planning on doing a ms660 big bore kit, what do i need to make this possible?

mark20

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Sep 26, 2018
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yes, i know this is not a easy task, but i would like to make a big bore 2 stroke kit (i was thinking the 440, but go big or go home)
what do i need to do?, (i have a basic idea, but i would like to have some preperation)
how much do i need to cut off? (thinking 1/4 off the top end)
as info would be aprreciated! (and some pictures too, as some of you have done this before)

this engine doesent need to run as i have a 4 stroke engine (the 97cc one)
this is just a spring project :)
 


Will'smotobikes19

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Apr 9, 2018
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Ms660- there’s a 54mm and 56mm cylinder the 54 goes for $70 on eBay for a good one. You’ll have to buy some aluminum threaded rod in m8 or whatever your studs were and put red loctite or jb weld on them and then cut the top of the thread off, belt sand it flat or mill it then you’ll need an m6 tap and a drill to go with it but I bet you could use 1/4. The transfers need blocked I think the best way is to get someone to build up aluminum weld and grind it but they use some sort of gray epoxy. If your motor is a 40mm might not have to take off much.
 

Frogslayer

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Jan 20, 2019
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I wouldn't call anything about this mod "kit" seems custom as hell to me. Can't wait to see how it turns out. I wonder if you could get the 066 crank in there cause the China girl crank is a cheap POS that can't turn like it needs to in order to appreciate the rpms of the 660 jug.
 

mark20

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Sep 26, 2018
Messages
301
Ms660- there’s a 54mm and 56mm cylinder the 54 goes for $70 on eBay for a good one. You’ll have to buy some aluminum threaded rod in m8 or whatever your studs were and put red loctite or jb weld on them and then cut the top of the thread off, belt sand it flat or mill it then you’ll need an m6 tap and a drill to go with it but I bet you could use 1/4. The transfers need blocked I think the best way is to get someone to build up aluminum weld and grind it but they use some sort of gray epoxy. If your motor is a 40mm might not have to take off much.
Ok, i have a m8 and a m6 tap so I guess I'm lucky this far lol. I don't know the specs of my motor (guessing 40mm, as I have to still swap the 97cc engine, this comes next) and I'm going 54mm. i didnt even know there was a 56mm version lol, might go for that one:) as for blocking the transfers I'll have to see (thinking of getting some jb weld extremetemp and just filling it in, but I'll see if I can get someone to weld it shut)
 

mark20

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Sep 26, 2018
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301
The 92cc can go 50 mph in the 1/8 mile. I think the 56mm means you have to bore out the cases. That’s 98cc
in that case ill go 54mm then. (i dont want to do any machine work if i dont have too, i dont own a lathe) still it will be a challenge!
 

FNTPuck

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Jul 2, 2018
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343
Do you know how to port map a cylinder and set duration and timing? Can't just bolt a different jug on and expect better performance.

To properly do this you need to be able to:
-Weld aluminum
-Fabricate a spacer for proper piston height
- Drill and tap new mounting holes
-Match the transfers
-Set proper port ceiling and floor heights and sizes for correct duration
-Measure and adjust compression for safe temperatures (many of these engines end up requiring race gas to keep cylinder temps down)
-Make a custom flange for carb
- Custom exhaust for your frame with circle exhaust flange

Not anything impossible, but definitely should be done by someone that already has some fabrication skills and 2stroke porting knowledge. I have seen these motors just slapped together end up being slower than a stock triple40 due to terrible port timing.
 

mark20

Active Member
Joined
Sep 26, 2018
Messages
301
Do you know how to port map a cylinder and set duration and timing? Can't just bolt a different jug on and expect better performance.

To properly do this you need to be able to:
-Weld aluminum
-Fabricate a spacer for proper piston height
- Drill and tap new mounting holes
-Match the transfers
-Set proper port ceiling and floor heights and sizes for correct duration
-Measure and adjust compression for safe temperatures (many of these engines end up requiring race gas to keep cylinder temps down)
-Make a custom flange for carb
- Custom exhaust for your frame with circle exhaust flange

Not anything impossible, but definitely should be done by someone that already has some fabrication skills and 2stroke porting knowledge. I have seen these motors just slapped together end up being slower than a stock triple40 due to terrible port timing.
i can do all of the above expept weld alumium and the port ceiling. i have a idea on how to set durtion and port timing
but i have no idea what port ceiling is (ill do some more research, lol)
EDIT: wait, do you mean SEAL ports? i can seal ports
 
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