Carb Questions...

Hi everyone, I am new to this board.
I recently bought a 1981 kz650 csr for 125.00 !
It has 9962 on it and has not ran in probably 10 years until last weekend. I have it running but it acts like it is starving for fuel, it won't idle, but when you rev it up it seems to respond well. I don't quite understand how the keihin/vacuum diaphram carbs work as far as the slide diaphram and what makes it operate correctly.
I have the carbs cleaned out(they were a mess!)
I put new plugs/wires on it. new float needles and float gaskets.
Played with the idle adjustment(the one that controls the linkage)and it will vary in idling. I have a clear fuel line on it for right now,so I can see that fuel it getting to the carbs. I don't like the vacuum line control on the petcock! What happened to shutting it off yourself? just something else to go bad as far as I see it..
I did not replace any jetting or brass parts in the carbs because I wanted to see how it ran(or if it ran)before I spent more money than its worth and realize that something else(like the tranny)is messed up. Process of elimination if you will. I still have some checks to make for vac leaks etc. but wanted to see if there is any insight out here.
I have done alot on it in the last three weeks, but there is still along ways to go.
Are these carbs a pain? Also I noticed that there is no idle mixture screws anywhere, how does that work?
hopefully someone out here can get me looking in the right direction. I assume these are the CV34's?
Thanks in advance!
Jeff

welcome ,,, check to see if you are running on all cyls,, you can do this by spraying some water on the pipes while it running, they should all look about the same, also look for any vacumm leaks, you said you started to look, but you need to check around the carb intake boots real close,
also checke the valve clearance.
it sounds like the carbs are still giving you problems, but you need to do a full tune up on the bike to eliminate mechanical issues

Yes, your problems are not unusual. Especially for a bike that has been sitting for a while Accumulated garbage and impurities, sediment, "kackified gas" (I learned that here it is the hardened gel like flaky film that appears on the inside of gas tanks that sluffs off and fouls carbs), all contribute to problems on decades old bikes.

As a novice new bike owner (still am one btw) I rebuilt my carbs twice trying to get them up to snuff. Someone here mentioned a product that I tried after the fact. In using it, I experienced a significant positive change in my bikes performance. It is "Sea-Foam", a gas/oil additive.

Apparently it serves to help clean out carbon deposits and grime and such. It might not be a bad idea to treat some fuel and run it through your system. There is a slight chance that it might improve the condition of your system good enough for you to be happy with the performance. All for about 5 bucks and time.

Just a thought for a quick fix possibility before you delve in deeper.

And welcome to the site.

Q

Hi jafilson,

Welcome to the board. Don't forget to post you location and some bike pics as soon as you can. We like pics:laugh:

My 82 kz750 has CV34's. The idle mixture screws are on the top "front" of the carb under an aluminum plug. Most of us just drill the plugs out for access.

I can recommend Sea Foam also. Might try it first to see if you can get things cleaned out.

Oh yeah, If you don't have one, a Factory Manual makes life a whole lot easier.

Thanks guys! I will try some of that sea foam. I have heard others talk about it. Thanks also for telling me about the idle mixture screw locations. I couldn't figure out how any carb would hold a tune forever..?
Another problem I found this morning..I put a new fuel line on between the tank and the carbs..it is a yellow transparent TYGON line(had some extra from my snowmobile project)so I could see fuel getting down to the carbs...well
it was kinked down below where I couldn't see it. So it must have been starving for fuel. I shortened it up so it couldn't kink anymore, now it runs alot better but i still am not happy with the idle yet although it is better.
I am going to put on a few more things and take it out for a short ride around the block, give it some time to clear its lungs! I realize that there are alot of possibilities for vac leaks in different locations and I will eventually replace the carb intake boots,they are pretty hard. I just want to go a step at a time until I know this thing is going to be alright...so far so good! And I only got a total of $263.00 dollars in the whole bike! parts and all!
(bout three tanks of gas in my Expedition)
Thanks!
I will get pics as soon as it is worth looking at! LOL!

I had flow issues as well. I nad no luck with the in-line filters. I got a newer bike's Suzuki vacume petcock. That finally allowed my bike to drink to its content.

Best of luck with the problem solving.

The 81 CSR didn't use Keihin CV34 carburetors from the factory... I would think an 81 KZ650 would be using VM24 mechanical slide carburetors. Something isn't quite right here. Later KZ650 models used BS32 Mikunis.

I am not sure what model these carbs are, but my book shows them and thats all I know on that.
I found out another problem...The boots,where they mount to the intakes, are leaking vacuum. I took off the carbs and boots this morning. I am going to use a little non hardening permatex on them. it is not the ideal fix but will work for now and will bet new boots later when I know more about the drivability of the bike. I also noticed that the screws for the boots were pretty loose, I missed that before assembly..oh well...I will put a very thin coat of sealer on so that none(hopefully) will get sucked into the engine. I think that will take care of my idle problem, for the most part. You could see it bacfire flames through the sealing surface! Thats how I found it! I found those idle mixture screws also! Thanks for the help on this guys!
I'll be back...................! Jeff

Okay..got it back together and no more vac leaks around the boots! I just put a thin coat of permatex on them. Temp fix..it idles real nice now so I put enough stuff back on the bike to take a ride around the block.
Everything seems pretty cool, but when shifting between gears, it does not idle down, so when you shift, the engine revs up when you pull in the clutch just enough to be weird.
It does idle down, but it takes too long.What could this be? nothing is hanging up like throttle cable etc. It just seems slow to idle back down? I don't know. Any thoughts would be appreciated. Thanks guys...Jeff