Bike will not "go"

Hi everyone.

I was hoping someone can help me with my "new to me" bicycle.

I have a motorized bicycle that I purchased a few days ago. It seems to be a relatively solid build. It's a heavy old Schwinn 5 speed with a 50cc motor. The rear wheel mount was altered/extended to allow the bike's five gears to be used to change the gear ratios.

I watched the original owner give it a few pedals and then sail down the road with the engine buzzing along. After he parked the bike, we stood there for a few minutes, chatting, and the engine idled smoothly.

Now that I have this contraption at home, I can't get it do anything useful. It starts, but that is ALL it does.

I open the fuel valve. I pedal down the road a bit with the clutch lever held in. I drop the clutch. The bike engine starts up immediately, and then... it does absolutely nothing to push the bike forward. If I pull the clutch back in, the engine dies. If I stop pedaling, the engine dies instantly. If I keep pedaling, the engine shudders, feels like it's fighting my pedaling, and then dies. In none of the above scenarios does the engine feel like it is actually making the bike move forward.

I have looked through the forum here, hoping to find some inspiration, but all of the "how to" threads seem aimed at a higher skill level than I currently have. I mean, if I *knew* that the clutch plate or whatsit-lever or thing-a-majig cable was causing the problem, or even what one was, then I'd probably be able to fix it, but I don't even know what technical term to search for to try to solve my problem.

If anyone could offer some advice, it would be greatly appreciated. My mechanical experience with cars mostly consists of putting gas in and turning the key, so I'm really lost here.

Lucas

Responses:

Tom - Yes, it would be nice to know what engine is in it. It would be nice to know anything. I don't know how to find that out. It is a two-stroke engine. The sticker on the side says "Star Fire." As to contacting the person I got it from... if I could do that, I probably wouldn't be here.

a.graham52 - The answers to most of those are, "I have no idea." There is a lever which I am guessing is a choke, but it only has Chinese characters at each end of the lever rangs, so I don't know what is open or closed. I've varied the speed I start it at from barely moving to going flat out. It doesn't seem to make a difference.

Jonny - I'll check that tomorrow after work and get back with you. Thanks.


Random note - I am definitely getting spark. I pulled the plug and spun the rear wheel, and I could see a blue spark jumping the gap on the plug.

Hi again!

I have tried adjusting the choke at various positions. Lifting it part of the way up (but not quite to the top) lets the motor start and sort of run for a few seconds, but there is no power coming out of it and it dies quickly thereafter. I've not quite got the hang of reaching down and adjusting that lever while I'm moving, so maybe some additional trials are needed before I rule out choke adjustment as the cause of my problems.

Allen - These are some pictures of the bike and engine setup. Perhaps they will give you a better idea of what I am dealing with. I think at least one should include a solid shot of the carb.

Tom - I think the fuel mixture should be 32:1. The guy I got it from didn't seem too scientific with his mixtures. He just threw in about two ounces of oil per tank, but that would work out to basically a normal 32+/- to one mixture. I have not put anything into the tank myself - it would have to run before I could use up the gas and need to fill it. lol I'd wonder about the gas quality, but I watched it start up easily a week ago, so I know it's not bad gas.

When I turn the petcock beneath the gas tank, I can see a small flow of fuel run into the clear tube connecting it to the inline filter and the carburetor. After a few attempts to start the engine, that tube is completely filled with fuel, so I take that to mean the motor *is* drawing gas out of the tank, right?

As to fuel flowing out of anywhere - Hmm. No, I can't say that I see any fuel dripping or coming out of anywhere when I turn the petcock on. It drizzles down into the clear fuel line and the filter, but I don't see any leak out of anywhere unless I repeatedly press the little primer button on the carburetor.

I really appreciate the thought you folks are putting in to this. I guess I bought it expecting a slightly more turn-key experience. lol I should know better after all the reading I did prior to buying this thing. I just figured that an already built setup would give me a better chance than throwing it together myself. I guess if the engine ultimately fails to work for me, I could always get a fairly inexpensive replacement since I've already got the modded bike frame, mounting hardware, and accessories, right?

Observation - A closer inspection of the engine reveals that part of the flange by the clutch (where the chain goes in to the engine) looks like it was cracked at some time and stuck back together with quick-weld compound and a random piece of metal for a brace. Hmm. That's kind of fishy but I don't see why it would stop the engine from running. I wondered initially if I had a compression issue, but the crack is on the chain guide not the body of the engine. The engine turns over super easy with the spark plug out and there is very solid resistance when I replace it, so I'm thinking compression is not the issue.

Lucas

Hello,

Well, I've made progress of a sort, but it's mostly the backwards kind.

I had some advice about checking gas flow through the carb itself, so I verified that there was gas by removing the screw at the bottom of the bowl. That gave me a steady flow of gas moving from the tank to the bottom of the carb (after the initial spurt that emptied the bowl itself), so I don't know how gas could be the issue.

Tom - After reading your misgivings about the plug boot, I attempted to double check the connection between the plug and the line. When I moved the boot, the wire snapped like a dry twig into three different pieces.

I guess whatever my problem was before is still there, but now I OBVIOUSLY have a spark issue.


I suppose the optimistic view is that maybe this was the issue all along? If the wire was failing, then there might have been just enough of a connection to get the plug to fire outside of the engine but not enough of a connection to make it fire under compression.

Does anyone know if it is possible to put new wire and boot on one of these things? The line looks like it comes directly out of a sealed box that is attached to the frame. I have a lot more experience with electrical repair tasks than I do with engine work, but I don't know what that boxy thing does or what is inside it, so I am not sure if there would be contacts I could solder a new line to or if I'll just have to replace it. Any ideas, before I spend more hours of my weekend breaking more stuff?

Lucas

Ok, this site here says I can replace the plug wire coming from the CDI by just unscrewing it and then twisting a new one into place. http://www.sickbikeparts.com/Manuals/Installation instruction for assorted products.pdf

Wow.

Tom, no wonder you suggest soldering this if just twisting the wire into place is the normal method of installation. I can't imagine just twisting it into place holds up very well after miles and miles of vibration.

Lucas

Just for laughs, here is the picture of the little thing that the spark plug wire came out of. It is now broken off flush with the case. I don't see any screws or bolts or any other way to take this thing apart in order to attach a new plug line.

Sigh.

Anyone in the Colorado Springs area interested in purchasing a slightly broken project bike?

I'm starting to think I would have been better off investing the money I spent on this bike into a couple pairs of good running shoes.

Lucas