When reeds fail

[Fishman43]

What are the symptoms?

[Wheelman-111]

Greetings:

It starts to act more like an old piston-port engine - without the correct port timing, jetting, compression, etc for it to work that way. In Flash I's case, it started to bog very badly off-throttle. A little at first, then worse, to the point of stalling. Eventually the only way I could start it was by holding wot and cranking with the electric starter for 15 or more seconds, whereupon slowly and reluctantly it would fire and gradually rev up. Remarkably, it ran just fine as long as I didn't let off the throttle. It's how I made it home. The culprit?

I had a pic but must've deleted it. The edges of some Gen 0 Carbon material had begun to split and fray. 0.25mm was too thin to last more than a couple hundred miles. Ran well until then though...

[Fishman43]

Thanks again Wheelman. Would metal reeds do the same thing? It would seem to me that when the reeds crack or no longer seat on the reed block that the motor would just push and pull air/gas mix back and forth trough the carb/intake/exhaust and no longer run. Does this seem like an acurate assumption?

[mousewheels]

Would metal reeds do the same thing? It would seem to me that when the reeds crack or no longer seat on the reed block that the motor would just push and pull air/gas mix back and forth trough the carb/intake/exhaust and no longer run. Does this seem like an acurate assumption?

No longer starting or running is a failure mode, if the resulting leakage is high enough or the reed broke. There are folks here that have had that experience. I worked on a fixer bike where the metal reed leaked, and would start only with a spray of starting fluid, but ran.

When running it was poor at slower rpm, (lean and would quit if idle not set high enough to start engaging the clutch) Mixture screw ended up being no where near factory setting. Running in midrange, lean and weak, Full throttle, better, but still sagging lean.

This is fairly close to what Wheelman's symptoms, where it ran only at full throttle except mine would not start un-aided.

[Wheelman-111]

Greetings:

I had a whole reply vaporize because I became "logged off". It' sounded 'zackly like Mouse's reply.

I'll add two things:

1. Metal reeds can do Very Bad Things when they break. Reeds are spring steel. Pistons are aluminum. Need I say more?

B. Lots of older snowmobiles I've had got through life without reeds or any form of intake flow control altogether. However they were ported very differently, and were raspy, snorty cantankerous beasts. Maybe that's why I liked them?

[Fishman43]

Lots of older snowmobiles I've had

You have snow Deepinnaharta?

[bottomfeeder]

Probably latent memories from a past life...hahaha. Carp..a.k.a. .. bottomfeeder

[Wheelman-111]

Greetings:

Not much snow in Tejas. Misspent youth in Quebec.
I had a 340cc Sachs twin that made 34HP. In 1973. Just a bit peaky...

[eliteguy50]

I had a 340cc Sachs twin that made 34HP. In 1973. Just a bit peaky...

they are just a bit different now, and have reeds, some even have 4 valves per cylinder

[Lunytune]

Not much snow in Tejas. Misspent youth in Quebec.

There's an old saying which I shall paraphrase, "Just because you move a Canuke to Texas, doesn't make him a Texan". I'm glad you like your new home, and most Texans WILL accept outsiders, more readily than some areas. I know.

I can also see why you have such an attitude about reeds, having had a serious failure.

I haven't had a failure yet, knock on wood, but one thing I believe to be a good test is wet compression test. Run a dry test, then run a wet test. Compression should come up considerable on a wet test. Not foolproof, but it helps to confirm or illiminate rings as the problem. On a recent test I ran, dry test was 75, wet test was 200. That told me reed was good, rings was the problem. Sure enough, I had a broken ring.