Topic: OEM vs Aftermarket Jet testing

[Tugboat]

Again, interesting what the manual says. Just a couple of years later, Honda started using press-in slow jets (in the 80/81 CB650 & GL1100) that were inside a tube so you CAN'T get to them in order to clean or replace 'em. In both cases, they reverted back to the normal "pull em out" setup in 1982.

[Tim2005]

I've known different makes of jets to vary in size before... when I was involved a lot with mikunis on 2-strokes the simplest way to compare different main jets was to get a throttle needle and slide each jet down onto it... as the needle is tapered if any jet had a different size hole it would slide further or not as far down, and was quite noticeable. 

[TwoTired]

I'm wondering if the size/number of cross drilled air holes would affect the liquid flow thru the jet orifice? The cross holes appear to be the same on both brand jets.

The cross holes effect emulsification and thus fuel/air delivery amounts leaving the pilot system.  But, they don't change the pressure differential for flow through the jet orifice which feeds fuel to the emulsion tube.

Cheers,

[TwoTired]

Again, interesting what the manual says. Just a couple of years later, Honda started using press-in slow jets (in the 80/81 CB650 & GL1100) that were inside a tube so you CAN'T get to them in order to clean or replace 'em. In both cases, they reverted back to the normal "pull em out" setup in 1982.

Actually, I learned how to remove the pilot jets inside the tube on the GL1100.   See the "Given a Goldwing" thread.

[brewsky]

You can easily see the difference in orifice size in the photo...

The pictures of the jet ends are a little misleading, as the smallest opening is buried INSIDE the jets in both cases.

The OEM Keihin design is much harder to clean, as there is a larger diameter "chamber" in between two smaller openings inside which traps debris inside.

You can soak them in cleaner, blow air or water thru them, run a wire thru and pick them up later only to find them partially blocked again.

I think this happens  not so much from particles that enter from the outside, but because built up varnish and deposits  are loosened by the cleaning processes and are too large to escape from the chamber.

It almost looks like the fat end of the Keihin has a pressed in plug to reduce it's diameter.
?

OK, what about the effect of removing the "plug" in the fat end of the Keihin jet to make sure it is clean inside?

I pulled one from a set that was COMPLETELY stopped up inside, and took forever to get a hole thru after soaking with a guitar string.

Now I am sure there is more gunk inside just waiting for me to re-install the carbs before breaking loose and blocking the inside hole again!