Ideal jetting on '79 KZ650C3...anyone?

Hi - I just put a Mac 4-1 exhaust and aftermarket Pods on my bike and upped the size of Main Jets from 102.5 to 105. (it had a really rough 4-1 header on it when I bought it). Its running great up to 5500 rpm but then starts to break up a bit and is inconsistent up to 8-9000. I would really like to know if anyone advise of the right Mains for this set up...? I don't know the needle settings but didn't think these were a factor above 5500 rpm...?

I went with 112.5 mains and 17.5 pilots on my '79 carbs i installed on my 78 SR 650. This bike is running a Vance and Hines 4:1 and K&N pods. Stock mains were like 92.5 or something way lean like that, stock pilots were 12.5's. The 78 carbs i got with the bike had the same jetting, 112.5 mains and 17.5 pilots. With the stock 79 carbs, the bike would hardly run off idle, lots of burping and hesitating. With the new jetting it is smooth as siklk all the way to redline. I can't see the mac system flowing much less than the Vance and Hines, so i wou,ld shoot for the 112.5/17.5 jetting, if you have adjustable needles, i.e. with the multiple notches to raise or lower the needles, then raise the needle by putting it one notch lower than stock, on mine it was the 4th notch, again the 79 carbs were not as adjustable, having just one needle position.

Thanks alot for the info - I'll try your recipe and see how it works.

2006hhr wrote:

I went with 112.5 mains and 17.5 pilots on my '79 carbs i installed on my 78 SR 650. This bike is running a Vance and Hines 4:1 and K&N pods. Stock mains were like 92.5 or something way lean like that, stock pilots were 12.5's. The 78 carbs i got with the bike had the same jetting, 112.5 mains and 17.5 pilots. With the stock 79 carbs, the bike would hardly run off idle, lots of burping and hesitating. With the new jetting it is smooth as siklk all the way to redline. I can't see the mac system flowing much less than the Vance and Hines, so i wou,ld shoot for the 112.5/17.5 jetting, if you have adjustable needles, i.e. with the multiple notches to raise or lower the needles, then raise the needle by putting it one notch lower than stock, on mine it was the 4th notch, again the 79 carbs were not as adjustable, having just one needle position.

I've got the same setup as you on my 78 650 Custom which I found was running a little lean. I was just about to go up on my jet sizes. I think I'll try your recipe as well. Thanks