Baseline jetting VM33's on 82 Kat 1000

[Tarbash 27]

I just finished completely rebuilding a set of vm33's that came on my 82 Kat 1000 I recently purchased. The motor is bone stock from what I can tell. These carbs came on the bike when I bought it and I would like to get them tuned properly.

I just rode the bike for the first time yesterday and some today. It is kinda running like crap at 1/4 throttle. It cuts out and wants to stall unless I rev it up when leaving from a stop. It is idleing ok, little rough. Carbs still need to be sinked. When cruising, its fine and higher rpm's, it runs good smooth. This bike has K&N pods and a large race exhaust which I cannot identify.

Now, it has 130 main jets and 30 pilots. To me the pilots seem a little big. I tried adjusting the air screws to the highest idle method, but I did not really notice and change when turning the screws. Pilots too big? Im guessing they are. I would like some thoughts or suggestions.

The bike also has a dyna 3 ignition which I have not checked the timing yet, seems fine, but that can be an issue too.

 

[trippivot]

20 pilots are a better choice/starting point.

remember to re-synch the carbs after every needle change on mech slide carbs.

130 is good but you might want to have a bunch of sets 127.5~142.5

33's are known for making the engine fall on it's face just off idle even tuned in.

 

[Tarbash 27]

I think I will try a set of 20's pilots, which I have already. I found a vm33 diagram which recommends 17.5 pilot and 132.5 mains for a gs1100e. So maybe Ill try that route.

http://www.sudco.com/vol33/35-36.pdf

 

[rapidray]

Start with 20 pilots, 125 mains, & the needles on the 4th clip position from the TOP of the needles. Mixture screws 1 turn out & it should fire right up. Then adjust the mixture screws CORRECTLY first, & tune from there. Ray.

 

[atb1998]

thanks for posting that Ray.. You just helped a friend of mine get his VM33s on his 1100 running a LOT better.. Read that last night. Showed him this morning. After a little garage time it runs great

 

[Greg B]

When I had 33s on my 82 Katana 1000, K&Ns, Kerker 4-1.
17.5 pilots
130 mains
needle at middle position
mixture screws 3/4 turns out
Ran perfect.

 

[Tarbash 27]

Well Im still having problems, The biggest problem is my throttle is sticking. It will stick once and a while. It has nothing to do with the throttle cable. When the bike is off, it snaps back hard and there is no binding in the throttle at all. Is is nice and smooth. In between shifts it will stay reved and even blipping the throttle it sorta gets hung up. I have the spring on the tightest position possible. I am rrunning just 1 cable, no push back cable.

I had the 20 pilots in it and the air screws had to be all the way in to get the highest idle, So I went to 22.5 and now there all 1 turn out. But it still dies, when you rev it up and let off, it will die. If you pull the throttle slow and smooth, it will idle fine. Im just kinda confused here. It seems at 1/8-1/4 throttle it still cuts out.

I tried syncing the carbs and got the fairly close, but there's too much fluxuation in the idle, so its very difficult.

I am running K&N pods and a large race exhaust.

Any ideas?

 

[srsupertrap]

Well Im still having problems, The biggest problem is my throttle is sticking. It will stick once and a while. It has nothing to do with the throttle cable. When the bike is off, it snaps back hard and there is no binding in the throttle at all. Is is nice and smooth. In between shifts it will stay reved and even blipping the throttle it sorta gets hung up. I have the spring on the tightest position possible. I am rrunning just 1 cable, no push back cable.

I would first try installing the other push back cable and see what that does. Based on your description of snaps back hard it probably won't do anything. I would still eliminate it just to rule it out.
Next question is when you return from riding and the GS is fully warmed up preferably hot, what is the idle rpm? Hangin rpm may be caused by the idle speed screw turned in too far to compensate for other jetting problems you mentioned. That idle screw should just barely be kissing the linkage. If you have it screwed in a couple of turns I would say that's too far.
Last could a intake or O-ring leak be the source of the hangin rpm that shows up when the GS is hot?
Another thought did you verfiy the float level measurements. Just my 2 cents hope it helps

 

[Greg B]

Good God,
Get the dual cable throttle. VMs can hang WFO at full throttle without the second cable to pull the slides closed.
Motion Pro makes 'em. About $40 IIRC.
Alternatively, the throttle assembly for a GS750. Can't remember the year. But it is a dual cable throttle & the right handlebar switches in a unit.Take up less space on the bar than adding a stand alone throttle unit.

 

[trippivot]

I love mine problems and all!!!

