D-Motor

[M61A1]

M61A1. They are not actually that heavy. the Buell XB12 ss long is under 200 Kgs Some of the frames are (on the tourers) but all tourers are heavy. The heavy parts are the flywheels and the gearbox innards. The rest is alloy. Push rod engines can be lighter and less bulky. Some have balancer shafts and that adds weight but they are not rare either. Nev

http://www.skyray.us/engine.htm

Personally I thought 204lbs was heavy, but opinions vary. Also, I vaguely recall looking as an S&S basic motor and that it was around 90kg bare.

 

 

[facthunter]

I think I would rather have a wider angle vee motor if I went that way. You could run it without balancer shafts and less flywheel weight. If you manage a direct drive even less flywheel weight. The Guzzi might be a good base for a light motor.(worked on). I think you should build one from scratch then there is no compromise.. They are pretty simple. nev

 

 

[bexrbetter]

FOUR valved heads have always needed to be liquid cooled to survive really. They get too hot between the exhaust valves. There are exceptions (Speedway engines on alcohol etc)

Have to take you to task on that one Nev, various Japanese motorcycles have been made in the millions with 4 valves and air cooling starting with the Honda XL250 Motorsport of 1972.

 

They were around in the early teens and so were desmodromic valves (1913 Delage ) nev

You were a teenager in 1913?

 

 

[dazza 38]

Have to take you to task on that one Nev, various Japanese motorcycles have been made in the millions with 4 valves and air cooling starting with the Honda XL250 Motorsport of 1972.

 

You were a teenager in 1913?

I have to agree I have owned 3 different Honda air cooled XR motorbikes with RFVC (Radial four valve combustion) . They were fairly bullet proof. Plus valve adjustment was super easy on them with their separate valve caps .

 

 

[M61A1]

I have to agree I have owned 3 different Honda air cooled XR motorbikes with RFVC (Radial four valve combustion) . They were fairly bullet proof. Plus valve adjustment was super easy on them with their separate valve caps .

The early XRs had a lot of problems with cracking between the exhaust valves and the plug hole. I had a lot of trouble finding a head that that wasn't cracked for a rebuild.

 

 

[facthunter]

Thanks M61A1. Just because a few trail bikes didn't crack, doesn't prove that manufacturers over the years didn't have that fundamental problem and to prove the point very few are built today. In the high output area ALL engines are four or more valves and virtually ALL are liquid cooled. Nev

 

 

[Vev]

various Japanese motorcycles have been made in the millions with 4 valves and air cooling starting with the Honda XL250 Motorsport of 1972.Hi Bex,

 

That's very true, but I can recall a couple big failures in the early years of Yamaha move into 4 strokes and the TX500 would have to be leader of the pack.

 

Cheers

 

Vev

[bexrbetter]

The early XRs had a lot of problems with cracking between the exhaust valves and the plug hole. I had a lot of trouble finding a head that that wasn't cracked for a rebuild.

A singular model run had a problem while all the others didn't, as usual in their history Honda pushed and pushed the envelope until they broke and then backed off leaving the owners of that model suffering and the problem wasn't the head, it was the stupid 1.2 litre oil capacity that made them overheat. (Honda was desperate to get the weight down to 2 stroke levels). The owners who weren't vigilant about regualy changing oil and keeping it's level correct suffered . Serious riders fitted a decent oil cooler.

 

XL 250, XL 350's & XL 500s were totally bulletproof and XR 400 & XR600's unkillable and made until the year 2004/2000 respectively and millions of them still getting around today.

 

In the high output area ALL engines are four or more valves and virtually ALL are liquid cooled. Nev

You suddenly changed the goal posts to "high output" to support your argument.

 

Fact; Most motorcycles went to water cooling to meet increasing stringent ride by noise compliance tests and other emmissions requirements. Harley Davidson and Moto Guzzi, who still make a 4 valve air cooled, get a 2dba exemption.

 

Just because a few trail bikes didn't crack,

Not a few Mate, millions of them over a 30 year+ history. Add to that the nature of the way they were ridden as well, ie; thrashed.

 

 

[facthunter]

I always said higher output. Harley do not currently make a 4 valve aircooled motor. They last made them in the 20's and only for racing. Fuelling Rivera made aftermarket heads for the bigger ones some years ago. I get the message Bex. You will argue when you can but terms like" bulletproof", unkillable and thrashed are not too scientific. Most British motorcycle makes, except Norton, experimented with 4 valve heads in the 30's and most of them tried bronze as a head material and then stopped making the four valve after a few years. (RUDGE excepted), who continued with them till the end. The engineering problems encountered are well documented and that is where I get my information from.. I also work with people who are still building drag engines and high performance stuff that is right on the cutting edge.

 

I'm NOT your MATE, and if this is the tone of "put down" discussion you want to indulge in, Let me inform you that I'm not interested in it. Nev

 

 

[geoffreywh]

of course, some of the longer winded models had (have) 5 valves per cyl....

 

 

[facthunter]

That was mainly Yamaha wasn't it? When you "flow" these heads they certainly perform. Haven't they tended to come back to four? Nev

 

 

[geoffreywh]

I'm out of the bike world now so I haven't kept up with develpments.....But the trend has always been bigger, lighter and more powerful.

