Motorized Bicycle Repair





Introduction: Motorized Bicycle Repair

About: I live in Portland, I go to school at PCC, and work on projects in my spare time. I'm studying Renewable Energy or Engineer haven't decided yet. I have a motorized bicycle that is my pride and joy. I love tr...

I got into a bicycle accident recently and badly damaged my motorized bicycle. What happened was I riding at night and struck an unmarked road island (which was new construction). I was thrown from the bike and landed on my left shoulder breaking my collar bone. I was rushed to the hospital and x-rays made sure nothing else was broken. Thankfully I was wearing a helmet other wise I would have had a cracked skull and a severe concussion. PLEASE! Wear a helmet when riding any kind of bicycle it saved my life.

Step 1: Damaged Bicycle

After the accident you want inspect the frame, rims, moving parts, and other parts for damage. The front rim is ruined and the carburetor insulator assembly. To get things rolling I took note of the damaged engine parts and ordered them for my Honda here at eReplacementParts. The down side is it will take about a two month to be delivered but I'm in no hurry with a a broken collar bone. I have a replacement rim and a replacement tube sitting in the back yard...........some where.

Step 2: Repairing the Engine

Start by disconnecting anything that connects to the carburetor assembly like the fuel lines and throttle linkage. Then unscrew the bolts in the air cleaner and remove the air cleaner and carburetor. Then, disconnect the spark plug, unbolt the cover, and remove cover. Be sure to set the cover aside where it wont get stepped on. Next remove the air inlet guide cover (the metal plate) by removing the philips head bolt. Lastly remove the carburetor insulator (the black thing which in my case is broken).

Step 3: Putting the New Parts on

If the gasket material stuck to the metal like me, scrap it away with a plastic tool only. Do not use a razor blade as it will gouge the aluminum ruining the surface. Once clean, use rubbing alcohol to remove oils from the gasket surface. Install all the parts and gaskets. Then put the gaskets on and put everything back together. Lastly prime the engine and test it out. In my case the engine started right up. If it didn't start for you check the spark plug, check the to see if there is fuel, and unrestricted air flow (including the choke).

Step 4: Replacing the Rim

Take the damaged rim off and replace it with a new one. Then inspect the tire and replace it if there are rips, tears, and bulging. Mine didn't show any damage so I reused it but my inter tube was shot and was replaced.

Step 5: Inspect for Frame Damage

Check that everything is okay with the frame and front fork. Check for cracked welds and signs of a bent frame. Make sure the fork is not bent and moves freely. Everything looks good no visible cracks but I will monitor the welds before every ride.

Step 6: Take It for a Test Ride

I took the bike for a test ride and have found the head tube bearings are damaged and need replacing. Inspect for any other things that are out of place or feel different. Check and recheck welds and other parts of the frame for cracks after the test ride.

After the test ride the head tube was rather stiff after looking at the races in the head tube I saw the reason. The bearings left an impression on the race. To temporary fix the problem I loosened the head tube and re-greased the bearings. Then went on another test ride and filmed it.



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15 Discussions

Hope you're feeling better. I broke my collarbone longboarding at Mt. Tabor and ended up with a plate and 9 screws so I can totally sympathize with you!

2 replies

Ouch! did it break through the skin? They didn't do any surgery with me, they gave me a sling and discharged me. Also, how did you get off the mountain?

I was taking PCC's Longboarding 101 for the 6th time just to hang out and skate with buddies up there. Right before class my hubby and I had hopped across the river to Vantucky and gotten married at the Courthouse and he had taken my car to go shopping while I skated. One of the guys in class had broken his collarbone in a motorcycle accident 6 weeks prior and was recovering from surgery so he was observing his sons skate. He drove me to the ER with his arm in a sling and hubby met up with me there. The bone didn't break through the skin but was broken in 4 places and 3 pieces and I had about an 1.5" lump where it was poking upwards.

Hope you feel better soon. I once had a vintage K&S Bike Machine Engine powering my bike straight into a truck. The tailgate was down and handlebars were cut clean through and into my stomach. I was in surgery for 7 hours while they got truck bed out of my gut. You wanna know what caused all of that? When I applied the brakes they wouldn't work. They were brand new brakes, too. So I tried to shut off the engine. Wouldn't work. I think someone tampered with it. Ah, college. Anyway, feel better.

1 reply

Oooh that sucks that's why if I was to do this again with more money the bike would have disc brakes. But I'm in college and can't afford it and by the time I'm out of school I'll own a car again


3 years ago

I'll bet that surprised the heck outta ya! In all my 35 years of cycling, I've never seen a rim bend that bad--awesome crash dude!
I agree about the fork, it's bent. I'd guess it is steel and may be bend-backable, but would only recommend a reputable frame builder or LBS for that. Replacing a firm is pretty simple, but as already stated you have to pay attention to the length of the tube that goes through the frame.
Good luck bro!

1 reply

Yes I was surprised because one moment it wasn't there the next it was. I remember a loud bang and something similar to TV snow and I was on the ground. I didn't move until the ambulance came.

Good job. It feels great to repair something rather than replace. And if you do it yourself, it feels even better.

instructables needs like an anti spam thing for posting comments. It wasn't posting my comment even after like 10 page refreshes. Then I hit the Make Comment like 20 times and it posted my comment like 15 times. I had to slowly delete my repeated comment.

Wow what a crash!

I did a crash at night time on my bmx bike and yup I went right into an unmarked construction area in a public place.

I was cruising near my max pedal speed about 16mph-17mph and the street lights didn't light up a small patch I was going into. Once I got within a few feet, I was like holy crap... I only seen the first 2x6 or 2x8 so I quick reaction jumped just to get the front tire to clear that first board and I knew back tire will hit a bit. But then I seen a higher board behind it like a 2x8 or 2x10 and was like "oh hell". I am pretty good at controlling my bmx bike, so I got more jump momentum from front tire bounce and I tried to get my back tire to clear it. but back tire hit and flew straight up and then I just stepped over the handle bars and my feet landed on the ground at full running speed hoping the bike wouldn't tackle me down.

I had no idea they were doing construction and this is a bike/walk trail that I frequently used for years. They setup the concrete footing forms to pour in a new sidewalk, and I have no idea why a new sidewalk, there was already one before.


Also do you know how swappable forks are? I have a scrap bike with a nice fork thinking about using it.

I'm doing better and able to ride a bike again but I have to be careful. If I fall again I could break my collar bone again. I was going to inspect the fork this Sunday. I don't know how to properly take the forks off so I would be happy to use your instrutables. Thanks you

Forks are pretty easy, If you can find some broken scooter and take the forks apart on that that'll give you an idea of what you're up against I've done it it's pretty easy just gotta be careful of bearings falling out or losing a piece.