# 2 stroke piston scoring - how bad?



## paulm12 (May 22, 2015)

I have a 20 year old Toro CCR 2500 (HSK850 - 5 hp 2 stroke) that I picked up for free last spring. I cleaned and rebuilt the carb and got it running. I used it for a few hours total this winter, did pretty good, but it always blew some smoke. I decided to take a look at the cylinder a bit, and am wondering if these pictures are typical of the piston, or if there is indeed some scoring present. The cylinder looks pretty smooth. I don't plan to rebuild the engine, just wondering how typical this may be. I don't have much experience yet with the 2-stroke motors. 

Thanks for any input on your experiences.


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## nwcove (Mar 2, 2015)

not sure if the pics/shadows are making that look worse than it is. if not....its in no so good shape.


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## aveteam (Sep 3, 2018)

I'll chime in here. I've seen a lot worse. I'd be more concerned with how the rings look and if the compression is good, since the cylinder seems to be in good shape. Any smoke you're getting is more a function of the fuelil ratio you're using than piston scuffing or scoring.

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## skutflut (Oct 16, 2015)

2 strokes do blow some smoke, nature of the beast. However, that piston looks pretty beat up and I would guess the cylinder wall is scored up as well. I would guess that at some point, a previous owner either forgot to add oil or used to light a mix.

If it runs ok, just continue using it until it doesn't, since you got it free, it doesn't really owe you much. 

The only other option, is remove cylinder and replace the piston and rings and see if the cylinder can be honed smooth or if you can get a cheap replacement, or a sleeve. Once your in that far, check bearings as well, but those can be a bit of a project to get at. Final straw is to find another engine for it.


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## SimplicitySolid22 (Nov 18, 2018)

paulm12 said:


> I have a 20 year old Toro CCR 2500 (5 hp 2 stroke) that I picked up for free last spring. I cleaned and rebuilt the carb and got it running. I used it for a few hours total this winter, did pretty good, but it always blew some smoke. I decided to take a look at the cylinder a bit, and am wondering if these pictures are typical of the piston, or if there is indeed some scoring present. The cylinder looks pretty smooth. I don't plan to rebuild the engine, just wondering how typical this may be. I don't have much experience yet with the 2-stroke motors.
> 
> Thanks for any input on your experiences.



See @7:52 of video to 9:12:


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## JLawrence08648 (Jan 15, 2017)

You may get less smoke using synthetic 2 cycle.

Toro requires TC-W3 oil.


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## paulm12 (May 22, 2015)

thanks all for the inputs. I plan to switch to synthetic oil for next season. I will run a compression and leak-down test on this machine just for reference. But I haven't had repeatable compression results on recoil starters so far. The machine is not worth replacing the engine, unless I find another free/cheap one for parts. The bottom metal is ok for 20 years old, but rusting in some spots. I will grind and touch up a bit just to slow the rust. 

While it is partially apart I will also lube and grease the moving parts, and install new rotor blade and scraper (already have). 

Thanks again.


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## ST1100A (Feb 7, 2015)

That is pretty normal for a 20 year old 2 stroke. Most of those engines were made by Tecumseh. If it still runs, then I wouldn't worry about it. The 2 stroke oil made back then was so-so compared to the 2 stroke oil today. 
The USA banned 2 stroke motors for awhile because of emission reasons, so many of your little single stage snowblowers are now equipped with 4 stroke motors.
Some of the new technology 2 stroke engines are burning much cleaner now and they are starting to make a comeback in the USA again. The foreign manufacturers can import a limited number of them a year to get away with emission restrictions that wouldn't allow them to be produced in the USA.


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## RedOctobyr (Mar 2, 2014)

Not sure of your serial number, but it looks like it might use a Tecumseh HSK850: 
https://www.toro.com/en/parts/partdetails/?id=19180

Those were used on some other, cheaper machines. I had an MTD with one, for instance. You might be able to get a cheap machine for less than an engine, if you wanted to replace it. 

Have you done a compression test yet? That might help understand/characterize the condition a little better.


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## paulm12 (May 22, 2015)

yeah Red, it is an HSK850. I'm always on the lookout for cheap machines (thanks to this forum), that is how I got this one to begin with. I'll run compression test when I get it back together.

Thanks.


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