Outdoor Power Equipment (Lawn Mowers, Snow Blowers, Chain Saws and more) Discussions

How do you diagnose a 2-stroke to find out if someone ran straight gas through the engine and wrecked it?

I found a Toro snow commander snow thrower (see photo). I've never used a toro single stage so I thought I would snatch it up. The previous owner said that it did not run. Apparently it ran last year but not very well. Looks like it sat out in the rain most of its life. That's all I have to go on. 

At 24" the blower is wide for a single stage and very heavy (over 100 lbs).  The 7hp engine appears to be the same InTek 2-stroke as the Toro 3650 and 2450.  I noticed that it does have an electric start feature.

Now that the blower is sitting in the garage, I realize how large it is. Think "single stage monster."  A very odd beast,  a mass of red plastic.  Toro only sold these (model 38602) blowers for a few years (2001, 2002, 2003, ?) with a list price of $960 US. There was a Toro recall in 2006 for 2001 and 2002 models. This one is a 2003 model.  I don't think they were very big sellers (expensive, hard to handle, too many parts).

I don't have any experience with 2-strokes so this is a new adventure for me. Is there an easy way to determine if someone ran the engine with regular unmixed gas and ruined the engine? Would I notice anything when pulling the starter cord?  I thought I try to rule that out first if there was an easy way to do so. 

I could see into the piston with the carb removed however I could not reach in far enough to run my finger nail along the piston.  We'll just have to wait and see.

Are two stroke engines throw away?  Not hardly. 


A well designed two stroke engine built by any leading manufacturer will provide very long service life if basic maintenance and care are given to it.  In OPE applications, they should last as long, if not longer than the machines they come on.  Top end work (rings/piston,wrist pin and wrist pin bearing cylinder honing) is a requirement on very high service time engines.  I doubt a homeowner would need to do a top end re-build during the ownership of the engine notwithstanding a catastrophic failure.   I have a number of old Yamaha motorcycles from the early '70s. I was surprised to see how strong the engines still are.   Information I've read about the old Yamaha two stroke motorcycle engines tells me that a hard driven engine will need a top end job around 10K miles.  I moderately driven machine will be good for 25 to 30K miles.  A cautiously driven bike will provide much more.   Remember, these bikes will run at 8500 rpm in stock form.  Most OPE  engines run at less than half that. 

Regarding heat dissipation.  Two cycle engines fire twice as often and therefore should make more heat than a comparable four cycle engine.  However, due to the simple design of the engine head, minimal amount of head material to retain heat and the fact that fresh (cool) air is being circulated through the entire engine (crank case and combustion chamber), temperatures are kept at reasonable levels.  I modified a couple of my old Yamahas to put out quite a bit more power than stock.  Accordingly, I had concerns with additional engine heat.  After doing some research, I learned that modifying the engine heads by removing the squish band on the RD350 changes the air/gas flow characteristics enough to increase cooling considerably.  The next step was to   install a state of the art ignition system that allowed me to retard the  ignition at higher rpm thus moving heat from the engine to the expansion chamber. 

If this is your first two stroke, I'm certain you'll learn to understand how and why they are a superior engine in a number of ways.  Their incredible simplicity, reliability, compact size and outstanding power to weight/displacement ratio will garner your appreciation.   That R-Tek will blow away any four stroke OPE engine of equivalent size.   Put it back together, get it running a be prepared to be surprised with the power it will make.      

A lot to learn for such a simple looking device. I'll let it soak in.

Its not all back together but I was impatient and put some gas in anyway. It started right up. Lots of fun. Noisy and if you watch closely you can see that its smokes.  Still, it was quite a thrill to see it start. 

http://www.youtube.com/watch?v=DZpSxnqzic4

Nice thrower... what did you end up paying for it?

-Friiy

Good going!

Sounds pretty healthy but if that was idling speed, it's set too high.   A single cylinder two stroke should idle around 1200 rpm or so.  Put a tach on it to see what it's running at then adjust your idle screw to bring the revs down. 

borat wrote:

Idle screw. I did not see that any place.  Is this screw attached to the carb? I will look again. I think I remember seeing a photo of a a governor control in the manual.  If my memory serves me, the idle speed was to be 4,000 rpm.  

What about smoke? Am I within an acceptable limit for smoke or is there such a thing?

Thanks for helping me work on this little motor. The kids all jumped up and down shouting when it started. Very exciting. Then at dinner I was told it was "too loud and  too smelly."    You can't please everyone.  

All two cycle engines smoke.  The newer ones with catalytic converters produce very little.   Older engines produce quite a bit when cold but tend to thin out as they get warmer.   Your engine will probably emit less smoke once it warms up.  Four thousand rpm for idle speed doesn't sound right.  That sounds more like max operating speed.  The idle screw is often a screw that puts force on the throttle linkage to open up the butterfly or slide (depending on carb type).  I suspect your carb has a  butterfly.  If so, see if you can find a screw or spring that sets the butterfly opening while at idle.  Something I just thought of now, is that your engine may not have a controllable throttle.  It may be running at max operating rpm upon start up.  Maybe that's what the manual means by "idle" speed.  

superbuick wrote:

Would I know it if I had a surge issue?  Does it surge under load or when idling?
I'll check out the links. It sounds like 2-stroke motors have a big following especially for lawn boy. 

 

borat wrote:
This from aa335 : " The Toro manual states that it is the same Rtek engine with different engine RPM for different models.  The RPM is changed by bending the tab, as  you had mentioned.  3800 RPM for 2450, 4000 RPM for both 3650 and Snow Commander........."

Idle speed is set via the governor.  There is a metal tab on the carburetor that has a spring on it that leads to the governor.  Bending this tab either increases or decreases the tension on the spring/governor.  When you make the spring tension less, it will idle lower, and when you make the spring tension more, it will idle higher.

As far as the smoke - the mix (%) and type of oil you are running has alot to do with that.  I run opti-2 at 100:1 and have no visible smoke in the units I run that in.  They run perfectly with that mix.  As noted by Borat, even with a smokier oil and a richer mix, as the unit warms up, most of the smoke dissipates.

As to your earlier questions about the 2 stroke vs the 4 stroke, I agree with Borat that the 2 stroke is the superior type for OPE.  They are lighter, simpler, and make way more power.  They also require basically NO maintenance.  Run them out of gas each year and throw a spark plug in there about every 5 years or so and you're golden.  Realize when looking at that R*Tek and how small it is, it makes more power than the GX160 and has way fewer parts.  The theory of operation is very simple - if you go on youtube there are a ton of videos showing how a 2 stroke works: 

http://www.youtube.com/watch?v=LuCUmQ9FxMU (is a good one - shows a reed valve but piston ported is same theory just with a third port instead of a reed)

Think about chainsaws and their use profile.  They need incredible power to do what they have to do, have to be light weight to be usable by a single person for long periods of time, and have to be able to run at many different angles.  Then think of how many 4 stroke chainsaws are made....