Pumper carbs, Whats out there?

[1fifty1wheel]

As the title says, what pumper carbs are out there?
Obviously there are 100's but looking at 28mm.
What was your experience on the one/ones you have, Where did you get them, $$ value, etc.


Want to know the good, the bad and the ugly.

Cheers

 

[sean01]

ok heres your options... there may be more around but either way your up for some big bucks...
and the biggest problem is not many companies make pumper carbs in a small version..
Yoshimura R&D - TM-MJN Carburetors 28mm w Dual Stack Funnel
CARBURETOR KIT: HONDA MONKEY FCR28H

heres a bit of info
accelerator pump carbs - Planet Minis

and heres a bit of a guide to wat keihin have kickin round
Keihin Fuel Systems, Inc. | Products

this should get you started.

 

[no_crf50_here]

that thing look aggressive!

 

[1fifty1wheel]

hmmmm, the keihin is lookin good. Just gotta decide on downdraft or normal......


EDIT:
Hmmm.....
That Yoshi is sexy though! Just sent a query on whether they post to us.
Will through up a reveiw on which everway i go.

 

[no_crf50_here]

Aus post could learn a thing or two from you. Post will never be late again *grin*

 

[cozza123]

how much would this increase performance on a z50?? my TT250 has got a pumper carb on it

 

[sean01]

the further away the carb is from the valve the more air speed you get in the inlet which promotes good upper rpm torque as well as better fuel atomization, and is easier to tune due to the carb not getting false signals from the valve.

so when choosing your carb (sidedraft or downdraft) make sure the rest of yr engines setup suit's it...

ie... low duration high lift cam for downdraft carb (because the carb is basically bolted to the head)
or high duration and high lift cam for long or standard length manifolds..
also the lobe separation angle of the cam plays a big part as to what carb/manifold setup to use...

so basically what im trying to say is be careful what you choose and make sure you do you homework or else you may be building either a slower/equal engine or an engine tht will perform like a pig...

hope i havent confused you....

 

[sean01]

how much would this increase performance on a z50?? my TT250 has got a pumper carb on it

no good on a z50 unless you have a massive BBK/stroked engine with a big valve head of at least 27mm inlet valve.

for carb size selection the you want the diameter of the carb to be as close or a fraction larger to the inlet valve...

ie.. on a engine with an inlet valve of 27mm you wouldnt want to run anything bigger than a 29mm... you can run bigger but you will sacrifice bottom end respose but gain top end.
and if choosing smaller then you loose top end and increase bottom end response..

i think the correct calculation for a 4 stroke race engine the venturi size of the carb should be 110% of the valve diameter...

also remember that the manifold and port diameter plays a big part in response and performance..

 

[cozza123]

haha i just rebuilt the thing to much fussen around and effort to even think about it will stay stock for now how bout a 125 lifan engine? dnt realy care wat i do to that

 

[sean01]

max a standard 125cc would handle due to it being not real torque'y would be 26mm, but a 24mm would be best suited as youd probly find the 26mm would produce no bottom end response...

 

[1fifty1wheel]

no confusion here sean. Just having problems chasing an online store.

Will keep hunting later if i don't receive a reply from Yoshi in a few days.

Cheers

 

[sean01]

yeah you might have better luck posting a thread on planet minis.

but yeah you dont see to many of them getting around...

heres a pic hillz found of one http://www.miniriders.com.au/mini-chat/9549-official-post-pics-your-bike-thread-47.html#post252748

and heres a thread of someone doing a build with one in mind http://www.miniriders.com.au/tech-talk/25280-yx-4-valve-heads-9.html#post254447

good luck and be sure to let us know wat yr plans are, as someone here may have already tried/done the build you have in mind and may be able to give a little info..

 

[thump*140]

1fifty1wheel i've got a 30mm mikuni pumper sitting around... You asked for good bad and ugly, well the mikuni covers the last two, BUT i didnt play with it at all.
Comes standard on the Atomik Blitz, i turfed it because i wanted an OKO 26mm, and getting the stock carby OUT of the Blitz frame, is an utter, utter, utter bastard...
Not sure how it would go if you spent some time playing around on it, but it's there doing nothing if you want a pumper to start playing with, to see how they go...
pm me if you wanna play..

 

[DvDRip]

pm me if you wanna play..

thump you are now officially the MR #1 HOMO!! hahah

 

[thump*140]

oh come now DVD, no one will ever take that Mantle away from Hillz and Milfboy. ha ha ha

 

[tassie01]

Question about downdrafts ?
Even if the carb is mounted on the head, could you use a longer velocity stack, similar length to that of the stock manifold, for the bigger revving smaller bores ? To get that Higher velocity ?

 

[sean01]

velocity stack will help when wide open, but its because the slide is close not the backside of the carb.

your manifold creates a turbulence and when the valve is shut fuel gases actually float backwards and forth untill the valve is opened again. when the slide is close to the valve it gets valve turbulence which plays games with the carb...

 

[themountain]

there is a certain distance a carb has to have for a specificy rpm band....look up some dragster sites ...somewhere forsure is a calculator for that...maybe here(was too lazy to search)
Wallace Racing - Automotive Calculators

 

[HACKMUNCH]

drz250 uses an oval bore tm28-1. the drz oem tm actually measures around 31mm i have both here, i am selling the drz250 carb for $100 + shipping if anyone is interested.

 

[themountain]

yop...thats a good alternative!!