k&b carb

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david kye

david kye

Member
Joined
Feb 11, 2013
Messages
18
Wondering if there are any other options

out there for a 3.5 k&b as far as carbs other

Than black,red,gold k&b,and a Perry Carb

I'be seen pictures of an os Carb on a k&b

but not shure what would have to be done to

Get it to work

Tuning these k&b's can be a real pain

just trying to make it easier

If all else I'll buy a Perry but just wanted to get

some input before I do

Thanks
 
Not sure why your having tuning problems but to be honest the black or gold K&B carbs on a 3.5 are really simple, and easy to get a needle. No low speed just a high and a built in idle bleed hole. The Perry's are also good but I do not see any gain to be had. What's your fuel and are you running a pipe? Glow plug? Fuel tank, filter and location in your hull? What boat and prop? Many factors here will affect hitting a needle. Most K&B carbs I ever tuned are between 3 1/2 and 5 turns on the needle. Mic
 
I agree with Mic, the K&B carbs, especially the gold and black are easy to tune. 3 1/2 to 4 turns OUT will work very well.

Please keep in mind, if you are going to race it according to IMPBA Sport B tunnel rules, you can only use the gold or black carbs. The other K&B carbs, ie., red or purple, were not manufactured on the factory engines. They came later on. I think the NAMBA OPC rules are the same but someone needs to speak up if they know better. Cannot use the other brands, OS, Perry, etc/., as they were not stock factory supplied.
 
Thanks Mic and john for the reply running 3.5 ss motors on

30% nitro

topspeed three and a prop from mark

Main proplem is low speed

I have to run them at about 1/4 throttle

to keep them running or even to crank

Mid to full throttle seems great and I can get needle

Pretty close for a good topend

Two stock 3.5 ss motors with gold Carb

and one ss with pipe and red Carb

all have same issue

and dubro filter
 
Last edited by a moderator:
If your issue is low speed it may be more related to too cold a glow plug and or too much head clearance. Old bearings and air leaks will kill a motor also. We generally start out very rich say 5 turns and work in an 1/8 turn at a time till it comes on then back off a little rich. It takes 2-3 laps to get to full temperature when running. You can check head clearance with plastiguage. I found some blue which measures .004-.009 at the local auto parts store. between .006-.008 is where you should be. Mic
 
thanks for the info

i'll be checking the clearance soon

was wondering of 45% fuel would also be better than the 30% i've been running

also been running mc-9 plugs
 
On the gold, check that the barrel is rotating the right direction, so that the idle bleed hole is exposed at idle and part throttle. Looking down the carb, the barrel should turn open and close on the air bleed hole side.
 

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