main jet inconsistancies!!! beware !!

OK OK... I trumped it up a little, but I am sitting here comparing two #165MJ's... one has the little Keihin star logo, the other is of unknown manufacture with no logo. The no-namer is 1-2 mm deeper at the aperature end(not the threaded end). I compared my other keihin jets to no-name and they all have the same 1-2 mm diff.

Does it matter? Are origional Keihin jets superior? Is this not a major variation for something as precise as carb jets??

As I recall from my MC mechanic days they are flow rated.Number is based on the actual flow capability and not the hole size/profile.

I always thought they were sized.

A 165 was 1.65mm. Not 100% sure...

I'm talking about the first opening. The opening first has a larger hole (big enuff for the tip of the needle to go into), then it steps down to 1.65mm. The step occurs about 1-2 mm deeper on no-name than on Keihin jets. Has anyone ever noticed this before, and should it matter? I wondering if the clip position would need to be changed to compensate.

[This message has been edited by ballistic (edited 08-01-2001).]

I'm glad that you posted this question Balistic. I ordered a 180MJ from the dealer and it was shorter than the stock 165. I chose to not even try it till I got more info.


I called sudco and asked one of thier technicians. He said Keihin flow tests every single jet they produce, and he he does not have the same confidence in aftermarket jets. His advice was to stay away from anything other than the origional.

I closely compared my two jets further and notice that Keihin has a finely radiused edge, the no name just has a sharp edge. Hhmmmm....

For the sake of argument I am going to delay rejetting today, till I get the Keihin jet.

Ballistic, I'm no engineer but perhaps the shorter jet with a smaller hole does provide the same flow rate as the longer stock jet. Is this simple mathmatics?


I have also noticed the difference on replacement jets. I don't trust the jets without the Keihin star and never use any others. With something so precise as this, small changes could make a difference.

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