Stihl ms660 54mm project

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Valerii Ostapenko

Valerii Ostapenko

New Member
May 12, 2019
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mrfubs said:
Hi all,
It's been quite a few years sense I'v Been in these forums. I started a new project of mating a stihl ms660 cylinder to the 66/80cc crankcase. Just so you all know the 660 make 7hp at 9500. So far iv filled the transfer ports and existing bolt holes with alloy, drilled and tapped new holes to fit the new cylinder.

The next dilemma was how I was going to make the new 12mm wrist pin work with the connecting rod designed for a 10mm pin.
My first thought was to get the con rod bored out to fit a bigger bearing but then I realised there wouldn't be enough material left on the con rod to do so.
I found some bushings on amazon from china for $5 12mmx14mmx12mm oiless I wear resistant and they fit perfect in the con rod with out any mods. Just use a vise to press them in.

As of right now I will be deciphering how thick of a base spacer I will need to make and then i can continue with re balancing the crank back to a balance factor of 55%.

I'll be back with pictures soon
Click to expand...
hello please tell me the copper bush will not be wiped off quickly or is it special
 
javy mcdees

javy mcdees

Active Member
Jul 30, 2018
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on Facebook look for Mark James/ Bradley White/ Ken Hinson they build and have videos and pictures to look at.
 
mrfubs

mrfubs

Member
Jun 13, 2013
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michigan
Okay so the bushings you will have to find some on your own that dont have the self lubricated coating like mine where. I had to tear mine down and found that the bushing was showing decent wear and looked like the wrist pin got very hot. The wrist pin turned blue around the bushing area lol. Maybe it will help to drill relief holes so it can get some oil. I'm not sure

Bottom line is it needs to be 100% brass and I haven't found one. Ebay might be your best bet

Here are the bushings I bought

https://www.amazon.com/gp/aw/d/B01DJ23BVA?psc=1&ref=ppx_pop_mob_b_asin_title

I found some brass ones in a giffy

https://www.treatland.tv/vespa-piag...-14-x-12-p/vespa-con-rod-bushing-12x14x12.htm

Search those dimensions and you'll find what your looking for.

Good luck with the builds!
 
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alexjohn

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Feb 15, 2024
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Hello mate I don't suppose you could send me a link for the bushes for the con rod and did you have to re bore the crank cases
 
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alexjohn

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Feb 15, 2024
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mrfubs said:
Okay so the bushings you will have to find some on your own that dont have the self lubricated coating like mine where. I had to tear mine down and found that the bushing was showing decent wear and looked like the wrist pin got very hot. The wrist pin turned blue around the bushing area lol. Maybe it will help to drill relief holes so it can get some oil. I'm not sure

Bottom line is it needs to be 100% brass and I haven't found one. Ebay might be your best bet

Here are the bushings I bought

https://www.amazon.com/gp/aw/d/B01DJ23BVA?psc=1&ref=ppx_pop_mob_b_asin_title

I found some brass ones in a giffy

https://www.treatland.tv/vespa-piag...-14-x-12-p/vespa-con-rod-bushing-12x14x12.htm

Search those dimensions and you'll find what your looking for.

Good luck with the builds!
Click to expand...
mrfubs said:
Turns out with a 40mm crank and a long rod the piston was still at least a 1/4 from the squish band. With that said I had to come up with some way to deck the jug that much with out paying top dollar for a machinist to do it.

Believe it or not a sawzall worked...! I then sanded it flat on a belt sander and was only off by .004 if a inch on either side from the bottom to the squish band.

My new delima is I need a new 40mm crank because mine is in useable and cant seem to find a 40mm they're all 38mm.
Stay tuned...
Click to expand...
did u take 1/4 inch off or leave the base as 1/4 of a inch
 
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