Bike starts up as if it ant to start!

[Greg58]

James remove cover for the magneto and remove the spark plug and lay it on the head to do this test, pedal around with the clutch released and you should see the magnet rotating and the plug firing, if the magnet is not turning check the clutch. If its turning and still no fire try a known good or a new plug gapped at 25 or 26.

 

[Greg58]

Take a picture of the magnet installed on the engine so we can possibly help. The magnet can be put on backwards.

 

[Greg58]

Look at the thread below to check the carb assembly
https://motorbicycling.com/threads/motorized-bicycle-carburetor-install-and-rebuild.302/

 

[crassius]

I'm thinking the motor is doing nothing except changing sound as the slide opens - no fire at all. You really need a compression check before screwing around with it anymore.

 

[T james]

I'm bout to look into to someone. Because I'm sure its something simple. But I'm sure I'll try fixing it before I do (mainly due to pride and knowing I'm pretty good with my hands). Its like it wants to start but can't. I'm wondering if it not getting enough fuel. So I'm going to clean carb and inspect it. Then install 66 jet. Put rotor back in line with woodruff key. Then give her a try. But I'm certain when magneto wired correctly to 2 cdi I have (one stock the other an aftermaket but identical to stock but purchased off amazon with good reviews). I got no spark pushing bike while grounded to bare metal on cylinder head and spark plug was plugged to cdi and cdi wired to magneto. Kill switch is/has been unplugged until problem solved. Fuel in bowl/line. Carb cylinder that hold needle etc. is not drench but wet enough to know fuel is passing through it. Also spark plug. When it clutch engaged it. Piston seems to start but only for a few seconds before dying out. If it starts and I give it gas with choke open. Its a muffled typed sound where you can hear the affect. Of throttle engaging. And I either get no acceleration or a spirt of acceleration as if its recognizing throttle being pulled. Then may bogg but not shut off. Then start to recognize throttle again and accelerate for only a secongd or 2. Then bogg out of acceleration again. As soon as I pull in clutch. Motor immediately shuts off at any point....I'm trying to see what I'm missing.

Ok, so when I got off work. I disconnected every wire to the motor and cdi. And rode bike with just nothing but spark plug. To my surprise it sounded just as it did last test run! When I engage clutch it sound as if motor has fired up (based off hearing the sound of lawn mower running and signs of good compression but only for a second or 2 after engaging clutch as described in previous comment). But obviously it can't be firing if it doesn't have the ignition system hooked up at all!!! I am I right or am I right (and that equation seems simple as 1+1 in my mind). And as I said in previous comment I was getting some spark from stock cdi. When I grounded it on cylinder head. When it motor stopped working. But when I conducted test last night on new and stock cdi. I got no spark from stock chinese plug or NGK B5HS (which motor has never started since installed). But both spark plugs work fine in motor before it just stop running. So I'm going to install brand new cdi and magneto coil. Sand off contact surface between on coil and motor as I did current one. Clean and inspect carb. Then install 66 jet into carb. Since I'm in Norfolk,VA which is less than 7' above sea level and that was the smallest jet that came with a set I bought off amazon. Then I'll give a few last attempts to start it. Before I call in a professional. Thoight about buying a new carb, but as Ive said the motor sounds just the same assembled correctly. As it does with nothing connected to motor except spark plug to keep compression.

 

[T james]

James do you have a compression tester? I have one from HF that works well, I would make sure the compression was good. The pop could have been a seal on either side of the crankshaft, if you had the magnet off you saw the seal, there's one the same size only wider on the other end of the crank behind the small gear. If the seals are in place and the compression is good it could be a blown cylinder base gasket. The compression should be around 90 psi or close. The pop could be a broke ring or wrist pin bearing, you can remove the head and move the piston down and look for scratch marks also.

I did see the place on crankshaft where it should seal to engine surface that magneto coil bolts to. That's revealed after removing rotor was not flush with engine casing. Crankshaft was lopped sided to on the left side (to try best explaination). So I tapped on it horizontal to the right.with a hammer to level it out....

 

[T james]

I'm getting a compression tester from Harbor Freight tomorrow!

