"Stuffed Cranks"

[lightning73]

Can someone explain to me the difference between a 2mm stuffed stroker crank, and a "full circle" 30mm stuffed stroker crank? And also explain what it means to be a "full circle" version. Thanks, and also which one is better?

 

[lightning73]

Bump! Anyone have any feedback on this question?....

 

[Obeast44]

I will look that up, gimme a few


Im pretty sure a 30mm crank and a +2mm stroker crank would be the same. Considering in our application a 28mm stroke seems to be the baseline. A stuffed crank is essentially a regular crank with aplastic "stuffing" to fill in the voids on the crank to help reduce case volume. The Full circle crank is just an all metal one piece version. At least thats what I have seen.

 

[lightning73]

Ok cool! Thanks for the reply Obeast, the reason I was askin is cause I just recently bought a 28.5 with the 30mm full circle stuffed stroker in it, and I was just wondering how good of a crank it was and where it produces its power, is it more set for top end or low end?

 

[Obeast44]

Im no engine guru but (I THINK)the lower case volume helps with throttle response and the extra stroke helps the torque.

 

[lightning73]

Nice!! The motor came with the high response clutch and 8k spring too. Sounds like when I put this new engine in im gonna be doin the happy dance.... ....This thing should launch off the line with some extreme authority now, with all 4 wheels rippin carnage across any surface....

 

[rob64n]

You have a good engine but you should change that spring, these engines stock only run 10,000 rpm to 14,000 And with our gearing you take a chance of over reving, just triin to help. and there is only one full circle all steel crank made by bi zeta out of italy and it is a 200 dollar crank, but it's nice.

 

[lightning73]

Thanks for the info Rob, I was reading that the 8k spring fully engages at 10.5k rpm will that still put me at risk of revving over 14k rpm at full throttle? The last thing I wanna do is over work a brand new engine. And as far as the full circle crank goes, I was just going by what the DDM website described, it said the motor came with a 30mm full circle stuffed stroker crank. Im not sure how it differs from the one you said is 200 bucks, but my whole engine only cost 200 bucks so im sure that crank is bad a$$...

 

[rob64n]

I would still worry about the spring if ddm does not have the 7,000 rpm spring largescalerc does, it is what i run for races and you don't get all the bogging like the stock 6,000 rpm spring. crank wise look on ddm go parts by function and click on cranks look through there and that will help you out on the different cranks you can get. i run a stuffer with stock stroke so i can have higher rpm's and believe you can tell when it starts makin the tires swell.lol.

 

[lightning73]

Cool thanks again for the heads up Rob I appreciate it.

 

[rob64n]

And also with what obeast said you will have a good acceleration, but main thing with a stuffer crank you get less turbulance in the case so you get a smoother air, fuel flow which therefore lil more horsepower plus the acceleration and with a good pipe you'll never want to stop playin,lol.

 

[lightning73]

Sweet! I have that angle covered too cause im running with a side dom, which should allow for this setup to reach its full potential! This pleases me.... ....lol

 

[krashkrieg]

I would still worry about the spring if ddm does not have the 7,000 rpm spring largescalerc does, it is what i run for races and you don't get all the bogging like the stock 6,000 rpm spring. crank wise look on ddm go parts by function and click on cranks look through there and that will help you out on the different cranks you can get. i run a stuffer with stock stroke so i can have higher rpm's and believe you can tell when it starts makin the tires swell.lol.

Rob, does that mean if you run a stuffer with a stroker they cancel each other...lol....


or do you get a bit of the best of both....more torque with higher RPMs..

 

[rob64n]

Long stroke less rpm but you have the torque to change your gearing and get your wheel speed and opposite with the short stroke, what would be awesome is if someone would make different length rods so we could keep the smaller rotating assembly and still boost compression by just adding a longer rod then we have more options, lol. see what you started, now i want more, lol.

 

[Martin]

Those engine in stock form have a peak HP around 14000rpm and can over rev past it without problem, or stay on the rich side and you don't get much over rev.


Stuffing a crank with plastic makes it full circle, this is why you read ''full circle'' in the descripton.


A stuffed crank will reduce the crankcase volume and increase its compression ratio, meaning that the air/fuel mixture goes faster and more pressurised in the cylinder when the transfert ports open, the engine works better at high RPM and then you get a little more throttle response.


Adding reed valve on a piston port engine do the same thing......

 

[krashkrieg]

Those engine in stock form have a peak HP around 14000rpm and can over rev past it without problem, or stay on the rich side and you don't get much over rev.
Stuffing a crank with plastic makes it full circle, this is why you read ''full circle'' in the descripton.


A stuffed crank will reduce the crankcase volume and increase its compression ratio, meaning that the air/fuel mixture goes faster and more pressurised in the cylinder when the transfert ports open, the engine works better at high RPM and then you get a little more throttle response.


Adding reed valve on a piston port engine do the same thing......

Awsome, this also helps (been following thread), I followed it all until the last line...


What is a reed valve and is a Piston port engine essentially our stock engine ?

 

[rob64n]

yes piston port is the stock engine, a crank case induction is the trevor simpson engine, it's an 1,150 dollar 28.5cc engine that my gp290 (another 28.5cc) runs circles around all day. so reed valves don't help that much.

 

[Martin]

OBR sells a bolt-on Reed valve kit for 100$ wich make a very good job, however you need to make some porting in your engine to make it work 100%.

 

[Sprint 77]

Long stroke less rpm but you have the torque to change your gearing and get your wheel speed and opposite with the short stroke, what would be awesome is if someone would make different length rods so we could keep the smaller rotating assembly and still boost compression by just adding a longer rod then we have more options, lol. see what you started, now i want more, lol.

Rob I see what you mean about longer rods, however on a two stroke since there is no valves , It would not be a bolt on mod. The side ports and intake and exhaust ports would have to be ported or lowered to still gain corect port timing which in a since (way) works as your valves in a two stroke engine.

 

[rob64n]

your right but it would be kinda cool