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need help with K&B outboard carb

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need help with K&B outboard carb

Old 02-06-2009, 03:59 PM
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all8up
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Default need help with K&B outboard carb

I have an older K&b outboard with the early carb that won't stay running... It acts like its lean all the time, like u have to keep choking it to keep it running. I fixed the tank so it will pressurize, and replace the carb gasket, which helped some, but now I am thinking of trying on a different carb, and was wondering if anyone has one for sale? Or what carb would be a good choice? what about these perry carbs? has anyone tried one? if so, which one would be best? thanks, Kerry
Old 02-06-2009, 04:18 PM
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Default RE: need help with K&B outboard carb

K&B gold carb works well on the 3.5s -see your in kansas get the bug someday swing out to our club we run on sunday afternoons in the summer time here is our site link with more info

www.wrcpbc.org
Old 02-06-2009, 06:08 PM
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all8up
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Default RE: need help with K&B outboard carb

thanks, for the link, and the reply.. I forgot to say this is for a 7.5.. the carb I have now has the high speed mixture, and the low speed idle screw. I may try a perry carb. I see where they have some with a .625 outside diameter .. has anyone tried these on a K&B? thanks in advance!
Old 02-06-2009, 08:33 PM
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Default RE: need help with K&B outboard carb

well that kills the gold carb idea then lol not 100% sure what would be best for the 7.5 inboard i know a red carb with a machined adapter works- Im putting a 7.5K&B inboard in a mono Im building and pulled the carb off it to run an exhaust throttle set-up if you think this carb would do the trick for you (please check around first) I would sell it does take a remote high speed needle though that i do not have..
Old 02-06-2009, 10:04 PM
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all8up
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Default RE: need help with K&B outboard carb

that would work size wise. If I can find a needle. I'm not sure if my needle would work or not..
Old 02-07-2009, 12:17 AM
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Ron Olson
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Default RE: need help with K&B outboard carb

If it sounds like it's running lean then it probably is.
The carb that Mike showed you I don't care much for. My ex-brother-in-law had one of those and the low-speed mixture screw kept falling out and then the final straw was the carb barrel breaking in half. I prefer the older carbs on the 7.5's, the ones with the low-speed needle inside the throttle arm.
As far as a Perry carb goes, I tried one on my 7.5 OB tunnel and didn't like it.
Old 02-07-2009, 05:45 AM
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Default RE: need help with K&B outboard carb

I agree with Ron, if it sounds lean it probably is.. try richning it up a few turns before you start spending money as you might not need to.
Old 02-07-2009, 07:49 AM
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all8up
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Default RE: need help with K&B outboard carb

You can turn the needle all the way out, where it is just barely hanging, and it is still lean. I think the barrel is so worn that there is air leaking past it causing the lean condition. I took the carb off my 3.5, and found a piece of 3/8 rubber gas line, and used it as an adapter holding it in place, and it fired right up! so I think a new carb would be a great place to spend money, just not sure which carb. thanks for the replies
Old 02-07-2009, 08:18 AM
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all8up
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Default RE: need help with K&B outboard carb

Hey Ron, is this like the one u prefer?

http://cgi.ebay.com/K-B-7-5-Carburetor_W0QQitemZ200305831034QQcmdZViewItemQQpt ZRadio_Control_Parts_Accessories?hash=item20030583 1034&_trksid=p3286.c0.m14&_trkparms=72%3A1205|66%3A2|65%3A12|39%3A1|240%3A13 18|301%3A0|293%3A1|294%3A50
Old 02-07-2009, 11:15 AM
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Default RE: need help with K&B outboard carb

all8,

this is the for your carb: http://www.mecoa.com/kb/carbs/Carb67.pdf

This is the one that Ron likes and the one I had: http://www.mecoa.com/kb/carbs/carb4061.pdf

I doubt very much that the barrel is worn out, something else on the carb is causing the problem. check all those "O" rings and make sure they are all there.
take it apart, clean it and replace if you have to.

Dan.
Old 02-07-2009, 12:23 PM
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Default RE: need help with K&B outboard carb

Yessir, that be the one!
When you're saying that it's old I will assume that it may have sat around for some time. You may just have some junk built up in where the needle sets so no matter how far out you go it could be restricting fuel flow.
Old 02-07-2009, 12:43 PM
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Default RE: need help with K&B outboard carb

Pipe cleaners are usually way too thick to fit through a needle, but if you look good in the dental isle at the store they have these little floss things that look like a tiny bristle brush. Those work excellent for cleaning small passages and I use them all the time for things like this.

You can also soak the whole carb minus the O-ring in Hoppe's No. 9 gun cleaner for a day from KMart sporting isle clean as a whistle without even touching it. Cuts all the old hardened oil all by itself in places you cant reach. It's better than kitchen type degreaser because I've found that stuff will loosen gunk, but it doesn't really float it off. It stays like goop stuck to things. The Hoppe's eats at it all the way down to the metal.

If you suspect the aluminum body being worn from the barrel, an easy way to check is coat the surfaces with red grease and assemble.

The red grease has a very hard time disolving in fuel, and will temporarily seal the carb air tight around the barrel long enough for you to do a tuning check.
Old 02-07-2009, 08:20 PM
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Default RE: need help with K&B outboard carb

OK, upon further investigation, I realized my carb does have the low-speed needle inside the throttle arm!!!! and the low speed needle was all the way in... so my next question would be, where is a good starting point on this carb? I was told 5 turns out on the high speed, and I have no clue on where to set the low speed.... I would much rather listen to u guys..... thanks, for all the help.
Old 02-07-2009, 11:28 PM
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Default RE: need help with K&B outboard carb

ok, so if it has an LSN in the throttle arm than you don't have the disc.

bring the LSN out and flush, than go in 1 turn, that's where I would start.

Dan.
Old 02-07-2009, 11:29 PM
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Default RE: need help with K&B outboard carb

OK, thanks a lot, how far out on the high speed?
Old 02-07-2009, 11:42 PM
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Default RE: need help with K&B outboard carb

Most K&B carbs, 3-1/2 turns out on the high-speed but your weather conditions can make that vary.
Old 02-08-2009, 09:01 AM
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all8up
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Default RE: need help with K&B outboard carb

OK, thanks alot. I noticed it seemed way rich now at 5 turns out, and would die out. The barrel has some play in it if pulled in and out, but this may be normal... I thought about stretching the spring a little, so it would stay more consistent as it seems to change the mixture if moved in or out. ( I am adjusting the throttle by hand) It may cure itself when I hook up radio gear... thanks again, Kerry
Old 02-08-2009, 05:56 PM
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Default RE: need help with K&B outboard carb

ran the engine today with high speed 3 1/2 out, and low 1 turn in from level, and it was smooth as silk!!!! I can't wait to get her goin!! You guys are awesome!!!! I have to redo all the servos next.. and go prop hunting.. this thing had a octura 455 on it when I got it, and from what little I have read, it's too much prop... if anyone has any props for sale, or 1/4 scale servo's, let me know... Any suggestions on a radiobox design, or prop selection would be greatly appreciated.... My Dad recently passed away, and I have decided to get back into rc boating, to help keep my mind occupied.... here are some pics of my fleet!!
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Old 02-08-2009, 11:49 PM
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Default RE: need help with K&B outboard carb

First, just to let you know, you can't place wanted type of postings on this site, it's against the rules.

With that out of the way, the props that you want to look at are the Octura X-447, 448 450 in wither 2- or-3-blades and the 646/3. A Prather 235 will do also.
A 1/4 scale servo isn't needed. Something like the Hi-tec HS-645MG wil do the job.

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