Chain saw more resilient?

flyinace · #1 (**permalink**) 09-13-2008, 12:24 AM

Well my bike engine engine (ryobi weed eater) died today...I probably got about 100 miles out of it...Some of you may have seen the pictures i posted about a week ago...Seems the engine locked up on me, i haven't pulled it apart to see exactly what the problem is but it sounds terrible when i manually turn the drive shaft (of course it won't run). I figure that engine was just not built to push a 190lb guy around town. I used great oil and tried to take care of it the best i could.
So my question is...Do you think a chain saw engine will last significantly longer? It's great having a bike that gets 100 MPG but it's not worth it if i have to buy a new engine every few months. Is there a chain saw engine that is as easy to attach a drive spindle to as the ryobi weed eater? It had a threaded end that i could just screw a bike peg on... Any suggestions? Thanks!

deacon · #2 (**permalink**) 09-13-2008, 07:29 AM

The only weed eater I ever had that locked up was because I ran out of gas. Out of gas = no lubricant. Was it a new engine or did it already have a lot of wear. You have to remember most of us are working with engines that probably already have a lot of hours on them. Some were even abused by the previous owner.

That said the two chainsaw engines I have seem to have a more solid feel but I haven't used them long enough to know. I think they are less likely to vibrate apart which has been my problem.

I think Dan has it right a weed whacker bike is a light urban form of transportation. It is best for running to the store or used for short trips. I don't think it will hold up to commuting, but then again I haven't been doing this long enough to know. I don't even know about the chainsaws to be honest. The two I have feel stronger but I don't have a lot of time on them.

If you want mounting ideas read the thread chainsaw 2 the sequel. I have a pretty fair guide there.

**Bikeguy Joe** · #3 (**permalink**) 09-13-2008, 08:23 AM

Dragging the rpm down and heavily loading small two cycle engines will kill them quick.

Let them rev! That's what they were made to do.

flyinace · #4 (**permalink**) 09-13-2008, 10:57 AM

What do you mean let them rev? The engine on the bike would reach very high RPM, although i doubt it was as high as it would be if it weren't pushing a tire. I did have the drive spindle pushing against the tire so it was very snug but i'm sure there was still a lot of slipping going on...Is it better to have a lot of slipping?

My average trip was probably 7 miles. I would ride to work so each day i rode about 13-14 miles...Deacon, would you consider this a commute? Is it meant for shorter rides of only a mile or so?

flyinace · #5 (**permalink**) 09-13-2008, 11:19 AM

Oh, and i forgot to mention it was a new engine, used only for this bike.

comfortableshoes · #6 (**permalink**) 09-13-2008, 11:36 AM

What were you using for mix? My ryobi calls for 32:1... Any lower and it starts to make a god awful noise, when I first bought it, it sounded seriously bad. I ran some 20:1 mix through it and she's still running great. I've put about 45 miles on it(since I started keeping track) and I weigh in at a sad 200lbs. That 31cc has no issues pushing my fat a$$ around.

The 2 strokes for weedeaters are meant to push a light weight drive head at a high RPM- they are designed for high RPM for long periods of time. I run mine at WOT as often as possible.

On downhills I'll lift the engine up off the tire because the tire spins faster than the engine can go. And the engine can't pull in enough mix to lube itself.

Here's a question are you using the clutch that came with it? I assume not...

I also found that the high end on mine had to be turned out very rich- 3 full turns out other wise it ran to lean and sounded like carp.

flyinace · #7 (**permalink**) 09-13-2008, 01:03 PM

The sad thing is that i was still on my first gallon of gas and i used the oil that came with the engine. The bottle just said to mix with 1 gallon of gas...I did not use the clutch...
Does anyone know what the difference in RPMs are between a typical weedeater and chainsaw?

comfortableshoes · #8 (**permalink**) 09-13-2008, 03:15 PM

Here's something for you. I went out on my ride today- got about 1.5 miles away from the house when the engine started to bog and in general act funny. At the start of the ride the engine wouldn't bump start even after I had warmed it up I pull over and see that the kill switch on the housing seems loose. I start it up again and get home.

I get home and the pull start starts acting funny and making a loud metallic knocking sound, then the pull start wouldn't work...

So I pull the engine off and look, the fly wheel is loose, I pull it off and the key has shredded the inside of it. I'd been riding with a BMX peg not tightened down, it had let the fly wheel come a little loose and thus not engage with the key on the shaft. Also because the fly wheel is loose it's knocking on the magneto.

So I switched out for a peg that will tighten down on the shaft all the way, swap out the shaft sleeve for the one on the craftsman- it's a tad longer, reset the key, tighten down the magneto, clean and gap the plug and put it back on the bike- verdict? Starts like a charm 2nd of 3 rd pull no more knocking noise. Knock was definitely the flywheel hitting the magneto, jamming- fly wheel getting caught on magneto.

I've yet to take it out for a run and will in a few, and I'll let you know the verdict. Worth a look though- check to see if that fly wheel is loose. Pull it and see what the inside of it looks like.

flyinace · #9 (**permalink**) 09-13-2008, 04:45 PM

Well i pulled the whole engine apart (wish my car was this easy) and it was just as i suspected. The piston had major damage to it. As i pulled it out of the cylinder i could hear it scratching against the cylinder wall..I've never taken a 2 cycle engine apart, but it seemed surprisingly dry,except near the crank shaft where there was a bit of oil. I'm thinking it must of overheated since it was not spinning at full speed because of having to push a bike and not simply cut weeds. I'm hoping a chain saw will do better.

deacon · #10 (**permalink**) 09-13-2008, 05:06 PM

I would say cut back on your tension next time. If it over heated the engine was under a strain. It would probably be better to let it skip than to have it bog down a lot.

My lil 25cc would get hot and run like crap but that was when I had the tenstion too high.