Jetting a PWK 30mm carb on a Mugello 225

[iLambretta]

Greetings......

I am desperately in need of some help with my LIS150. I run a BGM 30mm PWK copy, Mugello 225 and ScootRS Pipe. I am running a large Evergreen Foam Fiter. I am looking for some jetting advice for the needle and main jets. I have the scooter idling well and pick up up to 1/3 throttle is good. However once I get above one third to one half throttle, I get unbelieveable boggy and the scooter stalls out. I have been trying to do plug chops to see what is going on but this is proving really challenging as the muggy warm start issue kicks in and I basically have a fouled plug everytime, the only way to get the scooter to restart after this occurs is to pull the filter and run open mouth......so I am honestly not sure what I am looking at when I pull the plug.
I am currently using a JJH needle on the lowest clip, a 40 idle and a 132 main.
I have a full set of idle and main jets and also have the following needles
BGM's PWK30 standard needle (have no idea what that equates to)
LJH
JJK
JJF

Thanks for any help you can provide

[drunkmunkey6969]

Here you go matey.....

http://scootrs.com/tech.cfm?tip=tunecarb
and
http://scootrs.com/tech.cfm?tip=jetpwk

[iLambretta]

Here's the thing....THAT's my scooter on that tech page for the Mugello 200+ & 30mm carb

[storkfoot]

If you compare the bgm needle with your JJH I reckon they'll be nearly the same, if not exactly the same.

I think your way too rich on the needle. I'd keep the JJH in for the time being but change it to 2nd clip from top. Pilot, leave at 40, but if the starting from cold is not brilliant, maybe go up to a 42, maybe even a 45. Also, your main looks a bit on the big side and always make sure your float is set right.

Lastly, I think the ScootRS tech pages talk about tuning the carb with the main jet out. I struggle with this, personally, as there is a big overlap between all the stages of throttle opening. Be aware that even the main jet can effect performance quite low down and conversely the pilot runs well into cutout and needle territory.

Let us know how you get on. Good luck

PS, is your filter on the carb and through the panel?

[coaster]

It sounds like you are way too rich on the needle as Storkfoot says. A GJH needle is weeker and might help. As for the idle, how far out is your idle screw? That might give an indication as to wheather its around the right size.

As for the warm start issue, get into the habit of turning the petrol tap off before you turn off the ignition and don't turn it on again until after the engine has started. Works every time for me

Keep us posted

[iLambretta]

Storkfoot and Coaster - thanks guys for the advice. If it stops raining here, I'll try these recomendations. To be honest, I think I've tinkered with the bloody thing too much since I got it and now it's just out of whack......
As far as my filter goes, I got this awesome large foam filter and bellows from Scooter-center (it's an evergreen - I'd never heard of before as I was previously running a smaller RamAir). The bellows are for a larger belmouth carb, but it clamps down real good and seems to provide plenty of air
http://scooter-center.com/catalog/produ ... anguage=en

Thanks again for the help - much appreciated

[iLambretta]

Coaster - one more question mate if I may....I do use your technique of shutting of the fuel and allowing the bowl to empty a bit before switching off...and while that does help, it is impossible to do this when I am trying to do plug chops.
is it safe to be dialing in the carb jets while running without a filter? As this would get over the warm start issue. Is there a huge difference in jetting with an air filter and without?

Cheers

It sounds like you are way too rich on the needle as Storkfoot says. A GJH needle is weeker and might help. As for the idle, how far out is your idle screw? That might give an indication as to wheather its around the right size.

As for the warm start issue, get into the habit of turning the petrol tap off before you turn off the ignition and don't turn it on again until after the engine has started. Works every time for me

Keep us posted

[storkfoot]

............Is there a huge difference in jetting with an air filter and without?

Yes, if you're going to run a filter, you need to jet it with the filter on. As you've no doubt discovered, performance varies a lot between no filter, and filter.

I haven't tried one of the filters you link to, but their bellows look wider than the usual "stretched" GP bellows which I have tried before, and therefore it should be easier to jet.

The problem with bellows, in my experience [but I'd personally welcome other ideas], is that the jetting has to be spot on ie. at it's leanest, before going too lean, if you're going to keep the spitback * in check. This is especially the case if your inlet timing is on the high side.

From what I've learnt, by trial and error, is that it's a lot easier to jet a carb either open mouthed, or with a decent filter without the bellows ie. straight out of the panel, than with bellows.

* carbs work by sucking air in as the piston moves up the cylinder. If the previous stroke blew out an over rich mixture, then this mix hits the bellows and is still hanging around [rather than going through the panel into the open air] when the piston goes back up the cylinder and sucks up a load of over rich mix. This is bogging, ie running on an over rich mix.

I hope this makes some sense. In your case, first of all, weaken the needle, keep the filter arrangement, and see how it goes

[sean brady scooters]

just for interest.....for anyone using the bellows /filter set up.............
i have always found what is needed here is a simple 1mm hole drilled through the lowest part of bellows etc..............
this drains any excess of fuel build up............

[chris2470]

Hi All at Scootererotica,
This is my first post and I hope it will be of some use to you.
I currently run a 30mm OKO which runs perfectly crisp, plug chops all look spot on.
I run a stage 4 200 Indian top end and PM pipe, the settings are:
NO Filter
Needle JJK 2nd clip from top.
Main jet 125
Pilot jet 40
Air screw 1 1/2 turns out.
I hope that will be of some use, if not try here:
http://www.duncanracing.com/techfaq/Tec ... ting.phtml

Best Regards Chris