revtothelimit - motorbike forum

https://www.bikebound.com/2020/12/08/src-475/

OK, we're going radical today... lets see what you make of this one

I like that.

I like how they’ve kept the 80’s Aprilia look but there again I’m a fanboy of the 70’s and 80’s.

If a company like Kawasaki were ever to reintroduce a modern 2 stroke they’d attempt to style it like a mini H2.

Yep I like that

I remember not buying an RS250 for £1600, when no one wanted them.

...and no one ever wanted an NSR400, they looked so horribly dated, but look at the money they fetch now.

Very nice

That's lovely.

I can't put my finger on it, but it looks weirdly Chinese ebay to me.

What was the 200bhp 2 stroke monster that someone sold a few years back? Basically an NSR500 for the road, I think it was a German firm?

Mr. Dazzle wrote: Tue Mar 16, 2021 8:32 am I can't put my finger on it, but it looks weirdly Chinese ebay to me.

What was the 200bhp 2 stroke monster that someone sold a few years back? Basically an NSR500 for the road, I think it was a German firm?

Ronax?

KungFooBob wrote: Tue Mar 16, 2021 8:39 am
Ronax?

Thats the badger!

Actually only 160bhp now that I've looked it up, so clearly little better than a moped

I saw one at a trade show (it wasn't even a motorcycle show) a few years back, amazing bit of kit.

KungFooBob wrote: Tue Mar 16, 2021 8:13 am I remember not buying an RS250 for £1600, when no one wanted them.

...and no one ever wanted an NSR400, they looked so horribly dated, but look at the money they fetch now.

I was only talking to guy yesterday who bought an nsr400 new for £3600 around 1982 he was saying they’re fetching £8k now and how he wishes he’d kept it.

I nearly bought an RS250 before buying my 996...I was looking at both and just happened to find a good 996 first. Still kinda wish I'd bought the 250 when they were reasonable money!

KungFooBob wrote: Tue Mar 16, 2021 8:13 am I remember not buying an RS250 for £1600, when no one wanted them.

...and no one ever wanted an NSR400, they looked so horribly dated, but look at the money they fetch now.

I know someone who had a new one in spring 1985, it seized multiple times, Honda eventually gave him his money back.
I also know someone who has an immaculate one that he stored in his loft in bits for years to avoid his ex wife claiming it as part of the divorce settlement

The bike is nice, but there are quite a few RS250s with YPVS/Banshee engines, you can get one of these engines to give 80bhp with reasonable reliability relatively cheaply.

I'm actually more interested in the other 2 stroke mentioned in that link, the one Kawasaki patented. A 2 stroke connected to an electric generator, but with poppet valves too. Obviously quite a departure from what you traditionally think of as a stroker, but pretty clever.

2 strokes are potentially very clean and efficient, which is why they're still used quite a bit in ships and trains. The downside is the narrow power range, which is even narrower in the big industrial stuff. That's not a problem when you're using it at a constant speed to power a leccy generator.

The other big downside is the need to put oil in the fuel and the subsequent smoke (opinions may vary on whether this is actually a downside ), so Kawasaki propose a supercharger to get around that, which is also what they do on the big stuff. If you supercharge the inlet you can keep everything 'above' the pistons and remove the need for transfer ports. You can then have a bottom end much more like a 4 stroke with pressure fed bearings etc. and not add oil to the fuel.

I imagine a 100cc 2 stroke running at 10,000rpm constantly will sound pretty annoying though!

So 2 strokes may yet make a comeback, albeit in hybrid electric vehciles.

Ship and train two strokes don't need oil in the fuel, they work differently to conventional two strokes, they have two pistons in one cylinder that suck mixture in at the bottom of their strokes and compress it at the top of their strokes.

https://en.wikipedia.org/wiki/Napier_Deltic

If i can't clearly see the engine, then generally its not for me, but I quite like that. I particularly like the way they've gone back to a more traditional sized seat unit with making it look like a Deliveroo bike.

Le_Fromage_Grande wrote: Tue Mar 16, 2021 1:29 pm Ship and train two strokes don't need oil in the fuel, they work differently to conventional two strokes, they have two pistons in one cylinder that suck mixture in at the bottom of their strokes and compress it at the top of their strokes.

https://en.wikipedia.org/wiki/Napier_Deltic

Yeah that's exactly my point. They don't need to 'use' the bottom side of the piston and crank cases, so they can have a four stroke type bottom end.

They don't have to have two pistons per cylinder but they can. The simpler more common way is to have the inlet port where the transfer port is on a bike type 2T.

Downside is they won't work without forced induction. Since you're not using the underside of the piston to push air around the transfer port (yeah I know the exhaust helps too before you say it ) you need to force the air in some other way.

So if you look at this diagram, on a bike type engine the 'in' would be one end of the transfer port, the other end of which goes to underneath the piston. You can also just connect it directly to the inlet manifold, but only if you've got a super/turbo charger. That then means the cranks etc. aren't exposed to the fuel/air and you can make them like a 4 stroke, removing the need for oil in the fuel.

Fascinating stuff in that link,as Dazzle mentioned.
https://www.cycleworld.com/story/motorc ... ke-hybrid/

https://en.wikipedia.org/wiki/Split-single_engine

Looks like the first supercharged two stroke was 1905, I thought the first ones were DKW in the 1930s, the DKWs are fantastically loud.

The big stuff is almost invariably supercharged/turbocharged rather than having transfer ports, it's more efficient. It's also more expensive, heavier and more complicated.

Ship engines are turbocharged (and about the size of a small house)