Scooterotica

You're too lean at tickover which is why your engine dies. A 32 pilot is too small for a Mugello, try a 38.

storkfoot wrote:You're too lean at tickover which is why your engine dies. A 32 pilot is too small for a Mugello, try a 38.

i'm glad your online, your the oracle when it concerns these carbs

few questions

1 tried a higher pilot and she wouldn't tick over at all
2 air screw, if wound all the way in, i'm i right in thinking it needs winding out to around 1-2 turns..
3 idle screw, where does this need to be around at
4 bought some needles from scooterkoln, bgm pwk needles... but the code etched onto them are pw 21, 24, 28, 30 ???? any idea what these translate too
5 why is it dying when throttle is used

regards lee

leehuggy72 wrote:
i'm glad your online, your the oracle when it concerns these carbs

few questions

1 tried a higher pilot and she wouldn't tick over at all
2 air screw, if wound all the way in, i'm i right in thinking it needs winding out to around 1-2 turns..
3 idle screw, where does this need to be around at
4 bought some needles from scooterkoln, bgm pwk needles... but the code etched onto them are pw 21, 24, 28, 30 ???? any idea what these translate too
5 why is it dying when throttle is used

Lee, I'm no oracle, mate, I just persevered with them
1_ I find that odd but it would, of course, depend on your mixture screw. My 186 Muggy/ bgm PWK 28/ PM25 would no way have ticked over on a pilot as small as a 32. Your choke is definitely working OK? This is really important. Take the carb off and look in the back of the bore whilst you activate the choke. You can easily see whether the choke works Ok on a PWK.
2_ You can have the air screw out as much as about 3 turns but if you're having to turn it out that far, you should drop the pilot. The reverse applies too. There is no set air screw setting, each engine is different. The idle screw needs to have the slide lifted a few millimetres from the base of the bore, otherwise there's no mix getting through.
3_ No. I was told a 28 is a JJH but when I fitted a proper Keihin JJH, it was different. I think you'll find you'll need to drop your needle as at mid clip you may find it too rich. Setting the needle is a lot easier if you use correctly lettered Keihin needles as you know where on the progression they are leaner.
4_ jetting, air mix, kink in fuel pipe, worn out slide,it could be a lot of things. Is your float set at 21 or 22?
Paul

Choke is fine, had a look from behind earlier today and you can see it lift to show the whole of the hole

Air screw i see what you mean

keihin needles where the easiest place to get one, allens??

float level setting, to be honest i thought it was set standard, how do you do it???

cheers

Lee, if it's any help, my Mk1 Mugello 186 with PWK 28/30, BGM 120 (standard indian flywheel) and Sito Ancilotti has the following jetting:

Pilot - 34

Main - 138 (Yes I know that's huge but I holed 2 pistons on smaller mains )

Needle GJH needle in top clip

Timing is set to 17 degrees

Squish was about 1.3 when I originally built it.

Starting from cold can be a bugger if I havn't used it for a week or so, maybe I could go up in the pilot but it runs just fine otherwise, nice and clean through the rev range and doesn't 4 stroke too much on feathered throttle.

When starting I have found that it likes the throttle to be closed (warm or cold start), wait till it fires and be ready to open the throttle a very little way untill you can feel that it's caught, then blip it until its warmed up.

Good luck

leehuggy72 wrote:4_ jetting, air mix, kink in fuel pipe, worn out slide,it could be a lot of things. Is your float set at 21 or 22?
Paul

doesn't the pwk 28/30 carb have a standard 19mm float setting, does it need to be adjusted

leehuggy72 wrote:

leehuggy72 wrote:4_ jetting, air mix, kink in fuel pipe, worn out slide,it could be a lot of things. Is your float set at 21 or 22?
Paul

doesn't the pwk 28/30 carb have a standard 19mm float setting, does it need to be adjusted

It's agood idea to check it but it would have to WAY out to cause your problem at tickover

float measures 20mm from carb face to back of float..

i've put a 38mm pilot in, she kicks off and ticks over to a degree

air screw is at 2 1/4 turns out

idle was set by winding out, then winding out till slide moved a couple of mm

take choke off she eventually dies

No air leaks anywhere, carb rubber or manifold to cylinder? I've heard that spraying WD40 over the joints while the engine is running will reveal iot there's an air leak as the engine will run smoother for a few seconds....worth a try?

Also, have you checked that ther fuel is running through the tap and that the breater in the cap isn't blocked?

The float height is very important on these carbs and it's also very easy to disturb the floats when you're taking the float chamber off. As Coaster says the float height shouldn't be the issue with tick over but a couple of mms either way can be the difference between starvation and flooding when you're on the road. 19mm is referrred to on US websites, however, I found this was too weak and, at times, at full throttle caused starvation. 21 or 22, trust me .

If you take the choke off and it dies this still indicates it's too weak. This means you need to richen the air screw and or pilot, or alternatively, as Coaster says, you've got an air leak somewhere.

Allens in Bingham will supply the needles and jets.

I haven't used the OKO pattern version before but remember that these carbs are copies in the same way Jetex are copy dell'ortos. Copies aren't always as good as originals as I'm sure you know. I persevered with mine and I learnt loads of stuff about carb setting that I'd forgotten in the 20 years or so that I was away from scooters. That said, having also set up a TM24 Mikuni on my other scoot, I found the Mikuni to be easier to set up although exactly the same principles apply to setting up a Mikuni, as a copy Keihin. Why it was easier, I don't know. Maybe it's just better made, or the issue lies with the compatibility of the PWK with the porting of the Mugello 186 [other people have said this too].

The reason I say all this is that you could spend months with the OKO and spend a lot on jets and needles, and then still find it's not quite right. If I still had my Mugello 186, and knowing what I do now, I'd go TM24.