Starting to hate my carbs,Why can't they just work

IIRC the 77 650s came with 102.5 mains and 15 pilots. For pods, and 4 to 1 pipe, I think that a good starting point would be 110 mains and 17.5 pilots. But as others have said all other things must be right, compression, valve clerance, timing, no air leaks on the carb holders, correct fuel level. I am pretty sure on the 17.5 pilots but you may have to go up another on the mains depending upon how well the 4 to 1 flows.

As others have said it takes trial and error to get the this correct.

Rustbucket650 wrote:

Ok, I recently rebuilt my carbs and trying to get everything running right. Its on a 77 kz650. I think I have a pretty good understanding of the individual settings of the carbs but just cant seem to find the right combination of carb settings to run properly. Ive gone bigger jets, smaller jets, different needle position, synced, idle air/fuel screws, check float levels.......repeat process a 100 times. Too rich too lean, no power, no idle etc.

Im wondering if anyone can share some carb settings with me and what has been working for them. Again its a fairly stock 77 kz650, with pods and 4-1 exhaust. Stock carbs (tried these mains so far from 97.5-105 and pilots 15 - 20) I am in florida so usually warm weather at sea level if that factors in to it as well. ) Any suggestions on at least a starting point for the right carb setup (ie jets needle position etc. ) would be awesome, or if anyone knows of a similar post that already covers this.

What are the chances of us persuading you to throw those garbage pods in the trash and put the stock airbox back on ? If not, you are going to spend countless hours attempting to dial in a good compramising jetting baseline. I tried jetting and old GS700 for pods, and flat out gave up, what a friggin' nightmare. I could not get rid of the famous "midrange bog". I put the stock airbox back on, and jetted one size richer on the pilots, and added one .020" shim under the needle. The GS ran FANTASTIC ! As a total ballpark suggestion bump your mains 20 (yes I said twenty) jet sizes larger for pods and a pipe, and see what that yields... good luck and hope you have a ton of patients... (I didn't ) LOL

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The 97.5 jets might have been stock in 77 if you had the smaller 22mm carbs.

rstnick and a few others have suggested good jetting for your setup, and you need to make sure all the other items mentioned like valves, and air leaks are fixed first.

So many guys throw on pods and a pipe and hope for a good horsepower increase and despite re-jetting all they get is a rough running ride, and frankly I know that's from the pods. God it's only a 30+ year old 650...what do we hope to gain, a couple maybe 5 horsepower?? All the trouble just isn't worth it in my honest opinion. But I digress. If you have or can get a stock airbox then put it back on, with a KN or UNI foam filter. Keep the 4-1 pipe and you'll have a good running 650. The cheapest horsepower increase for a 650 is to replace the engine with a 750.

Do not know if you are aware of the kz650.info forum, but there is a great deal of information on the site. The link is for a post on jettting and has lists of what many users are using. You will notice that there are many different setups for basically the same changes. forums.kz650.info/index.php?topic=1853.0

As most have said here all else has to be correct, or carb settings will not make a difference. I know that it is a pain, but it does take trial and error - only changing 1 thing at a time. I know that many suggest to get rid of the pods and return to the stock air box as this has solved many a users issues. I have had pods on my 77 650 since shortly after I bought it new and have not had any real issues with them.

As to what type of carbs you have I am pretty sure they are vm24ss but yes some 650s did come with vm22ss carbs. IIRC they were the b2a and d2a from 1978. The 22s have an additional vent looking thing at about 10 oclock in the intaken (see the pic below the 22s are on top and the 24s on on bottom). You can also messure the carbs - take a scocket that is bigger than 22mm and less than 24mm and open the slide all the way up and try to place the scocket into it. It will not fit in the 22s but will fit into the 24s.

The 22s did come with smaller size mains than the 24s did. A general rule for jetting when adding pods and 4 to 1 pipe is to go up 3 sizes for the main and one size for the pilot. But this is just a starting point and trial and error will lead to the correct settings.

I have attached a doc I have found online - I did not create it so can not take credit for it - that has some usefull information on starting points for jetting when makeing changes to air filters and pipes.

Ok I did not know I could not post a pdf file so here is the file I was talking about in a doc format

gd4now wrote:

Ok I did not know I could not post a pdf file so here is the file I was talking about in a doc format

Attachment Simple_Jetting_Guidelines.doc not found

I am VERY surprised 650's only need approx a 3 size richer main to run pods and a pipe. My pod/jetting experiences however are more geared towards CV type Mikuni carbs, those 650 carbs look like older style VM slide type carbs. So maybe VM's are not so fussy with the addition of pods....I think i'll just shut my mouth are keep reading and learn I don't want to be giving out bogus info !..

Yes IIRC all of the 650s prior to the 82 model year had vm style carbs and most had vm24ss as stock. As I posted I am pretty sure the 79 b2a and d1a models came with the vm22ss but I could be wrong, it certainly would not be the first time. :blink:

The later model years did have cv32s as stock much like the 750s from the same year. As I said in the post that doc is just a guide or a good starting point. If you look at the link I posted you will see there are several folks with 650s that are running different jetting with the same mods. It just takes trial and error to get them right depending upon elevation, humidity, type of pods and how well the pipe flows ect.

Don't feel like you are giving bogus info - none of us, well I certainly do not, have all the answers and I learn by reading about others knowledge and experinece. I have an early 650 with vm carbs so I do know something about them but I know very little about the cv style carbs, since I have never worked on them. Yet the info you have passed on could prove valuable to me in the future if I move to that style of carb or get a machine that has them.

H1Vindicator wrote:

Did the bike run before the airbox was removed & new pipes were installed?

There it is.... the voice of reason... At Last

I want to thank everyone for offering so much help on this site. I almost feel bad because I always ask questions but dont yet know enough to provide any answers.

From what everyone says I think I'm going to throw in the 17.5 pilots and jump to at least 110 mains and see what happens. Im pretty confident that the carb boots are in good shape as I just replaced them as well. If still doesnt run right afterwards think ill check the valve clearances because everything else seems ok. (Timing, good spark, new electronic ignition, etc)

Forgot to ask. I think the carbs on currently are VM22 but I also have a set of VM26 I believe from a kz900. Would It make much of a difference (performance or smooth running) to start from scratch and throw on the VM26 or keep trying to dial in what Ive got?

Rustbucket, I discovered what was causing my problem the same as yours. My carbs were set up for use with a vacuum petcock. I don't have a vacuum petcock, and needed to block the port that would supply vacuum to the petcock. On my carbs it was the vent on the #3 carb. This could be the same as your setup. When ideling two of the vents didn't draw a vacuum but #3 did. Once I got this blocked, and then properly synced the carbs I'm golden. Just something else to check. Personally, I would start with the stock carbs. By starting with the VM26's you are introducing another variable to a scenario that already has a lot of variables to sort out. Pods, and exhaust are already causing complications, as you well know.