87 VR, Coasting Enricher system, is it necessary?

[Gearhead]

Hello! My 87 VR with lots of miles has 1 or 2 damaged coasting enricher diaphragms. Those pups are spendy. I'm under the impression that these valves:

 

1) Allow part of the air into the pilot circuit and are normally "open" with the spring pressure.

2) They only close under very high engine vacuum, higher than idle vacuum. This happens briefly when the engine is revved and the throttle suddenly chopped closed, or when using lots of engine braking.

3) Under this condition it's common to have a lean misfire, which allows unburned gas to go in the pipes and pop. By closing part of the pilot air, this systems enriches the pilot circuit under this coating condition.

4) It has NO OTHER FUNCTION or impact on the running of the engine, other than the pops in the pipes and associated emissions.

5) A leaking diaphragm would cause two things, first, a small vacuum leak, and second, the enricher might not "enrich" under high vacuum.

 

Is this all correct? IF SO...can they simply be disabled by plugging off the vacuum where it comes into the top side of the diaphragm? This allows the springs to keep the diaphragms down, coasting enrichers OPEN, the full pilot air flowing, stops the vacuum leak, and makes the diaphragm inoperable. More what I'm asking is, are there any other side effects to disabling this system?

 

Full Story:

https://www.venturerider.org/forum/showthread.php?141445-87-VR-carb-problem&p=1062867#post1062867

 

Thanks!

Jeremy

Edited July 29, 2019 by Gearhead

[MiCarl]

So long as you close off the vacuum to the diaphragm you should be fine. Just popping on coasting.

[Patch]

They can also be repaired using a shop latex glove and the black Mr.Gasket. Just paint it with a thin layer cut the size patch that covers the complete diaphragm, then with a dry art brush lay the patch over, let dry over night...

Patch

[Gearhead]

I just wanted to offer an update on the particular question I posited about the Coasting Enricher system: "Are there any other side effects to disabling this system?" (Read OP for details.)

 

I don't have a bulletproof conclusion due to the way everything has gone down, details in my main Carb Problem thread.

https://www.venturerider.org/forum/s...67#post1062867

 

But at this point, my testing suggests that the answer is NO. If you block the vacuum ports to the Coasting Enricher diaphragms, I believe the carbs will work just fine with the exception of popping in the pipes on decel. I had not found much on this topic, so I wanted to offer my semi-substantiated conclusion to wrap this thread up. Take it for what it's worth!

[Patch]

I just wanted to offer an update on the particular question I posited about the Coasting Enricher system: "Are there any other side effects to disabling this system?" (Read OP for details.)

 

I don't have a bulletproof conclusion due to the way everything has gone down, details in my main Carb Problem thread.

https://www.venturerider.org/forum/s...67#post1062867

 

But at this point, my testing suggests that the answer is NO. If you block the vacuum ports to the Coasting Enricher diaphragms, I believe the carbs will work just fine with the exception of popping in the pipes on decel. I had not found much on this topic, so I wanted to offer my semi-substantiated conclusion to wrap this thread up. Take it for what it's worth!

 

As explained it is not about vacuum it is about atmospheric pressure which allows for the psiphoning which if not correctly switched will create a rich condition.

 

It will click you'll see

Patch