Top Performance 47mm BBK *one in the pink*

[deuce217]

Hey guys wanted to share my BBK fun on my 2000 Aprilia SR50. It has a Minarelli no di-tech engine. I bought with the 47mm SINGLE ring Top Performance BBK and Top Performance Replica Pipe. When I bought it in 2012 it would run but not accelerate. It has 41 original miles on it.


I did a compression test and it turns out it is at 90 psi. This explains why it will not go fast at all, I thought my tester was bad and tried, jets, it runs best with a 100 main right now, forgot to check the slow jet. I revs decent on the stand but under load, no Huevos.

I decided to look inside because the old lady I bought it from knew literally nothing about it other than her husband bought it and never drove it. I feared the cast cylinder had rusted over the years from never being usedI was wrong

Its has a 22mm mikuni carb runs like a turd...

I took it apart to see whats up. Nothing weird looking, but the ring is definitely not seating. When I reassembled it I used plenty of 2t oil and it seemed to have helped the compression for about half of my block. Then it was back to being a turd.

I have a new piston ring headed my way and a hone. I will keep you all in the loop. Feel free to throw in some knowledge I am new to these horizontal engines.

[paulpauly7]

give that piston a polish befor you fit the ring .

[deuce217]

Ok guys thanks, I will pull her back apart when I get a chance. It was not running premix either, do you guys run premix on something with a 100 main jet? Or do you think the pump is good enough?

[Wheelman-111]

Greetings:

That piston looks like it's had a hard life. It's pretty scored, and I suspect the reason for low compression if the bore has corresponding chafes.

I don't know the stock bore size, but assuming the increase with a 47mm slug is similar to the 40% a similar increase nets on Hondas, then the pump alone definitely isn't enough. Maybe that's why the piston looks so sad. Perhaps that's an Athena bore? Is there a Polini or other quality kit for the SR?

It looks to me like you need an oversize or a whole new bore to get this right. Then run at least 128:1 in the tank along with the pump.

[LMH]

Thats what single ring pistons look like after a few hours of riding when not broken in proper. Jasil Top Racing is top notch, better than Polini or the Athena kits, or most others. Stage 6 is what you want for quality and killer power.
The Mina powered AC Aprilia uses a 40x 39.2 (bore x stroke).

[deuce217]

Thanks guys,

I heard a lot of good about this BBK from the aprilia crowd especially when matched with the replica pipe it has. Its amazing it has all this stuff on it and only 41 miles. I will hone this bore, as it looks untouched by the piston and pray the new ring seals, then sell this thing, unless I like it then it will collect dust with the rest of the rides. I like how small the elites are, this thing is like a full size crotch rocket.

[deuce217]

These springs on the exhaust header... I do not recommend taking them off. It is way easier to remove the bolts from the jug. Those springs are as tight as red clutch shoe springs, naturally I took them off instead of the bolts. I thought it was going to be "faster".

[LMH]

I use needle nose Vice grips when doing those springs. Total pain.

[deuce217]

Graphite,

Is yours carb'd now or are you running injection still? If you are using ditech, what ecu are you running?

Lovemyhonda,

Yep, thats what I used. Praying they did not slip because I would smash my fingers into concrete.

[deuce217]

I love the ditech cluster. Those are way too cool for a scooter. But I guess you get what you pay for.

[DirtyE]

The polini kit comes with something to adjust the fuel regulator. A spacer, and a deeper bowl or something like that. You can order the regulator adjustment alone as well. I put it on my stock cylinder ditech. I converted to carb shortly after. Ironically enough, when I converted to carb my first big bore was a blue piaggio due plus from top performances, with a stage 6 r1200

[deuce217]

This is for sale guys first 1000.00 dollars takes it. I dont have any time for scooters for awhile. About 50 original miles. The combustion is low because the rings did not seat and it sat for 12 years before it was broke in.

[deuce217]

Brandon,

I would do this plus some cash for the beta. Gyros are not my thing. Space is my issue too. Im into heavy machinery and every square foot is crucial.

[deuce217]

I might be willing to do some trade towards a BA disc swap. Call me up if you wanna chat. If I was smart I would swap pistons and rings, hone and sell that pig. But time is too limited. I am building a larger CNC milling machine at the moment. Here is that youtube channel where I am posting that project. https://www.youtube.com/watch?v=KvgYHDyZ-DE there are a gang of videos on this project. Should be about 4k on the mill when complete and should make aluminum chips rain!

[deuce217]

BA disk swap? I know how time goes for sure. Checked the link, looks good. I wish I knew how to operate and design parts.

BA= Bad *