To reed or not to reed?

To reed or not to reed? that is the question.

I’ve just bought a Keihin PE 24mm for 12 Euros!!! ( copy and new)

But, I don’t have a manifold for it, so I’ve got 2 choices.

I use a base gasket as a template and get a local shop to fabricate a manifold for it , using photos of a Polini/Mallossi manifold as a guide. What angle should it be and what length , height etc??

I go and buy an old barrell with a reed valve from a Honda NSR, Yamaha or a Kawasaki and cut off the reed intake area(?) and have that fabricated to fit on to my engine block , again the same questions ie; angle, length and height ?

At the present time, I don’t want to split my engine cases and do the inlet porting for the reed. Would it still run okay with a reed and carb just bolted on? I know it would work better with the porting.

Any ideas ,chaps???



Hi Grimesy66, I agree with Adrian. You can get manifolds for bigger/downdraught carbs from all good scootershops, or second hand.
Reed valves can be a good way of saving fuel and increasing smooth acceleration, but you need to do a lot of work on a classic scooter engine.
Don’t spend silly money having a manifold made, just get a Del’Orto one for a PHBH 28mm. The rubber should fit fine. Take advice from a well known/respected scooter shop
Mike (Happy House S.C)[:)]

Hi all,

I’ve decided to ditch the reed valve idea at the moment. I went back to the bike shop and showed the guy a photo of a kiehin manifold and he then produced one! ( Funny,coz’ the first time I asked he said he didn’t have one??? ) Any way I bought it for 2 qiud. I’ve taken the carb and manifold to my scooter man here in Bangkok and he’s going to work on it. He seems to know his stuff.

I’ll let you know and then ask some more questions about jetting[:look:]

Curare, I think you might have misunderstood me. I don’t want to put a M/cycle barrel on my scoot.I was considering cutting off the reed valve ONLY . I think I asked you before about doing this and you correctly said it’s alot of work and expense. Although I’ve seen a couple of converted Vespas here, I’ve no idea how well they run or where to have it done.

JuanK, Re; ScootRS, I tried to order from them before but I was informed that ScootRS don’t sell in Asia!!! Because of Asian fraud!!! Correct me if I’m wrong but isn’t Vietnam in Asia??? ( Buyer Beware )

Many thanks for all your input.


hello Grimesy66,

yes, I realized I misunderstood your question.

I doubt a carb that small would be worth reeding Grimsey.

Wouldn’t ScootRS have a manifold for that?

#1. Connect the carb to a gastank with a hose, tilt it to find out what angle where the float stops working, i.e. when the carb starts to leak. This will be the angle that you can’t use. Reduce the angle with 10 degrees and you have the max. ANGLE.

The length and height, you can only use the space in the sidepanel, with rear wheel spring fully compressed.

You have to have a gaspump as well.

#2. To fabricate a reedass’y from old bikeparts, is a challenge, but a nice project. But if you don’t rework the casing, you will only add a restriction, as the slidevalve will still be in charge.


to fit a bike barrel you need a lot of work on the engine cases, and I don’t advice you to do it or to let somebody do it that doesn’t have previous experience on this field. If not you will collection a long list of mistakes and mechanical faileures.

I don’t think you should consider as a starting point a carb!

Think about a reasonable project that some day you will be able to achieve, make a list and start buying or start saving.

Look for a plain manifold to fit the carb to the engine, they turn up on Ebay from time to time. I got a CDC one for a 28mm Dell orto for £10. I’ll keep my out for you, don’t spend money trying to make one, they are out there. Cagiva Mito 125’s use PHBH 28mm Dellorto carbs if you have bike breakers over there, or look at scrapped motox bikes to see if they have decent Mikuni, or Keihin carbs.

That looks easy enough to make an adapter plate for to fit it to your motor.