78 KZ650 What are these carbs?

A friend of mine just bought this KZ650 which had been sitting for a while. No one is sure how long. His second bike and he knows very little about them but can ride well. Anyway I took one look at it and told him he needed work before he could ride it. It will start and runs like crap but leaking gas from #2 overflow. Boots and intakes boots are cracked and hard. Oil smells like gas. So I'll pull the carbs and see if I can stop the petcock from acting like it's on prime all the time. That will help while it's just sitting but I want to open the carbs and clean/refurbish them. problem is I don't know that I've ever seen these. Says Mikuni but look like Keihin smooth bores.

Untitled by j_dvorchak , on Flickr
Any help identifying them would get me going.

Those are the stock KZ650 carbs. If the bike is a 1978 KZ650-C2, KZ650-B2, or KZ650-D1 they are Mikuni VM24SS (24mm) carbs. If the bike is a 1978 KZ650-B2A or KZ650-D1A they are Mikuni VM22SS (22mm) carbs. The easiest way to tell the difference between the two different carb types is by the presence or absence of the orifice at the 10:00 position of the intake mouth side as shown below. Ed

thank you sir!
Now he asked about pods and I said I'd check on the forum to get the popular consensus. I have lots of experience with CV carbs and virtually none with these. I'm checking on pricing for the air box boots and comparing that to K&N or other quality PODS. My initial thought is stick with OEM air box. But I said I'd ask here.

I'd stick with the air box but VM carbs are easier to setup with pods.
Steve

jdvorchak wrote: thank you sir!
Now he asked about pods and I said I'd check on the forum to get the popular consensus. I have lots of experience with CV carbs and virtually none with these. I'm checking on pricing for the air box boots and comparing that to K&N or other quality PODS. My initial thought is stick with OEM air box. But I said I'd ask here.

Comparing the price of airbox boots to the price of pods isn't going to give you the pricing info you need. When calculating the price of pods you will need to add in the price of multiple sets of jets, jet needles, etc. plus the hours it will take to stumble on just the right combination of parts it will take to get the engine running well (if you're lucky). If cost is an issue there's no way the cost of installing pods can compete with cost of installing airbox boots. Ed

I can't seem to find any info on the carbs. What I'm looking for is preset the mixture screws? I have a clear tube setup to test but it is always helpful to have a float height adjustment to set them to initially. Then fine tune with clear tube.

Since the air box is in tact and he just bought a new paper air filter I'm going to go back to stock. I don't have the time or the inclination to try to tune this thing by guessing at the jets.

Right now the bike starts with the choke (enrichener) pulled but then has a slow return to idle even when warm. It will run and idle with choke off (after warmed up) but mid range (off idle) stumble, slow return to idle. All symptoms of clogged pilot jets and vacuum leaks. Also has visible cracks on the intake "insulators" outside. Carb clamps are gone and he has hose clamps installed. The clock shows 29k so it needs a complete tune up. Valve lash, tensioner adjusted etc.

The good news is he put new plugs in it and it seems to be firing on all 4. So the major problems are carb related. The tank is actually very clean and he has a fuel filter inline.

I did find a VM carb rebuild PDF so I think armed with it I can do all the work I need.


www.google.com/url?sa=t&rct=j&q=&esrc=s&...m=bv.152479541,d.amc

I would not recommend buying aftermarket rebuild kits. The metal parts in them very often are not precise. Be sure to keep the parts for each carb separate from the parts for the other carbs. Mixing parts between carbs can sometimes cause problems since the carb parts wear together. Also, the chart below may be helpful. Ed

Got the carbs out. Pretty easy actually. No 4 Intake insulator was actually loose and I could move it easily by hand. I took it off and cleaned both surfaces and looks clean so I put it back on and tightened the screws! All of the others were tight and surprisingly in good shape. I have the orifice so these are VM22SS.

The air box boots are hard and I'll probably have to use my heat gun to get them out of the air box. OEM or is there another more inexpensive option?

Carbs are in about the shape I thought they'd be :

Untitled by j_dvorchak , on Flickr

I had a set of those carbs in a box of parts I got with a 78 C1 police bike. Wondered what they came off of myself until I saw 650ed's pdf above. Thanks Ed. Mine were the 24's but I put some 28's on the bike.

I have found these type of carbs a little easier to get running correctly with pods than the CV type. If the stock parts are usable I would stick with them as engineering is done. It can be a pain in the ass to get them in and out on some models.

Those have both air and fuel mixture screws?

My particular set only has mixture screws (pilot) that I can find. The air screw has the casting but is not drilled and tapped.

And my mixture screws were
1 - 2 turns
2 - 2 turns
3 - 2 1/2 turns
4 was 3 turns.
Since they were all over the place I preset them all to 1 turn out. Also had to replace the O-rings on each.