 

[crassius]

thought so, you're not firing at all

I would not change carb jet until after I had spark - one thing at a time works best.

 

[T james]

thought so, you're not firing at all

I would not change carb jet until after I had spark - one thing at a time works best.

Well I saw this after. I took apart carb and inspected it. Reattached to motor. Changed jet to a 66. Aligned rotor with woodruff key. Made sure stator has proper spacing from rotor. Checked stator with multimeter it read 315. Checked both cdi and got good blue spark from BH5S and BH8S. Then took her for a spin. And it seemed to studder like it was about to start. Then just got back to just piston movement. I'll test compression Friday when I get compression tester from HF. If pressure is good (which I doubt). I think the pop may have been bearings. Thats why its off alignment behind rotor. If pressure test good. I'll just get a pro to look at it smh. If compression bad I'll replace bearings.

 

[T james]

Think I finally found the problem. Crankshaft bearings pictures.

 

[crassius]

had you read any threads about seals, you'd have seen that I always put a screwdriver under each end of crank to pry up and see if bearings are bad - could have saved yourself a lot of work

best now to get new motor rather than try to fix mains

 

[T james]

Nope never thought to. Just went with the typical "engine won't start" troubleshooting.tips. Spark, cdi, magneto, etc. But I ordered two 6202 bearings. I've watch quite a few videos and it doesn't seem too hard to do. Beside removing and replacing main bearings. You really think its just best to junk a brand new motor for $12 parts? While broken down I've ported intake/ehaust. And skirt of piston on intake side. I'm going to try and fix. If no luck just use it for parts. In my next build for the summer. A schwinn Occ bike!

 

[crassius]

getting new bearings on without getting crank out of true somewhere in process of splitting/sealing cases and pulling/fitting bearings can be hard - a 2nd motor will let you ride while attempting that

 

[T james]

Ok

 

[T james]

I think its small gear sprocket has damaged woodruff key from torque. So it only catches at certain point (like a clutch u have no control of) to initiate motor but can't handle the torque of motor starting. Which explains reason why it won't fire up once clutch released pedalling 10mph or more. I just hear compression of piston going up and down and a squealing from small sprocket side. But if Im just starting/barely pedalling it will give off a sound as if your just not going fast enough to fire up engine. I rode it for the sole purpose to ride as bike. And attempted to start it. I pedaled as explain before with not much torque under recommended speed to start it. And to my surprise it actually fired up and responded to throttle for about 10-12 feet down the street. Seem like it was about to pick up speed. Then immediately stopped responding to throttle or pedalling. When attempting to start again I just hear that squealing from small sprocket side of motor....I'm certain its not the bearings, cdi, coil, spark plug or rotor position/key.

 

[crassius]

so, you open everything and look - no big deal

 

[T james]

Opened up carb today and to my surprise no fuel what so ever after gas line being open since last night. But I did agjust arms for bowl to trigger fuel shut off. I think before problem started smh (for what idk hungry for more speed but after reading threads I realize I was really lucky for to take it out the box hook it up and it actually run with no problems at 25mph or better). Lesson learned. I also see when I pedal the rotor tends to get stucks at certain points (not every time tho) when It should be rotating just as sprocket is. Which is when I hear squealing from rotor magnet seizing up at certain point! That must be why it sounds as if it two strokes here n there. And it responds to throttle when rotor magnet does seize up!!

 

[crassius]

armature there is supposed to sit tight around the circular boss on the case - loosen it a bit & wiggle it till it drops in

 

[T james]

Ok so the squeling is the drive gear slipping. It doesn't rotate like it should when clutch engaged. I'm going to buy a new screw for drive gear. And tighten it up this time with an impact drill!

 

[T james]

My screw to tighten drive gear is stripped where you put flat head to tighten it. So I'll order a new one. Do you think I need to order another washer too. Event tho the stock washer for drive gear is fine. Just thought putting 2 will grip gear better when tightened. This has to be the reason it would start when riding slower than recommended. Because at low speed/torque. The drive gear moves as it should. But once I speed up or engage clutch it slips.