Modern Vespa

https://www.scooter-center.com/en/intake-manifold-for-reed-valve-lth-vespa-vna-vnb-vbb-vbc-gt-gtr-sprint-rally-px-cosa-reed-valve-below-si-carburettor-3331597

Local dropped an air filter screw in the carb and it idled till it didn't. Bolt on slim reed valves seems decent for OG cases! Bummer it doesn't work with the autolube but it's better than nothing.

pretty cool... would love to see a report if someone uses or plans to.

Very cool!

"Cannot be used with an oil pump" is a strong statement, and while it may be true with this design, the Stellas used the same basic reed, but supported the oil pump. Of course, those reed blocks are getting harder and harder to find, but whaddyagonnado.

I'll bet you could use it with a Stella airbox if you didn't mind drilling the hole for the 2T to get into the carb. You'd also want a bushing around the drive gear between the cases and the airbox.

does this mount in the air box or under?

interesting idea, but it just looks questionable all the way around.

Gotta mount under. LML made a non-autolube bike with a VERY similar looking reed.

Heard from Mark @ Scooterspeed. He said pass. Said no matter how flat he got the cases, it still leaked.

Didn't DRT make a same product 8-10 years ago?


Seems like the juice isn't worth the squeeze if you can't keep the autolube. And what is the benefit of the reed anyhow? Is it just so you can use your existing 20/20 or 24/24 low profile carb and carb box?

the 3 star rating is a little concerning...
others have already noted.
have to say - are you SURE that the damaged rotary pad is unworkable?

FMP's video on this is - in my humble opinion - a little too black and white.
My own experience - damn thing ran great with a trashed pad.

I'm not saying you can max power with a poor pad - but I'm not sure there is any real data that says you have to go reed when the pad is less than super tight in clearance.

Is the engine not running well?

I haven't checked the pad yet. Had to disappear for a few days for some work. Hoping next week to be able to investigate.

What I do know is I was able to remove the tapered air filter screw from the inlet with a magnet and also removed a small bit of aluminum. I can feel more in there as I rotated the flywheel.

Plan A is to do a motor swap so the owner can keep riding. We'll decide to trash, send out, whatever at that time. Always hoping for the best but mentally preparing myself and the owner for the worst.

that was kind of my thought as well. it's just introducing the possibility of more air leaks in a place that's already known to be a pain in the ass to get squared away leak wise.

it would awesome if somebody made a small reed intake that could accept 20~26 round/flat slide carbs like the polini one for small frames.

The rotary pad on my p200 is pretty scored. Wouldn't know it though from how it went down the road or carb spitback. It ran just fine.


I'm not sure how accurate the feeler gauge method is for ruling out a bad rotary pad. I think the leak test (filling the closed rotary valve with 2t and seeing how fast it leaks through) might be better. Annnd…how does it run or is there spit back?

I wouldn't carve up my case to go reed based on a feeler gauge measurement. If I decided to go reed, I would choose a better one that would offer more carb options.

That pad would clean up just fine with some JBWeld, too. My VBB's motor looked worse than that when I opened it up. I agree that the leakdown test is the real measure.

It's also worth considering whether the scoring runs the entire length of the pad or not. If it doesn't then it'll still be sealed for most of the time the valve is closed, and is de facto just extending the port timing a little.

There you have it.
Pull the bolt out, start it up, and see if you've gained a little high end performance from de facto longer inlet timing.

🙂.

When rotary pads give you scoring, make scorenade.

🙂

Ahh, the sound of something metallic getting eaten by the rotary pad - someone should make a SKA tune with that sound added for effect!

Pulled the flyside half to investigate. Enough damage that it needs repair, but nothing that's the end all. Gonna price out repairs vs new cases. Owner is happy keeping it stock.

That doesn't look too bad. I recently found similar gouges in a set of project VBB2 cases that I have -- but only in a few spots in the crank recess area and not on the rotary pad beneath the intake. I decided to experiment with the legendary JB Weld and razor blade fix technique and it seems to have worked well. I acetone-cleaned and heat-gunned the cases majorly before applying it. It's now cured for more than a week and it feels smooth enough to go for the full engine rebuild soon.

That screw damage on the lip is going to be tricky. You can fix it with JBWeld if you let it set up a little bit, then put a piece of plastic wrap sprayed with mold release, anti-spatter, PAM, etc. on it and close up the cases overnight.

I did it to the Smallstate 1.0 cases on a much worse screw-up than that and it sealed tight. For a while.

I'd do that for my own, not for a customer.