KZ650 float settings and tuning problems

Quote from Clymer pg 148

"The vacuum switch normally allows fresh air pulses into the exhaust port but shuts off air flow during engine braking. This helps prevent backfiring in the exhaust system due to the greater amount of unburned fuel in the exhaust gas during deceleration."

Plug each outlet on the valve cover and try it.

Post edited by: tubbytwo, at: 2007/12/18 14:06

ok, finally got the guages. actually finally got time to get back to it. removed smog valve and capped off the valve cover holes. popping seems to have stopped. does anyone know what the vaccum should be at 1500? and what the vaccum should be at for about 5500?



jim

Post edited by: jccwall, at: 2008/01/30 13:00

Post edited by: jccwall, at: 2008/01/30 13:02

update, popping has stopped. carbs are synched. only thing im concerned about now. is it is smoking a little. excess fuel smell. wondering if it is because of larger pilot jets and/or larger needle seats? bike actually runs real good. also keep in mind #2 cylinder has slightly lower compression. any ideas?

thanks for all your help on this one everyone.

jim

jccwall wrote:

carbs removed. on initial test. added oil to cylinders, rechecked and all went up to 180.
jim

rings are pretty hosed if you see a 60 psi shift. On mine, they quote stock compression at 155 and 120 as the service limit. If your stock is 180, then 120 is probably out of spec.

Post edited by: bountyhunter, at: 2008/01/31 13:27

jccwall wrote:

update, popping has stopped. carbs are synched. only thing im concerned about now. is it is smoking a little. excess fuel smell. wondering if it is because of larger pilot jets and/or larger needle seats? bike actually runs real good. also keep in mind #2 cylinder has slightly lower compression. any ideas?

thanks for all your help on this one everyone.

jim

If all cylinder's compression came up to 180 after the oil squirt, it's probably the rings. Bad valve sealing doesn't improve with oil added.

Smoke may mean blowing by the rings or oil coming down past the valve guide seals (which also fail regularly when they get old) or both.

If the rings are hosed, you probably should see smoke blow out the pipe when you are accelerating hard.

The cheapest fix would be to buy new standard pistons, +1 oversized rings, and a hone. Hone the cylinders, file the end of each ring to get the nominal end gap for the bike and it will seal a lot better. It isn't as good as a complete bore job, but it's cheaper. Check the net and you may find a deal on some NOS pistons and rings. BTW, the local machine shop here charged me $60 per hole to bore so it isn't outrageously expensive to do a bore if you choose to go for that.

I have heard some people just do a hone and install +1 rings into the old pistons to get better seal, but I would not recommend it. You get a lot of blow by around the rings and through the piston grooves when they have wear, so the compression might not come up as tight as you want without new pistons. If you plan to ride it a while, I doubt that would be acceptable.

This place sold me NOS factory piston and ring sets for $36 each. Don't know if they have yours, but it's worth a look:

www.cyclewareables.com/

Post edited by: bountyhunter, at: 2008/01/31 13:46

i don't doubt that part of it is burning oil. since it does have a bit of smoke on rapid acceleration. but it does have a bit of fuel smell to it.

have no doubt in my mind that it does need a rebuild. not sure if the owner is ready to put any more money into this, after all we have just finished doing.

but thanks for the info just the same.

jim.
(learning more as i go)