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Have someone build new wheels, using your stock hubs, new rims and spokes. Not cheap, but finding good oem wheels at a low price would be extremely difficult. I have used Hagon's and Central Wheel (CWC) in the UK. I am sure there are other companies in the US and continental Europe.

nope. i checked the disc thru the window in the crankcase  and didnt see any damage. I agree, def metal. Id swear it was a 2-3mm ball bearing by the marks it left,  but there's nothing that size in the crankcase or intake. its a fkn mystery as to what it actually is. i mean, i'll find it. one way or another. 

Are there any check valve balls in a separate lube system?

Does anyone know how much lower/ thinner the 1973 RD350 seat foam was, compared to the 74 and 75? I think the lower/ thinner seat just looks so much better.

When I read the dimension table, it appears that the belly section diameter is around 150 mm. This is way more than normal. I'd say somewhere between 90 and 110 mm seems more appropriate for a 185 cc single. In AG Bells book, the belly should be around 2.5 times header diameter, max. That would be the header diameter next to the port if using a tapered header.

The 60's and 70's design formulas like Bells have been left behind a long time ago. Much larger belly diameters are common now as is bigger stingers and stinger length considerations.

I still believe 150 mm is extreme. What is the largest diameter on a "FMF Fatty" pipe for a 250 MXer? I seriously doubt it is much over 120/127 mm (5 inches). And just the packaging aspect of finding space for a 150 mm belly section would be a serious challenge.

Extra question:
Why didnt RD's have a mechanical advance?
It is odd to me that the spec for 400 is farther advanced than 350. Maybe someone can explain this to me. Thx!

2 strokes actually need the timing to be retarded as revs increase, so opposite of 4 strokes. Modern electronic 2 stroke ignitions do this. However, a mechanical regarding mechanism may not have justified the added cost. So constant timing it was.

As for the difference between 350 and 400, this is due to the longer 62 mm stroke vs the 350's 54 mm stroke. Converted to degrees BTDC, it becomes pretty much the same.

When I read the dimension table, it appears that the belly section diameter is around 150 mm. This is way more than normal. I'd say somewhere between 90 and 110 mm seems more appropriate for a 185 cc single. In AG Bells book, the belly should be around 2.5 times header diameter, max. That would be the header diameter next to the port if using a tapered header.

Hi,
I have mentioned in earlier posts that I am less than happy with a pair of stainless Higgspeed exhausts I got for my RD350A. One of my complaints are the apparently oversized headpipes, which I would like to taper.
The straight header section, approx 120 mm from exhaust port is quite straightforward to fix, either by machining tapered sections from thick wall SS hydraulic tubing, or by cutting out a wedge, squeeze the pipe shut over a tapered mandrel, and re-weld.
The bent part is where I may encounter problems. Making pie cut sections of a straight tapered pipe is one way, hydroforming a new section is another, and cutting out a wedge, like described for the straight section is the third.
Any suggestions or recommendations on what would be the easiest way? The taper will be quite moderate, maybe 1 degree. Note that the material will be SS, so not the easiest to hydroform I guess....

Some of you may be familiar with older European 2-strokes, but for those who are not, Zundapp was one of the most highly regarded brands, until the late 70s at least. A Zundapp 50 was sort of the tiddler equivalent of a BMW 900 or 1000.
So check this out:

https://www.facebook.com/andisfunktionspunk/videos/1408224216416402/

130 km/h (81 mph) 😁

hell yeah. looks great. where did the cone design come from/get calculated?  the fab looks fantastic. love the hanger bolt method.

Thanks.  They are clones of the Vanguard pipes.  Manifolds and the silencers are mine.

I wonder why the diffuser cone is made from 2 sections? On the pictures both sections appear to have the same angle, and I cannot see any bend either. Just limitations with regards to roller width, or am I missing something here? In any case impressive work!!

They do look great  

Agree! I really like how tightly they are tucked under the engine. I really dislike a huge air gap between chambers and engine/ frame.

I have to ask: why the vanguards and not something like specII's? (for example) i didn't think they (vanguards) made good power. the craftsmanship is pretty amazing though, well done indeed.

Mark,
The dyno sheet on the Vangurd site shown 43 hp with stock porting, and at pretty low revs. A totally stock 350 would not be much over 30 hp on a dyno, I believe. So how much more power would a set of Spec 2 or JL give on stock porting?

full plans/specs here

https://vanguardcycles.wordpress.com/2010/10/01/how-the-vanguard-v1s-are-made/

The dyno curve indicates that these should be excellent street pipes, that do not push peak power rpm too high for reliability/ longevity. At least that is how I interpret it. But how do they compare with for example JL and Spec 2 below 5500 rpm?

they showed up at work like 40 mins ago. lol.

they are the basic street tune pipes, the only ones i was able to find where i didnt have to mod the body work. thats was a non-starter for me. they are however 18 lbs lighter than the stockers.

That's an impressive weight reduction. A Yamaha twin or Kawasaki triple?

FWIW, the stock LC gear lever and linkage is not really a good design. The "arm" for the linkage on the pedal is VERY short, and I assume the arm on the shaft is fairly short as well. This leverage ratio will exaggerate any slop in the heim joints, and cause higher loads/ more friction at the pivot and the shaft. So it should not really be a surprise that shifting is less than perfect after 40 plus years. Still, the already mentioned adjustment may well be required.

So, what does this actually do to improve things?

If you mean adding emulators, it apparently enables you to adjust compression damping (with the little spring tension), and rebound damping (with oil weight) individually. I say 'apparently' because I don't have any experience with them. But if Mark says they work, I'm all in 

It's more to it than that. The compression damping curve is improved, i.e higher low speed damping forces, and lower high speed damping forces. This cannot be achieved with the stock (or even modified) fixed orifices