Problem with coaster brake arm


New Member
Local time
3:37 AM
Nov 21, 2008
Hello all, I'm new to the motorized bike scene and looking forward to getting my bike running. I had borrowed a bike from a friend for a few weeks and had a blast and loved every minute of it. I bought a kit of my own a few weeks ago and we installed the engine onto my friends bike for the break-in period, and purchased a bike of my own earlier in the week. This is where I ran into a problem.

I'm currently trying to mount the sprocket to the rear wheel and while it is mounted, when attached to the bike, the coaster brake arm seems to be locking the wheel from turning. I did get a different rim as my friend suggested I get one with a Shimano CB-E110 brake instead of the stock one that came with the bike (he said it was a much more reliable brake). All 9 bolts are locked down and the sprocket seems secure, but no matter what I can't get it to turn and so I know if I try and hook up the engine to it, its going to damage something. I'm hoping its just a case of me over-tightening a part or something simple like that.

Any suggestions as to what I can look for or try in order to get the wheel turning freely? I can take pictures and give you the model of the rim tomorrow as the bike is at my office.

Thanks in advance for any help anyone can provide.
on a Murray, we under cut the sprocket to clear the brake arm, and use button-head allen bolts.


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Yeah, that seems to be the problem I am having. If I remember right, the arm wasn't clearing the bolts on the sprocket. The two things I found doing some additional searches that my instructions didn't list were to bend the brake arm so that it clears the bolts, and the other thing, which seemed odd to me, was that the rubber washers for the 9 bolts, I saw one guide that had both washers inside the spokes around the hub. All the other guides I have seen, as well as my friends bike, had one on the inside and one on the outside, between the spokes and the sprocket. I'm not sure which would be the right method, but I'm leaning toward the other guides that all show one inside the spokes and one outside..
You may not think it would hold but it does. 1/4 inch machine bolts phillips head gets that sprocket almost flush. It's been on MOOP 2 since it's build and it's held well never loosened or anything.
Make sure you get lock washers along with regular washers. I imagine if you like you can also double up on the nuts.


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OK, I got the wheel turning freely again, turned out I forgot to removed the dust cap, and it seems that with the sprocket mounted, the wheel wouldn't turn. I ended up replacing the bolts with a set of hex head 1/4inch bolts that were just far more robust than the ones included with the kit. I felt a lot better with the fit on the wheel using them.

However, I have a new problem, but I don't want to clutter the forum with numerous posts. My problem now is that after reassembly, the chain seems to "pop" when passing over the sprocket, and I noticed the wheel pulls to the left until it rubs the frame and jams. It did this once with the engine on and luckily I was able to kill it without causing any damage, but then when I took it back in, realligned the wheel, and simply pedaled the bike around a bit, it did it again. Its not any particular section of the chain or the sprocket since I marked the both of them and it never happened in the same place twice

I had to call it a night because it was getting too dark, but I'm hoping someone can tell me what to look for in order to fix this. It doesn't seem to start the popping and shifting until I am on the bike, as I rolled it next to me for a good 200 yards after I adjusted it the first time, but it started shortly after I get on. There is no wobble to the sprocket that I can see, and I tightened the bolts holding down the real wheel as tight as I could get them when I came back after the second try. They weren't loose per se, but they were able to be tightened down a bit more.

Any suggestions for what I can do?
Well, solved my issues with the wheel rubbing the frame and the chain popping. The chain pop seemed to be something with one of the links as it passed over both the wheel sprocket and the engine sprocket. I used a small file and shaved off a tiny amount of metal from both the sprocket teeth and the chain link that was acting up and the pop went away.

For the frame rub, it seems I didn't tighten the bolts that secure the rear wheel as tight as I should have, as I mentioned before, and that seems to have solved my problem. I just took the bike for a couple laps around my apartment complex and it performed well, though I seem to have a lack of power on even a small hill. The engine already had its full break-in period on another bike before being attached to mine, so I don't think that's the issue. If I gaped the spark plug too wide, could that have done it? I'm pretty sure it is gaped to .20, but I'm not 100% sure. The break in was done with the Chinese plug it came with, and I replaced the plug when the engine was transferred to my bike.