Scooterotica

hello all,

can somebody point me in the right direction for the round type main jets needed for my keihin 28mm copy

i think the type i need are N424-27-xxx but i bet i'm wrong...

the main and pilot in my carb at the moment have no markings on them, so i assumed they are standard size for the carb..

135 main 38 pilot..

any help would be appreciated....

186 mugello, pm copy pipe, will be used with remote filter...

Those "N" reference numbers are possibly Keihin factory numbers. I think that only the main importers, Allens, tend to use them. I have a v2 Mugello with a proper PM expansion and a bgm copy PWK28. I've seen needles from ScootRS with no markings in the past but I've never seen a Keihin pilot with no markings.

Where did you get you carb from? There are many different copies of Keihins around. Some are better than others. If you have a decent copy then you're probably going to need to buy a few marked jets and needles as it would be a miracle if the unmarked set match your engine exactly

If it's any help, my set up is:

Pilot: 42
Needle; bgm one is marked "28"__it's possibly a JJH equivalent- 2nd clip from top.
Main; 115.

I think Corrado on this site stocks some Keihin stuff. Other than that, in the UK, Allens Performance, and Off Road Only do.

Hi storkfoot,


As you can see, the main jet is totally different to what you will have...
My problem is do i replace the whole main jet and holder or try and source jets which are the same as i have..
8mm length x 5mm thread x 6mm dia... like i said there's no markings on these.. the nearest jets i've seen is 99101-393 but has a groove running round the citcumference of the jet


was bought off a friend very very cheap thought i'd put it to use..
its in good nick never been used..

Right, I think that may be an old ScootRS one with a different ie longer atomiser, and shorter main. It's also possible it's an even cheaper copy ____does it have a plastic slide as opposed to a chrome one?

If it does, I had one of these and I think I've got some main jets for it somewhere. However, if you don't know the precise origin of your carb, from my own experience, I'd recommend you start with a good copy ie. bgm, or an original Keihin with properly numbered jets. Probably not what you wanted to hear, mate, but just sharing my experience

its from a motocross shop thats all i know...

its in good nick, the slide is a cast ally type, not plastic or chrome. looks ok..

had the needle out and that doesn't have any markings on it, i guess its a standard jjh type

i'm gonna give it a go n see if its any good. if not then i haven't really lost out that much as it was practically given to me.

storkfoot if you do have jets then i would gladly have them, tell me what you want for em

leehuggy72 wrote: its from a motocross shop thats all i know...
...... if you do have jets then i would gladly have them, tell me what you want for em

OK, mate, I'll help you if I can. I admire your spirit

If you send me a PM with your name & address, I'll send you the main jets I've got which I reckon will be near the ballpark, say, 110 to 125. You need to be aware that these are not Keihin jets, they are Vietnamese copies so whether they are drilled correctly , I really don't know. Also, Keihin jets go up 0, 2, 5, 8 etc, these don't, goodness knows why not

Other things to thing about :

It's from a bike shop, is it definitely for a 2 stroke?
If you take the slide out, measure the slide gap [across the arc] and post how big it is. If the carb was for a bike and not a lammy, the slide will be too lean. If it's the wrong slide (I'll let you know), pass the carb back to your mate as you can buy a good Keihin copy for the price of a genuine chrome Keihin slide.
Some of the Lammy cable choke adaptors I've seen for Keihin's are shocking. Make sure your choke works!
The floats on Keihins are temperamental. US sites say to set it at 19mm. In my experience it runs weak at this in the UK. Set at 22


Good luck

i'm glad i'm in your hands ha ha

never so simple is it...

scootrs do them don't they , it says 28/30 does this mean it can be adapted to run as a 28mm

i'll measure that slide......

taken slide out and the arc circumference is 34mm

the width of the slide is 30mm

hope this helps..

:shocking: , don't have too much faith just yet, mate

I'll check the slide for you tomorrow hopefully but, I think, that sounds right for a lammy. I'll get the main jets in the post too

The ScootRS one is an oval bore, 28mm width, 30mm height. They are supposed to give a better throttle response than a circular bore but, essentially, they are the same carb in my experience.

The slide, as you say, is 30mm width. The cutout in the front of the slide (when I say Arc, I mean the " ( " shape at the front ) should be 18mm at the bottom, and 5mm in height. If it's bigger than this, it might be for a bike.

For your info, I've today received a JJK and GJH needle from Allens____£16 delivered. With Keihins you seem to find that quite a few dealers stock pilots and mains, but not needles for some reason