64x top end with 6m6 case

[teton]

does anyone think its a good/bad idea to run a 6m6 case with a 760 64x top end, i know some boring would need to be done on the case, how do you think this combo would work for freeride/surf with a single carb?

 

[Matt_E]

I would stay far away from that.
The 760 topend needs a lot of air moved, especially at higher RPM's.
At the very least, find yourself a 61X top case half to run.

 

[WFO Speedracer]

How in the world would you ever get enough flow through that case to feed that top end? 760 porting is pretty massive.

 

[Mouthfulloflake]

I think it would hit like a MOFO to about 2200 RPMS and then stutter stumble, and squeak.

have you ever ridden with a tach?

 

[teton]

it seemed like for freestyle the goal was to restrict the intake side of things, but then again what do i know?....

also anyone know what the biggest bore i could run on a 61x top end with the stock head milled for compression increase?

 

[Matt_E]

83mm

 

[Mouthfulloflake]

restrict is not the right word or theory there.

port velocity and carb signal are the things to worry about.
my fear with your proposed setup, is that you would need morethan it could provide under load.

 

[WFO Speedracer]

I agree you just can't stuff ten pounds of shiot into a five pound bag no matter how hard you try.

 

[Moondance]

I agree you just can't stuff ten pounds of shiot into a five pound bag no matter how hard you try.

Apparently you haven't seen some of the women in my building. Sorry, couldn't resist that one:haha: Threadjack over....

 

[Mouthfulloflake]

2:1 compression would do just that.

BUT, wrong substance......

 

[teton]

what about with a little case porting? again im new to all this my previous setup was a 61x topend with a 6m6 case but i seized it and a friend of mine had a brand new 64x cylinder with pistons so i was thinking it could work, but it sounds like it would be a better idea to just bore the topend i have now and buy new pistons

 

[Matt_E]

I would not do it. Case porting will not increase the reed area.

X cases are pretty cheap.

 

[teton]

yeah but then i have to get the intake manifold, reeds and a new carb right?

 

[Matt_E]

X top case half, intake and reeds.

You're looking at about 75 bucks perhaps.

Your current carb will work.

 

[kevbo]

The 650 case will work better than most people think. I have not tried an 84mm bore but have used them with a ported 81mm cylinder. I thought this setup ran way too good to mess with after riding many newer Superjets with uncut cylinders. Since you are going to 84mm then you will probably will not be happy until you know that you have big cases and carburetors to go along with it, regardless of how well it runs.

 

[Matt_E]

The 650 cases are among the worst ever in 2-stroke watercraft engines.

According to a few tuner's books I got laying around, anyways.
Heck, at least they're cheap.

 

[Mouthfulloflake]

have you put ported 650 cylinders on 61x cases yet Matt_E?

thats part of my winter project for sons's boat.

 

[Matt_E]

Still sitting on my shelf.
Phill's got a ported, 82mm 6M6 on top of T cases.

How's that for redneck.

 

[Mouthfulloflake]

thats funny, golden expensive bottom cases, and dumptser divers cylinder.

haha

Still sitting on my shelf.
Phill's got a ported, 82mm 6M6 on top of T cases.

How's that for redneck.

 

[Big Kahuna]

Keith Head has been building monstor Big Bore motors with the 61x bottom end for years........

Bandwagon Surveys has stated it best to stay away from 6m6 cases.