1974 Yamaha SC500

[tbhamrick]

Hello everyone. I've got a 1974 yamaha sc500 that was my grandpa's. He bought the bike and 73 and died in 74. He had it stretched out for hill climbing at the time but it is now back to stock. According to the story i was told, it was in pieces in the garage when he died. His brother put it back together and kept it in his den for years. When i was just a little kid he gave it to my dad because he was moving and couldnt take it with him. We rode it about 5 times and then my dad just put it in the barn unfortunately. When i turned 16 I pulled it out and started messing with it. It had a mouse nest in the carburator and no air filter at all. I cleaned it all out, replaced the gas and put new oil in the crank case. I tried to start this thing for a week straight and failed miserably. I live on top of a mountain so I tried rolling it all the way down and it finally started. I rode it back to the top and holy crap, fastest thing i've ever ridden. I'm 20 now and was about 17 at the time. Basically what i'm trying to do is restore it. The tank is pretty much perfect, and there is no rust besides some surface rust on the rear springs. I want to put it back to original condition as best i can. I need to rebuild the top end, new fenders, it doesnt have the spark arrestor on it and i really dont want to put one back on cause my grandpa liked it loud so i've heard. If anyone has any knowledge of where i can get any parts at or help with being able to kick it over. I'm pretty sure the top end is blown as of now. It was blowing white smoke the last time i rode it. I'm in the military so its been years since ive been back home to work on it. But i need to get it done, and i'd like to start on it as soon as possible. Any help, or shared knowledge would be greatly appreciated. Thank you.

[citabjockey]

Congrats on your project choice! I brought one back from the dead a year ago. Fun bike!

Blowing white smoke means right side crank seal is gone. To replace that you remove the clutch and the primary drive gear from the crankshaft. You probably need the left (magneto) side seal as well, you need a flywheel puller to get to that. You can get a good one from motion pro. Get a pod airfilter for it if you don't have an airbox. Also, get new brake shoes for it right away. The old shoes delaminate with age and if that happens in the front while you are riding it will hurt lots.

The crank seals are hard to come by for that bike. You should become a member of the yamahaenduro.com forum. There are guys there that have quite a stash of parts -- including some of the stranger engine components from old SC500 and MX models. Plus they know tons about these bikes.

Here is a summary of my project:

[tbhamrick]

Thats awesome! Thanks for the help man. Your build is pretty sweet. Hopefully i get mine running like a champ again.

[tbhamrick]

Also. I have an air box, but the bracket thing that holds the filter in place was somehow lost. I think my mom accidentally threw it away. So putting a pod filter on it may be my only option unless i can find my bracket and a filter.

[citabjockey]

There is always this one...

http://www.ebay.com/itm/NOS-Yamaha-Filter-Element-Guide-MX250-MX360-SC500-363-14458-01-/140761711838?pt=Motorcycles_Parts_Accessories&hash=item20c60d44de&vxp=mtr

 

Also. I have an air box, but the bracket thing that holds the filter in place was somehow lost. I think my mom accidentally threw it away. So putting a pod filter on it may be my only option unless i can find my bracket and a filter.

[Uniflow]

citabjockey, have you any close up pictures of the balance shaft on the SC500?

[twosmoke595]

please post pics i love builds like this !!!

[citabjockey]

This is the only shot I have of the balancer drive system. I don't have a pic of the shaft itself.

citabjockey, have you any close up pictures of the balance shaft on the SC500?

[Uniflow]

Thankyou, that's quite a drive setup. Looks like spare TX500 cam drive sprockets, perhaps they had some left over from that disaster.

[Uniflow]

First fuel injected twostroke motorbike to the top of Thompson's Track. this weekend just gone.

[Uniflow]

Opps, probably put this in the wrong place.

[Uniflow]

[citabjockey]

please do start a new separate thread on that fuel squirting bighorn.

[oldneverslow]

I have a '74 ex hillclimber converted back to MXer also. They can be an addiction as I have a second disguised as parts stashed around the shop so the wife thinks there's only one.  If you can't locate parts email me and I may have alternative suggestions (bearings, seals, ?) or an extra in my cache. I have thicker head gaskets and made thicker base gaskets. After one seizing because a head stud stripped during my second ever moto, I removed the head studs. Drill the opening out to accept 12mm bolts. Then locktited them in. Then cut and ground off flush and drilled and tapped to accept original head studs. For some reason, the cylinder aluminum becomes unstable and the little studs pulled out. Make sure to follow the Yamaha bulletin about the ignition module, use a 1974, or use aftermarket ignition. The original had a massive advance curve giving the bike its bad*ss image. (deserved) If the auto compression release is attached, replace it with a bolt and copper gasket. My second race resulted in a small seizure scoring the piston when the spring gave up when the bike got hot. Don't mean to ramble but  you are motivated for great reasons and I'd love to hear about your progress. Your post is why I joined this blog. HAVE FUN!