I love mine problems and all!!!

lovely VM 33's fall on their face when you stab into the throttle even if the idle circuit is perfect. learn to control the slow and gentle throttle input from yer right wrist. if you get them on the lean side then they hang up when the throttle is closed and between shifts with or with out the 2nd cable.. hell you get them perfect and the humidity goes down instant lean condition-- vice versa-- humidity goes up yep rich condition

these are racing carbs and the smoothness/predictability is at 1/2 throttle and above. that is where they run the most predictable and best. sooner you get used to it sooner you know if you are going to keep them or get acc pump type flatslides or best yet CVs'

my set I love after I got used to their idiosyncricies.

mine are set like this;
20 pilot
needle at 4th groove
I flux between 135 mains and 137.5 sometimes 140 when weather changes from 900 feet altitude and 2700 feet altitude I change the main and adjust the air screw.


I have found they are ultra sensitive to humidity changes more so than temperature. it is most apparent just off idle into onto the needle. (RIGHT WHERE YOU NEED IT TO BE CONSISTENT)BUT NOOO just off idle is a B!&*H to keep consistent. as well as return to idle.

hold wrist still and wait it will rev up and smooth out.- when it hangs up pull in the clutch and wait it will settle down just takes a micro second or three. tough to do in traffic but on the track who cares about idle and low end transition.

engine temp is a smoothness factor as well.

my engine;1087 cc 40mm intake valve 35 exhaust valve .425 cams(lc 102 int lc103.5 exh) 11-1 compression engine open header timing static at 39 B.T.C.


I call total BULL for any one that claims these can be "perfect at all times"

or has had a set that were "perfect" for the street NOOO! not 33's

my advice is
1.buy more main jets
2. keep complete notes of weather(temp-humid-baro)
3. spark plug color check often
4. keep carb tools on board

I have always said CV's are best for street riding. keep up the good fight you figure out what makes you happy one way or another.

 

[Tarbash 27]

Well, I have a dual cable throttle on here now, Im just running 1 cable, I have always done this with my other bikes. I had never had this problem with the hanging thottle on my GS750 and 29mm smoothbores. I had both cables on it when I got the bikes, but there was a bunch of resistance and binding in the throttle with the other cable.Maybe, Ill give it another shot with the dual cables, I just dont want to have to push the throttle back.

I can get it to idle fine, but if I rev it up, it will come back down and just die out, it will not return to idle unless I feather it. I will check for intake leaks tomorrow, I probably have the idle screw in too far also. Ill do some tests tomorrow.

 

[49er]

Well, I have a dual cable throttle on here now, Im just running 1 cable, I have always done this with my other bikes. I had never had this problem with the hanging thottle on my GS750 and 29mm smoothbores. I had both cables on it when I got the bikes, but there was a bunch of resistance and binding in the throttle with the other cable.Maybe, Ill give it another shot with the dual cables, I just dont want to have to push the throttle back.

I can get it to idle fine, but if I rev it up, it will come back down and just die out, it will not return to idle unless I feather it. I will check for intake leaks tomorrow, I probably have the idle screw in too far also. Ill do some tests tomorrow.

Trippivot's given you some good data and advise. They are race carbs and aren't designed to be perfect, just off idle. 29's are a far more street friendly option.

I find my VM26's stumble slightly off idle when the weather is hotter and more humid, even on a set of perfectly tuned carbs. I still wouldn't swap them for CV's though.

 

[Tarbash 27]

Well I have been farting around with this and seem to have the pilots tuned fairly well with 22.5's and 1 turn out. But I'm till having throttle sticking problem. Its real bad and very annoying. I have the dual cables on there and they both move freely. I have the spring on the stiffest setting and the throttle snaps back hard and moves freely.

But when the bike is running and I just tap the throttle at say 1/8-1/4 turn. It will get stuck at like 3,000 rpms and just scream. It will only go down if I push the throttle foward. Could this have to do with the jetting at all? I really dont see anything mechanically causing this. It seems to idle fine, the idle screw is in about 1 1/2 turns. There seems to be no intake leaks, I took the boots off and cleaned all the crud out.

 

[rapidray]

That is a mixture screw adjustment issue & I think you have a 1 size too BIG pilot jet in there now. Ray.

 

[Tarbash 27]

Alright, well I"ll go down to a 20 or should I go to 17.5. I still had this problem with a 20 the other day. Ill go swap it out now and see what it does.

 

[rapidray]

Have you adjusted the mixture screws to where the MOTOR tells you it wants them? Ray.

 

[Tarbash 27]

Maybe you could elaborate, because I'm obviuosly do this wrong.

 

[rapidray]

With the engine warmed up & idling, starting with #1, you slowly turn the screw in or out till you get the fastest idle it will do on that cylinder. If the idle jumps up a bit turn it back down to normal & move on to #2. Then do 3 & then 4. The motor will "tell" you where it wants the mixture screws. That is is easiest circuit in ther carbs to tune. I won't be suprised if you end up with the 17.5 pilots back in it. Ray.