need help on .21 k&b... how old???

[Shnick]

need help on .21 k&b... how old???

i got a motor off of ebay last night, it is a K&B 3.5cc, it has the carb out of the side next to the flywheel. it comes with a barrel type exhaust. the K&B website has model #8916 shown, it has the carb on the front... can someone tell me the difference between the two or how old this thing is? If i got skrooed on this deal oh well, i only paid 46 bucks for it... im gonna get a decent exhaust header for it, and bearings gaskets of course, and throw it in "project lemon". i'd like to put the carb where it's supposed to be, but do i need to??

also, if anyone has parts laying around, please let me know...

Thanks, Shnick

 

[Shnick]

Re:need help on .21 k&b... how old???

other side of the engine

 

[rcboatlover]

Re:need help on .21 k&b... how old???

I don't know how old it is, but I can tell you the difference from yours and the newer style. The engine you bought is an exaust throttled engine. Meaning that the speed is controled by cutting off or opening the exaust. The carb is called a venturi and only controles the amount of fuel / air mix. Some people like this type because the engine can change speed faster than if using a regular carb. $46.00 sounds good to me. It looks pretty good in the picture. As for changing the carb? You could put a different one on it and remove the exaust throttle, but the carb would have to be mounted in the same place. Not on the top like the other ones you have seen. I would leave it the way it is and give it a try.

 

[[email protected]]

Re:need help on .21 k&b... how old???

Schnick,

It's a so-so motor. I've owned some before but for $46 you can't go wrong. It's an early 70's design.

My suggestion for the carb is buy one of the rubber tip extensions that the r/c car guys use. It will act as a splash gaurd for the carb. This way when water gets into your hull the vibration doesn't bounce it right into it and stall the motor out.

 

[Propjockey]

Re:need help on .21 k&b... how old???

That particular exhaust throttle has a lot of slop (read...loose), and is a booger to get a reliable low speed setting on. But, hey, who needs idle! ;D

You can get a barrel type exhaust throttle for it, but a regular carb and good header would be my choice. If you rotate the front housing to put the carb on top though, the crank timing will be 90 degrees off.

 

[Kez]

Re:need help on .21 k&b... how old???

Shnick,

Judging by the exhaust flange and the head, it was probably made in the mid to late 70's. I have four of these engines. K&B added the mounting lug reinforcement web, which you have, in the mid 70's I think. They have also started to machine the head and reinforce the exhaust flange bolt area in the early 80's.

I agree with Propjockey, the exhaust throttle has a lot of slop and will eventually wear to a point where you can not really idle the engine. I would add a barrel type exhaust throttle (Prather and Steve Muck used to make them). I would also locktite the bolts that hold the exhaust throttle. If it vibrated loose, the engine will scream full tilt and you will not be able to shut it down....Not a good thing in a small pond. I learned the hard way.

Kez

 

[GTR]

Re:need help on .21 k&b... how old???

Hi Shnick,

The motor is between 1976&1980 - 12mm crank, short reach plug head. Most likely has a liner with a wide flange with cut-outs for the head bolts. Kez is right about the crank web reinforcing being late 70's & they beefed up finning to exhaust flange. Can't turn the crankcase to put the carb on top or the motor will run backwards - basically the same crank as the early outboards but with a short crankpin - eg they run the opposite direction from normal. Depending on when it was made K&B started to put the year in the serial as the last 2 numbers. If you don't want the barrell muffler I will take it off your hands drop me a mail.

GT

 

[Shnick]

Re:need help on .21 k&b... how old???

WOW! what a response!!

Ahhhh! now i see the exhaust throttle, i didnt see it at first... looking at the model number on k&b's website ( http://www.modelengine.com/parts/89.htm ) its a whole different animal... i think i got #8906...

anyone got parts for this thing laying around somewhere??

oh yeah, I told the guy i bought the boat from i'd post his website on the board... he sent it to me from hong kong, its a very light hull weighing in at 1.47 lbs. his site is http://www.foot88.com/~leo/20030317.html

his order page http://www.btorcboat.com

he also has a site with building pics: http://www.foot88.com/~leo/index.html

I copied this from an email to me: My target is to build a web site exclusively for r/c boating. Customer can choose: hull type, hull size, hull color, driving type, fiber material, engine brand, engine displacement, etc. You can also choose color: white, red, yellow and uncolored.

If they want to buy a boat from me, he/she can specify the color and fiber material. Carbon fiber, metal flake, peral white are all possible.

Shnick