end throttle is impossible to clean up on them dellys. buy the way wot is the correct method for setting the float height???

[storkfoot]

Take carb off scoot and remove float chamber. Tip the carb on it's side and angle it so the float is just resting back. Then measure the distance from the top of each float to the bottom edge of the housing (the bit that connects with the float chamber). Measure both floats (they have to be level) and also check that the float needle is seating right. You sometimes have to slightly bend the tab on the float to adjust this.

Carb choice? Everyone has a different view on this and almost all 2 stroke carbs, if set up right, will work well on a Lammy.

[storkfoot]

The level of petrol in the float chamber is controlled by the float but the speed at which it gets into the float chamber is another thing which is where opening out the float needle seat comes in. I never had to do this on my bgm PWK but I did on a previous oval bore PWK which may have been the ScootRS one (not sure about that as it was bought second hand).

I've just compared the 3 PWK carb I've got (old 28/30 oval bore possibly ScootRS with a dull finish slide; genuine Keihin 28 but with a chrome 6 slide; and a bgm 28 with a 3.5 chrome slide).

I was planning to use the genuine Keihin but with the bgm 3.5 slide and float [the genuine float has a different code stamped on it and seems heavier] on a TS1 I'll be building soon. However, whereas the genuine Keihin has a brass float needle seat and a smaller float needle, the bgm float needle seats straight into the alloy casing ie. there's no brass seat.

I didn't think to compare the bore of the opening I'm afraid which, with hindsight, would have been quite useful to know
I'm not sure how this will help you with your Muggy, mate, but it might be quite useful to others who persist in messing around with these carbs