Bike Won't Start - Don't Know Why

K

Kvett

New Member
Okay, so i recently installed an 80cc engine onto a bike of mine, and it won't start. When i release the clutch, i can hear the pistons moving up and down, but it never fires. I have removed the spark plug and tested the spark outside the cylinder. There is a good spark. I have also disassembled and cleaned the carburetor. The bottom of the spark plug smells of gas, so i know it's getting fuel. Could it be that the spark plug is not firing under the compression? If so, what should i do? any suggestions would be fantastic...I'm starting to become quite frustrated.
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Thank You so much!!!!
 
ok...is your gas and oil mixed properly...is your trottle working...no sticking....check the gap on the spark plug...020 to.024....now wiring...from the engine...black(ground) to black from the CDI...blue to blue....white leave alone.....kill switch...power wire to your power wires...your ground i prefer to the frame...your choice...gas and oil 20 to 1 if you use regular 2 stroke oil....i use amisol...sabre and i'm at 80 to1 forever...ha....i'm the guinne pig...its great. remember when you mix your oil and gas, do it in a 1 gal. can...oil first than put gas in...shack and go. well i hope this helps...oh...is the clutch engaging properly....check all that and if that dont work...get a hammer...ha...what kind of plug are you using? NGK...the best i think...some of the kit ones are messed up...Dennis
 
I think it might be the wiring and the plug. How bright should the spark be when testing on the cylinder? maybe my spark is too weak. also, is it possible that I'm not even getting a spark once it's under compression?
 
...its possible to have a weak spark if the wiring is wrong, but than, which i have done, blew up my CDI...so check your wiring...to be safe only hook up the ebgine to the CDI wires...no white...blk to blk abd blue to blue...check your spark plug gap and if its foiled out replace it...sounds like your getting gas...so get on the wiring...leave the kill switch off for now...do you have a integrated kill switch...small soiderd wires in there can come loose...do that for now...process of illimination...you'll get it...than i'll tell you a few more things...just make sure all the bolts are snug...incase this takes off...ha...go getem...talk at you later...Dennis
 
Excellent advice from an experienced MB'er!

I will add:

1) The factory bullet connectors between the engine and CDI are really crappy...make sure that they are tight by crimping the female end lightly with a needle nose plier.

2) When these engines are new you really need to get peddaling at a good clip before releasing the clutch.

I have had several customers at the shop that would release the clutch too early, and the engine would pop over a few turns before the rider came to a stop.

Pedal it up vigorously...release the clutch...and keep peddaling so that the engine continues to turn over.

Crack the throttle as you are peddaling, then return to idle, crack it open again...listen for the engine to sound like it wants to start...then crack the throttle back to that point that made the engine pop pop.

Once it is running, (and you no longer need to pedal), go easy on the throttle...You don't want to push it early on.

Jim
 
...its possible to have a weak spark if the wiring is wrong, but than, which i have done, blew up my CDI...so check your wiring...to be safe only hook up the ebgine to the CDI wires...no white...blk to blk abd blue to blue...check your spark plug gap and if its foiled out replace it...sounds like your getting gas...so get on the wiring...leave the kill switch off for now...do you have a integrated kill switch...small soiderd wires in there can come loose...do that for now...process of illimination...you'll get it...than i'll tell you a few more things...just make sure all the bolts are snug...incase this takes off...ha...go getem...talk at you later...
Excellent advice from an experienced MB'er!

I will add:

1) The factory bullet connectors between the engine and CDI are really crappy...make sure that they are tight by crimping the female end lightly with a needle nose plier.

2) When these engines are new you really need to get peddaling at a good clip before releasing the clutch.

I have had several customers at the shop that would release the clutch too early, and the engine would pop over a few turns before the rider came to a stop.

Pedal it up vigorously...release the clutch...and keep peddaling so that the engine continues to turn over.

Crack the throttle as you are peddaling, then return to idle, crack it open again...listen for the engine to sound like it wants to start...then crack the throttle back to that point that made the engine pop pop.

Once it is running, (and you no longer need to pedal), go easy on the throttle...You don't want to push it early on.
 
was there any mention of choke?

choke full on and pedal your a$$ off, release clutch. POP! POP! choke off, do it again.
 
I throw in my two cents.

I push the tickler button for a couple of seconds, then use 3/4 choke and the above mentioned slowly opening of the throttle.

Sometime wide open throttle and a little choke work too.
 
Hey guys, the other day i was at petro canada getting gas for my bike, i filled my 5 gallon tank and put a bit of gas into my bikes tank to even off the price, when i got home i poured the oil directly into the tank and shook the bike, the next day i began having some troubles starting the bike, i would have to pedal up to 20hm/h and wait for about 5 seconds then she would fire up, when the engine is hot, it starts a bit better. Once the bike was started it worked perfectly like nothing was wrong accept for the fact that it also would not idle, so i drained the gas, cleaned the carb, and cleaned up the fowled spark plug and it was still giving me troubles starting. Today it took about 20 seconds at 20km/h to start it and once it did it ran fine accept for the idle, when i pulled into tim hortons the bike stalled. I tried to fire it up again and it would not start, ive checked for spark the old fashion way, touching the wire while riding the bike and it defiantly is sparking, it wants to start i think because you hear a bang every couple of seconds. Can anyone help me? Im out of ideas, the weird part is last night i went on a 30km ride with a buddy of mine and it ran the whole time once it was started.
 
