Topic: 74 CB 750 K4 Carb Slow Jet Question, Will These Work?

[manjisann]

I am trying to find the slow jets for these carbs. On Jetsrus.com it says they are no longer made in the correct length. The correct length is 28mm but the ones still made are 32mm. The website suggests just cutting them down with a dremel. What I am wondering is whether I can just leave them 32mm long? How will this affect the fuel air mix?

Thanks,

Brandon

[TwoTired]

Are the emulsion tube holes the same size and number.  Is the internal orifice in the same position as the shorter ones?

[wrenchmuch]

I am using 32's cut down to 28 mm . There are 4 emulsion holes . I added 4 more so it matched the stock ones . I needed #35's and this is the only way I could find them . Plug colour and overall performance is good . As for the questions raised by TT regarding dimensional matches between the two ? I can't speak to that .
Mike

[xenoscr]

I just bought 32mm #42s and left them alone. My bike runs better than ever. The way I figure it, the bottom is just further into the fuel. If they where shorter and not below the fuel line in the bowls then I'd be worried. Plugs look good to me so far. I ran them on a 2 hour ride the other day, no problem.

XeNoSCR

[manjisann]

xenoscr, that's the same sizes I need!   I was thinking the same thing, I just wasn't sure if I was missing some sort of physics that would cause me problems. I just hate the idea of modifying these things (dunno why, i've modded so much else on the bike 

TT, assuming all other things being equal, if just the large diameter part is 4mm longer, would it make any sort of difference? It's not that I don't trust xenoscr's experience, I just am curious about the technical aspect of it all.

Thanks guys!

Brandon

[xenoscr]

I'm a bit curious as well. If there's some long term ill effect then I'd like to know about it of course. My un-expert thinking is that it's not going to make any difference being 4mm further below the surface of the fuel. Any pressure difference is going to be so minute that it's not worth worrying about. But I will accept an expert telling me why I'm a moron as long as they explain it well enough that it makes sense.

XeNoSCR

[TwoTired]

I can't see why the length of the tube makes a difference until the fuel level gets low enough to starve the jet tube inlet.  What I would be concerned with is fuel level in the float chamber relative the orifice position.  That's the height that the fuel must be drawn to get to the actual metering orifice, and percolate into the emulsion tube.

I suppose a longer jet tube might be more likely to pick up debris sloshing around in the bottom of the bowl.  Usually the main, which has a larger orifice, would suck these out before the pilot jet could get it.

That's my armchair analysis, anyway. 

[manjisann]

TT, thanks for weighing in, I'll take your armchair analasys any day! Between that, and Xenoscr running them already I'm comfortable to try them. Already placed my order, hopefully they get here soon as my idle circuit is kinda weak.

Brandon