Case stuffers

Bear45-70 · Post by **Bear45-70** » Mon Sep 08, 2008 1:18 am

Has anybody thought about using case stuffer to boost performance?

Bear45-70 · Post by **Bear45-70** » Mon Sep 08, 2008 4:03 pm

Does anyone here even know what case stuffers are?

adark248 · Post by **adark248** » Mon Sep 08, 2008 4:34 pm

Bear45-70 · Post by **Bear45-70** » Mon Sep 08, 2008 5:01 pm

Case stuffers are devices mounted in the crankcase area to reduce the volume of the crankcase. Which significantly increase low speed air velocity. This dramatically improves low/mid range throttle response and improved power throughout the RPM range. Quite often mounted behind V-block reeds but not always.

keithw · Post by **keithw** » Mon Sep 08, 2008 5:29 pm

On the old RD-350 motorcycles they would put corks in the crankshaft balancing holes to reduce the crankcase volume. Yes, I know what case stuffing is.

keithw

Bear45-70 · Post by **Bear45-70** » Mon Sep 08, 2008 5:31 pm

I would think the Spree engines would be prime candidates for stuffers.

Post by **noiseguy** » Mon Sep 08, 2008 5:42 pm

There may be an opportunity there in filling in the oil injection shaft and running premix. There's a fair bit of volume in that port.

PimpinSpree · Post by **PimpinSpree** » Mon Sep 08, 2008 10:07 pm

im not fully understanding. Why would you gain anything from the bottom end being smaller?

Bear45-70 · Post by **Bear45-70** » Mon Sep 08, 2008 10:53 pm

PimpinSpree wrote:im not fully understanding. Why would you gain anything from the bottom end being smaller?

Because on a 2 stroke the fuel and air charge gets sucked into the crankcase as the pistons rises in the bore. Then when the piston drops, the fuel and air charge is forced into the cylinder. The smaller the area of the crankcase the higher the compression in the crankcase and the more charge forced into the cylinder. In effect raising the compression in the cylinder also. Which of course increases performance. I've seen a number of racing outboard 2 strokes use this proceedure effectively. Oh and stock Johnson and Evinrude V-4, 135 and 140 horse engines also used these stuffers.

Clivester · Post by **Clivester** » Mon Sep 08, 2008 11:48 pm

On the other hand it also means more resistance to the piston power stroke (tending to rob power) and the reed valve will have to bear more pressure. I think much will depend on how well Honda tuned the crankcase (read as "I guess you'll have to try it!).

Clive.

Bear45-70 · Post by **Bear45-70** » Mon Sep 08, 2008 11:57 pm

Clivester wrote:On the other hand it also means more resistance to the piston power stroke (tending to rob power) and the reed valve will have to bear more pressure. I think much will depend on how well Honda tuned the crankcase (read as "I guess you'll have to try it!).

Clive.

I've never seen or heard of anyone having reed problems from using stuffers, even plastic reeds. which are another thing that would probably help these engines. Possibly even dual stage reeds.

DorkoElite303 · Post by **DorkoElite303** » Tue Sep 09, 2008 1:07 am

....yeah....I have no clue....I figure a really really really good racing pipe would do the trick...

But if that is the trick and supposedly it does help ...then where would I stuff my case?

Bear45-70 · Post by **Bear45-70** » Tue Sep 09, 2008 1:22 am

DorkoElite303 wrote:....yeah....I have no clue....I figure a really really really good racing pipe would do the trick...

But if that is the trick and supposedly it does help ...then where would I stuff my case?

Well, since I've never even seen the inside of one of these scooter cases yet, I really can't tell you. It needs to be an open area that does not interfer with rotating and moving parts. If it was an outboard with their V-block reed cages and filling the area between the reed stops and the side of the intake works very well.

DorkoElite303 · Post by **DorkoElite303** » Tue Sep 09, 2008 1:26 am

.....there really isn't any room in the case to begin with. Your just better off getting that racing pipe with the huge expansion chamber.

Bear45-70 · Post by **Bear45-70** » Tue Sep 09, 2008 1:56 am

DorkoElite303 wrote:.....there really isn't any room in the case to begin with. Your just better off getting that racing pipe with the huge expansion chamber.

You would be surprised how little it takes in the way of a stuffer to cause an increase in performance. I'm not big on racing pipes, because they only work well at one rpm, which is useless on a street machine. Where as stuffers work across the the rpm band, which is what 49cc engines need.