I really don't know a whole lot about tuning old bikes ( I'm 18 ) ... It's a 1980 KZ-650E1 LTD with an aftermarket coil, Kerker exhaust, bigger Spark plug wires, and a Straight feed petcock. When my dad first got the bike it ran great.. couldn't even hold on to the bike... but a buddy of his told him he should put the OEM petcock back on it ( it had a Drag style Petcock on at the time) so he did... silly us didnt know what we got ourselves into with the whole vacuum petcocks ( a blast from the past)... so soon after the diaphragm goes bad in it and we rebuild it... at this time the bike wasnt running like normal... so we took it to a guy at a bike shop and he got it to run better... but still not as good as it did before.

So after a year of tinkering with the timing , dwell, cleaning the carbs/jets, and i did put a drag petcock back on it... he got angry with it and gave it to me instead of selling it... i don't want to sell it because its a great bike...but it just isnt the same... anyone know what I'm doing wrong??? What can I do and go over to tune it back to its ball breaking power?? can anyone give me a list of things to go over??

 

I do think keeping the original vacuum petcock in place is the best idea. (You won't have to worry about leaking fuel everywhere in the event of a sticking float, or bad float needle.)

You could check and lubricate the timing advance mechanism. If the advance doesn't operate freely, you'll have ignition issues in the upper RPM range. Other than that, the aftermarket exhaust may be causing an air/fuel mixture problem if the wrong jets were used.

 

Well the previous owner is the one who set this thing up with Kerker exhaust, drag petcock, and bigger jets... and it was running perfect until we put on the stock petcock and made adjustments for better fuel economy... thats where we messed up... so I know there is a timing issue, along with air/fuel and ignition problems... when it gets above 5500 revs it starts stuttering and gets more choppy the further up it goes... I just wish we haden't messed with it because it seems its going to be very time consuming to get it back to where it was... so i guess ill have to find a service manual to help fine tune things since there really is no one around here locally who will take an old bike like this one...

 

you might want to get that service mannual. hope it helps you out with the settings you need to get it running good again.

 

Hey,

Do you the have Mikunis with the accelerator pump? I spent weeks chasing the same symptoms on a 79 KZ. Turned out to be a combination of 3 things. Petcock diaphram was leaking into the vacuum port, also there are 2 diaphrams for the accelerator pump. The black (lever side) was OK but the vacuum cut (red triangle shaped) was pinholed. Replaced red one and rebuilt petcock. If you have points old Kaws are notorious for voltage drop at the points, this can cause wild timing and backfiring problems (and pipe bluing, My poor Kerker is BLUE!). Check voltage at points with bike running. Mine was getting only 5-7 volts. Used a foglight relay from switch to battery to points I now have constant 12 v. Bike screams now! Good Luck!