zrx carbs attempt at vac adv nipple

[petejw1966]

hey melb,
one of the guys on the .com site
worked it out, 
heres a link

http://www.xs11.com/forum/showthread.php?t=30780&highlight=zrx+carbs

ive done the mod already
and it works well.

[melbxs]

What was the final outcome of this Pete?

I read somewhere that someone was using a 0.5mm diameter feed to the vac advance and it worked fine. Have you read that too?

[petejw1966]

that mod didnt work,
thought it mite have,
going to solder the bottom of the brass barb
and drill a tiny hole in it and see how it goes,
still much happier with these carbs than the stock mikunis.

[petejw1966]

thanx eveready,
the pics make the bike look better than it actualy is,
but its getting there.

i changed the bolt out to an old rubber inlet barb
and pressed it in and smothered it in silicon,
seems to have done the trick

[Eveready1100]

Might just be that you've got the nipple in the best position for getting vacuum as compared to the stock location on the inlet rubber. Hope it works out ok for you. I've heard that the ZRX swap is one of the best sets to get a more tractable engine, with better economy to boot.
   That bike of yours is looking sweet, I must say. Wish I had the time to tend my old girl like that.

[petejw1966]

hi eveready,
i tried using a restrictor, i used the aquarium type valve
the same that attaches to the vac guages,
so i could adj the vac, problem was no matter how much i  restricted it,
it pulled the vac adv at idle fully on. 

i ended up replacing the bolt with a barb from an old inlet
holder and made the hole slightly larger, it seems to be working
better this way but its leaking air, im going to silicon it over nite
and see how it goes.

these carbs are still much better than the mikuni ones
ill video tape it when i get it sorted out.

[Eveready1100]

Pete, you'll probably need a restricter in the line to limit the vacuum to the advance unit. I was reading your post and I thought it was for the fuel taps/octy till I got to the last bit. Lots of new owners have dramas with the ignition if they mistakenly hook the advance line to the carb nipple. have you changed the inlet rubbers and not got the little nipple on the LHS one?

[petejw1966]

yeah they are melb,
his got his fitted on the 78 model engine
with mechanical adv,
mine being the 81 doesnt have the mech adv.
i put em on today,
the mod i did isnt working atm, stlill going to play with it a bit more.
when i hook the vac adv up to the carb nipple, im getting full adv at idle
resulting in the engine pinging under load,   its runs better with the vac adv
disconnected.
still more playing but its still running better than the mikuni carbs.

[melbxs]

Is it the ZRX carbs that kiwi has on his rat bike? Super nice response and very free revving if they are.

[petejw1966]

ive got a set of zrx carbs that a while ago i had
started messing around with, because they didnt hav a vac
adv nipple like the mikuni carbs i wasnt happy with how they
were working
so heres my attempt at putting a vac adv nipple onto the carb.

i wouldve liked the hole to be a little closer to the butterfly but more importantly
it had to sit behind it.



i used a bolt with a hole drilled into the center so i could thread it into the carb body
also so i could have something to attach the vac hose onto.



i also tried to put a groove into the butterfly similar to the mikuni carb



havent tried it yet, at worse if it doesnt work i can block the hole and connect
it to the carb boots.