Engine Trouble Recently Rebuilt engine won't start

SpeedBoi

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#1
I'm letting you guys know that I rebuilt the engine recently in case i did something wrong and that is why it won't start.

I just replaced the cdi and stator coil on the bike, as well as getting a new spark plug. I got spark outside the engine when I turned the wheel with some force. I noticed if I didn't turn the wheel as fast I couldn't see a spark. Maybe weak spark? I'm pretty sure I installed the stator coil correctly as well as the magneto.

Anyways I assumed my spark was good because I could see a decent spark and decided to tackle the fuel side of things. Next thing I tried was pulling my carb off and taking the fuel bowl off. I blew into my main jet and the fuel intake to make sure there was nothing in there to prevent the fuel from flowing. Put the carb back on and it still wouldn't start. Next I tried to lean out my mixture using the c clip in case their was too much fuel in the mixture for it to combust.

I'm having a very difficult time telling whether or not there is fuel in my cylinder. I tried to smell the spark plug and it smelled faintly of gasoline, but upon shining a flashlight into the cylinder it appeared mostly dry.

Im considering spraying some starter fluid into the cylinder into the engine and then trying to run the motor. I figure if it runs even for a second on the starter fluid, that must mean I have good spark, and I can rule that out.

Lastly, compression. When I rebuilt the engine I put all new gaskets back in. Now, I did cut these by hand so they might not be perfect, but they all seem to be fine upon first glance. With the spark plug out, and putting my finger over the spark plug hole, I can feel some pressure on my finger as I turn the engine over. Not sure how much I should be feeling, but the pressure doesn't seem to go away if I hold the piston at the top, so I'm pretty confident my head gasket is good.

I've admittedly been a little lazy about going threw and checking everything, but I figure y'all will yell at me if there is anything particularly stupid that I've neglected to check.

Thank you all in advance for your help :)
 


crassius

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#2
if you pedal a lot, spark plug should be visibly wet - a few drops of fuel in cylinder and put plug back in and a few pops should be heard if it is just fuel problem

you really need a compression check

what gaskets did you make???
 

SpeedBoi

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#3
I made the gaskets out of gasket material that I bought from advanced auto parts.

I made a crankcase gasket, a cylinder gasket, a head gasket, an intake gasket, an exhaust gasket, a clutch cover gasket, a magneto cover gasket, and a fuel bowl gasket for the carburetour

I shall try putting some fuel in the cylinder and see if I can hear a it pop
 

crassius

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#4
the crankcase gasket, cylinder base gasket, and intake gasket might be leaking - you might want to smear some good sealant on those - I like non-hardening permatex gasket sealer

a compression test might tell you more
 

SpeedBoi

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#6
Did a compression test, only got 60 psi and could hear air leaking out somewhere.

Do I need to cut all new gaskets, or just reassemble with same gaskers and some gasket sealer
 

crassius

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#7
I'd use factory gaskets if I were not desperately in a hurry - for case and intake, if homemade gaskets didn't look really good, I'd just use the permatex without a gasket - for base gasket (especially if the motor was the kind that need two gaskets there for spacing) I'd look gaskets over very well and use lots of sealer

for new motors from factory, I usually just put 2-stroke oil on the base gaskets unless the case halves meet with a bit of a lip between left/right sides

BTW, check my note about stupid old people about earlier this week when I heard hissing during compression test
 

SpeedBoi

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#8
I don’t have time for new gaskets, but Ill try and cut better new ones and use some sealer.
Thank you so much for the help!
 

SpeedBoi

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#12
Hey guys just got back from camp.

So I ended up rebuilding the engine with all new gaskets and using seal-all on everything bc I was desperate. Anyways the compression test still didn't work and the bike wouldn't start so ethier my compression test sucks and something else is wrong or it is leaking somewhere else. At this point I highly doubt that the gaskets are the problem. Maybe I installed my piston rings incorrectly and I am getting blow by resulting in no compression? again highly doubt this but any input would be helpful. I am pretty confident fuel and spark are not the issue because I checked those thoroughly before realizing compression was the issue.

Any things that I should check/checks I can do would be helpful. I am out of ideas so I'm left to the mercy of these forums to save me from buying a new engine. Thank you all again for all your help :)
 

crassius

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#15
that's a hard reading to guess from - could still be a seal that is just leaky rather than blown, or could be any gasket

I'd also look at ends of crank to see if a main bearing is bad and allowing crank to move up/down in seal.
 

gary55

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#16
Why did you rebuild it, and what did the cylinder look like. That's super low compression and it won't run till it is brought up.
 

SpeedBoi

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#17
The seals look fine to me, I’m having a hard time finding a way to turn the engine over so I can try and see/hear where the leak is coming from.

When I rebuilt it I drilled balance holes in the crank and installed new bearings. Not sure what you’re looking for when you ask what the cylinder looked like but I can slide it off right now and take some pictures
 

gary55

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#18
Undo 1 of the mag. wires, put a socket drive in a drill and spin the engine with the socket on the rotor nut. With the clutch locked you should be able to do this and find your leak. The cyl. question was about scoring.
 

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