1978 KZ400 build help

So I have this 78 kz400 that I have gotten running/riding but I have some problems and could use some input:

1.) It stars cold with no choke no problem (its about 70 degrees outside everyday here) and sounds/seems great. but when it gets hot, the rpms drop slowly after revving.
2.) It does not like to rev past 6000 rpms when in gear, cold or hot does not matter.
3.) the exhaust pops when decelerating

Things I have done to the bike:
- cleaned carbs and put new cork plugs in the hole in the carbs where the rubber one used to be. I think it is a hole for the second main jet but regardless there were rubber plugs that weren't totally sealing and now they are sealed with cork plugs
- messed with the float level (pretty sure it is right)
- messed with the timing advancer/points (pretty sure everything is it is right)

Popping on deceleration and slow return to idle speed are two
indicators of a lean mixture. And for the things you have done
to the bike. What are you using for a reference? And where are
you located? Altitude? Weather? High and low temp? Fuel being
used? All these can effect a carburated air cooled engines
performance.


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Ok I was pretty sure it was lean but I'm confused why it starts so well with no choke. I'll start rejetting. I am using the factory manual from kz400.com. I am in fort collins CO, so somewhere around 5,000 feet above sea level. right now the highs are 70's and the lows are in the 50's. I'm using the lowest grade gas which up here is 85 octane.

quick update i was riding in 1st at 6,000 rpms and listening to the engine and i hear a high pitched metal clanking sound... could it be a valve adjustment issue?

When I get a 'new' bike a compression test is done.
Then valve lash is checked. If valve lash is altered
a recheck of compression is done. This will give a
good idea of cylinder sealing. As for the noise your
hearing, drain all that 85 octane gas. Use a high octane
gas. These old air cooled engines need it because
they have a higher operating temperature than thier
watercooled counterparts. Usually any noise that
is mechanical will be there at all rpm.


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Thanks for the help.
Ok I'll go ahead and do those things. but in the mean time I have another question:
If I bump up the main jet size, do I need to bump up the pilot jet size with it?

No.


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Ok so I was checking the valve gaps last night and I thought it was similar to my 76 kz400 but it turns out it wasn't.
I loosened a bolt on the right side of the valve cover and pulled a 5 inch bolt horizontally out of the valve cover, then I removed the correct, giant bolt from the rear right side of the valve cover and watch the rocker arm drop back in to the engine. I managed to pull it back out and run the rod that holds it in place (the 5 inch one i removed) back through it and it seemed like it was all fine and good. However I must ask, did I mess up any settings, besides the gap, by pulling that long rod out and arbitrarily putting it back in?

Also when I was adjusting the gaps i really struggled to get my feeler gauge flat in the gap because I had to bend it a little bit to fit it in there. Any suggestions?
Thanks for all the help Nebr_Rex,
Adam

Adam970 wrote: Ok so I was checking the valve gaps last night and I thought it was similar to my 76 kz400 but it turns out it wasn't.
I loosened a bolt on the right side of the valve cover and pulled a 5 inch bolt horizontally out of the valve cover, then I removed the correct, giant bolt from the rear right side of the valve cover and watch the rocker arm drop back in to the engine. I managed to pull it back out and run the rod that holds it in place (the 5 inch one i removed) back through it and it seemed like it was all fine and good. However I must ask, did I mess up any settings, besides the gap, by pulling that long rod out and arbitrarily putting it back in?

Also when I was adjusting the gaps i really struggled to get my feeler gauge flat in the gap because I had to bend it a little bit to fit it in there. Any suggestions?
Thanks for all the help Nebr_Rex,
Adam

Does it say to remove those bolts in your factory service manual??

Honestly, the service manual was rather unclear when it came to valve adjustments but in retrospect I can say that the one long bolt does not need to be trifled with in valve gap adjustments.

Have you modified the bike in any way? Is the airbox and filter installed? Any modifications to these parts mandates significant work to rejet the carbs. And since you are living at elevation, your carbs will be rich so act accordingly.

Adam970 wrote: Honestly, the service manual was rather unclear when it came to valve adjustments but in retrospect I can say that the one long bolt does not need to be trifled with in valve gap adjustments.

What? The Kawasaki Service Manual is clear on how to adjust the valves. What manual did you use? :dry: Ed