what could possibly go wrong

[SteveM]

Meant to say as well re the chain case. Using a coaxial frame (swingarm pivot in the center of the front sprocket) would make it so much easier. I can only ever remember Spondon doing a coaxial frame which us a shame. Zero tightening or slackening of the chain through the rear wheel arc should help chain life as well as meaning you could run the chain tight so less clearance needed on the enclosure.

BMW G450X has a swing arm pivot as you describe. Unfortunately not sold any more.

 

[Deleted account 190920001]

BMW G450X has a swing arm pivot as you describe. Unfortunately not sold any more.

Yes looks like it does. That's 2 I know of now

 

[SteveM]

Here's a close up of mine with the swinging arm off for you Marki.

 

[Deleted account 190920001]

Thanks for that.

 

[Bendy toy]

Only trouble is Bendy that 2 strokes are banned in many parts of the world over a certain size. Doesn't matter if they are clean or not 2 stroke = not allowed. Although you say they are clean I would love to see some proof. They were anything but clean in the past and for all their simplicity they couldn't half be a right pain in the backside to keep running properly. Direct injection may be an option for cleaning it up a bit although not so good for lubrication. Would be especially beneficial with forced induction as so much would blown straight out the exhaust port otherwise. I am in no way saying it couldn't be done just it wouldn't be easy in the modern age where emissions mean everything.

Two strokes were indeed filthy with fresh unburnt mixture sucked down the exhaust and blown back in by the pipe resonance but otherwise lost down the road. The new BRP Rotax 800 as used in their Skidoos beats all of the very stringent US EPA rules for emissions. It's also powerful and more economical than similar power fours strokes. The latter are usually 1200s and a lot heavier.

They breathe clean air so anything "lost" down the exhaust dilutes the emissions. Fuel is injected adjacent to the spark plug after piston ports have closed. It has exhaust port valves giving a type of variable valve timing.
The benefits are:

• Smooth at part throttle something old strokers could never offer,
• Low oil consumption (around 50%) because there is no petrol to wash the oil away
• Better FUEL economy - stratified charge
• Good volumetric efficiency - fuel isn't vaporised in the crankcase displacing charge air
• Less noise and less cylinder wear as the piston isn't clattering about
• Less servicing - no oil to change and no valves, no cams and cam drive systems
• Oil use is not much worse than a four stoke that uses 4 litres every 5000 miles.
• No problems disposing used oil - its burnt.
• Emissions improved due to air dilution,
• Catalyst of course and very low Nox because there are no hot spots in the cylinder head.

The US EPA has really hammered down on emissions including cold start. Rotax stuck with 2 stroke because its cold start is so much cleaner than four strokes. Power density is high so an 800 twin makes the same as a 1200 four. Its also got a better lugging ability at mid range. A stalled snow mobile can get into big trouble.

It begs the question why only Rotax are doing it. It's often said that USA banned 2 strokes. They simply clamped down on emissions and noise and the old strokers couldn't compete. Also, the Japanese especially saw the 4 stroke taking them up market. Who's to say that attitude isn't still prevalent at corporate levels.

Manilla Phillipines is blighted by filthy old two stroke bikes used as taxis. Envirofit retrofitted direct injection systems have chopped emission by 90% improved power and given better fuel economy. The owners can't afford to replace their bikes and the small four strokes need more servicing not to mention the used sump oil disposal. The old strokers just keep on going. It's all gone quiet probably because the manufacturers want to sell new bikes rather than keep the old ones running.

http://www.cleanenergyawards.com/top-navigation/nominees-projects/nominee-detail/project/37/

 

[Bendy toy]

Meant to say as well re the chain case. Using a coaxial frame (swingarm pivot in the center of the front sprocket) would make it so much easier. I can only ever remember Spondon doing a coaxial frame which us a shame. Zero tightening or slackening of the chain through the rear wheel arc should help chain life as well as meaning you could run the chain tight so less clearance needed on the enclosure.

Norton did this with the police rotary engine bikes. They had rubber tubes around the chain rather than a slab sided box. The double row chain was replaced at 80,000 miles showing no sign of damage or ANY wear (stretch) but they were concerned about fatigue failure.

 

[The bigun]

Are you sure they used double row chain on the final drive as I've never seen a norton rotary with that set up

 

[Roymondo]

The Norton Interpol 2 did NOT have a duplex final drive chain (although the Benelli 900 did).

 

[Bendy toy]

I (thought) saw it when researching the Norton Rotary as a possible classic resto project.
Probably bad information.
I'll keep looking
Duplex makes good sense if the chain wheels are well aligned. But a duplex will suffer when they are a bit "out".
Duplex primary chains on Brit bikes last really well when oil level is kept up. Not doing the same job of course.
My pre unit Tiger 100 chewed primaries because the chain case was badly sealed and threw the oil out.

 

[Roymondo]

Not sure what your point is, Roymondo.
As I said, my GS has done 13k miles since March this year and I expect to have taken that up to 16-17k miles by next March. A fair annual mileage on two wheels or four.
I'll get it serviced when required and I'm not expecting any problems. If there are, I'll get it fixed with the BMW extended warranty.
Traversing continents? Did 2000 miles in September going through France, over the Pyrenees into Spain and back in under a week. Does that help?
I know guys who do a thousand miles a year on their bikes. It's their money, as long as they're enjoying themselves.
I will turn 60 next month and expect to do at least the same mileage next year and enjoy every minute. Ride it while you can.

