K&B Pro Help!

[JohnBoy]

K&B Pro Help!

Have 7.5 Pro with Silver Bullet pipe. Head at .017. 40% nitro. Having a problem getting it on the pipe. I bought the smaller carb #9445 and seem to have the same problem. The mid range sucks. Any ideas? Do I need to sleeve the stinger down a bit? How do I know if the piston sleeve needs replacement? Now that I think about it I replaced a broken crank and the problems started. Could the crank timing be off?

Any help greatly appreaciated,

John Smith

 

[GTR]

Re:K&B Pro Help!

Hi John,

Really dumb question but did they give you the right crank? If they gave you a normal direction crank it would run but behave a bit strangely. Can you confirm the crank you got?

cheers

GT

 

[JohnBoy]

Re:K&B Pro Help!

Not sure if it's the right crank will check when I get home. It fit and looked the same when I matched them together before installing. Engine runs great in upper rpm but takes forever then hits the pipe and launchs. I usually run a P-240 but have also run 235 and 230. The smaller props make the boat much slower and handle like crap. With the P-230 when it hits the pipe the boat stands straight up and flips over. Motor gets on the pipe a little quicker with the smaller props but always at the same rpm. Anyone have any pipe set-up info for the Pro and silver bullet combo. If I sleeve it down won't that give me more bottom end and make it hit the pipe sooner? What sizes do I start at and where do I find the sleeve pipe? Does anyone have a good enough eye to tell me if it's the right crank by looking at a picture?

John Smith

 

[Jerry Dunlap]

Re:K&B Pro Help!

Hi John,

I could be wrong, wouldn't be the first or last time, but I think there's only one crankshaft for the Pro 7.5.

As someone with a little experience with model outboard tunnel boats, let me offer you an alternative. I was looking for a strut bracket yesterday, which I managed to find, and also came across a spare 7.5 Pro can muffler.

John, I think you're trying "to run before you crawl and walk" with your tune pipe motor. Here's my suggestion: Remove the tune pipe, install the stock can muffler(I'll loan you my extra one if you don't have one), and just get the motor running. This hobby isn't any fun if the motor don't run.

Jerry D.

 

[JohnBoy]

Re:K&B Pro Help!

I have run the motor on the stock muffler for 2 years. It runs good on the muffler but slower. I will put it back on any see if it is the pipe causing the unwanted throttle reponce. I refuse to leave the stock muffler on since I have tasted the speed with the pipe. Is there only one crank that fits the Pro or will a inboard crank fit and run screwy?

I also have a question concerning head clearence. I am going to sand the sleeve for .008 clearence. Should I sand extra off so I can use the copper head shim or can I leave the shim out? Should I grind off any sharp edge created on the sleeve top inside bore?

 

[Jerry Dunlap]

Re:K&B Pro Help!

John,

I didn't know you had run the boat with the muffler. Personally, I think you'd be better off working with just the flangle on the top of the sleeve and I think .010 would be fine. The shim can be left out. A sharp edge at the top of the sleeve is o.k., just make sure the head slips tightly into the sleave without having to be force fit.

Jerry D.

 

[JohnBoy]

Re:K&B Pro Help!

OK set head clearance to .010. I checked the crank and I'm sure it's the right one. Can anyone help with the size the stinger should be on this silver bullet pipe? Can I expect better midrange by reducing the stinger outlet size? Tomorrow I will try the original exhaust can to see if it runs good or if I picked up some other problem.

Thanks, John Smith

 

[Joe]

Re:K&B Pro Help!

JOHN

MOST OF THE TIME WHEN YOUR ENGINE WANT COME ON THE PIPE GOOD YOU NEED TO BACK THE PIPE OFF A LITTLE. SLIDE THE PIPE BACK FROM THE HEADER TILL IT COMES ON THE PIPE LIKE YOU WANT IT TO. ALSO WHEN YOU SLIDE THE PIPE OUT YOU WILL HAVE TO RUN IT A LITTLE LEANER THAN YOU DO WITH IT PUSHED IN. BEST WAY TO REMEMBER THIS IS ( SHORT AND FAT OR LONG AND LEAN ).

JOE

 

[JohnBoy]

Re:K&B Pro Help!

Thanks, Joe. My pipe is pushed right up to the header. Never though of that one but I like the price tag. Free!!

John Smith

 

[waterbug]

Re:K&B Pro Help!

JOHN

You need to go to RCBOATS .COM

Don't come out until you've read it all, it will help you 1000% .

 

[JohnBoy]

Re:K&B Pro Help!

Kind of lost. I found rcboats.com but could not find dogpile.

John Smith

 

[waterbug]

Re:K&B Pro Help!

That's it dogpile is a search engine .

Sorry john, punch in dogpile then click on it. type in //www.rcboat.com/ dogpile will say 0 found, scroll down to google the 2 one and clickon it- MWD and associates past tec articles.

I think there is away in at Als hobby shop too.

 

[Mark Hopper]

Re:K&B Pro Help!

John, Sound to me that you are trying to run the pipe to short. Try backing it out about 1/2 inch or so and try that. How deep are you running the prop? That could also make a difference.

Mark Hopper

 

[JohnBoy]

Re:K&B Pro Help!

Mark, I know the boat is not set-up right. I am green when it comes to nitro boats, but im learning new things each day. I am positive the problem is the pipe length. When i changed the crank and started having problems I remember I butted the pipe right to the header. When it was running good the pipe was about 1" from the header. Never thought of it until someone mentioned it. My prop is as high as it will go and probally needs to be dropped a bit when I get it running good. I'll be willing to bet all my problems where caused by mounting the pipe too close to the header. thanks for the help. i will post results after I lengthen the pipe.

John S

 

[Ron Olson]

Re:K&B Pro Help!

Somthing to look at down the road. The carbs that come with the Pro are a little big. Try to find a Red carb to put on it.

 

[JohnBoy]

Re:K&B Pro Help!

Ron I have a #9445 carb on it. It should run great when I lenghten the pipe.

thanks, John s

 

[JohnBoy]

Re:K&B Pro Help!

Well seems the problem I've had for the last month with the midrange was the pipe length. I pulled it 3/4 inch from the header and leaned the remote needle 1/4 turn. The boat is running perfect thru the corners and very fast on the straights. There is no bog in the midrange and power is crisp and smooth. I also noticed a difference from dropping the head clearance to .010. I left the pond today with a hugh smile!! ;D

Thanks to all that helped,

John Smith

 

[Mark Hopper]

Re:K&B Pro Help!

John,

Glad to hear that you got it going. If you are like me that won't be the last lesson you will learn that way. It's those kind that you will probally won't forget.

Mark