Originally Posted by oldbmw

The high seat heights are mostly a result of the switch to wet sump engines (cheaper to manufacture) which allows the manufacturers to put all the works (engine, gears and clutch into one casting ) cheaper to manufacture, it also totally negates ALL the improvements brought about by modern oils, as the engine contaminates the gear oil and the gears chew up the engine oil. (shared same oil). This is why cars get 10k miles out of engine oils, and more than double that out of gear oil. Basically we are being sold a lie. So whats new?

Originally Posted by Ian

Mmmm....don't most dry sump motors also have shared gearbox and engine oils? LC4 for sure, Rotax 4T family? Most Japanese 600cc+ singles?

The only exception I can think of is the Honda motor that powers the Montesa 4RT trials bike (itself derived from the CRF250) which has separate gearbox and engine oils.

I thought that 'oil sharing' is the reason why we have motorcycle specific 4-stroke oils i.e. they're designed to work in the engine and gearbox. And why it may not be wise to use car engine oil in a 4 stroke motorcycle i.e. it's not designed for use in gearboxes.

That said, I'd guess a bike with wet sump engine is cheaper to produce than a dry sump - no oil tank etc. But isn't one advantage of a dry sump engine that the oil can be circulated externally to the engine and therefore be cooled?

Originally Posted by Ian

Is the WR250R not heavy for a 250cc? The 2008 Yamaha WR250F is 106kg. OK, the F is an enduro bike, but 20kg difference?

Mind you the new Tenere is also quite heavy when compared to others in the '600' class.

I would hope that an aftermarket bigger tank would be available, but you never know. In the worst case, one could always have one made.

Be interested to hear about the wet sump issue in more detail.

Thanks.

Originally Posted by mollydog

The Japanese somehow figured this new fangled "Wet Sump" mallarky quite a while ago....like maybe 1956 or so, since Honda copied verbatim the Gilera and MV Augusta GP inline four race bike designs...both wet sumps IIRC. And by the mid 60's it became standard on most all Japanese bikes. Seems to work quite well since about 98% of all Jap bikes use the wet sump design. (Not counting 2 strokes, the new CRF's, and possibly a few other obscure models??)

BMW are wetsump, but had teh sense to keep the oils separate.

We would need Kevin Cameron to detail all the advantages of Wet sump vs. Dry sump from an engineers perspective, but I can assure vintage motor heads there are several good reasons why they went this way nearly 50 years ago.

Yes, cheapness of manufacture, suited the American market where neither economy or roadholding was of any consequence.

From cost of manufacture, to effecient placement of gearbox in the case to allow motor to be smaller/lighter and more mass centralized, to carrying more oil capacity....where gears actually help cool off the oil.

A wet sump bike 'has' to have a higher centre of gravity, because the crankshaft is above the oil, therefore wll above the bottom of the crankcase, unlike old Brit bikes.
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Somewhere along the way they learned how to build a clutch that doesn't shed bits (usually) to using much improved oil spray distribution / filtering /cooling techniques to keep things happy, all in a relatively small, light ALL Aluminum package.

Early on, what the Japanese really had that the Brits didn't was knowledge of latest Metalurgical tech. This knowledge was given the Japanese by the US military after WW2 (who stole it from the Germans!!! True!) in an effort to give their industries a boost. We gave them all kinds of technology...including the transistor....which soon after led to the end of Points ignition. The Japanese are also the world's best reverse engineers. Now Triumph are playing that same game....see new 675 triple!!

Having grown up with, raced and pushed pre-unit, right side shifting Triumph's and BSA's, I was thrilled to own my first Honda 50 in about 1963. You COULD NOT blow that bike up....and trust me...we tried. Every guy I ever met riding early Brit bikes blew them up at some point (including yours truly), everyone had a story about the 4000 mile valve train/top end and drive chains made of butter. (Jap chains weren't much better in the early days)

Perhaps you would have had better luck if you tried a Unit construction Triumph, ( the whole range was unit construction then albeit with separate oils) no use comapring a 1963 Hondy witha 1939 triumph bike.

Brit bikes worked great in rainy, cool UK. But not so great in the S. California desert, if ridden hard. They did great at Ascot Park (where I raced a Bultaco Pursang) ALL the races were at night!

I note the 1961 24 hour record for a 500 cc by Velocette still stands at just over 100mph.

Both Honda's current motocross racers (CFR250/CRF450) use seperate Oil/Gear Box compartments. I've forgotten the technical justification for going this route. But who knows, maybe they are now re-examining this concept? It's appealing in many ways....

perhaps these high strung bikes need the right oil in the various bits to survive.

I like the idea of using oil optimized for the engine...and gear box oil optimized for the gear box...this has an undeniable logic to it. And these motors are so small it amazing....I think they got the idea from Vertimati Bros
motor.
Nope, old Brit bikes

The main problem for years with combining Engine and Gear box oil is molecular shearing (or whatever the true technical reference would be). This happens when whirring gears break up oil molecules. Sheared molecules at some point cause the oil to lose film strength, which can then be broken down by heat to where protection is lessened.

which means the poor design has negated teh advantage of using long life high performance oils.

But for 20 years modern oils have been up to the task of resisting this breakdown. On my dirt bikes I still change oil about every 500 miles. Hard miles, redline miles, bogged in sand miles, at full throttle in 35c temps.

How long do you think a Jap all in one machine would last on monograde dino oil ? these poor mechanical designs have only managed to work by abusing the properties of new synthetic oils. Old Brit bikes had similar servicing periods on Dino oils. This is why cars and those who do not mix oils have 2-4 times the service intervals.

Patrick

Originally Posted by Dodger

It is debatable that the Japanese had superior metallurgical technology to the British ,certainly their bikes of the sixties and seventies were made of inferior alloys that turned to powder once the "varnish" had peeled off and the engine cases of these bikes were glued together to make them oiltight .

Originally Posted by Dodger

The bikes were able to fulfill a market need based on performance and price and hence their success . If the British "captains of industry " had had the vision and drive of Soichiro Honda then Brit bikes would be still world leaders .Technology was not lacking but business acumen certainly was .

Originally Posted by oldbmw

How long do you think a Jap all in one machine would last on monograde dino oil ? these poor mechanical designs have only managed to work by abusing the properties of new synthetic oils. Old Brit bikes had similar servicing periods on Dino oils. This is why cars and those who do not mix oils have 2-4 times the service intervals.

Originally Posted by Dodger

It is debatable that the Japanese had superior metallurgical technology to the British........