 

 

[facthunter]

Geoff, you would wonder when enough is enough. You would have no trouble killing yourself on a lot of them. Not safe without traction control (In the wet especially). Nev

 

 

[dazza 38]

The early XRs had a lot of problems with cracking between the exhaust valves and the plug hole. I had a lot of trouble finding a head that that wasn't cracked for a rebuild.

I had a 1983 XR 250 (2nd hand) , a brand new 1986 XR 350 (the last one made) and a brand new 1995 XR250 but I did look after mine. A few mates had them as well without having problems with cracked heads.

But to be fair, I had at the time heard of cracked heads. I had never came across one though.

 

 

[facthunter]

Most alloy heads show cracks with time. You just have to look hard enough. The inserts worry me when the cracks go near the valve as they have then lost their "fit", otherwise you just keep riding them. Don't know about being so 'carefree" with an aero motor. Bit more at stake there. Nev

 

 

[Vev]

Do any of you guys remember the 4 cyl, 32 valve, oval piston, duel conrod Honda NR500 GP bike back in the late 70's... Complexity at its worst but you couldn't help but admire the engineering at the time.

 

 

[facthunter]

It was done to get around some rule or other. Don't think it was doing it for long. Honda try a lot of trick stuff. Some not so useful in the practical sense. Their advertising annoys me sometimes (I must admit) You would think they invented nearly everything a when much of it has been around for years. The French were great innovators in the early 1900s with engines. See if you can Google 1913 Peugeot Race motorcycle. Pretty innovative with design ahead of the metallurgy of the time. Nev

 

 

[Old Koreelah]

Do any of you guys remember the 4 cyl, 32 valve, oval piston, duel conrod Honda NR500 GP bike back in the late 70's... Complexity at its worst but you couldn't help but admire the engineering at the time.

Yes Vev. We diehard four stroke fans thought that bike might finally take the fight to the two strokes. We devoured every rumour about its engineering, but it soon disappeared without a trace. I would love to read a reliable account of its development.

 

 

[Vev]

See if you can Google 1913 Peugeot Race motorcycle. Pretty innovative with design ahead of the metallurgy of the time. Nev

Very cool Nev .. Nothing is new is it.. as you said the metallurgy was more the issue of the day. I seem to recall some backyard motorcycle engine builder developing variable valve timing back in the 50's for their IOM "specials".

All great fun!

 

 

[bexrbetter]

Do any of you guys remember the 4 cyl, 32 valve, oval piston, duel conrod Honda NR500 GP bike back in the late 70's... Complexity at its worst but you couldn't help but admire the engineering at the time.

It raced for 2 years with Freddie Spencer on board, it wasn't quite quick enough but more to the point they tried too much with the monocoque chassis that was hard to sort out.

 

A friend of mine owns one of the 750 road bikes.

 

if this is the tone of "put down" discussion you want to indulge in,

I'm sorry you see being corrected as a put down.

 

I didn't even go near roadbikes such as and especially the Suzuki GSX-R range that blew everything watercooled away for many years and gave huge bulletproof service life to everyone that owned them. Alas, for emissions control they had to go to water cooling for tighter bore clearances to comply with exhaust emissions at cold start up - and they got heavier and slower while doing it and took years to get back to the same weigh and power levels, it's well documented.

 

 

[bexrbetter]

Most British motorcycle makes, .

... are now defunct and with good reason. Ironically they were the ones who taught the Japanese intricate aluminium casting techniques that took the Japanese to where they are today.

 

and then stopped making the four valve after a few years. (RUDGE excepted), .

Rudge actually devloped the radial 4 valve originally although typically Honda claimed they did.

 

 

[Keenaviator]

Alas, for emissions control they had to go to water cooling for tighter bore clearances to comply with exhaust emissions at cold start up - and they got heavier and slower while doing it and took years to get back to the same weigh and power levels, it's well documented.

 

My GSX1250FA is watercooled, fairly large capacity, not terribly powerful (HP) but is very smooth and torquey. It's the nicest bike I've owned and can't get the silly grin off my dial every time I ride it. :)

 

Laurie

 

 

[Vev]

I didn't even go near roadbikes such as and especially the Suzuki GSX-R range that blew everything watercooled away for many years and gave huge bulletproof service life to everyone that owned them. Alas, for emissions control they had to go to water cooling for tighter bore clearances to comply with exhaust emissions at cold start up - and they got heavier and slower while doing it and took years to get back to the same weigh and power levels, it's well documented.

 

Hi Bex.. Wasn't the GSX-R oil/air cooled? The earlier GSX were 100% air cooled if I recall correctly?

 

Cheers

 

Vev

 

 

[Old Koreelah]

My recent introduction to a GSX-R, on a racetrack, toughened me up considerably. Light, nimble and very powerful. They spins so fast that it's said they don't rev, they vibrate!

 

 

[bexrbetter]

Hi Bex.. Wasn't the GSX-R oil/air cooled? The earlier GSX were 100% air cooled if I recall correctly?

Correct and correct, both outstanding models and both very successful in Superbike racing.