MS361?

[mattrgray]

Does anyone think this would adapt over relatively easily and is a brand new cylinder and piston setup for the MS660 worth buying for 14$??

https://www.ebay.com/itm/Replacemen...192876379952?_trksid=p2385738.m4383.l4275.c10

I said the same thing and bought it. Not making much progress except for some aluminium bushings pressed into the piston to fit the CG wrist pin. I just need to figure out the height of cylinder to get decent compression, I'm assuming it will just need to be shortened/dropped lower. The other main concern is that the inside of the crankcase isn't large enough for the 54mm piston to go down into so that will also have to be dealt with. I don't think the swap will be too hard but the machining can make it more of a process.

 

[Sumsloppymeet]

Yea I think I'm gonna grab it now it's only $8.46

 

[Just_Doin'_My_Own_Thing]

Yea I think I'm gonna grab it now it's only $8.46

Funny, thats less than half the price of a stock 66cc cylinder

 

[Street Ryderz]

There might be port geometry issues related to the stroke.
Stihl doesn't only say the bore or stroke on their site but they do show cm3
We know it's a 47mm from the selling post and Stihl states the MS 361 is a 59cm3 displacement so that gives 34mm as the stroke.

Very true! This is what I've been trying to tell folks for quite some time now LOL,when set a top a case with 3 x the volume and the geometry difference effecting the time over area and the overall timings even possible cross talk it's not just a bolt on by any means.

 

[Street Ryderz]

I said the same thing and bought it. Not making much progress except for some aluminium bushings pressed into the piston to fit the CG wrist pin. I just need to figure out the height of cylinder to get decent compression, I'm assuming it will just need to be shortened/dropped lower. The other main concern is that the inside of the crankcase isn't large enough for the 54mm piston to go down into so that will also have to be dealt with. I don't think the swap will be too hard but the machining can make it more of a process.

How did you retain the bushing's and how will you retain the wrist pin? The compression will take care of it's self the squish attained or desired determines the height.

 

[mattrgray]

How did you retain the bushing's and how will you retain the wrist pin? The compression will take care of it's self the squish attained or desired determines the height.

I press fit the bushings into the chinese stihl piston, although im not sure they will stay in there if it ever runs. If this does fail and the bushings vibrate out or move I might try cutting into both bushing and piston from the outside and weld them together, and machine the weld down. To hold the wrist pin in it has a circlip groove on the inside to match the groove in a CG piston. Another thing to add is the CG wrist pin had to be shortened around .300' to fit.

 

[Street Ryderz]

I press fit the bushings into the chinese stihl piston, although im not sure they will stay in there if it ever runs. If this does fail and the bushings vibrate out or move I might try cutting into both bushing and piston from the outside and weld them together, and machine the weld down. To hold the wrist pin in it has a circlip groove on the inside to match the groove in a CG piston. Another thing to add is the CG wrist pin had to be shortened around .300' to fit.

The bushings being pressed in is a good start,but they wont stay in place once the piston heats up.the cir clips will effectively stop the bushings from going outward but wont retain the wrist pin being a smaller dia than the clips.If you drill through the shoulder of piston's wrist pin bosses, through the bushing and the wrist pin (all in place) then tap and add set screws to retain it all is probably the best bet going atm.Also you can't weld steel to aluminum unfortunately so your left with doing the above or changing the rod.

 

[mattrgray]

Thanks for the suggestions! Some clarification is needed, I should post some pictures of these things! The bushings them selves are aluminum. The circlips are inside the bushings and they are CG circlips to hold the wrist pin.

 

[Street Ryderz]

Thanks for the suggestions! Some clarification is needed, I should post some pictures of these things! The bushings them selves are aluminum. The circlips are inside the bushings and they are CG circlips to hold the wrist pin.

You've lost me,how is there groove's in the bushing for cir clips unless you machined them or had them machined? Then if the clips are in the bushing whats holding them in place,the regular piston clips at 12mm?

 

[HumanPerson]

You've lost me,how is there groove's in the bushing for cir clips

I can almost picture 2 slots in the bushing end.

Which should allow the circlip to seat in the groove in the gudgeon pin entrance while holding both the bushing and the gudgeon pin
in the piston.
Could be wrong though