nice action pic

[izitbrokeyet?]

No doubt bigger is better when it comes to the open end of the crank……..I just like to make sure there’s enough steel there to keep it together at 30krpm

 

[Tony]

Great!!!

I am happy to see that it still works fine. I can remember this mod greatly increased the perf of my K&B, the "propeller" shape idea comes from my best mods engine O.S 21 RZ (dead after 4 years of intensive mods and high RPM) . Did you use my "Mirror leg"

I do not understand one thing and you guys can help me.

K&B 21 O/B is a realy strong and long life engine but as soon as you lighten the flywheel the con. rod breaks!!

I did the same mods on my Thunder Tiger 21 O/B (Crankshaft , carb, lightned flywheel) and it goes perfect and I reach uncommon RPM (far above 30'000 ).

I only use 25 % nitro and I run not that much rich. (small movie will come)

By the way I am preparing CMB 21 (inboard) and I will keep you informed. I found a lot of small things to mod. For instance the exhaust port on the crankcase is dramaticly bad ( bad surface and uneven)...

Yes as you see Paul I am going to give all my little secrets and then everybody will share with their own experiences. We gonna break the 65 barrier with a 3.5cc tunnel (i hope ???!!!??)

I found a lot of good notes on engine mods but after destroying 5 engines I noticed that it is better first to perfectly finish the engine , no rough surface which means real mirror polish, nice finish on the sleeve instead of doing 5 inches holes to help fresh fuel and exhaust ! supercheck the carb especially on some engines...

More will come with a thousand super clean pics of mods with before and after mods...If you guys agree.

Antoine

 

[Propjockey]

More will come with a thousand super clean pics of mods with before and after mods...If you guys agree.

Heck Yeah!! Let's see them pics!

Start a new thread for K&B .21 mods.

 

[duc]

We totally agree!!

 

[Tony]

Some pictures...to start with... were sent to Paul because I did not know how to post them. (not really clear: alt+..?)

I hope you are going to share some pics too guys.

Thanks for your help Paul.

Antoine

 

[rhomodel]

Tony I think the conrod breaks as it is made just to handle th enormal rpm range and is not strong enough for the high rpm and even worse acceleration and deceleration that you can achieve with a lighter flywheel.

Julius

Ps sure I would also like to see some insight info on helping a K7B perform better

 

[izitbrokeyet?]

I dont have any K&B mod pics since I havent done one in a while (Oscar got my last one).....but there's some things you can do to Novarossi's that help a tad without any changes to timing. like angling the floor of the lights. Using a aftermarket head, or modifying stock head and combustion chamber/ squish angle. or modifying the close side of the crankshaft

JP cuts on a New "S" sleeve

left to right: stock, Art .190cc with half flat squish, flat .17cc

two cranks one stock one modified the Close side of the induction (timing not changed) sharpened "close" side and transitioned "close" slide of the back of the window

 

[XtremeRcBoats]

Here are some pictures of Antoine's mods on his CMB:

And his OS 21 RZ:

 

[Tony]

Thanks Paul!

What a really nice sleeve!!

I want to try the 2"boosters " so called which are the 2 holes on top right and left of the exhaust light. It is supposed to give more top end but I heard that it curbs the torque as the compression of the explosion goes out sooner....Some of you tried?

The mods you made on the intake of crankshaft are great. I do the same and it really increase the performances. You may check the new shape I did on the exauhst of the crankshaft. It seems to help high revs as the angles are more opened. The needles settings became more "touchy" too.

If Paul does not mind I will give him more pics especially on the CMB carb which got several imperfections. I noticed that having a really clean carb with a straight intake ( no rough surface) and drilling a small venturi shape on the bottom of the carb gave the top end power that I was looking for.

Thanks for sharing Izitbrokeyet

 

[izitbrokeyet?]

CMB LS MODS

 

[Tony]

What a nasty piston here. I never seen that big cut on a rc engine before. Is it suppose to help side induction or just ligthened the piston???

Really nice job

Concerning the sleeve why have not you sharpened all the bottom? Did you try polishing the crankcase ? I did this but sometimes i fail the trick and I remove too much material.

 

[izitbrokeyet?]

On the sleeve, I only sharpened the part of the bottom that will help to feed the ports. I leave the rest blunt because removal of any more material only increases the volume of the crankcase.

The piston looks like this because there is only a small bridge of material between the Piston ports and the skirt when you raise the skirt to feed the boost port. removal of the bridge makes the shape you see here. It's ugly but the seal is still good after lots of use (no sign of piston wobble)

Unless I am mistaken Ackerman does the same on his.

 

[izitbrokeyet?]

I don't polish the crankcase. I'm not sure I understand what it would help. I do typically ease the angles where the port canals from upper crankcase come into the main crankcase. I do this to help transition the fuel/air from the case up into the canals.

 

[Tony]

Did you check the new CMB evo 3 for cars ? It has a new sleeve with the boosters on the exhaust and there is no by pass through the piston. I know that picco 21 marine has no by pass through the piston because they consider that a heavy piston maintains the torque.

Are we lost???

If you are using 65% nitro you should certainly maintain the torque but here I only use 25% so I need to try to check the improvements.

By the way we seem to be alone ... Where are the other racers???...they want to keep their secrets..???

 

[izitbrokeyet?]

Tony,

I have not seen a EVO3 yet. I have seen a 2004 Evo 2 ls that doesnt have piston ports . I think removing the ports was a mistake. I believe the 2004 Raptor motors still have the piston ports though. The new LS auto cranks look alot like your modified crankshaft

 

[XtremeRcBoats]

Wow nice pics. The piston on the CMB look great.

Antoine, here are your pics.

Stock:

Mods:

 

[Tony]

Thanks again Paul

On the first pic I noticed a big defect on the carb and in fact when it was fully open the intake was disturb by this shiny area below the barrel. Since I removed it I have a much better high peak with better general behavior. Of course all the neddles settings had changed.

On the stock pic of the exhaust we can see the very rough surface , uneven, and even more it was too tight( left side and top) and the exhaust could not breath correctly. The mods braught also more power through the whole range.

 

[Bob Kensill]

Here is a pic of my Nova 21 tunnel running

 

[Bob Kensill]

Here is a pic of my HTB 360 with a K&B 67. Photo courtesy or Jerry Dunlap. Jerry do you remember this race?

 

[Bob Kensill]

For those with deep pockets,here is on of two 84" Apache boats I built with twin 2-cylinder Quickdraw engines. This boat was radared at just over 80mph.