I happened to notice that I had gone to reserve a bit earlier than I typically anticipate a month or so ago. In close proximity to this I also had the 10.25:1 pistons installed. So, as they mulled about into the same stream of thought in my subconcious, they merged and it occured to me that I was getting really bad, like 28 mpg, fuel mileage with 10.25:1 pistons.

A couple weeks ago, I was doing maintenance, (oil, filters, etc..) and when I removed the gas tank, I got a good clear look at the area on top of** the intake manifold, and there I saw a spring. On closer investigation, I also discovered a broken piece of plastic that seemed to cover some sort of gasket/diaphraghm. According to my Clymer Manual, it is a 'Coasting Enrichner Diaphram Assembly', but it has no name on the Road Star websites parts list, and the parts guy at the dealership had no name for it either.

Here is (hopefully it works) a link to the parts diagram , if the link doesn't work, it is part #s 37 & 35 in the 1999 Road Star XV1600AL Carbeuretor page.

Anyhow, 60 bucks later I have replaced it, and my fuel mileage is now lower and mid 40mpg range, that includes with the High Compression pistons, shotgun exhaust with minor baffle, full windshield, bags and a hundred pound wife.

If your getting poor mileage for no apparent reason, find this on your carb and maybe spray a little WD-40 on it while it is fairly cool and running, and listen to see if it sucks a little in and causes the rpms to dip a bit.


Ok, gotta run

Later

Max

Good catch Max! I don't think I've ever heard of that happening before. Something to do a visual check on when I change my plugs soon.

Thanks for the heads up.

Ratl.

COASTING ENRICHER - Feeding a Closed Mouth

You're blasting down the road and you see a hairpin coming up, so you close the throttle. This closes the butterfly valve. You and your 400 lb. baby (the bike, not the other love of your life), are still rolling with inertia, keeping the engine revs high. Now it can't get the mixture it's trying to suck in because the butterfly valve is closed, blocking the air flow.

To compensate for this there's an air jet in the lower diaphragm chamber that transfers ambient pressure to one side of the coasting enricher's spring-loaded cut off valve. The excess vacuum in front of the butterfly valve is transferred to a drilling that leads to the other side of the cut off valve. This sucks it open, allowing the pilot jet to feed more fuel to the engine, preventing an overly lean condition. (Pop. Pop. Pop.)

Yeah but, how do coasting enricher parts get into an intake manifold and if they do get into an intake manifold, how do they stay there and not get sucked into the valves?

Jim

Jimtec wrote:
Yeah but, how do coasting enricher parts get into an intake manifold and if they do get into an intake manifold, how do they stay there and not get sucked into the valves?

Jim

exactly what I was thinking. Hmmmm?

Yeah but, how do coasting enricher parts get into an intake manifold and if they do get into an intake manifold, how do they stay there and not get sucked into the valves?


Laying on top of the intake manifold ...

I could very easily see down behind the air cleaner after I removed the tank.


I have a few pictures of it all, it just didn't seem worth the bother to get them edited down to a size that the site will accept, with enough image quality to distinguish things.



Max

Max127 wrote:
Yeah but, how do coasting enricher parts get into an intake manifold and if they do get into an intake manifold, how do they stay there and not get sucked into the valves?


Laying on top of the intake manifold ...

I could very easily see down behind the air cleaner after I removed the tank.


I have a few pictures of it all, it just didn't seem worth the bother to get them edited down to a size that the site will accept, with enough image quality to distinguish things.



Max

I may have misunderstood, but, after looking at the parts diagram, I was under the impression that the parts you saw were on the outside of the manifold, not on the inside. Please clarify.

Ratl.

Neal, does the 42mm carb have this?

Max wish you had posted before now I have a stripped 99 carb that has those parts still on it I would have sent to you. Would have saved ya $60!

The coasting enricher cuts off the air from the pilot air jet at the bottom left of the carb mouth.