Yamaha SC500's ?

[Hoony]

one for the yamaha fans to inform me.

where do the SC500's fit in the picture?
how many models (2 only?) and what years?
did yamaha release them at the same time as YZ A Models ?
what problems do they have (i have heard piston seizures a plently)?

i am not in market for one . just curious?

[YZ360A]

Yamaha SC500's are nice a real collectable yamaha.

1973 sc500 is silver with Black and Red Stripe.
1974 sc500 is Yellow with Black Stripe.

Only realeased for the two years.
Frame and engine serial is 363-00? for the 1973 and is 363-10? for the 1974 model. (note the 1 in 1974).

They were realeased the same year as the YZ A models.

I had a real nice clean 1973 SC500 and man it was a rocket ship trench digger.
Also this bike started fine and seemed to run O.K. it sort of was a bit more vibration due to the larger size but it's the sort of bike you leave in 2nd or third gear around the whole track.

Also these are only a 4 speed box not a 5 speed like the mx250,360.

I think MAICO did a SC500 in the 1980's aswell???

Here a picture of my old girl.

http://bp2.blogger.com/_SELJKhS3P6c/Rlf0xiI3LTI/AAAAAAAAAA0/GZ4Rtmexpag/s1600-h/DSCN2638.JPG

and a 1973 model.



and a 1974 model.

[Freakshow]

More of a desert racer " steve mcqueen style".

the Big 2 stroke from what i hear was prity reliable, but was just too much of a motor for that frameset up and as yz said liked to vibrate itself to death.   I dont think it made much impact as the 360's and 250's smoked it by being more riddable on the track, so it didnt really deliver any advantage. i just was.

[Nathan S]

The 4-speed was supposed to be a bit of a limitation for MX. The article in VMX said that fitting a 5-speed helps heaps (legal for VMX? I think so - because the 5-speed was available in 1974 and you could legitimately claim the bike was a "MX360/SC500 special").
Also seem to recall comments about a pretty ordinary power delivery, that is supposedly fixed by a different ignition.

They seem to be one of those bikes that's collectable because they're flawed rather than because the're good - think TM400 style collectability.

[Graeme M]

Here's a couple of tests:

http://www.ozvmx.com/features/tests/sc500/sc500_1a.htm

http://www.ozvmx.com/features/tests/sc500/sc500_1.htm

[firko]

I had a 5 speed in one of my SC500s. In an SC500 the counter balancer is on the gear shaft instead of fifth gear. I fitted the entire gearbox from (I think, it was 20 years ago)  a DT250. Everyone told me that the bike would vibrate to death without the balancer but I didn't notice any extra shakes at all. Twenty years later that engine is still in semi regular vintage use in my old Champion/Yamaha flat tracker.

The pistons are the weak point in them. There are some cutaways ajacent to the pin area and the pistons crack there causing piston distortion and eventual siezure. Edgar Phipps re sleeved his SC500 barrel and fitted a CR500 Honda piston which gives the bike about 470cc. It runs like a Swiss watch with absolutely no problems. Its got a 5 speed MX250 box as well.

Nathans correct in his assumption that the ignition curve is a problem with them. I used an MX250 black box which gave a slightly more usable power curve. I actually tried a few differentYamaha ignition modules but never quite got it to the point that I felt the engines potential was being used. PVL ignition would be the hot ticket I would imagine. Perhaps IT 465 ignition with the heavy flywheel like I'm using on my RT1 360 project might be worth experimenting with. I also had a switch which advanced the engine a tad for easy starting.
The only problem with that was that it sometimes started in reverse, much to the embarrasment of myself and the joy of everyone else.

[DJRacing]

Aint the engine cases more similar to the DT360A than the RT/YZ? I think the SC500 is a way cool bike but I dont think I would ever own one(to shit scared to ride it  ). At 44bhp@6500rpm she would be a beast.

[Rossvickicampbell]

I have been in the fortunate position of being able to ride an SC 500 motor in a YZ B frame while I was chasing a big bore for myself.  Fitted with PVL etc.  I have only ever ridden two smokes and with the work done on this one the power delivery isn't too savage at all as they were supposed to be.  It is an absolute blast to ride and has power everywhere - 3rd gear is all you need when away.  The best part of the bike is when someone comes to pass you just a small twist of the right wrist stops their thoughts dead!!!!  Awesome piece of gear.

regards

Rossco

[firko]

Ross, if you thought the SC500 was a awesome piece of gear, let me recommend you try a 440 Maico. After owning both, I'm here to tell you that there's no contest. The Maico would win any drag race by 3 bike lengths and has a far wider power curve. 
Still, I like SC500s because they were an great example of a conservative manufacturer venturing outside the circle. They got it right a bit later down the line with the lovely 465 engine.

[Rossvickicampbell]

mmmmm - Firko - there are a couple of EXTREMELY nice big Maicos in our club - maybe I should try???

Rossco