brandongordon2002 said:
Hey guys, the other day i was at petro canada getting gas for my bike, i filled my 5 gallon tank and put a bit of gas into my bikes tank to even off the price, when i got home i poured the oil directly into the tank and shook the bike, the next day i began having some troubles starting the bike, i would have to pedal up to 20hm/h and wait for about 5 seconds then she would fire up, when the engine is hot, it starts a bit better. Once the bike was started it worked perfectly like nothing was wrong accept for the fact that it also would not idle, so i drained the gas, cleaned the carb, and cleaned up the fowled spark plug and it was still giving me troubles starting. Today it took about 20 seconds at 20km/h to start it and once it did it ran fine accept for the idle, when i pulled into tim hortons the bike stalled. I tried to fire it up again and it would not start, ive checked for spark the old fashion way, touching the wire while riding the bike and it defiantly is sparking, it wants to start i think because you hear a bang every couple of seconds. Can anyone help me? Im out of ideas, the weird part is last night i went on a 30km ride with a buddy of mine and it ran the whole time once it was started.
Click to expand...

What about your choke? Sounds like you should half choke it first then once it starts to get warm open it back up, could be a lot of things though.
 
u know, i had a similar problem, it prob wont be the same answer as mine, buy my kill switch on my throttle was stuck in the off position/ broken... look into that maybe?
 
Hey guys just to follow up on my troubles, i decided to take a look at the magneto and i knew the problem as soon as i removed the first screw, rust had killed the magneto and shorted out the coil, i opened it all up and there was lots of rust and i unwrapped the magneto coil tape that protects it and found that the coil had shorted and was broken creating a weak spark. I replaced it and all works great!
 
brandongordon2002 said:
Hey guys just to follow up on my troubles, i decided to take a look at the magneto and i knew the problem as soon as i removed the first screw, rust had killed the magneto and shorted out the coil, i opened it all up and there was lots of rust and i unwrapped the magneto coil tape that protects it and found that the coil had shorted and was broken creating a weak spark. I replaced it and all works great!
Click to expand...
Brandon,
If your mag was that rusty then you are getting water in there. Seal the hole where the wires exit the motor with silicone gasket sealer. Rain or water from washing the bike will not do the mag any good. I seal the mag cover with silicone as well as the wire exit. Good luck.
Tom
 
I have a similar problem - I got a kit off of Bikeberry and assembled it just fine (bike store said it was ok), got some gas and motor oil in a 20:1 ratio, then started pedaling and it won't start the engine! Any ideas? The gas tank is leaky too... got to get the fixed :P

By the way, my kit came with the CDI and spark plug already on the engine, but it came with an extra spark plug and this huge bolt that I don't know what to do with.
 
The 'huge bolt' is likely the clutch and sprocket tool.

Check for spark first, then if you have it, check for fuel flow to the carb. Let us know what you find.
 
Alright so this is my second build and the first works great, this one not so much. I have tried 2 different spark plugs and 2 different CDI boxes and it won't fire! The wiring is correct and was both times. There is a good flow of gas because when I take out the plug there is a little gas on the end. I have tried just about everything... the second CDI box I know for a fact works because it is now on my first build which I just got done riding. If anyone has any suggestions please help! Also how would I check my spark plugs (check spark?) to se if they are bad?
:-||
 
RedeyeRaab said:
Alright so this is my second build and the first works great, this one not so much. I have tried 2 different spark plugs and 2 different CDI boxes and it won't fire! The wiring is correct and was both times. There is a good flow of gas because when I take out the plug there is a little gas on the end. I have tried just about everything... the second CDI box I know for a fact works because it is now on my first build which I just got done riding. If anyone has any suggestions please help! Also how would I check my spark plugs (check spark?) to se if they are bad?
:-||
Click to expand...

if your cdi is fine...there is two possibilities...magneto....ground....dosconnect the kill switch...check your wire connection...same to same....white wire tape up...check the wires on the magneto....somewhere in that you'll find your problem....good luck and let us know when you are up and running....Dennis
 
RedeyeRaab said:
Alright so this is my second build and the first works great, this one not so much. I have tried 2 different spark plugs and 2 different CDI boxes and it won't fire! The wiring is correct and was both times. There is a good flow of gas because when I take out the plug there is a little gas on the end. I have tried just about everything... the second CDI box I know for a fact works because it is now on my first build which I just got done riding. If anyone has any suggestions please help! Also how would I check my spark plugs (check spark?) to se if they are bad?
:-||
Click to expand...
To check if your plug is firing you need to remove it, plug it into the boot, lay it against the cylinder head fins so the threaded end is securely grounded to the engine and rotate the rear wheel with the clutch engaged. You should see a spark between the plug electrodes. If not, replace the plug. Still no spark? Check your connection at the CDI where the plug wire screws into it and the plug boot. It sounds as if you have eliminated the usual problems such as incorrect wiring, defective kill button, etc. Try the plug test and get back to us with the results.
Tom
 
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