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K&B 65 Sportster

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Old 06-25-2007, 11:36 AM
  #1  
perpetualrepair
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Default K&B 65 Sportster

anyone have any input on these motors, i have bought one NIB cheap and can't get it to run properly,starts at about half throttle with the needle valve open 5 turns, revs and then dies, if you try moving the throttle no response at all, it appears to be getting plenty of fuel , no air bubbles, 13x6 prop, taken it all to pieces and checked the seals and the needle valve assembly all seem perfect. when it is running if you try to richen /lean it it revs and bogs down , almost as if the needle is bent,but it is as square as i can make out.
really don't want to give up on it but it is trying my patience. Thanks...
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Old 06-25-2007, 12:06 PM
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Default RE: K&B 65 Sportster

Hello,

I might not have much advice except maybe steer you in the right direction. I've been out of the hobby 18+ years and now getting back into it. I've discovered K&B is still around to some degree and owned by an outfit called MECOA (Model Engine Company of America). Maybe you've already been down this path. In case not, you can go to their website www.mecoa.com and get their contact/service information and talk with them. Maybe send your engine there and let them look at it. Back in the day, K&B was a very popular and reliable engine and a lot of people had them. I had a K&B 40 myself and it was a very rugged, easy to start, and reliable engine. Never gave me any trouble. Could you be using old fuel? Sometimes I would have an engine that acted like that and would suddenly run normal when I got fresh fuel. The fuel I used was in the range of 10%-15%. Hope it helps....Gary
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Old 06-25-2007, 08:27 PM
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Default RE: K&B 65 Sportster

Well, the Sportster is an unusual engine in the way it is built, or at least the metal they used. My dad has a .20, .45, and a .65. the .20 and .65 are great engines the .45 on the other hand....well. We think the .45 needs a new O-ring on the head.

Anyway, back to your question. My dads .65 is a good engine, it won't turn a prop as fast as say an OS .61, but I think it would lug a big prop.

I think the problem you may be having, if it is an engine with little or no runtime, is that they take a loooong time to break in. If I remember right one of the reviewers in one of the magazines I read said he put baking soda toothpaste in his and flipped if for a while...I'm not recommending this, although I might try it myself your mileage might vary. Once they are broken in they run good.

On the other hand, if it is a well used engine, the early models tended to wear the crank bushing and suck air and lean out....The .45 my dad has was given to him..actually he was given two, one complete and one in pieces....along with a new crankcase. The new crankcase had a bronze bushing but the original had the crank running in the aluminum. The aluminum had worn and air was getting in and leaning the engine out. The .45 is the oldest of the three engines, and the .20 and .65 he bought new....something else we found out from the .45 is that the 0-Ring can go bad and they loose compression...don't know if the O-ring went bad because of old age or handling while someone had it apart...we quit messing with it because at the time we couldn't find a suitable O-ring.

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Old 06-26-2007, 04:56 PM
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Default RE: K&B 65 Sportster

The newer verisions, if you will, have no O-ring. Well before K&B closed I had called them to order a new O-ring and the person I spoke to said they had a new head for the Sportster engines that did not use O-rings. She sent me a new head for my .20 free of charge. I thought that was pretty great .
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Old 06-26-2007, 05:04 PM
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Default RE: K&B 65 Sportster

try a 12-6 prop 10 % nitro fuel with 20% oil.how did you re install the disc?
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Old 06-27-2007, 11:27 AM
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Default RE: K&B 65 Sportster

tried every prop in the box from 11x8 right up to16x4 no difference, on the 65 the disk is the complete needle valve assembly?. if that is right it is just a push fit in the carb, i tried opening the low end screw an extra turn before replacing the disk but i think that could cause an air leak?. in any case it made no difference, really getting to me this motor, have had hard ones before and managed to get them right but this one is killing me. lol
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Old 06-27-2007, 03:53 PM
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Default RE: K&B 65 Sportster

little better today, took the spray bar to pieces and realigned the outer sleeve, the orifice was facing the front of the engine, it now faces down into the carb. ran a little better at least it would keep running while the glow igniter was in situ, still wouldn't transition though.
next i removed the fuel tubing and went with connectors to hold larger ID tube tight to the nipple, a little better transition still a bit sloppy though,
last thing to try was the pressure feed to the tank from the muffler, removed that and now i have an engine that will run, transitions reasonably well, it is fairly new, and no longer has me tearing my hair out, hope this helps someone else in a similar position, amazing that so much had to be done to get it running, and though a lot of people have commented on the motor and its good/bad points no one said a thing about the pressure, makes one wonder?.
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Old 06-27-2007, 05:33 PM
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Default RE: K&B 65 Sportster

where was the muffler pressure tap?when these first came out there was no pressure tap on the muffler.tose that added a tap found that putting it near the end of the muffler llike os engines had problems due to the internal muffler baffle..solution was to either remove the baffle or move the tap infront of the first baffle.
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Old 06-27-2007, 06:31 PM
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Default RE: K&B 65 Sportster

I remember trying with and without pressure, but I don't know if my dad settled on with or without. He hasn't flown either plane for a while...he has lots of planes. Seems like with the .20 we tried it without because we weren't getting a consistent fuel flow. But I think after the motor was broken in we were running it, I don't remember ever any trouble with the .65, even the break-in was shorter...but still longer than my ABC type engines. The only engine I've ever owned that absolutely wouldn't run with pressure was a Saito .45.

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Old 06-27-2007, 07:07 PM
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Default RE: K&B 65 Sportster


ORIGINAL: aerowoof

where was the muffler pressure tap?when these first came out there was no pressure tap on the muffler.tose that added a tap found that putting it near the end of the muffler llike os engines had problems due to the internal muffler baffle..solution was to either remove the baffle or move the tap infront of the first baffle.
it was in the first section of the muffler right beside the port so was getting the full benefit of the back pressure,
part of the problem was too much fuel and perhaps that was the cause, took hours of messing around to get it half decent, of course now i'm dubious about putting it in a plane, there will be a lot of bench testing done before i fly it. and it has to get a lot better in transition, will keep running it and see how it goes.
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Old 06-27-2007, 08:44 PM
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Default RE: K&B 65 Sportster



Here is a link I found from MECOA who is selling K&B engines now. Maybe they can help. http://www.mecoa.com/kb/58/5800.htm
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Old 06-28-2007, 06:59 PM
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Default RE: K&B 65 Sportster

I have a 65 that i bought used that probably has 200 to 300 flights.If i remember right in K&B's manual for the 65 it says not to use muffler pressure.I have been given 2 more 65's and replaced the o-rings on the needle valve assembly and they run great.Sounds like the muffler pressure was the problem.Hope this helps.
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