Big bore Spree piston?

keithw · Post by **keithw** » Tue Jul 15, 2008 12:27 am

Hello all,

I was digging through old posts looking for info on larger than .5mm over bore pistons for the Spree. At that time nobody had come up with a big piston. Has anybody come up with one that will work yet? I don't think 70cc is possible but 60 or even 55 would be nice. I'd even be happy with .75mm or 1.0mm over . I've got an extra cylinder that is at .5mm over now and being to go even a little bigger would be nice.

keithw

Kenny_McCormic · Post by **Kenny_McCormic** » Tue Jul 15, 2008 12:42 am

Some online honda parts dealers still sell .5 over pistons.

Post by **noiseguy** » Tue Jul 15, 2008 8:49 am

JCC makes an oversize piston for the Spree that will get you to 55cc. A user here named Maddog can obtain them for you through a shop in Hawaii.

keithw · Post by **keithw** » Tue Jul 15, 2008 12:29 pm

Thanks, I PMed maddog. Hopefully I hear from him.

keithw

mousewheels · Post by **mousewheels** » Tue Jul 29, 2008 9:14 pm

There is an oversized piston kit - piston, pin and rings on eBay right now.
Seller name is chopchop*123, sellers store name is 'alluneed scooter parts'
Current listing is 220263168103

Sellers words are "brand new. this will fit a honda spree, elite e, or honda elite sa50 (88-93). the size is 44mm. so it is 3 sizes bigger than stock. stock size is 41mm."

BTW: I have had no dealings or relation with this seller.

keithw · Post by **keithw** » Tue Jul 29, 2008 10:19 pm

Well, I've got a bid on it already. I had not heard of a 3mm o/s piston before and I'm real curious about it. It could be a Chinese piston from something else that just happens to work, or not. The big issue for most folks is getting the cylinder bored. Fortunately I've got a mill and boring head to do them.

I also located a source for a 2mm o/s piston in New Zealand that I've got on the way. Not sure how many he has but I asked to see.

Someone on Ebay is selling a ported and polished cylinder, piston, rings etc kit for the Spree. I'm real interested to see what it goes for.

keithw

Post by **noiseguy** » Wed Jul 30, 2008 11:46 pm

Are the N.Z. pistons from JCC? JCC (S. Korea) should be a high-quality piston; I'm not so sold on the Chinese pistons and rings.

A 3mm overbore on the Spree jug will make for some pretty thin walls...

keithw · Post by **keithw** » Thu Jul 31, 2008 9:38 am

I agree on both counts. The 2mm piston is on it's way so I'll see when it gets here. I haven't got the 3mm yet, still bidding. One of the problem with big bore mods is that the cylinder walls get thin. With less iron to soak up and distribute the heat it can develop hot spots and is generally more prone to overheating. My friend the old school two stroke guy hates overbore kits. He prefers to make the power with tuned pipes and porting. I am planning to go with e-85. With e-85 you must run much richer. Hopefully the added fuel will aid in cooling. In any case I don't expect to get a long life out of the big bore cylinders. Heck, with all the mods I don't expect to get a long life out of any of them. I've gone into this expecting to burn up cylinders, not from running lean but from just making more power than the cylinder can shed the heat from.

keithw

Post by **noiseguy** » Thu Jul 31, 2008 5:07 pm

You could always weld up a cylinder water jacket and go water-cooled... don't know how you'd seal the head though.

R/C guys create water jackets that seal against the bottom cylinder fin (they remove the rest) and then seal the head in at the spark plug... the jacket basically looks like an automotive oil filter.

If you look at the early Elite 50 jug, the finning is much deeper than the Spree jug. I think that re-working this jug (even in stock form) with a custom exhaust and cooling tin would be a better starting point than anything you could do with the stock Spree jug. The porting is much better even stock.

Kenny_McCormic · Post by **Kenny_McCormic** » Thu Jul 31, 2008 5:26 pm

noiseguy wrote:You could always weld up a cylinder water jacket and go water-cooled... don't know how you'd seal the head though.

R/C guys create water jackets that seal against the bottom cylinder fin (they remove the rest) and then seal the head in at the spark plug... the jacket basically looks like an automotive oil filter.

If you look at the early Elite 50 jug, the finning is much deeper than the Spree jug. I think that re-working this jug (even in stock form) with a custom exhaust and cooling tin would be a better starting point than anything you could do with the stock Spree jug. The porting is much better even stock.

Separate jackets for head and jug.

mousewheels · Post by **mousewheels** » Thu Jul 31, 2008 10:28 pm

Water cooling - yeah there's something to work on. I like the idea!
Seems like some work around sealing the cyl head bolts would be needed with a split jug/head cooling scheme. Maybe put some tubes in between the base to cyl top and seal them up?

---
You guys have any figures for ballpark min cyl wall thickness on some Honda scooters?

I am stretching a bit to another model here, but
made some quickie measurements on a Yamaha Pw50/QT50 cyl. These are stock 50cc with a 40mm piston. There's a history of 60cc overbores for these models, using a 44mm piston.

Cyl wall thickness at base of a stock Yamaha cyl is just about the same as the Spree at ~0.21". Going up from the base the Spree and Yamaha maintain or are a bit thicker OD than at the base. The Yamaha does not look like it gets wider or steps at the top. Made a quick calculation of before/after wall thickness - Yamaha bored to 44mm (60cc) -- 0.14". Spree 41mm to 43mm (55cc) -- 0.17"

So for approximation, we have a similar sized and overbored application, to the Spree overbore. One point note is the Yamaha cyl does not have forced air cooling (Its like a Honda Express). It's got larger fins and more of them, but still a little airflow goes a long way...

maddog · Post by **maddog** » Fri Aug 01, 2008 12:54 am

A larger piston will do nothing unless you can change the gear ratio!

Kenny_McCormic · Post by **Kenny_McCormic** » Fri Aug 01, 2008 1:48 am

maddog wrote:A larger piston will do nothing unless you can change the gear ratio!

It will give more take off power.

Post by **noiseguy** » Fri Aug 01, 2008 9:52 pm

mousewheels wrote: You guys have any figures for ballpark min cyl wall thickness on some Honda scooters?

Interesting... I remember looking at a 2mm overbore on the Spree and thinking that it wasn't any worse (in terms of thickness) than the Taiwan-made 65cc kits for Elite 50. I didn't take measurements though. With what you found, sounds like 0.17" wall thickness is workable.

A seperate head/jug water jacket would probably be best, but not simplest... where does one get the small water pump that this would need? Radiator could use a cheap auto transmission cooler if you kept the water at zero pressure through a radiator bottle, or you could pull stuff off a small wrecked watercooled bike, like the Ninja 250. How do the water-cooled kits on the market for later Elite 50's work?

Dac · Post by **Dac** » Fri Aug 01, 2008 10:27 pm

they have water cooled cylinder, heads, a water pump, and a Radiator.

This is a godly spree...

"homemadepowa" made this bike, its a spree, with a dio motor, thats a huge 100 something cc water cooled set up.

Not an elite, but you get the idea.