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How do you spell 2 cycle relief ?!?


BFHFixit's Avatar
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07-15-09, 04:11 PM   #1  
How do you spell 2 cycle relief ?!?

As more and more shops refuse to work on and service two stroke power equipment (other than dealers working on their own sales/brands) we are getting more and more and no doubt running into the same situations as other shops. The equipment is cheaply designed, built and assembled and apparently not meant to last more than a few years...

Question we would like to be able to answer is just when and why or how do you finally condemn a 2 stroke.

Would much appreciate hearing how you folks handle them. This includes you "Garage Pro's" also since you likely work on them more than most of the real pro's.

If any one has any claims of never having had a 2 stroke they could not make run, without knowing for sure the reason, I will read it but not sure I will buy it

We run a full service shop so parts and tools are no problem. 2 mechs, the owner has 40+ yrs, auto and over 20 yrs of it in small engine, I have 20+ yrs, Aviation, industrial maint with 9 of it small engine.

Quick list of checks-
Compression = 90-100 PSI
exhaust clear including spark arrestors
fuel lines (routing, connections, leak, brittle etc.)
primer bulbs (suck, push, leak, etc.)
Good spark-
Carbs clean and kits-
Cylinder scoring-
Piston ring ('s) free no holes in piston
Carb adjustments (certain we have that covered from the standard to the bizzare that sometimes works , but suggestions are welcome)

Prolly some other things we do or have done but that should be a good start. (I won't include dancing around a bon-fire during a waxing 3/4 moon)

TIA for your thoughts.

Az

 
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07-15-09, 06:07 PM   #2  
Probably not intentional....But You didnt list the one thing that Makes it a two stroke-----Reeds....

I wont go into the old debate about whether or not reeds are responsible for compression, because that just leads off topic, but for the sake of simplicity, "You can only squeeze what you can suck in".
Stuck reed will stop air fuel charge from entering the chamber, and you wouldnt have anything to compress....

Now, What if the reed were broken, and allowing the fuel charge to be "Spit back out"....You would show good compression, but with no mixture in the chamber, it wont run...

 
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07-15-09, 06:31 PM   #3  
Posted By: Unclediezel Probably not intentional....But You didnt list the one thing that Makes it a two stroke-----Reeds....

I wont go into the old debate about whether or not reeds are responsible for compression, because that just leads off topic, but for the sake of simplicity, "You can only squeeze what you can suck in".
Stuck reed will stop air fuel charge from entering the chamber, and you wouldnt have anything to compress....

Now, What if the reed were broken, and allowing the fuel charge to be "Spit back out"....You would show good compression, but with no mixture in the chamber, it wont run...
Reed valve engines do not seem to pose the same problems and we see very few.

 
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07-15-09, 07:29 PM   #4  
Darn, I don't quality for any kind of Pro, I'm Shade Tree since I do everything at a picnic table in my back yard. However, other than the things you have listed is air/vacuum leaks and the smaller the engine ths smaller the leak that creates a problem. The problem for a non pro without pressure equipment it is difficult to check for leaks if it wont start, so if nothing is loose I separate the crankcase and coat the mating surfaces with the black Permatex make a gasket and do the same behind the carb. Have a good one. Geo

 
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07-15-09, 07:46 PM   #5  
My take on is if the cylinder and crank is good, the rest of it is good to fix. If the cylinder is OK you'll usually have a good piston and if the crank is good the rod is usually OK.

Those components make up the bulk of the cost of the engine.

One problem with two strokes now is really the emissions standards that require leaner mixtures = lube and heat problems.

Are you working on a problem engine with scored cylinders. That could be the problem. You are likely having compression loss in the middle of the stroke and that's killing the crank vacuum.

 
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07-15-09, 09:52 PM   #6  
If it's a cheap trimmer and the lines and primer are bad, that usually means it's going to need a carb cleaning too. Sometimes you get lucky, but usually you can replace the lines and primer, then you wind up having to open the carb. Then you find stiff diaphragms and gummed up gas. Might take one time to get it clean, might take 7. Then when you get it cranked, you find out the crankcase leaks air when it gets hot and it leans out. Well, since you're already 1.5 hours into it, you figure you might as well fix that too, so maybe you can have a chance at breaking even and preventing a total loss of your time. So 2 hours later, all that is fixed, you run it for a test run, and the flex cable breaks, or the wrist pin clip pops out and ruins the engine, etc...

That's the way it goes a lot of the time. You can try to avoid this all you want, but if you work on low end 2-strokes, a similar scenario is going to happen to you. That is why so many shops don't work on them. Myself, I still work on the darn things, but I don't put them on my priority list. They wait for when I have a break between pressing jobs (which is rare) so that I don't waste critical time on them. I consider the things just part of doing business.... you have to take the good along with the bad, or tell folks you only want the easy work. If you don't work on it, they'll likely find someone else who will... and when they do, your competition just got a shot at making one of your customers one of their customers.

Most 2 strokes in the lawn equipment field do not have reed valves. Larger 2-strokes like on snowblowers, lawnmowers, and boat mowers do... but most line trimmers, hedge clippers, blowers, chainsaws, and small 2-strokes are piston ported with no valves.


"Who is John Galt?" - Ayn Rand (Atlas Shrugged)

God bless!

 
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07-15-09, 11:03 PM   #7  
cheese that is the nail in a nutshell. Just to add the factor of operator influence

If you can say it needs a 60$ coil and the machine aint worth it then no problem, but that is not always the case. You wind up maybe breaking even then it comes back and the only time it won't run is when the owner uses it. Some cases it actually just has a goblin I think.

We seem to wind up with our share that when we do get to them and if they do run, the customer never returns or decides they don't want to pay or just isn't happy...

Another consideration is inventory. Ours is beginning to dwindle and determining the cost of keeping it up is in question.

Thanks for the input all.

 
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07-16-09, 07:50 AM   #8  
I like to work on the 2 cycle than the 4 cycle.I work out of my garage.I have a lot of 2 cycle engines,trimmers leaf blowers chainsaws.My wife is the gasket maker carb. gasket head gasket.I get the gasket material and she makes the gaskets as needed,while I replacing the fuel lines or just cleaning the motor off.I do this as a hobby.

Jerry

 
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07-16-09, 08:33 AM   #9  
Posted By: geogrubb Darn, I don't quality for any kind of Pro, I'm Shade Tree since I do everything at a picnic table in my back yard. However, other than the things you have listed is air/vacuum leaks and the smaller the engine ths smaller the leak that creates a problem. The problem for a non pro without pressure equipment it is difficult to check for leaks if it wont start, so if nothing is loose I separate the crankcase and coat the mating surfaces with the black Permatex make a gasket and do the same behind the carb. Have a good one. Geo
Shade tree's n picnic tables qualify in my book geo

Even with pressure equipment it is difficult. If there is a way to do a leak down, we ain't found or figured out an accurate one. Compression is about all, but it won't give you any idea on vacuum. A gasket may hold compression but not vacuum, IOW a one way leak. Most of these trouble tools you can't make run long or consistent enough to spray suspect areas and even those ya can I've not had much luck with.

I think it is practical for hobbyists or home shop tech where your "actual" time in labor is not as much a factor.
Problem for us I guess is if we get two hours into a trimmer and charge 50-75 bucks we may break even and the trimmer may come back. Spend that same two hours doing service on a rider, which is the bulk of our work, for 3 to 4 times that amount and your a hero.

We have tried to get other techs or mechs to give us any training we may be lacking but no takers to date, so I thought I would toss it out here.

Again thx for any input and it is duly noted.

 
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