1978 KZ650 starter jet and starting issues

Hello,

I just picked up a 1978 KZ650 that had been sitting for eight years. The guy I got it from said it was having issues starting before he parked it. He bought carb kits but never installed them. I installed the carb kits (new jets, needles etc) but the bike is still having starting issues. Once it runs for a bit it starts fine but it takes a long time to start when its cooled. - Any thoughts???

In addition, when I was working on the carbs I found a jet screwed in above (or behind) the starter jet. A replacement jet did not come with the carb kit and the jet is not shown or labeled in the manual. Is this jet required? Could it be the reason for the starting issue? The jet is screwed in right on top of the starter jet...

Thank you

RTZ wrote: Hello,

I just picked up a 1978 KZ650 that had been sitting for eight years. The guy I got it from said it was having issues starting before he parked it. He bought carb kits but never installed them. I installed the carb kits (new jets, needles etc) but the bike is still having starting issues. Once it runs for a bit it starts fine but it takes a long time to start when its cooled. - Any thoughts???

In addition, when I was working on the carbs I found a jet screwed in above (or behind) the starter jet. A replacement jet did not come with the carb kit and the jet is not shown or labeled in the manual. Is this jet required? Could it be the reason for the starting issue? The jet is screwed in right on top of the starter jet...

Thank you

Hello, RTZ, and WELCOME to KZr!

The choke circuit is most effective when the throttle slides are closed fully down.

When first attempting to start a cold engine, the choke should be fully engaged and the handlebar throttle grip should NOT be touched while initially spinning over the engine.



ENRICENER (CHOKE) CIRCUIT



PILOT CIRCUIT



Good Fortune!

Describe in some detail on what you do when you try to start the engine. You may be doing something wrong. Ed

Thank you!!!!

I was using the throttle, I will try today full choke, no throttle and let you know how it goes.

Similar to my manual, the diagrams Patton posted do not display the jet screwed in behind the starter jet. Does again one know what this jet is for? If I am still having starting trouble should I try removing it?

Thanks again!

Some of the carbs that came stock on the (K)Z650s had an additional jet (#50 in size) that sits between the pilot jet and the fuel in the bowl, is this what you are talking about. If so it is not the starter jet, but rather an additional jet over top of the pilot jet.

From the info I can find this additional jet is only used on the carbs that have only a pilot screw and not used the the carbs that have an air screw.

RTZ wrote: Thank you!!!!

I was using the throttle, I will try today full choke, no throttle and let you know how it goes.

Similar to my manual, the diagrams Patton posted do not display the jet screwed in behind the starter jet. Does again one know what this jet is for? If I am still having starting trouble should I try removing it?

Thanks again!

When starting the bike using the throttle is a no no. You may want to try this:

Choke on full or just shy of full.
Petcock on.
Kill switch in "RUN" position.
Key on.
Don't touch throttle.
Don't pull in the clutch lever (for kick starting).
Use the kick starter to start it.

Sometimes the battery will have enough power to crank the engine, but so much current is used operating the starter that there's insufficient energy left to fully charge the coils. Kick starting eliminates the electric starter drain. Ed

If the bike has been sitting for a while like the PO said then the carbs most likely are going to be clogged up. You indicated you installed re-build kits but did not mention anything about cleaning them. I would bet those carbs are pretty dirty, I would take them back off and clean them really good making sure all the the tiny passegways are clean. When I say clean I don't mean take the bowls off and spray carb cleaner all over it. What I mean is a detailed cleaning. I would also put the original needles and jets back in after cleaning them as well. The problem with re-build kits are they are made by an aftermarket company. Their jetting sizes are going to be way different than mikuni's meaning their 105 main jet could be the same as a 110 mikuni so when you go to run the bike it will not be the same jetting as what you took out.

Thanks!

I just tried starting her again as per 650ed instructions and still no luck. When cleaning the carbs I soaked them over night in gas and cleaned all visible varnish, they were pretty shiny when I put them back together, but I can try it again.

gd4now, the jet I am referring is screwed in behind in the same port but not attached to the starter jet (part #41 in the KZ650 B1 1977 service manual).

Thanks again for the comments, does anyone have any additional thoughts? If not I guess I will remove the carbs, do some more cleaning and replace the original jets. :S