Add me to the long list of members that say dump the stock tensioner. Mine was pulled into the spokes about 20 minutes into my maiden voyage. Luckily, I was making a slow turn in a parking lot and didn’t get thrown off. But I still had a nasty bruise on my hip to show for the lousy design.
I don’t have a Tractor Supply nearby so I set about making a copy of
misteright1 99’s design made from what I could find. I bought the ball bearing nylon roller from Spooky Tooth and used the same type of “T” bracket that that
jasonh pictured above. I found mine at Lowe’s in the deck building section and cut it down with a hacksaw to the size I wanted. I clamped the bottom of the “T” in a vise and bent it over. With a little work using a hammer and the vise and I turned the bottom of it into a “U” shape to hold a bolt. The bracket was already snug around the bolt and I put some JB Weld on it to add a little extra holding power. For the tensioner arm I used a cheap stamped opened ended wrench with 2 washers glued on the outside of each end, again held with JB Weld. I went to 3 hardware stores looking for the right type of spring but didn’t find anything that was large enough to work. I finally hit upon the idea of using the spring off of a huge old fashioned mouse trap. Worked like a charm.
Mounting it to the frame was really simple because it required no extra fabrication. Just line it up on the 2 existing engine mounting bolts, drill 2 holes in the top of the “T”, slide on, and add lock nuts and you’re mounted. You’ll have to add/remove a handful of washers to the mounted bolt or roller to work out the best alignment.
A couple of things to keep in mind…as pressure is added to the spring, the inside diameter decreases so you’ll need to use a bolt that will move freely when spring is loaded. The tensioner arm needs to be long enough to tighten up the chain but not so long that it can rub against the back tire when under stress. My prototype is a little long but still works great.
