carb swap

hi i have swaped hitachi carbs on my xj750 for mikuni xj 600 carbs . not to sure as to float levels .are they the same or do i set them the same as 750 levels and will i have to change jet sizes to 750 . had to swap as itried to get float needles for 750 and was told yamaha europe had discontinued them

 

Float needles should be readily availble in the aftermarket. Chacal on this site carries them. The 750 fo use different jets but hard to say what exact size as I doubt many people are running Mikuni on them.

Set your float level using the tube method so the level is 3mm below the gasket line.

 

Different style carbs using different fuel levels..........size of the bowl, relative placement of the main jet versus the floor of the bowl, "tuning" issues (believe it or not, fuel levels are also a carb fuel mixture "tuning parameter", etc.).

I would recommend sticking with the recommended fuel level for those carbs.

Of course, I would recommend sticking with the 750 Hitachi carbs for that bike, because otherwise, you may very well spend half a decade or so getting them tuned right for that engine/bike!

 

OOPS right you are Len - Looked up the Mikuni and found 5mm instead of 3.


Check your service manual for the correct setting level.

 

thanks for reply but i have tried with two set of xj750 carbs to make one set but with no luck i have xj600s on. idles well but on drive it seems like its being starved of fuel would this be because of jet size ie 105 on xj600s and 120 on xj750

 

Mikuni and Hitachi jet sizes do not correlate the same, the numbers "mean" different things on Mikuni carbs than they do on Hitachis.

The best bet is to determine what size jets are currently in there, and then start experimenting. It's as if you've added pods to a regular 600 engine.....lots of trial and error!

 

thanks will have to try as i have tried everything with 750 carbs and i do have pods on and pipes are two pairs of two into one straight through pipes do you have any idea ruffly were to start many thanks