Waste of money .....

[koko64]

 

[MonsterHPD]

Not directly Ductati releated, but I think interesting anyway as a reference; in the sept/oct 2019 issue of Race Engine Technology magazine, there is an article about the White Alligator Racing Suzuki pro-stock drag bike, with a 2V Suzuki-based Vance and Hines motor; bore 89 mm / displacement 1851 cc, valve included angle 52°. Valve sizes not disclosed, but with those basic engine dimensions they can't be too far off Duc-relevant valve sizes.

The builder claims a min valve-to-valve clearance of 0.03" / 0.762 mm on overlap. The motor is a dual cam with a cam chain or that "allows for about 5° of relative movement in backlash between the rotating parts" (presumably crank °)

I find this pretty brave for an engine that is revved to to 14000 rpm and claimed safe to 14400 rpm ..... but it seems to work.

[Speeddog]

89mm bore by roughly 74mm stroke.
So M750-ish bore with a really long stroke.
14.4k rpm yikes!

I'm sure quite impressive valve springs, accompanied by a frighteningly large box of end-of-life springs.

0.030" is very close.
Remarkable.

[koko64]

Impressive. Must be Ti valves and tolerances less "than a bee's dick" as we say down here.

The saying, "the correct spec is what let's you sleep at night" applies here

[MonsterHPD]

Impressive. Must be Ti valves and tolerances less "than a bee's dick" as we say down here.

The saying, "the correct spec is what let's you sleep at night" applies here

Interesting. When  lived in Stuttgart I learned a german / schwabian expression, "muckasäckle", referring to the genitals of a male mosqito and meaning an insignificant amount ....
Serms some concepts are similiar across  the world :-)

[koko64]

   

[MonsterHPD]

Well,
I consider myself finished with the porting job, incredible how much time one can waste (?) on something like this. The ports are now about as good as I can make them given my plan and my knowledge. If I have really improved something, only a ride and a trip to the Dyno can tell.

2020-01-15 16.32.39 by torbjörn bergström, on Flickr

2020-01-15 18.05.06 by torbjörn bergström, on Flickr

I will have a pro do the valves and valve seats, then it will all go back together.

Coming back to the clutch, which I will also want to improve before the riding season starts. As I remember the clutch, and the way it looks on the spare parts diagram, it's a perfectly normal clutch (mine has no slip / servo function).  To improve it, I would have started by looking for some stronger springs as a start, but I may be missing something?
 

[pepeducat]

For the cylinder heads it's good but you can "clean" the exhaust side too and for the clutch already puts new springs

[MonsterHPD]

Oh no, no, no   Two broken clutches (large springs in the primary driven gear) which could have ended much much worse. Good idea, lousy engineering and even worse: a factory that won't realize/admit it. They have the same shit in Panigales.

I have a 750 clutch. More grabby, but that can be helped by grinding 10-15 grooves in the steels, in a fan pattern. The 696 clutch also fit (also without the springs).

Coming back to the clutch again.... I've taken the clutch plates out, and just as a couple of years ago when it was slipping badly, the plates look perfect, though I have not measured them.

I did take a look at the clutch basket and primary drive, since earlier I've not thought about it. I suppose this is what you mean, Lars:

2020-01-16 16.35.37 by torbjörn bergström, on Flickr

Presumably, the split hear and springs are there to eliminate backlash / reduce noice?

What happened to your clutches, and are the 750 / 696 clutches a straight swap onto the 800 motor?

Kind regards,
Torbjörn.    

[stopintime]

The dual mass (spring loaded) primary drive gear is known to fail - often with very bad results.

The basket on an 800 is, I assume/probably, as on mine, spring loaded - also a good idea catastrophically executed.

The drive gear pairs from 620, 750, 696 are not made with these springs and a more robust alternative.

[MonsterHPD]

The dual mass (spring loaded) primary drive gear is known to fail - often with very bad results.

The basket on an 800 is, I assume/probably, as on mine, spring loaded - also a good idea catastrophically executed.

The drive gear pairs from 620, 750, 696 are not made with these springs and a more robust alternative.

OK, thank you very much. I'll start the search :-)

[stopintime]

Remember that it's important they stay the original pair (for smooth and quiet meshing), so buy a pair from a trusted seller.

[pepeducat]

You should pass on dry clutch

https://www.youtube.com/playlist?list=PLal9wz_FWVTHV65yMFGch3x3BHBBhLR3V

[MonsterHPD]

I think a dry clutch conversion would a be a bit over the top right now :-)

This clutch from a 696 should do the trick, I hope, from the same motor:

20200118_155803 by torbjörn bergström, on Flickr

Now I just have to figure out how to get the primary gear on the 800 off, seems the I need some kind of a 4-pronged castellated socket ....

[stopintime]

The driven gear (basket) on a table. Roll the drive gear over it. Not completely dry - at least a tiny amount of oil. The sound should be very low, smooth, delicious, soothing, relaxing - making a mechanic happy. Any kind of rubbing, rumbling, resistance could mean they're not a pair.