Symptoms of broken or bent reeds.

[ULC Soulagent]

I did the same when making dual stage reeds for my imola many years ago using Malossi Reed sheets of various thickness but the price of them now probably makes it unviable.
Check out below link for Karting reeds, just might find one that’s suitable
https://www.mondokart.com/en/engine-acc ... mondokart/

[Rich Oswald]

Well would you believe it. I replaced my broken reed petals snd it still ran like a bag of shite. Changed stator and bingo, spot on. News to me that a dying stator can blow your reed petals. You live and learn.

Rich'

[Fast n Furious]

I doubt the stator was reponsible Rich Let's face it....... The stator is a Lambretta nemesis.
The 186 valve doesn't use any strain relief plates. The narrow crimp plate design allows the reeds to open as far as possible, which means they don't bend uniformally and the tips can potentially smash against the inlet port wall.
If that is what it takes to make a race scoot take the chequered flag, then so be it. After all, those reeds will get replaced before the next race and so, all is well.

That level of risk isn't fit for a performance/ touring road scoot IMO.
I do wonder if relief plates could be retrofiited?
Inlet port may need some dremmeling?
I'm assuming that because the only recomendation out there seems to be on "doubling up" on the reed petals, that there is nothing around from other valves out there that could make an "off the shelf" solution?
Maybe someone knows different?

[Rich Oswald]

Well FnF, it's a bit coincidental that both things broke at the same time. Plus I asked three good engine builders after the reed petals blew and all three pointed to the stator.

Rich'

[hullygully]

the back firing thru the stator probs blow thru your petals

[Rich Oswald]

the back firing thru the stator probs blow thru your petals

[Fast n Furious]

I find that the "back fire" happens after the reeds have broken not before.

[Storkfoot]

Not only had I been trying to jet the carb when the reeds were slightly worn out, I also had an air leak at the carburettor rubber manifold. The previous arrangement was a 30mm Granturismo inlet manifold attached to the carburettor via an MB stepped inlet rubber. These are made with the PHBL25 in mind and the ribs don’t match up with the TM24. I realised this at the start but I “thought it’ll be alright.”

Anyway, I am just about to fit the correct size inlet manifold and mate it with the carb by one of the CamLam car radiator style inlet rubbers. First impressions are that this will provide an airtight seal. We’ll see

[Storkfoot]

...

The “missing” at high revs seems to almost mimic a slipping clutch but it is a 7 plate LTH which I have checked. An air leak test was done when the reeds were changed and there is no visible signs of a leak now.

This is the first set of reeds I have ever had go, probably as I do replace them quite regularly. Thinking about it, I did have a backfire whilst revving on the stand. Also, whilst the reeds aren’t that old, those 2000-3000 miles have been done at high revs mainly...

Whilst the reeds and inlet rubber were part of the issue, the petrol pipe had an internal diameter of 6mm. Replacing it with one with an ID of 7mm appears to have resolved the missing which must have been fuel starvation. Sometimes we forget the simple things

[nickw]

That is interesting. Down at a local scooter shop and a fella from a scooter repair shop had called in for some petrol pipe explaining he had to change the diameter of the petrol pipe because the ve*** was not running properly and had put it down to starvation. I just said scrap the thing, why waste money on petrol pipe.

[Leotech]

I just rebuilt my friends GT240, I had just got it running and he appeared.

I left it with him in the workshop whilst I went to to the loo, I could hear him start it and rev its tits off, much more than I liked, then it misfired a couple of times so he revved it even harder, then back fired and stopped.

I returned and noticed he hadn't turned the fuel on, I put that down to the misfiring etc, then it wouldn't start even with the fuel on. He was revving it so hard on the stand that when it had ran out of fuel and backfired it blew the reeds out!

So that added an hours time to my pre Whitby work load to drop the motor and put new reed petals in, He asked where the reeds had gone and I explained through his cylinder and hopefully out of the exhaust.

New reeds fitted and it started again, the old reeds flew out of the exhaust pipe! I still don't know what possessed him to rev it so bloody hard! Some folk seem to have zero mechanical sympathy.

[ULC Soulagent]

New reeds fitted and it started again, the old reeds flew out of the exhaust pipe! I still don't know what possessed him to rev it so bloody hard! Some folk seem to have zero mechanical sympathy.

Expect to find him in a lay-by soon