Five valve heads for dummies ...

[SFMCjohn]

AFAIK none of the 5 valve WRs were street emissions compliant. Yes, some have plates, but mine would be a red sticker bike if it wasn't plated.

... ah, that's interesting ...
maybe the one's I've seen
with CA plates were on the
lines of the XR650s ... DMV'd and grandfathered in
before a certain year ...?

edit: went backed and looked
at a recent BARF WR ad and it was
a plated frame for a WR400 (also a five-valve)
that was for sale ... think the WR400 was kick-only ...?

 

[augustiron]

Yup, wr400 kick only, and has a tough reputation to start. ..

 

[SFMCjohn]

Yup, wr400 kick only, and has a tough reputation to start. ..

... guess I'll have to hold out for
a 1991-1999 Yamaha XTZ 660 Téneré ...
single over head cam, single cyliner, five valve ...

... or an Yamaha XTZ 750 SuperTénéré! arty
four-stroke, parallel twin cylinder, DOHC, 5 valves per cylinder ...

YZE750T Super Ténéré - 1991 Dakar winner and second and third
place, too ...

 

[Junkie]

I have a plated WR450, 5 valve, with magic button, and it's a fun bike, but it's similar to the plated XR650Rs and so on - it was brought in from Texas with "7600" miles on it.

Of course, I'm about to drop a couple grand on an engine/tranny rebuild.

It's an evolution of the engine in the WR400 you linked, but with estart, bigger bore, longer stroke, probably some other things. I believe I could put my top end on a 400 engine but I could be remembering wrong.

 

[SFMCjohn]

... do you run 17 inch wheels on
your WR450 ...?

 

[89fj]

I had a 98 YZ400 with a plate. My brother found it on l.a. craigslist. Really a fun bike but hard to start only after stalling it in the tight stuff. Engine was getting a bit tired. I should have kept it and freshen up the motor.

 

[2strokeYardSale]

Eddie Lawson won the 1986 Daytona 500 on a FZ750 ...

And later won Daytona on the OW01

And later won the Suzuka 8 hour on the factory endurance version.

Only the 750 and 1000 got 5 valve heads. The FZR600, FZR400, and FZR250 had 4 valves.

 

[Eric B]

I'm liking Tenere shots, John.

 

[SFMCjohn]

And later won the Suzuka 8 hour on the factory endurance version.

Only the 750 and 1000 got 5 valve heads. The FZR600, FZR400, and FZR250 had 4 valves.

[YOUTUBE]eQAuy-ZB3hs[/YOUTUBE]

... this video clip is fun ... in
a museum and you can glimpse
the ‘87 works endurance bike
and the ‘86 Daytona FZ behind
the 1990 8 Hour winner ... arty

... be interesting to compare the
bores of the 1000, 750 and 600 ...
Yamaha may have done the math
and figured the 600, 400 and 250
didn’t have enough room ...

Way back when Peugeot was designing
their successful Grand Prix racers
around 1910 they adopted the
double overhead cam so they
could tilt big valves into a hemispherical
combustion chamber on the small bore long
stroke engines of the time ...

3 liter DOHC four valve 1913 Peugeot engine ...
kind of see how offset the cams are for the
valves that would otherwise be too big for the
bore ...

I think Yamaha may have been
able to design a SOHC five-valve for the FZR 600,
but given the complaint about the SOHC 660 Tenere
(low compression, low red line), probably didn’t
make sense ...

... gets us back to the points about
the geometry of the three intake valves
just not being able to work compared to
four valves ...

 

[SFMCjohn]

I'm liking Tenere shots, John.

... Yamaha always made beautiful motorcycles ...

 

[Junkie]

... do you run 17 inch wheels on
your WR450 ...?

Yes, it's a fairly well sorted SM.

Excel rims on Talon hubs
Braking 4pot caliper/Braking 320mm rotor/Brembo 16x18
later YZ250F suspension (sprung/valved for supermoto)

etc

 

[SFMCjohn]

here’s a fun, short, article on five valve heads:

ASK THE MXPERTS: WHAT HAPPENED TO FIVE-VALVE HEADS?

 

[FLH03RIDER]

What about Honda's 8 valves per cylinder and oval pistons for their 4 stroke NR500 and NR750 engines?
I thought that was pretty Wild and innovative!
.

.

​

 

[Enchanter]

I bought an NR750 piston about 20yrs ago. When it comes to NR (not round) pistons, the most challenging thing to manufacture and get to function correctly were the rings. Because of that, I wanted them too. One set of rings were 2x the cost of the piston, and the piston was not cheap. After months and months on back order, I gave up.

 

[SFMCjohn]

the oval piston rings were one of the things I loved about the NR750 ... getting back to Mr Honda's first-principle roots--as I think making (better) oil rings is how he began his amazing career ...

edit: AI haz all the answers--

"Soichiro Honda's early career involved piston rings, as he founded the Tokai Seiki company in 1937 to produce them for Toyota. His initial attempt was unsuccessful due to poor quality, leading him to study metallurgy at the Hamamatsu Industrial Institute to improve his manufacturing process. After succeeding in producing high-quality rings, he secured a contract with Toyota, and later sold his company's remains to Toyota after wartime damage to establish the Honda Technical Research Institute in 1946, paving the way for his famous motorcycle and automobile ventures."​

of course, I have no idea how they make oil rings ... I only know Kawasaki made a lot of bad ones for KLRs ...

 

[Eric B]

I always wanted to see a demo of how they make the oval rings.

 

[flying_hun]

... guess I'll have to hold out for
a 1991-1999 Yamaha XTZ 660 Téneré ...
single over head cam, single cyliner, five valve ...

... or an Yamaha XTZ 750 SuperTénéré! arty
four-stroke, parallel twin cylinder, DOHC, 5 valves per cylinder ...

YZE750T Super Ténéré - 1991 Dakar winner and second and third
place, too ...

You could get one these that were actually sold in the US. I had one.

Next, do a deep dive into the valve train of the CX500. That one's unique.

 

[SFMCjohn]

my old room mate who got me into motorcycle club racing contested the old MuZ Scorpion Cup ... always had a soft spot in my heart for the yellow ones.

will check out the CX500 valve train ... was that a 3 valve/cylinder engine? guess I'll see ...

 

[flying_hun]

my old room mate who got me into motorcycle club racing contested the old MuZ Scorpion Cup ... always had a soft spot in my heart for the yellow ones.

will check out the CX500 valve train ... was that a 3 valve/cylinder engine? guess I'll see ...

Longitudinal v-twin. A watercooled, Japanese, Guzzi, but with an interesting twist to the cylinders/heads. I may be wrong, but IIRC the valves were arrayed radially too.

 

[SFMCjohn]

^^

two intake valves and one exhaust valve per cylinder is what I meant … think the Hawk GT was three valves per cylinder?

will see what I can find out, the CX500 is venerable enough that I should know if it has four valves or three off the top of my head.