New to me kz650. Check out the carb gunk ..

So, got a non running 78 kz650 the other day. Has a 700cc bore kit, electronic ignition, Vance Hines 4to1 and one owner since 1980..I check compression before I bought it, all around 150....So the carbs were the first step.

Figured I would do a quick clean and scope out the condition of the carbs , replace basic gaskets and clean the Jets...When I went to the next carb I decided to open all of the fuel line ports and blow some compressed air in there. This is what I saw on the "in" side for the fuel...I was blown away! I also found one of the carbs were bone dry..

members.dslextreme.com/users/bikecliff/i.../vm_carb_rebuild.pdf

Those carbs are case in point why I never even try to run an old bike until the carbs are gone through and all the O-rings are changed. cycleorings.com sells a VM kit that should have most or all of the O-rings you will need.

Don't forget the check the valve adjust too.

Haha exactly! Thank you for the tips...I was struggling to find an o ring kit , and this needs them bad.

The valves were also on my list, but I haven't actually had to adjust the valves on a bike before, so I will have to come here for some advice.


I also found it has 102.5 main Jets, isn't this stock? Shouldn't it be jetted slightly higher for the exhaust and big bore kit?

Welcome.
Yes, 102.5 main jets are stock on some models/markets.
What air filter/s does the bike have? Stock air box or 4 pod filters?
It's the air filter side that plays a big part; more air will require more fuel.

Post up some pictures of the rest of the bike.

With that much rust in the fuel inlet I'd be looking at a thorough cleaning of the fuel tank and petcock. Also a quality inline fuel filter before you put it back together.

one of the best ways I've found to clean rust is to take and dip those connecting fuel pipes in plain white vinegar at least overnight. Vinegar is a very effective rust eater and will not hurt any part in those carbs.

Thanks for all the suggestions! I cleaned the carbs with a dip and pressurized carb cleaner. Got new orings, gaskets , and Jets. Got the bike running at a smooth idle around 1300 rpm, with screws set to 3 turns out . The bike is running great except for the mid range. I ran it at 4-4.5k and shut it off and checked the plugs..Looks like it's burning ok, but may be too rich. Any one have suggestions? I have pods on the way (syncing carbs before I install to have a good baseline) so that should help with the mixture.

The main issue is the mid range is very soft if going WOT from 2-3k. I believe there is too much fuel, but I am not sure...Also found out when I shut down the bike, after about 2 min the carb fuel overflow dumps a bunch of fuel on the ground....Maybe float bowl setting?

I have a 4-1 Vance Hines, k&n filter ( no pods yet) 700cc (maybe 720? Bought from another owner) and electronic ignition.

Here are some photos of the carbs, bike, and spark plugs after the 4k rpm test. Sorry for the messed up order. The plugs are cyl 1 and 4.

Just curious. Did you check your mechanical advance unit for free movement? It's just behind the pulse gens or points if your's has points. Right side forward crankcase cover. No oil behind that cover so you don't have to worry about that.

Oh.. I forgot to mention. Good job on the carbs! You may have the floats set too high. I use a couple of short pieces of scrap 2x4 lumber to support the carbs, on the bench, in about the same orientation as they are on the bike. Then hook up a fuel source and always check for leaks while letting the fuel fill the carbs for 30 minutes. Actually if they are going to leak it will be within 2 minutes. But by using that support it's easy to do the clear tube check for fuel level while sitting on the bench.

Looks like I have electronic ignition! So couldn't be that right ? Here are photos.

Look through that hole in the center of the pic. You'll see the pin with an E clip on it. that is the weight pivot for your mechanical advance. Make sure that the weights move freely.

Also note that the entire pickup or pulse generator plate is set to almost full retard. Can you verify your ignition timing is correct? I am not familiar with that Dyna ignition so you'll have to research how to check ignition timing with that setup. If you timing is retarded it will seem sluggish from mid range on up.