Oddball engines and prototypes

[J.A.W.]

Is he using a staggered crank pin on the twin, to use the inertia torque, or is he gonna let it shake..

Hirth do a lovely compact 1 litre 2T triple, softly tuned at 100hp, & warranty the crank as good for a 1000hr TBO at 70% continous..
..it 'd make a great project bike mill..

[husaberg]

A very interesting article on the DB inverted V!

The Hirth two stroke is interesting too - "FLETTNER" in the other thread (bucket foundry) is working on what could quite possibly become a worthy competitor - it is a 750cc parallel twin two stroke, already working in other areas, (trying many other experimental projects as well).

He has a triple as well Will.

[WilDun]

Is he using a staggered crank pin on the twin, to use the inertia torque, or is he gonna let it shake..

Hirth do a lovely compact 1 litre 2T triple, softly tuned at 100hp, & warranty the crank as good for a 1000hr TBO at 70% continous..
..it 'd make a great project bike mill..

It doesn't shake at all, he has designed very effective balance shafts into it also an integral reduction box (for aircraft) and I think he's toying with the idea of a bike - however I think I should let him do the comments - he may choose to this when he looks in here now and then. - I don't want to say the wrong things and I don't know enough to comment any more really!

Yes Husa, he has a triple as well but that seems to be on the backburner.

[husaberg]

Yes Husa, he has a triple as well but that seems to be on the backburner.

He has many irons in the fire.
The triple is pretty much exactly the same as the twin with an extra pot

Yep, I said it and Jan may have said it too.

They were sand castings, pretty much identical to their racing engines. In fact the whole construction was, except that after the first version the racers got a chain transmission while the street version kept the original cardan shaft.
The crankshaft was bolted with saddles to the underside of the cylinder block that doubled as a lid on the big empty space of the crankcase. The gearbox was fitted from the side.
I tested the MV 750 S America-version in 1976 or so, together with the then-new Suzuki GS750 four-cylinder four-stroke. The Suzuki was at least twice as good in all respects and it cost half the price of the MV.

The works Benelli was a side loader as well.
With it seems a similar crank location they had some clever fly wheels.I think they were able to side load the entire crank assembly girdle by popping the sump and removable side plates
They actually by co-incidence borrowed a 250 Honda Multi at the time they did the four valve heads.

I always thought one of the cleverest things with the Britten was how they could change the crank or rods or pistons or gearbox by poping the bike on is back wheel and simply removing the sump.

[J.A.W.]

It doesn't shake at all, he has designed very effective balance shafts

"Shafts".. plural? Oh dear.. seriously though, no doubt he's put a bit of thought into it.. (albeit Manolis would not approve of such paliatives..)

Have a squiz at the Olds synchronous/synergistic 2T triple design ( scroll down the linked page - below, to find it)

http://blog.hemmings.com/index.php/2...stroke-diesel/

There was an earlier Roberts 2T mill that ran a rotating scavenge scroll/transfer drum arrangement that used the 120`sequential blow-down, AFAIR, too.

[WilDun]

"Shafts".. plural? Oh dear.. seriously though, no doubt he's put a bit of thought into it.. (Manolis would not approve..)

Don't quote me on that! - all I know is that the arrangement he uses is very successful - and yes , he doesn't only put a lot of thought into everything, he actually gets off his ass and does it, making most of us look silly!

[J.A.W.]

For sure..

This beasty triple could likely do with rocking couple - nullification bobs - incorporated into the PTO/jackshaft..

http://www.4x4tuff.com/ctsme8.html

[Grumph]

Was that before or after Britten tried the 5 valve heads as well.

After - John was not long dead at that point so i had the Britten boys on that they were in the business of building replicas for sale as there was a known ban on further development....
When John first showed off a 5 valve head, it was at a film night at Budget where he talked about his Daytona trip. He passed the incomplete 5 valve head around for comment. Afterward he approached me for comment so after i'd admired Rob Selby's machining skills, I asked if he had any idea of the advance curve required. I then told him to go to Tommy's yamaha and look on the fische where he could see for himself it was going to be a hard one to copy using a chainsaw magneto....AFAIK no one from the team ever bothered to look at how yamaha had done it....

I asked a couple of the riders who'd ridden the 5 valve engine and they both said it was flat in the middle compared to the 4V - and not noticeably better up top.

[husaberg]

After - John was not long dead at that point so i had the Britten boys on that they were in the business of building replicas for sale as there was a known ban on further development....
When John first showed off a 5 valve head, it was at a film night at Budget where he talked about his Daytona trip. He passed the incomplete 5 valve head around for comment. Afterward he approached me for comment so after i'd admired Rob Selby's machining skills, I asked if he had any idea of the advance curve required. I then told him to go to Tommy's yamaha and look on the fische where he could see for himself it was going to be a hard one to copy using a chainsaw magneto....AFAIK no one from the team ever bothered to look at how yamaha had done it....

I asked a couple of the riders who'd ridden the 5 valve engine and they both said it was flat in the middle compared to the 4V - and not noticeably better up top.

I have to fess up I actually passed on to John all the Cameron stuff he had initially wrote about it and the seven valve as well.
Cameron was particularly glowing of it (initially) but that was with a low comp. Once you raise the comp in those 5v it gets real silly really fast. (or slow as it turns out)
you can't have a decent comp or decent combustion its one or the other.
I never actually seen how they did the valve gear for it but guess they copied the Yam set up as well did they.
Anyway it goes to show just how clever Keith Duckworth was getting it right bang on in the first place.

[J.A.W.]

F1 is currently specfically rules limited to 4 poppet valves.. so there may be something.. in it..

Does Yamaha still use the 5-valve set-up - on their larger cylinder machines?

They did offer (valve clearance check-wise) - a fairly long service interval - on the old FZ's..

[husaberg]

F1 is specfically rules limited to 4 valves..

Does Yamaha still use the 5-valve set-up - on their larger cylinder machines?

They did offer (valve clearance check-wise) - a fairly long service interval - on the old FZ's

They gave up on it for real stuff a few years ago, they held onto it longer than they should have, corporate pride I think

[J.A.W.]

They gave up on it for real stuff a few years ago, they held onto it longer than they should have, corporate pride I think

Real stuff?

You mean for the flagship M1/R1.. as a racebike..

But for regular workaday stuff like adventure bikes, have they dropped it there - too?

[husaberg]

Real stuff?

You mean for the flagship M1/R1.. as a racebike..

But for regular workaday stuff like adventure bikes, have they dropped it there - too?

Not sure with all the stuff but the sporting stuff yes they all went 4V.
There might be some model runs still going i'm not really a Yam Guy.
the yzf450 lost them when it went back to front from memory.

[J.A.W.]

Not sure with all the stuff but the sporting stuff yes they all went 4V.
There might be some model runs still going i'm not really a Yam Guy.

Apart from the big FZR-to-R7/1 lines - what other "sporting stuff" used the 5 valves?
Anything smaller cyl-wise - than the FZ 750/4?
Don't think the 600/4s - ever did..

[husaberg]

Apart from the big FZR-to-R7/1 lines - what other "sporting stuff" used the 5 valves?
Anything smaller cyl-wise - than the FZ 750/4?
Don't think the 600/4s - ever did..

FZR750 1000 and early R1
The TRX850 TDM series
The XTZ series
the YZF's
Off the top of my head but as I said I am no Yamaha guy