K&B Sleeve Mods

[MarkScott]

K&B Sleeve Mods

All,

In the spirit of sharing knowledge, this information was passed along to me by Lee Garcia some 10 years back. I'm borrowing a previous pic that I believe Gener posted awhile back.

The differences between the two are:

1: The amount of port removed by eyebrow. This example does not remove as much. I take a 3/16 Dremel bit and raise the exhaust timing up to 180 or so.

2: On the upper / outside edges (see the dark red areas), take the same 3/16 bit and angle it 45[SIZE=8pt]0[/SIZE] up and 45[SIZE=8pt]0[/SIZE] in.. Don't take out too much, just enough to put an indent in the sleeve.

These two adjustments to the exhaust porting, along with cleaning up the intake / side ports so the air/fuel mixture flows smoothly are done to all my motors. I'll see about posting some pics in the next few days if they come out clean..

Mark..

OB Nut Racing.. Still looking for someone in the Bluegrass area!!!!!!!

 

[MarkScott]

Re:K&B Sleeve Mods

Ok, let's see if this works... May need to get Jack to post this for me if it don't work! ;D ;D

 

[Slideblues]

Re:K&B Sleeve Mods

Interesting Mark

I have still have the other pic, ya want me ta post it for compairision?

Gene ;D

 

[MarkScott]

Re:K&B Sleeve Mods

Gener,

Sure thing.. Don't know if I'd find the one you posted here..

Along with these sleeve mods, there is one other item Lee told me to do. This would be on the case.. After taking out the sleeve, look in the intake area, there is a dividing column (don't know what the official name is) that splits the two intake ports.. Again, this is on the case, not the sleeve.. Take your trusty dremel and remove this built up area.. Make it nice and smooth to allow the air/fuel to flow..

Mark...

 

[Slideblues]

Re:K&B Sleeve Mods

Here ya go,

 

[Jack Garcia]

Re:K&B Sleeve Mods

Now yer pulling the leg on the ole Killer Mark. ;D If there's anyone that has difficulties posting pics it's me.

I do like the bar in the middle, as you say Gene, And I do believe that 185 degrees should be max to save some of the lower lugging power. The thing that I don't agree on, that many boaters do is to remove the bypass bar.

It's there for a good reason, it supports the sleeve where all the portings are to keep the sleeve round.

And as far as polishing the bypass and inside of the crankcase and the outside of the sleeve, I may be spitting into the wind when I say this.

After the fuel and air gets past the carburetor it becomes a mist, then a vapor, and goes up the bypasses AS a vapor. Any thing that can help breakup the mist even more is a plus in my mind, so why remove any thing that will encourage this.

There, I'm all better now.

 

[MarkScott]

Re:K&B Sleeve Mods

Jack... ROFLMAO ;D Glad to hear that you are better now

I also leave the middle bar on the exhaust ports as Gene likes. The reason I posted was to put out the changes I make to the sleeve / case. Also, to hear what others think of these changes. Sitting in my supply of items is a 7.5 sleeve that Jim Irwin worked on. The by-pass ports have groves in them.. Believe 3 or 4. Would this make the mist turn into vapor as you like Jack?

Lastly, bypass bar ??? Is this the area on the case I described??? I've run with and without this mod. Really didn't notice that great of a difference. Then again, I'm just a llama

Mark...

 

[Slideblues]

Re:K&B Sleeve Mods

Well I'll take a stab at it here

I get lost quick on some of this stuff, so any you Guru's jump in here.

Its all about increasing flow through the engine, but too much, and your just pump'n raw fuel out the exhaust.

Gene ;D

 

[GTR]

Re:K&B Sleeve Mods

Hi Guy's

I have a few opinions (don't we all) about things to do or not do.

I like Jack and others do not believe in removing the bar because I can actually remeber why it was put there in the first place. With larger and larger exhaust port openings there isnothing to hold the piston stable and greatly increases the risk of it snagging the port on the upstroke.

