VM33 smootbores

Z1000Lover wrote:

I have run 25s in it and it still won't run right. But the 35s have helped a bit. I had a buddy that had a 79 LTD with the same 1015cc motor. He went to a Kerker pipe with pods, and his did not run worth a crap on low end til he piloted it up to 35. And his carbs were the stock 28s with pumps.

:huh: What ever works for you but I'll tell you straight up that in 30 years I've never seen anyone put anything larger than a 17.5 long pilot in the 28 pumpers. I've never even seen a 35 long pilot jet.

I can see a 30 or 35 in VM33's.

A lot of times the 29's & 33's don't like much air screw. Very common to have less than a turn out on them in my area.

Thanks for all the info

I went up to 22.5 on pilot, and 155 on mains

did richen up a little went to 14.4 afr from 14.7

went to p-2 on the needle jet and 160 main

is pig rich at idle now, and still lean on the top

although it did get down to 14.1, did a plug run and the plugs confirm it is still running a little lean.

can you guys actually see needing a larger yet than 160

motor has 223 camsm ign is advanced to 34

in all the posts here seems a 140 should work ?????

motor head heres a couple pictures

it seems odd that u have to run with such large jetting?? are u sure u dont have an air leak somewhere?? intake boots maybe??
Can u trust your a/f sensor?
how does it feel?

carb boots are good, i dont trust the afr but when i do a plug run, get it too wot in third or fourth gear, kill the ignition and push the clutch in and coast to stop, when i pull the plugs their all consistant but ceramics are almost perfect white, which tells me im running lean and that the afr gauge is close to been right, also the egt's getting uncomfortably high on top end.

engine feels good though, accelerates very well to top end,
bogs a little on the bottom now that the bottom end is running rich, but top end is very crisp, very fast acceleration, just lean on top ?

i dont think u can use plug color for a good test.it takes to long to color plugs with today's gas. imo.
i would develop a test for each circiut.
for top end i would time how long it takes to get from say, 50 to 70mph at wot.
try this with dif mains untill u find the 1 thats best. plug color will not be as accurate as this.
Maybe use the same test for the needle, but only open throttle to 1/2 way, and adjust the mph accordingly.
for the pilots i hold 1st gear at 3000rpm, for 10 seconds, or as long as it takes to get the car cruising steady, not excelling or decelerating. if it runs smooth your good, if it doesnt, adjust the air screws. u wont be needing perfection on this circuit for the track anyways.
do u get a bog if u go wot at low rpm's?

Cool looking car! The engine looks awesome. I like the top end oiling kit too. I sure wish they sold that set up for the KZ head. It doesn't make sense to me either that you'd have to go that rich on top but I'm very interested to see what you guys find out...

thanks for all the suggestions guys.

ill play with it some more this week.
ill go back to the original needle jet wich was 0-6, not an 0-8 like i thought it was, go back to 140 on the main jet and change the pilot to 30 and start over from their.

do you guys know what egts you normally see, my book says 1260 max for #2 and #3 cyl i peg 1400 when i really get in the throttle, thats whats scaring me and started me thinking its too lean. I dont hear any detonation or anything, i dont see any debris on the plugs indicating its really that hot in the chanber, just that if it is getting that hot wont last long running like that.

Thanks again

These carbs like engines that are 1150 and larger. Below that size the engines do not produce enough vacuum to give proper response with them. I had a set on a 1103 and could not get rid of the stutter/bog. Once i mounted them on a ported 1150 the carbs smoothed out. On 1200 and larger they really come into their own.

if u are at wot and u back out to 3/4 throttle do u hear a miss or something that indicates it's not quite right (like a minor stumble or miss)? or does it feel smooth??
if it has some indication of being off when u try that test, up the jet until it gets better or worse, then readjust accordingly.
the largest i got on the mains was 150 then i could feel it was off when i backed out at wot. i ran mine rich all over, in an effort to help the bog at wot from low rpm's.
do u get that bog?? u may need to be richer with the extra wieght and heat u have.
i would try to tune by ear for a bit and see what u think.
i dont get any plug color, with my rs34's unless i run a lot of miles.they are white after a couple of passes.
just make sure there are no aluminum flecks on the insulators. if u cut the threads off the plugs u will see a color ring at the base of the insulator. that is a better indicator than the top. u dont run long enough during 1 pull to get color at the top of the insulator.