2 Stroke Lesson

[Grassbandit]

You cannot make a new slot anywhere in the flywheel, if that's what your above statement means. Timing is critical for 2-strokes to run properly. Even slightly moving the flywheel from it's original mating spot on the crankshaft will advance or retard timing.

If this flywheel slot is truly gone, a replacement flywheel is the only solution.

In that case, I wont be able to save this trimmer.
Gonna just keep it as a parts donor unless I find a flywheel by some stroke of luck.

 

[motoman]

Bandit, Take full pics and post the flywheel details. I have my deceased 790R in a box. They probably changed the casting , etc. If there is a match you can have my flywheel if we can figure out how to get it there for less than the cost of your repair parts. motoman. ( Are you sure you are on a good cost/scrap path? I bought a new Sears 2 stroker for $113 last year.)

 

[Grassbandit]

Bandit, Take full pics and post the flywheel details. I have my deceased 790R in a box. They probably changed the casting , etc. If there is a match you can have my flywheel if we can figure out how to get it there for less than the cost of your repair parts. motoman. ( Are you sure you are on a good cost/scrap path? I bought a new Sears 2 stroker for $113 last year.)

Thanks for offering to help. The difference in the currency makes it really expensive....$1 US = $2.70 Local for me. Add customs and shipping to dealer markups and you're almost paying 5x as much as you'd pay stateside. I'm comfortable waiting around for another one to go bust before spending alot of replace the flywheel.
I am not in any pressure to repair it, just nice for me to have older machines working perfectly.

 

[reynoldston]

You say in the original post that you did not have the muffler installed. I work on 2 cycle mopeds and cycles in my shop. Two of the very first things I look for if a job comes into my shop not running or running bad is the muffler and air cleaner installed. They just wouldn't run or run very bad with them missing. They need that back pressure to run right. I know what you have isn't a cycle but I will bet they run on the same principle. Some of the people that race 2 cycle bikes will modify the exhaust system to get more power.

 

[Grassbandit]

You say in the original post that you did not have the muffler installed. I work on 2 cycle mopeds and cycles in my shop. Two of the very first things I look for if a job comes into my shop not running or running bad is the muffler and air cleaner installed. They just wouldn't run or run very bad with them missing. They need that back pressure to run right. I know what you have isn't a cycle but I will bet they run on the same principle. Some of the people that race 2 cycle bikes will modify the exhaust system to get more power.

hmmmm I'm really getting a lesson on this one! Surely I'll be adding your advice to my knowledge base.
Normally I can get trimmers to start without the muffler, especially in situations where they get blocked with carbon. In this particular situation someone else pointed out the flywheel as the culprit since I got the engine to pop and they were indeed correct.

 

[motoman]

Today the stars are aligned for trivia. I knew more knowledge wouldpour into this thread. Here are a few facts which may surprise about 2 strokes...

An engineer in East Germany (yep , before the wall fell) developed 2 strokers producing over 3 horse power per cubic inch. A hot US V8 produces 1 hp plus.

Two stroke race bikes(500cc = 30 cu inches )about 10 years back produced 200 HP (check me) and were unmagageable on the track because the power hit threw riders off and killed some.

Indeed the exhaust is important as stated. Take a look at 2 stroke motocross bike mufflers. The bulge was slowly developed so the mixture trying to exit is thrown back into the chamber for added power. :thumbsup

PS Grassbandit, Your Ryobi flywheel does look like I remember mine. I have not removed it because of the doubtful cost benefit, right?

 

[Grassbandit]

Today the stars are aligned for trivia. I knew more knowledge wouldpour into this thread. Here are a few facts which may surprise about 2 strokes...

An engineer in East Germany (yep , before the wall fell) developed 2 strokers producing over 3 horse power per cubic inch. A hot US V8 produces 1 hp plus.

Two stroke race bikes(500cc = 30 cu inches )about 10 years back produced 200 HP (check me) and were unmagageable on the track because the power hit threw riders off and killed some.

Indeed the exhaust is important as stated. Take a look at 2 stroke motocross bike mufflers. The bulge was slowly developed so the mixture trying to exit is thrown back into the chamber for added power. :thumbsup

PS Grassbandit, Your Ryobi flywheel does look like I remember mine. I have not removed it because of the doubtful cost benefit, right?

Everybody thanks for your pointers and insights.
Motoman PM me and lets hash out the details.

 

[motoman]

Bandit, Go to youtube where a gentleman shows detail of a flywheel bore/key. It shows the aluminum casting with a cast-in alum key which was a surprise to me. His problem was the key broke off, shifting the timing. Patience, I will try to pull off my old flywheel. Who knows, maybe my Ryobi's "death" as similar. What is your zip?

 

[Grassbandit]

Bandit, Go to youtube where a gentleman shows detail of a flywheel bore/key. It shows the aluminum casting with a cast-in alum key which was a surprise to me. His problem was the key broke off, shifting the timing. Patience, I will try to pull off my old flywheel. Who knows, maybe my Ryobi's "death" as similar. What is your zip?

I wonder how or why the key would have broken off?
Perhaps an attempt at removal was incorrect....good luck with getting yours off.

 

[motoman]

Bandit, Many on the forum might also think that an aluminum key is a strange material selection. Doubt that is aircraft alloy so seems like it is not as good a selection as steel, and much more subject to fatique cracks. I will try to pull mine and report. I would think any used ones require crack checking before using. There was a neat little 2 can test kit available at auto stores a few years back. Use the cleaner, then the penetrant dye and read it under a black light. Who the hell has a black light??? Just sayin...BTW after the youtube photo I looked again at your pic . It kinda looks like "whoever" may have ground off two nubbins adjacent to the key centerline , put a different taper on and then filed a keyway?
If that is so your poor little engine may be trying to start with spark + or - 20 degrees to TDC