In relation to the ridge in the case between the liner on the intake ports - it has two benefits, it supports the liner in that region and it decreases crankase volume. Too much crankcase volume on a two stroke is a killer and harms it's efficiency. The greater the volume of the ports the lower the velocity of the charge - you can have too much of a good thing.

Have a look at GP bike engine design and you will see some of what I mean they have very well defined port channels and the minimum crankcase volume they can get by with.

As I said just MHO as I'm no expert.

GT ;D

 

[Ben Stein]

Re:K&B Sleeve Mods

I’m mirror what Gary said regarding crankcase volume. I’ve removed the “ridge” and could not produce any improvement in performance. I have since stopped removing it, because there was no performance enhancement associated with this mod. There are lots of small mods that can add up to substantial improvement in output from a K&B motor, this isn’t one of them.

I’m of the opinion that if you feel compelled to grind on a crankcase……make sure the boost and transfer channels line up with the corresponding ports on the liner.

My 2 pescitos

 

[izitbrokeyet?]

Re:K&B Sleeve Mods

Ben,

You really should loosen up a little………try throwing in a smile or two ;D ;D

 

[nitrotoys]

Re:K&B Sleeve Mods

Well to add some of my own info, that bar in the exhaust helps support the sleeve, and it helps in keeping the piston pin from comming out while engine is running.

Now piston and sleeve modds, Has any one seen Andy Brown modded P/S??

he cuts a hole in the piston itself, and then just under the transfer ports, he adds another hold in the sleeve, so when piston is TDC you have 4 openings into case instead of 2.

I found I like to take the edge off the bottom of the sleeve, and then work "alittle" around the ports of the sleeve. YOU CAN Take TOO MUCH OFF and acually LOSE preformance.

I found that its nice to go fast, but its nicer to have a realible engine that is STOCK and runs and starts for you every time out ;D ;D WE all know how that goes.

NT

 

[Jack Garcia]

Re:K&B Sleeve Mods

Mark, the so called "bypass bar" is the web of material that runs up and down in the middle of the bypass.

As for the Irwin grooves on the bypass ports. If they are running across the sleeve I would say yes they help to atomize the vapor.

 

[MarkScott]

Re:K&B Sleeve Mods

Here's a pic of the stock K&B 3.5 case. On some motors, the area inbetween the intake ports are removed. I can see how this would stress the sleeve once it has been removed.

 

[MarkScott]

Re:K&B Sleeve Mods

Now a shot with the bar removed.

 

[MarkScott]

Re:K&B Sleeve Mods

Here's a shot of what mod's I do to the exhaust ports of the sleeve. It's been years since I've removed the middle bar.

 

[MarkScott]

Re:K&B Sleeve Mods

Lastly, this shot is of the by-pass (transfer?) ports with grooves in them.

Jack, would this make the fuel/air more atomized????

 

[MarkScott]

Re:K&B Sleeve Mods

Comments? Thoughts? Suggestions??? Once I made the changes to the exhaust ports, it did help the performance/speed of my boats.

Mark

OB Nut Racing: Having fun with a dremel on rainy days

 

[nitrotoys]

Re:K&B Sleeve Mods

I dont think i have ever seen that done to the transfer ports, Please let me or us know what the performance gain is on that.

And on the sleeves, (exhaust) side, you can grind out the top going towards the snerial (spelling totally wrong) to open the exhaust port more without changing the timing, will help more gases come back in.

raising the port tho, will increase the timing.

Have you done speed tests yet with them mods verses stock?

As far as modds go, some people overlook the PROPS, and thats where you can get a good gain just by cuting and grinding them down and pitching them.

Thanks for the pics OBNUT

 

[snowdog-2112]

Re:K&B Sleeve Mods

Nitro,

I know OB Nut is bad about not running sharp props. I can't say what speed increases I've seen but I've heard as much as 5-10 mph just by using a clean, sharp prop!

Thoughts?

Snowdog

Speaker of the obvious...or not so obvious!