Dave, Mike,
Thanks for your comments. The reason for my plan of going one step further than the DR650 hub +1plate mod is, that I seem to remember reading that when the silent muffler entered the equation, even the DR650+ clutch started to slip.Then again, I am prone to overkill, and the stock clutch is already slipping in an unmodified engine.

I surely don't intend to diss your experiences, you have both been into this game for over a decade, so  I will probably just stick to the stock modification with one plate extra on a DR650 hub, and the DR650 springs.I already have the Sneazy cams ready.

If I do proceed to try these special metal discs, I will have them vater jet cut, or perhaps laser cut, from 3mm thick steel plate. Mount in the lathe in a custom designed chuck and turn each side one millimeter. This may have to be done simultaneously on both sides, to acheive proper parallel faces, with a custom cutting tool, but I am a toolmaker, so not to worry too much about that.

One thing I do not understand, is the function of the so called wave washer. For one, in my book, it is not a wave washer at all, it is a disc spring, and a pretty stiff one at that.
A real wave washer between each of all the metal discs, weak enough to be compressed easilly by the coil springs, but strong enough to separate the discs during clutch disengagement, now, that would make sense, but the disc spring as it is, leaves me with out a clue of what it's function can be.
I seem to recall some talk in the club house of Yamaha Club AArhus, late one evening, back in 1969, about some clutches that had an o-ring between the metal discs, just a tad bigger in diametre than the friction disc thickness, designed to separate the clutch plates during disengagement, but I cannot find them in any spare part catalogue from that time, so It was probably just some idle pondering.

What exactly happens to the clutch function when the wave washer is omitted?

The valve distance I quoted to 28mm was from my rusty memory, it is 38mm of course, and that pretty much limits the maximum valve diameter to 37.5mm. That could bring about a 13% increase in inlet area, perhaps less, since the air entering close to the near overlap
would seem to be working against each other. A flow bench would be needed to find out.

I would like to read some about port flow, seat angles, seat width etc, can anyone recommend a good book to start me off.

Cheers, Finn Hammer

All,

Lots of good advice and well taken it is. Yes, I will stick to the DR650 clutch mod with disc. spring in place, as Suzuki intended all along. (jeez, would I like to pick the brain of that Suzie engineer who thought that disk spring thing out).
The oil pump speedup hardware is almost finished now, I am only waiting for a carbide drill for the holes in the big gear. As mike has already reported, these gears are hard to machine. Case hardened, good stuff.

I have an extra Cylinderhead, now. (Thanks, Dave).
I was amazed to see, that the main factor determining the crooked exhaust port, and the main obstacle in straightening it out, is that the exhaust valves are 8 mm shorter than the inlet valves.
The seating surface of the inlet valves allows a fairly ok port, but the seat of the exhaust valves cannot avoid obstructing the port.
8mm valve stem saved, how utterly pathetic.

One mod down, a lot more to go.

Cheers, Finn Hammer

Mike,

Thanks for your kind words.

I have saved the drawings in PDF format, but I am not sure how to get them across, please advice.

I don't think bigger valves for now, probably next winter.

Cheers, Finn Hammer

Ok, I missed the ZIP possibility, but here they are:

One piece of advice: Don't skimp on the carbide inserts when you turn those wheels. They wear out real fast turning that case hardened stuff. That is normal. stick to 0.04" deep cuts, and go slow.

I mostly always do my work in CAD before touching the lathe controlls, it keeps the failure rate low. I thought for a while that I should offer this mod as a service to interested parties, but nobody wants to do this more than once, I think. It would take some serious tooling to take it up on a regular basis.

Thursday I get the DR650 clutch hub, the springs and also the cam chain guide, looking forward to work on those parts.

I also got David Vizard's book, Port and Flow Test which looks like it is going to be a good read.

Cheers, Finn Hammer

All,

Delivered in a velvet pouch, buy do they know how to talk to us over at Wiseco!
Only slight concern: now that the bore will be enlarged to 96mm, a stock top gasket will protude 0.5mm into the combustion chamber. I think, not a lot, but should I be concerned about it?

Cheers, Finn Hammer

Dave,

And you did a beautifull job resurfacing those heads. Looks like you opened up for bigger inlet valves too.

Cheers, Finn Hammer

Reading through the many pages about this wonderfull little bike, even the ideal diametre of the exhaust header is covered. 45mm/1.75" outside diameter pipe gives 1.65"/42mm inside diametre.
I feel there is no way around using that exact dimension, even though I am going to use a 94mm piston. (Yes, I know, I just showed a 96mm Wiseco piston, but just at the same moment I came to realize that for one, that piston would be low on compression, it would also not have any squish area, which I believe is the direct way to low end grunt).
So I purchased a 94mm flat top Wiseco (well, dished top, really). But with the 10.5:1 compression ratio and squish area.
But back to the exhaust header.
Getting that thing mandrel bent here in Denmark is possible, but probably not in single numbers, so I have been looking to get a 180deg. part with the correct centerline diametre. This is not easy, but whereas the stock header is bent in a 210mm cenderline diametre, I managed to get a part bent to a 169mm centreline.
Question, will this look ok?
Hard to say before the parts arrive and I can get them welded together, this is what It looks like in drawing, perhaps a bit whimpy, but then, better look whimpy than be whimpy.
Blue is the stock header, black outline is the one I intend to manufacture

"better look whimpy than be whimpy"  

I agree Finn.  However, I doubt that it will look whimpy.  Given the work that you have already presented, I bet it will look great.

You will not be disappointed with that 94mm flat-top.  It runs great.  Makes excellent power and the fuel economy is off the hook.  Can't wait to hear how it runs with that 1.6" header.

FYI, you can also get that flat-top design in a 97mm.