stock 28mm

I have a 74 Z1 900 stock motor with a Vance and Hines 4-1, and K&N filters.. My question is what size jets should i be running to get the best performance?? Thanks

I think the rule of thumb is up 2 sizes for every mod. Not sure what the stock sizes are but 3 or four sizes bigger would be a good starting point.

The "rule of thumb" thing started when some guy on the XS1100 forum put together a chart that listed how many step sizes for each mod... While this sounds great, it doesn't take into account that some carb assemblies are richer from the factory than others. The early Z1 assembly with #112.5 mains and #20 pilots running a P-6 needle jet and 5J9-3 jet needle provide a rich pilot circuit and rich mid-range... these areas are far richer than most race carburetors (VM29 or VM33). You can run pods and an aftermarket pipe using the stock main jet but performance will improve if you bump the size some... #120 is about right.

As far as the original XS1100 "rule of thumb" settings, they stink for use on the BS34s that come on an XS1100 or any other CV carb based on my personal experience.

Thanks for the info!! Now time to get to work on it LOL!!! Mike

I have a stock kz1000 with 29mm smooth bores and v&h open exhaust with dyna coils and ignition with the biggest jets available and my bike runs nice and strong. I think that with the flatsides it greatly improved the performance of my bike. Going to rebuild with a 1428 kit this winter so I guess I will need some flatside 40's. Time to show every one who calls my bike a dinosaur just what a dynosaur this bike can be. Can't wait to see what it becomes.

I have a stock kz1000 with 29mm smooth bores and v&h open exhaust with dyna coils and ignition with the biggest jets available and my bike runs nice and strong. I think that with the flatsides it greatly improved the performance of my bike. Going to rebuild with a 1428 kit this winter so I guess I will need some flatside 40's. Time to show every one who calls my bike a dinosaur just what a dynosaur this bike can be. Can't wait to see what it becomes.

saxjonz - Wow. Thanks for the great info. I am always confused trying to remember actual jet sizes and rejet info so using the "biggest jets available" will be a LOT easier to remember. In the future whenever anybody asks me what jets to use? BIGGEST JETS AVAILABLE!

GET 'ER DONE!

wiredgeorge wrote:

saxjonz - Wow. Thanks for the great info. I am always confused trying to remember actual jet sizes and rejet info so using the "biggest jets available" will be a LOT easier to remember. In the future whenever anybody asks me what jets to use? BIGGEST JETS AVAILABLE!

GET 'ER DONE!

:lol:

wg obviously needs to bone up on 29mm smoothbore flatslides. :lol:

Lol. Don't know the exact size. I just asked my bike mechanic about what size he put in the carbs and that is what he told me. It wouldn't really matter if in fact those were the biggest you could go if you have a 900 and stock mics. Sorry if that didn't help.

Perhaps you might just get better carbs like those flatsides I won't be using any more and then you will have better carbs to work with and you won't have to worry about the jets because you will already have them in the carbs the BIGGEST JETS YOU CAN BUY. lol But you are right. Sorry if I upset you. I thought maybe you might be interested in them. They are much better than stock.

I had the same setup with the Big K&N pods with 117.5s and it worked great also had stock gearing.