K&B problems

[OldStyle]

Hello

I have a thread started over here already http://www.rcuniverse.com/forum/K%26B_7%255_problem/m_1779988/tm.htm

Anyways I was asking about a airleak at the back of the motor right around the flex shaft (crank) like it seems its comming out around the middle

the front of the motor also leaks oil out and it ends up spraying onto the carb and onto the boat too. If you look at the pictures you can see what I mean

Thanks

Pics are also here of the motor areas im talking about and my boat.

http://www.geocities.com/fevj232/boat.html

[OldStyle]

Guess my question would be what would these leaks be caused by ?

The motor is a k&b 7.5

[BoatDoc]

how much runtime do you have on that motor? it almost looks like that lower bearing is on it's way out! couldn't see the upper bearing too well, but might be the same thing. i would recommend a new set of bearings and a gasket set, along with new hardware. sounds like a lot, but it's not really. it's not difficult to do either if you can find a small press or something you can tap the bearings out with. check out the K&B website if you haven't already. you can get the manual, along with a parts list and an exploded view of the engine. i downloaded them for my 3.5cc engines and they are a great help for doing maintenence. here's the link:

http://www.modelengine.com/kbindex.htm

by the way...i recommend the hardware and the gaskets because it's just a good idea to replace them if you're going to be tearing down the motor, but it's up to you. if i remember correctly, you can also send the motor back to K&B for the work if you want.

[Ron Olson]

Yup, it looks like you have some bearings going South! Look at the bearing cages carefully, usually if they are bent, that will tell you which one or ones are going bad. The upper bearing should have some leakage and there may also be a weep hole near the flywheel that gives the oil somewhere to exit. You might want to consider replacing all of the bearings.

[OldStyle]

Alright, I will round up some bearings. The top dosent seem to be leaking air, just oil. The bottom one however hisses when I blow in the carb. The motor came with the boat, It was supost to have a new piston/sleeve IT has great comp still just needs some tlc. When you say running hardware what are you refering too? I have a new flex cable in there right now and the prop is in good shape.

[BoatDoc]

the hardware i was refering to was the various hex nuts and whatnot on the engine. every time i tear down a motor i always seem to find at least one that's getting worn. K&B has the hardware together as a package and you can buy it right from them. you might consider getting a spare drive cable too, i broke one a little while ago and instead of waiting to order one, i was just able to break out the extra right away.

[Hydro Junkie]

If you're ordering parts from K&B, you might also want to consider a backup crankshaft and conrod. Unless the rod has been replaced with a rod with bearings at the lower end, the bushings in the rods do wear down over time. I had one fail in an inboard 7.5, which cost me the rod and crankcase.

[OldStyle]

Ya mine still just has the copper colored bushing in the conecting rod, K&B only lists the bushing style, still a good idea tho. I should get another drive cable too.

[Hydro Junkie]

The conrods with bearings are made by RPM. Last I knew, they were well over $50.00 EACH :(

[OldStyle]

:eek: Maybe next season "hehe" Im sure its cash well spent but not for this motor, I have never had a nitro boat yet. I have a savage with a sirio .27 in it. I hope this prather lapcat is quick with the 7.5 on it. Im going to order everything I need to get this motor running good in the morning and I will let ya know how I make out. I will also get a new carb.. Thanks for the help

John

[BoatDoc]

a prather lapcat? i was going to ask what kind of hull that was! even with all their little "problems" i love K&B engines. the great thing about K&B is that the engines respond very well to a variety of modifications, so when you want more speed, it will be quite easy to get it! everything from exhaust throttles to port/polish and whatever you can think of...you can do! i'm into the 3.5 cc motors, but a lot of stuff is similar between the two, and i'm sure a few of the other guys have experience with K&B motors, so when you're ready for more power, just ask and someone will help you get it!

[Hydro Junkie]

I have three K&B inboards, a 7.5 and two 11s. The only problem I've ever had was a bad bushing in a conrod. I'm having a hard time of it, though, waiting to get a boat on the water :(

[BoatDoc]

i only have two K&B's. both are 3.5cc's. one is stock, the other is mod'ed like you wouldnt' believe! the mod motor is about 17 years old and all the stock parts are there except for the bearings that i replaced last year! that race motor is the reason that i love K&B so much. they may not be the absolute fastest thing on the lake, but thay last forever!!!!

[OldStyle]

Thanks guys, ya I will get it going good and try the boat for a few tanks and then see what I want to do, I know with the savage the stock motor lasted 3 weeks before I needed more "hehe" But I also have to get my driving to swimming ratio down 1st ;)

Any tips to look out for in this hull? It is in very good shape

[OldStyle]

Sort of a cool pic...
http://www.geocities.com/fevj232//boat1.html