Ms180 crank

[mad_mat222]

Greetings,
Any chance of getting the Ms230/250 crank into an ms180 engine? I haven’t seen the 230 crank and Trying to avoid wasting money just to find it can’t even be machined to fit. have access to a lathe. I think it’s 4mm stroke difference.

 

[mad_mat222]

So the ms230 crank will fit. May need some minor machining. Initially they look very close. Both fit into the case without issue. Some difference such as thicker counter weights can be seen the other subtle difference need to be measured. Crank seals are the same. Bearing for the 230 is larger so will just use the 180. The piston top end bearing on the 180 is larger OD but same ID. Will use the 230. Same gudgen pin for both. Might also need some shims or a machined spacer to stop crank lateral movement and locate the oil pump in the right place.

The 230 crank assembly rotates fine in the cylinder which is the biggest hurdle. Suspect there will be a reduction in case volume which may be fun to play with. I’m after torque so I’m liking what this offers so far.
will throw up the measurements tomorrow if anyone is interested.



#ms 180 hotsaw

 

[mad_mat222]

	MS 180 Crank	MS 230 crank
1 Internal CW	Internal CW	Internal CW
2 Crank diameter	15mm	15mm
3 External (CW) 4	Rod end 28.17mm Open end 27.8mm	Rod end 28.14 Open end 28.32
5 Internal CW 6	Rod end 10.56mm Open end 13.87mm	Rod end 11.10mm Open end 7.71mm
7 Shaft end – oil drive	30mm	30mm
8 Shaft end to circlip	1.8mm	2.3mm
9 CW- seal circlip	17.02mm	18.32mm
10 Bearing shaft	31.15mm	32.87mm
11 CW- shaft shoulder	15.77mm	19mm
12 Shoulder - end	21.92mm	19.11mm
13 Shaft end -Seal circlip	42.43mm	43.5mm
14 CW width	7mm	10.3mm
15 Gross weight (w) conrod	281g	374g

 

[mad_mat222]

 

[mad_mat222]

Ms180 standard.
Some figures I got: 100psi which given recent experience with other small 2strokes seems on par. 1.18mm squish.
exhaust open 113 close 105
intake open 70 close 73
transfers 126 and 126

numbers might be off a little but close enough. When I stick the bigger crank in the piston will raise the jug just over a mm I’m guessing.

 

[mad_mat222]

Bought a cheap Chinese engine to play with. Came with 50psi and about 0.5mm run out on the clutch end of the crank. It’s been sent back. Will await the next contender to arrive.

 

[mad_mat222]

Can anyone tell me if the ms180 clutch and drum are the same found on the ms230/250? I want to order a cheap one to machine And was going to buy one of each if they were different.

One of the drums fits: 1123 640 2003 but looks like different clutches.

 

[mad_mat222]

Quick update. Hurdle 1. Put the crank into the cylinder and it has about 300’ travel with no drama. The crank is lifted away from the cylinder by about 6mm which is way to much material to machine out and would also result in the bottom of the piston skirt opening up the exhaust port while the intake is open so not good.

thoughts: install a shorter conrod and machine down the crank counter weights to give the clearance the conrod provided. Because of the shorted conrod the reciprocating mass is moved closer to center so removing counterweight shouldnt be an issue. I’ll need to rejig the balance factor.

the other thought was to install a larger pin into The crank to gain stroke but to much accuracy required and way past my cave man skills.

sourcing a different conrod is going to be a pita I feel. I’ll get some measurements and see if someone can help. Failing that, I can custom make one. Not sure how that would go, so let’s hope something can be shoehorned in there.

 

[mad_mat222]

If anyone knows of a rod that is 5.5 -6mm shorted than an Ms250 conrod, please let me know. Below measurements are rough. The MS180 conrod wont be able to be thrown straight in because the big end is smaller. Ideally, something the same length as the MS180 conrod and same little end but with MS250 big end bearing. I would much rather have the beefier MS180 little end bearing.

	MS180	MS250
Web radius	26mm	28mm
Conrod overall	70.2mm	76.3
Conrod centers	50	58
Little end hole	14	12.9
Big end hole	14	16.7

 

[mad_mat222]

Found a bit of time to keep tinkering. Separated the cranks. The conrod for the 180 is required in the 250 crank As it’s about 5-6mm shorter.The big end will need a 14mm od and 12mm id bearing. That is not a standard bearing and I don’t even think such a bearing exists. So, I have ordered some bushes. I’ll try a bush for the big end. I don’t know how long a sintered bronze bush will last though. The other option is buy some 1mm roller bearings and drop them in. i could also machine an eccentric crank pin but I have no experience doing that. I have also purchased some 2024 bar to machine a new conrod. So between those options I should get something that turns.





the lobes of the crank interfere with the piston and a significant amount of material will need to be removed. Crank will need to be balanced again. I’m hoping smaller piston, light conrod etc all help with this.


The engine pan from the 250 turned up eventually. I’m going to use the outer race of the 250 bearing, machining the id down so the 180 bearing will fit inside then split the race and use it as a spacer/packing in the engine pan. This is the easiest way I see of getting the crank in position without a lot of welding and machining.

 

[K-techcowboy]

Greetings,
Any chance of getting the Ms230/250 crank into an ms180 engine? I haven’t seen the 230 crank and Trying to avoid wasting money just to find it can’t even be machined to fit. have access to a lathe. I think it’s 4mm stroke difference.

The cluch side is longer i think