KZ 650 Problem (stumbles off idle)

I bought a 78 KZ650 B2A and I have adjusted the valves replaced the points and condensers and the wires. The carbs have been cleaned and new jets put in. My question is that when I go to open the throttle quickly from idle it will bog down and try to stall. The bike idles fine and runs fine on open throttle but I can’t figure out what the problem is. Does it sound like a carb, ignition timing, of some other problem. One thing that I saw was the bike came with #90 main jets and this seems like it is a little small. Any help would be great.

Post edited by: onuLine57, at: 2007/06/25 13:59

Welcome. The main's seem a little small to me too, I'm not sure but I thought they have 110's but not sure. On the bog you can check the timing advancer to make sure it moves freely.
Mark

Ya I saw that WG said that the 78-79 came with ths small jets and that 102s can be put in i think. I was going to pull the advancer off tomorrow and look at it.

Hi there,

sounds to me u might forgot to freshen up the sprakplugs.. (in other words get new ones) I had excactly the same problem . Changed the sparks and hey presto runs like a dream..

sorry forgot that...the plugs are new too.

when you see a stumble off idle like that from what i have seen you will probably have to adjust the pilot screw since that is what effects that part of the circuit in the carbs

I have it set at 1 and a half so im thinking i should turn it in a bit and see if it gets better is that correct?

The only way to know is trail and error go in first if it gets worse go the other way

Do you have a header on it and pods? My bike was doing the same thing on the stock 15 pilot. So I put a 17.5 in it and that helped but ended up w/ a 20 and now I'm all good..

no its the stock air box and filter and stock exhaust. There is a small exhaust leak where the header and muffler meet on the left pipe though. Im going out now to play with the pilot screw.

Post edited by: onuLine57, at: 2007/06/25 19:25

Mine did the same thing to til I adjusted the air mixture screws just right, but generally I am not sure if these bikes can handle sudden throttle burst like that but be very slight at adjusting air mixtures if you do.

Alright I closed the pilot screw a bit and lowered the needle one slot and it seems to be a bit better, I will know for sure after work tomorrow. Another problem im having off and on is that when i push the choke down the rpms want to go up on their own. Any ideas on this?