Aprilia SR50 Basket Case Rebuild

[chacha]

Just picked up a basket case SR50.

This scoot has been floating around between friends for a little while. The one that owned it first is mechanically inclined but financially challenged. He is the one that tore her down and then didn't have the cash to buy the parts to fix it.

He then sold it to friend "2", who says he is mechanically inclined. Friend "2" has had the scooter for about 2 years. In the same condition as when he bought it from friend "1". For some one that use to work at a motorcycle shop as he says I figured he would have worked on it a little more in the past 2 years. Either way, he did buy the new top end assembly and put the gaskets in the head, but that is as far as he went with it from what I have seen.

Now, I own it. I think I'm looking at a total tear down since the engine has been open for over 2 yrs so who knows what has collected inside it.

Here it sits after I got it home.



The old piston.

[biketherapy]

looks like a big project. Is this the fuel injected one?

[chacha]

It's the carb model. I've been researching on it today and it has the Minarelli 50CC liquid cooled engine.


My wife wants to help with the rebuild so it should be a good little project for us or be the cause of a divorce

[B02S4]

PM inbound.

[btcn]

Yep, a BIG project! But as long as you enjoy it it'll be fun! Good luck and look forward to seeing it come together.

[skibum69]

I'm waiting for the extra cash to order a 70cc big bore kit for mine

[chacha]

I just ordered a gasket kit, oil seals, as well as a new plastic cover that goes over the supply oil pump/ magneto area.

The parts won't be here for a week or so. I have to leave for work this Weds for 3 weeks. When I get back I hope to have the motor apart and cleaned before having to leave again a few days later so this thread might be a slow mover for a bit.

[Cortez]

Cool, good luck with it.
It's one of the best and fastest 50cc scoots on the market for years now, will
do over 50mph stock, should be good for about 6hp with stock exhaust and
reacts well to leovince zx or rr pipe (15-20% more power).

[chacha]

Well it's been a long time since an update but here it goes. It's winter here and been cold and snowy so I finally got around to putting the top end back together this week. I was originally going to split the case and do a full rebuild but the main bearings still rotate very freely with little play so I decided to skip that.

I did pull the flywheel and magneto to replace the oil seal on the crank and also to inspect the oil pump plastic drive gear. All that looked fine. I did find a small metal pin stuck inside the flywheel and magneto. It is over an inch long and I have no idea what it goes to. It seems to have been there for a while as the inside of the flywheel shows wear from this pin rolling around. I didn't have the flywheel holder tool so I improvised.





I got the new piston and cylinder on and the engine bolted back into the frame. I don't have pictures of that since my camera battery was dead and I just wanted to get it done that day. But here she is before I loosely bolted the seat, fuel and oil tanks back on.




I spent pretty much all day yesterday findling with the carb and wiring to make sure I had spark and fuel. Most of the hoses where brittle or the wrong length. The oil pump hose was cut so I had to redo that. I didn't have a key for the scoot so I removed the key lock then turn the switch with a screw driver.






But she does start and Idle now. I'm missing a lot of body hardware but that is easy to replace. I will need to make some brackets and I am missing the airbox so I will have to find on of those. I've been looking into it and I also think that somewhere along the line some one replaced the carb with a different one. The model number is not the same as the info I can find about a stock motor.

[btcn]

Wow, looking good! A LOT better than it started out!

[mamba24]

any update on the build?, planning to buy one on cl and pretty excited on riding it this spring.

[chacha]

It's on pause at the moment since I am out of town for work until mid March and then I have to refinish some furniture when I get home first.

I will be ordering some different size jets to play with the carb settings. It starts first kick and idles fine. I just can't get over 1/4 throttle or it dies.

[chacha]

Okay so this has been on pause still but I ordered a few items today. I toyed with the idea of trying to dial in the aftermarket 19mm carb that is on there. I think a 19mm is too big for a 50cc scoot. So I found a new 12mm carb which is listed as the stock size in the manual and I also found the stock airbox online so I figured that would be a good baseline.

Now it's just waiting for the parts to arrive.

[brianwheelies]

Originally Posted by chacha

So I found a new 12mm carb which is listed as the stock size in the manual and I also found the stock airbox online so I figured that would be a good baseline.

Now it's just waiting for the parts to arrive.

12mm is stock? That seems awfully small. I think the aircooled minarelli's run 14 to 16.5mm stock.

[chacha]

This one is a liquid cooled minarelli. I thought it would have a 17.5 mm but after finding a parts fiche for the 97-2000 model years it is listed as a 12mm. Even when I e-mail AF1racing asking about a stock carb he sent back a link for a 12mm.

I'll have to see how it goes then.