So I was on a long bike ride today, went from one side of Seattle to the other. I hit an area of road that is really rough, railroad tracks, cracks in the pavement, and thousands of potholes. My chain tensioner rattled lose and slipped into the spokes of my rear wheel, busted all of my spokes, mangled the wheel, locked up the chain and broke something on the engine side of things. Now the front sprocket spins so freely that I can almost get it to spin by blowing on it. Also, where the tensioner was, the frame got bent. It was pinched already because I tightened the tensioner too much [see pic: Frame Damage ], but when the tensioner got caught in the spokes it spun around on the tube and actually bent the damaged frame in a way that it sort of corrected it. When I was riding, I was going maybe 30mph and all the sudden my rear wheel locked up, I started fishtailing, and the engine started revving like crazy. Even more unfortunate than my bike getting destroyed, at the time of the accident was the fact that I was 5 miles from home and I couldn't even push the thing because the rear wheel was all mangled. Luckily after a mile or so of scooting along and wearing a big hole in the tire, a friend was able to come get me. We put a tarp down in the back of his suv so any gas that leaks wouldnt get on his carpet. I was always fantasizing about what I was going to do with my next bicycle engine, and now I get to do it sooner than I thought. Anybody port and polish their engine?
Sorry to hear about your bike... I put a small screw through the chain tentioner & into the frame to keep it from moving (& falling off), works perfect! Yes, I've done a little port work to two of my bikes, I port matched the intake manifolds, exaust pipes (& gaskets)to match the engines intake & exaust ports... I really didn't want to get into opening up the ports themselves! (not that I can't do it) I also smooth out the inside bend of the intake manifold. These mods made the bikes a little quicker off the line and gave them a little more top end!
Whoaa, That's gotta suck, sorry to hear that Mike. I've had my tensioner ripped spokes out and lock up the real wheel and messed up a few chains. But nothing like that. Did you pull the clutch in the second the wheel locked up? I always ride with one or two fingers on the clutch for this very reason.
Gee must be an epidemic. I did that last week as well. I just got my bike back to running. My chain came off and wrapped around the wheel. I ruined the wheel but the bike and engine survived. I'm glad you weren't hurt. It is when I started missing my friction drive electric motors. Also when i got really serious about the weed eater friction drive. I was able to clear my gear lock up on the side of the road and ride the bike home with the broken spokes and all. I almost decided to try to carry it home by hand. But I'm not that ambitious. I have left my bike chained to a pole several times and walked home to get the car. When I sell my big old mercury I'm going to have to get a cell phone just for emergencies. I'm the last person in America, with good credit, who doesn't have one
I put the Norman shims under my tensioner before I tightened it and have had no problems at all. He just splits a peice of tubing and slides it in between the frame and tensioner. Works very well...................
I used a piece of heater hose he first time for my tensioner grip... last time the bike was fat enough.
Mike i wonder if there is a shear pin on those gears. My dad had an outboard motor that had them on the prop. Maybe it just sheered the pin that holds the gear on.
Chain tensioner now theres a sore spot. I got tired of it the other day that I took it off shorten the chain and things are ok so far. I have a little slack in the regular chain but I dont pedal that much so it should be ok. Going to try and make all my bikes without them. I have been installing two kits and both have striped trying to tighten then up.
There are a key or two in the sprocket end of the shaft if I'm seeing the diagram right. You engine may be O.K.
yeah thats what happened with my dad's outboard motor it just sheered that pin and he lost the prop. Better than an engine. if he sheered the pin like that it would be a blessing.
The is a small key on the front sprocket and small keys on the clutch and the small gear on the engine all are fairly easy to get to by using the puller that comes with most engine kits do put a little oil or never seize on the puller threads before you use it as it helps to keep the threads from gauling. I did a modification to the idler bolt I used the lathe and drilled the bolt out and use a high grade bolt through the idler and can pinch it down so it won't move or loosen up. I also have drilled and taped the idler mount and put in a small bolt or sheet metal screw so the idle mount can't flop over into the spokes. That way I don't have to walk home and drag the bike cussing all the way. I have a post on the bikes engine total tear down shows all keys and where they are all you need to do is look at it.
Thanks for the tips guys, I'm going to dive into it tomorrow. In the future, I'm going to put a screw or some type of pin to stabilize the tensioner. If you guys want to see the destruction, check out some of the pics: Tensioner Disaster
a true mess glad you survived it.. My wheel looked a lot like that I just took the tire and tube off and junked it.
Wow ! Glad you were not hurt ! I read this and took mine off. I took another link out and the chain fits fine without it. Thanks for the heads up and showing this ! motorbiker
I hope you got your chain/sprocket all worn in before you chucked the tensioner. I got rid of the buttery, easy strip bolts that held the tensioner on and used grade 5 bolts. I also used big, cupped washers under the tensioner. I've never had one come loose.
Norman When you say"I also have drilled and taped the idler mount and put in a small bolt or sheet metal screw so the idle mount can't flop over"does this screw run into the bike frame?Thanks,Ron
Yes I did. I tried to fit the chain the first time without the tensioner but I could not do it until the chain stretched some. It seems to not be stretching much now after about 2 tanks or so. To me it looks like if the chain comes loose or if the engine locks up it could become very tight on the bottom putting large pressure on the tensioner causing it to spin or even bend into the spokes. When I pop the clutch to start it also puts pressure on it. Bad enough having a chain come loose. A loose chain and a tensioner bent into the spokes I can do without. motorbiker
Yes Ron I drill onto the frame and either tap or you can drill right through and run a bolt all the way through. You don't need a big bolt a 6-32 or an 8-32 will work just something to keep the tenchioner from rotating in to the spokes. Changing out the low grade bolts is also a good idea. You can also drill the tenchioner and use a # 6 sheet metal screw. What all this does is pin the tenchioner form rotating into the spokes. I have a fix for the bolt that holds the idler form coming loose as well but a guy will need a lathe to do the mod. if you want this mod I can do it. For a small fee. I'll post the info soon and pictures so all can see. sound good?
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