TBH, no - it doesn't help much at all. Wifey's perfectly ordinary car did about twice that mileage in four days when I drove us down to Fuengirola and back. I didn't regard it as being remarkable, or even worthy of comment. I simply expected to get in, turn the key and drive it (which I did). My point is that 12,000, 15,000 or 20,000 miles in a year is somehow thought to be indicative of a reliable, better than run-of-the-mill motorcycle but in reality is simply par for the course for everyday cars. And regarding your remark elsewhere about 100bhp per litre - Just you try using all that power for the full 12,000 etc miles per year and see how long the thing lasts...

It's great that you are happy with your GS (I'm happy with mine, too - despite its muchless than perfect durability over 35k miles).

 

[comberjohn]

A certain Dr Gordon Blair of Queens University in Belfast reckoned that turbo charged two strokes with direct injection would be the way to go as regards emissions and efficiency. Think that would have been thirty years ago or more. He did a lot of development work for Yamaha's four strokes around that time.
I'm imagining that they would be a different animal from the Kawasaki triples.
Thought I read recently that KTM were doing some development work on two strokes?

 

[Bendy toy]

Ford had a fleet of naturally aspirated DI 2 strokes running in Fiestas during the late 1990s.
They were clean, quiet, powerful, good economy, cheap to build and cheap to maintain.
The top brass chickened out.
JCB considered a two stroke diesel when they went away from Perkins but Cosworth sold them on four strokes.

 

[Deleted account 190920001]

2 stroke diesels are common enough but they are usually big, like really big and in ships. They were pretty common in trains as well the napier deltic being one.

 

[Bendy toy]

A certain Dr Gordon Blair of Queens University in Belfast reckoned that turbo charged two strokes with direct injection would be the way to go as regards emissions and efficiency. Think that would have been thirty years ago or more. He did a lot of development work for Yamaha's four strokes around that time.
I'm imagining that they would be a different animal from the Kawasaki triples.
Thought I read recently that KTM were doing some development work on two strokes?

Isnt KTM owned by BRP as are Rotax Skidoo and Evinrude

The huge ship engines are all two strokes. They have a wet sump and blow air direct into the cylinders. Just as with Detroit V8s air doesn't blow through the crank case.

Yamaha had a two stroke diesel twin with rotary exhaust valves.



Honda have patents to revive the 2 stroke diesel. They could be a way to sort out the Nox issue that's scuppered VW. No hot exhaust valves and reduced peak temperatures.

This is a BRP two stroke article
http://articles.sae.org/8157/

http://www.brp.com/en-us/innovation/eco-performance-technologies/2-stroke-engines

 

[The bigun]

Ford had a fleet of naturally aspirated DI 2 strokes running in Fiestas during the late 1990s.
They were clean, quiet, powerful, good economy, cheap to build and cheap to maintain.
The top brass chickened out.
JCB considered a two stroke diesel when they went away from Perkins but Cosworth sold them on four strokes.

All this is way of topic I mean would you swap your gsa for a 2stroke chain driven bike I don't think so . Whilst touring who wants to mess with chain adjustment or taking chain guards/casings off for a puncture then there's the 2 stroke needing topping up hassle hassle . I'll stick with the gs thanks only thing I worry about is it overheating when stuck in heavy traffic something I've never bothered about on my jap bikes as for the known weaknesses I've only had fuel strip issues its the only vehicle I've ran out of fuel with but I love the thing didn't think I'd ever like a bike so much and to answer the op original question don't worry about the what might go wrong things if you like the bike as I do just fix em when it happens simples

 

[Deleted account 190920001]

All this is way of topic I mean would you swap your gsa for a 2stroke chain driven bike I don't think so . Whilst touring who wants to mess with chain adjustment or taking chain guards/casings off for a puncture then there's the 2 stroke needing topping up hassle hassle . I'll stick with the gs thanks only thing I worry about is it overheating when stuck in heavy traffic something I've never bothered about on my jap bikes as for the known weaknesses I've only had fuel strip issues its the only vehicle I've ran out of fuel with but I love the thing didn't think I'd ever like a bike so much and to answer the op original question don't worry about the what might go wrong things if you like the bike as I do just fix em when it happens simples

I certainly change to a chain driven bike. I have high hopes of the chain lasting a lot longer than the 14k my GSA FD lasted even I was to never lube or adjust it. People get all bent out of shape with the idea of adjusting a chain. Seriously, its 3 flats of the adjuster somewhere around every 3000-4000 miles! A lot of people service their whole bike as much as that including changing the FD oil which takes a hell of a lot longer.
Shaft drive is great when it is right but sadly that's something bmw didn't manage to do for quite a number of years.

As to the 2 stroke, why not. If it was avaliable, clean and reliable. The boxer would be a lot narrower and lighter along with considerably less maintenance.

I do agree with you that this is all way OT though and apologies to the OP.

 

[Bendy toy]

I'd happily swap my GS for a properly designed two stroke using current technology.
But I want Hossack suspension and on the fly ride height adjustment.
Done right it would be more powerful use less fuel and have less weight. And not sound like a Vietnamese tuk tuk.
Chain drive with a proper enclosure would look like a shaft. With oil lubrication chains will last for ever but are still cheap to replace. Unlike the oil lubed GS FD which but fucks its bearings every 50K miles.
Narrow minded prejudice keeps Harley in business with prehistoric engines because they look cool. It also prevents any genuine innovation. Just like the new 750 Hardley made exactly like the Japanese versions.
Innovation can be quality and look great. All it takes is some vision and creative design.

 

[Greenman14]

With a Scotoiler a chain will last 20k miles easily, and I only ever adjusted mine when the back wheel was out for a tyre change. I'm not that bothered about the oily crap on the back wheel either, but it is easy to clean off if you can be arsed.