Power can be found http://www.thumperta...w-80-questions/
These motors are closer to a weed whacker than a motorcycle. They're designed to run consistently with no maintenance
for a long, long time. A now deceased friend of mine who was giving me pointers during the porting experiments thinks he could squeak 15 hp out of one. And I bet he could have. If I had known he was gonna kick the bucket in March, I would have sent him a complete motor and a blank check and told him to go nuts.
I'm still aiming for twelve, which is about three times the power output of a stock PW.
Granted, he's a go kart guy, and a very well respected go kart guy, so it probably wouldn't have made any power below 5K, which is near the max RPM of these motors in stock form. According to my calculations, this motor will self destruct around 11K.
More than likely, I'll call my PW80 experiments done when I throw a rod through the case, so I really do intend to find out how far you can push this 1970s era lawn equipment design.
Unfortunately, I have a limited amount of time to work on it right now.
From the referenced thread, and a few notes on other things.
Smacaroni, on 17 January 2011 - 06:05 AM, said:
I highly suggest choking the bike up and leaving it that way till she learns to shift. That's what I did with my daughter and it worked out quite well. While great for new riders, the bone stock choked up bike isn't much fun stuck in first gear.
Power, well, um I have a secret mod in the works, but it's at the machine shop and I don't want to say anything till it's done. Everything else has been documented here.
From my notes, the best bang for the buck was
#1 adjust/clean the carb, as with almost any new-to-you bike.
#2 FMF (although I've since learned the stock pipe can be modified)
#4 Boysen reeds
#5 re-jet (if you do the above all at once, or you should verify after each #2-#4)
#6 mill head or deck barrel. I recommend 1.5 mm.
#7 raise ports using 1 extra base gasket.
15W fork oil. There's some difference between that and regular motor oil. I don't know what though. You can find fork oil at at motorcycle shop.
Speaking of suspension... I'd also recommend looking for a KX60 parts bike if you'd ever consider making any suspension changes, it's much more effective than anything available in the after market at a minimal extra cost. I.E. there's a bogus fork kit on ebay for $44. For $75 the local machine shop pressed a new steering stem onto KX60 forks which allowed them to mate to the PW.
The X-tender doesn't do a whole lot, but it's $25 plus shipping.
For the cost of the parts bike, I used an angle grinder, a welder and a drill bit to adapt the KX60 swing arm to the PW.
Ingenuity + machine shop: $155. An extra $86 created an undoubtedly better bike. But you've got to find the parts bike before you need it as buying the pieces off ebay would not be worthwhile.
This was a reply to someone else's question, I recommend the KX60 shock as opposed to the X-tender. It's a little more work to get it to fit, the cost is roughly the same and it's world's better.
There's a # 4.5 as well, which is modifying the reed cage, basically you install the reeds, mark the cage where the reeds over lap and cut everything out leaving 0.5mm or 0.020" overlap for the reeds to seal on the finished piece, so 0.75-1mm or 0.050". You will remove the dividers so you can't go back to factory reeds unless you replace the reed cage. With what's left, grind and polish till a near-mirror finish and make sure it's a smooth
Now once you get through this list, things become more dependent upon what you want the finished machine to do. Since I've moved into the road race circuit, my future mods will be of some interest to trail riders, but probably not ideal for a six year old plunking around the woods. More than likely the finished bike will be a high strung, low ground clearance (even with the KX60 suspension - you'll see when it's done), narrow harsh power band machine. That's how road race bikes are. Trail bikes are much better off with a wide consistent power delivery and a decent amount of torque. But the max HP numbers are going to be much smaller.
At the stage the bike was at before I decided to replace the top end, it would still be a decent trail bike and made roughly 50% more power than stock (a guess, I've never dyno'd a stock bike, but I'd like to).
But I can't do anything till I get the Chinese top end working consistently or I get my Yamaha cylinder back from the machine shop.
The good thing with the PW80 no matter what your goals are is it's cheap. You can buy a used one for $300-500 (well in the US, Maple Leafs fans are charged a premium for some reason). Used factory parts are plentiful. As long as you don't do stupid things they run forever.
In the mean time, I have the KDX/KX mini-moto bike keeping me busy: http://www.thumperta...mebody-stop-me/
Edited by Smacaroni, 15 June 2012 - 03:31 AM.