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Hi everyone,
So the story starts.....
I bought a jr 50 for the kid, shined her up and got it running.....ran but no power..... so i completed all the mods- remove jet and restrictor plates, clean exhaust, added holes in air cleaner lid....still nothing.... it run and idles fine just had no power what so ever when there was a load... bought a compression test and only had 75psi.... so I ordered rings for it and a seal and gasket kit (its leaking oil from the left side (I think around the sprocket)..... so now I have a few questions..
1. What is the recommended torque on the head bolts, and case bolts?
2. Is it possible to pull the left side of the case apart, replace the leaking seals and gasket without disrupting timing, and other important functions?
3. how long is the break in time before I should retorque the head bolts?
4. Does any one have a service manual pdf?

Any help would be appreciated!
Thanks
 

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I'm in a similar situation, I have a '78 JR50 that was originally mine as a kid, now I'm getting it ready for my 8 year old. I have done quite a bit of research online and have found the manual which is fairly bare bones. Mine would not run properly so I got a new carb/air filter from ebay and it created a situation where it would sometimes run okay but if shut off it would not restart. I pulled the exhaust off and found that it was not blocked with sludge (the most common problem) but I'm cleaning it anyway. The problem I have is I found the exhaust pipe filled with gasoline so I'm thinking that I have to mess with the float settings, while I'm at it I'll remove the extra jet to wake it up. Also very similar to you, I found that I have 75 psi compression which is grossly inadequate, a two stroke guy who has fixed many of these things told me that he has seen them run on as little as 85 psi but below that it won't work reliably. I must warn you that merely replacing the rings will do nothing worth the effort to change them, instead order a top end kit off ebay like I did OR have the cylinder bored and get an appropriately sized piston and rings. They also have gasket kits available but I would just live with a bit of leaking. All of the torque reqs are in the manual, let me know if you are interested and I'll send you a link to it, I'll have to search a bit. This is starting to get expensive but a new top end should take care of everything, if not it'll be a nice boat anchor.
 

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Hi everyone,
So the story starts.....
I bought a jr 50 for the kid, shined her up and got it running.....ran but no power..... so i completed all the mods- remove jet and restrictor plates, clean exhaust, added holes in air cleaner lid....still nothing.... it run and idles fine just had no power what so ever when there was a load... bought a compression test and only had 75psi.... so I ordered rings for it and a seal and gasket kit (its leaking oil from the left side (I think around the sprocket)..... so now I have a few questions..
1. What is the recommended torque on the head bolts, and case bolts?
2. Is it possible to pull the left side of the case apart, replace the leaking seals and gasket without disrupting timing, and other important functions?
3. how long is the break in time before I should retorque the head bolts?
4. Does any one have a service manual pdf?

Any help would be appreciated!
Thanks
1./3. personally, i've never gone with spec, if it felt loose, i just tightened it.
2. yes, because you have points, magneto and coil. it will only go back 1 way, you will just need to check/set points
4. i have a service manual, i'll link it when i get home

if it's leaking around the sprocket, i would just let it leak. self oiling chain.
 
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