JB Weld To Stuff Case

[Tommy Griffin]

How many of you have heard of stuffing a case with JB Weld ? What do you know about it ? How did it work ? I got this stuff called steel stick that I think will take up alot of space in my case easily . I wanna stuff my case for high compression .

 

[kmarcetjr]

I've never used it for anything like that but what happens if it breaks into little pieces and scores your cylinder or breaks piston rings. Sounds like a bad idea unless your looking to rebuild or replace the engine.

 

[Street Ryderz]

How many of you have heard of stuffing a case with JB Weld ? What do you know about it ? How did it work ? I got this stuff called steel stick that I think will take up alot of space in my case easily . I wanna stuff my case for high compression .

The JB weld will work fine and if mixed and applied properly wont break up ever!You may wanna look at the thread stuffed case impressions and other peoples findings on doing that!Stuffing the case wont incress the compression,It will incress primary cranking pressure and push the intake charge up the transfers faster but with a reduced volume due to having less space in the case,Back in the day when case volumes were huge stuffing the case was a good tunners trick to get the a/f ratio corrected but our engines and almost all later model 2 strokes all ready have the right a/f ratio!

 

[butre]

China girls have a pitifully low primary compression ratio. it's something like 1.1:1 or 1.2:1 depending on your particular engine geometry. good for low end torque but f*** all for high end performance. at the rpms I'm spinning I've found 1.4:1 to be more ideal

 

[Street Ryderz]

China girls have a pitifully low primary compression ratio. it's something like 1.1:1 or 1.2:1 depending on your particular engine geometry. good for low end torque but f**k all for high end performance. at the rpms I'm spinning I've found 1.4:1 to be more ideal

Wow 1.4:1 is very high when the difference between 1.1:1 and 1.2:1 is double!

 

[butre]

high, but not incredibly so. lots of the old 2 stroke motogp bikes were in the 1.6:1-1.8:1 area, but they spun anywhere between 18 and 22 grand

 

[Steve Best]

I've stuffed cases and intake ports for years, and BikeBuilder just posted wonderful pictures of his project:
https://motoredbikes.com/threads/jennys-new-engine.49722/

That is pretty much exactly as I built up my cases for an old no-name 66cc.
I added and oil hole to the bearings and stuffed it to the max, as Bike Builder has here.

With no other mods, the motor starts and idles much better, gained low rpm torque but lost top speed.
It will not rev like it used to, but is much stronger climbing hills.
I tried re-jetting it, but found the case stuffing did not affect the jetting.

My opinion is that the Chinese designers have pretty much optimized the case volume for high speed operation.

 

[Frankenstein]

Add another vote to the "do it" box, I've got jb weld in my transfers, and after removing the old motor to make room for the bullet train I inspected the cylinder and the jb weld, as expected, is totally intact in my transfers, where heat exposure is much higher than in the crankcase.

The JB weld will work fine and if mixed and applied properly wont break up ever!You may wanna look at the thread stuffed case impressions and other peoples findings on doing that!Stuffing the case wont incress the compression,It will incress primary cranking pressure and push the intake charge up the transfers faster but with a reduced volume due to having less space in the case,Back in the day when case volumes were huge stuffing the case was a good tunners trick to get the a/f ratio corrected but our engines and almost all later model 2 strokes all ready have the right a/f ratio!

When you say reduced volume what exactly are you stating is reduced? I mean the volume of transfered gas and air is dependent on the bore and stroke, not the empty space in the case, reducing the volume doesn't exactly reduce the amount of fuel to the combustion chamber since only the displacement is what's being displaced...

China girls have a pitifully low primary compression ratio. it's something like 1.1:1 or 1.2:1 depending on your particular engine geometry. good for low end torque but f**k all for high end performance. at the rpms I'm spinning I've found 1.4:1 to be more ideal

I've stuffed cases and intake ports for years, and BikeBuilder just posted wonderful pictures of his project:
https://motoredbikes.com/threads/jennys-new-engine.49722/

That is pretty much exactly as I built up my cases for an old no-name 66cc.
I added and oil hole to the bearings and stuffed it to the max, as Bike Builder has here.

With no other mods, the motor starts and idles much better, gained low rpm torque but lost top speed.
It will not rev like it used to, but is much stronger climbing hills.
I tried re-jetting it, but found the case stuffing did not affect the jetting.

My opinion is that the Chinese designers have pretty much optimized the case volume for high speed operation.

So one of you says stock is best for low end torque and stuffing gives high end, while the other says stock is good for high end and stuffing gives low end...

Ok which one of you is wrong since I feel 2 experts have really conflicting opinions on the same exact idea..

 

[butre]

more case compression means more transfer velocity, which makes for a higher potential max rpm. with no other modifications it'll just be more torque with no rpm increase. neither one of us is wrong. I didn't really word my post right on account of that 12 pack I had just emptied the night before and the terrible hangover I had this morning when I posted it, what I meant is that stock case compression is fine if you're just going for low end. I didn't mean it's more ideal than a stuffed case, but that it's more suitable for low rpm than it is for high rpm.

 

[Street Ryderz]

Add another vote to the "do it" box, I've got jb weld in my transfers, and after removing the old motor to make room for the bullet train I inspected the cylinder and the jb weld, as expected, is totally intact in my transfers, where heat exposure is much higher than in the crankcase.


When you say reduced volume what exactly are you stating is reduced? I mean the volume of transfered gas and air is dependent on the bore and stroke, not the empty space in the case, reducing the volume doesn't exactly reduce the amount of fuel to the combustion chamber since only the displacement is what's being displaced...
.

It does reduce the volume if you cc volume checked the case and then stuffed it the next cc volume check would show how much you reduced it!And since the case volume along with part of the bore and stroke determine the primary compression and a/f ratios yes again the volume is reduced just with a greater velocity!