K&B 7.5 IB marine mods

[Ken Webb]

Anyone have any mods for the above? I have 2 rear rotor low time motors and would like to make work on. Also have a K&B brand tuned pipe for them.

 

[brad nichols]

Maybe mister Brown may have some answers as he was looking for K&B parts this year? It would be good to hear what he has done with them!Brad

 

[RonShaw]

Replace the piston/sleeves with ducted fan pipe timed P/S, head clearance .010-.012, reduce bowl volume (Keeley head), etc. I always liked the Irwin tuned pipes for K&B engines. Really wakes them up. You could also buy a Novarossi 46 DD, and it will scream right out of the box.....

 

[Ken Webb]

Where are the old K&B guys. I know your out there.

 

[brad nichols]

Calling Andy Brown, could you let us know what you are working on with the K&B's? It would be great to know what you have found? Any other K&B people have some comments?

Brad

 

[Kez]

Replace the piston/sleeves with ducted fan pipe timed P/S, head clearance .010-.012, reduce bowl volume (Keeley head), etc. I always liked the Irwin tuned pipes for K&B engines. Really wakes them up. You could also buy a Novarossi 46 DD, and it will scream right out of the box.....

I still have a new IB marine engine and I just checked the P/S. Mine came with pipe timed just like the ducted fan version. I think the O/B came standard with the non pipe timed P/S.

I have been advised by members from this forum to remove the little bridge in the drum housing as they tend to break. I did that and later on I found a disk housing which I understand is the way to go. I set the clearance at 0.002"

Thanks, kez

 

[Ken Webb]

I have 2 low time 9080 rear rotor motors sitting around . might put one in a rigger someday. Right now other projects take priority. I''ve heard over the years about head and rotor clearance, and would like to know what they are.

 

[Duck899]

For what its worth, I ran K&B 7.5's for years. Disk and drum. In hydro's and mono's and sport 40's.Disk engines of course made more power but were prone to breakage, drum engines were timed a bit tamer and required some mods to the closing timing. With that being said, when you got them screaming, the bearings would not hold up because of the very small balls in the big bearing and little front bearing. I found that I could get 3 great heat races and then they would start to go away. These are older technology from the 70's and early 80's. When I switched to macs in the sport 40's, it was no contest. The mac 45 on a bad day would outpull the K&B 7.5 on its best day.

I ran them untill I ran out of bearings and front ends. Great engines in their day.

 

[Andy Brown]

We are running the K&B 7.5 for the purpose of a little R&D. The disc is more consitant running than the drum. It launches better and pulls more prop. The disc clearance should be set at .003" or as close as possible without dragging.

Our K&B is now fitted with a MAC 21 drum system, which flows more than the K&B disc. Looking forward to testing that set up soon.

We ran K&B's in the 80's and yes they broke often....sometimes on the last lap just to come short of a major event victory!

 

[Hydro Junkie]

Are you only experimenting with the 7.5 or are you working with the 11 as well?

 

[Andy Brown]

7.5 only.

 

[TimothyJones]

I hope no one gets offended, but in the 90's maybe earlier everyone called them Ka-Booms.

I think that's a shame because I'm sure they have smart people there and could make a beefy motor.

They ran very well until something happened and then it was just a paperweight.

 

[Ken Webb]

Ka=boom is a common name for them. Use to have bearing problems and I believe rod problems. I have 2. One had bearing failure.Came apert while running. New bearings (not K&B0 installed.The other is still ok. It's been 20yrs or more since last run. These 2 motors also have rather massive con rods.

 

[Terry Keeley]

Guys up this way started making cranks!

 

[Ken Webb]

Talked on the phone the other night to a K&B guru. Best advice, don't try to mod anything internally if you don't know what your doing. Also gave me a couple tips on how to set up motor. Very interesting conversation and much appreciated. I won't say who it is because he may not want to be bothered with a lot of calls.Just my thought. No secrets, just minor improvements. He also told me that if I install a 7.5 K&B in a JAE 45 it would be one bad azz rig.

 

[brad nichols]

They are a lot lighter than the PICCO's and CMB's but at a cost of reliability.

Brad

 

[Ken Webb]

I was told that some problems with K&B is some mods made to them by engine hackers trying to out engineer the designer.

 

[Duck899]

I was told that some problems with K&B is some mods made to them by engine hackers trying to out engineer the designer.

This happens to all engines

 

[dwilfong]

The first eng I got when I started R/C boating 6 years ago was a K/B 7.5

There where plenty to be had cheep.

I was able to get new rods (Dog bone) from MECOA at that time. Ran the you know what out of those eng.

Had a mono and the drum intake worked real good with a .450 carb. Cut the crap out of the case and the liner to try different things.

Only thing that broke was the piston skirts and the bridge on the drum.

Used the small pin crank and it never broke or any bearing failures.

The eng is very light and will fit in a .21 size rigger.

I bet this would make a killer .45 SAW setup.

 

[Ken Webb]

I was told the engines are built light weight for airplane racing. Designer flew formula I guess. Also Ruger (gun manuf) also did the casting in their sister casting plant and used a different method than the Italians. I think it's called investment casting. I doubt Mecoa will ever produce any new engines since . At one time back in the day we broke rods and bearings. I guess that's been handled.