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When I did a quick check online I don't see a lot of skinny 18" tires.

- Dunlop recommends the TT100/K81.  No sportmax in 18" sizes that would fit
- Avon race tires are no longer available and Roadrider 2 have limited availability and that is possibly old stock.
- Continental have some nice looking ContiAttacks but many sizes are out of stock.  Looks like I could go with a 90 front and 110 rear but they are a lot more $$$ than say a Bridgestone BT46
- Bridgestone BT46 seem to be available in 90/90 and 100/80 front and suitable rears
- Shiko 712 are probably available but not sure I want to go that way.
- Pirelli list a new version of the old Phantom tire we race with decades ago, but no suitable sizes
- Metzler lasertec is available in 110 front and 130 rear which is a bit too wide IMHO

Not sure what else is available.  Looks like many of us are using old tires 

What about for an RZ350? I have a pair of CompK Metzlers 100 front and 120 rear which I fitted in 93 or so and they still work but it's time to treat the old girl to some new rubber.

I have fitted multiple sets of BT45/46 and Shinko 712s to GT750s but need something that sticks to our crappy roads for the RZ

Thoughts, suggestions?

Not exactly the best set up for the street.  If you want to use the RD400 bottom end, keep the 115mm rods, use a lift plate and then work out what changes you need to make to porting to make that all work. 

6 transfers are better than 4, but you could usefully increase the reed area and use even larger carbs if you insist on using that top end. 

I fitted a 409-OO 64MM bore "TZ700" on an RD350 bottom end and it is really mild. For the street it would be best to port it to what you want in terms of port timings to get the time/are that matches how you plan to use it. You can use any of the commercially available software such as Bimotion or MOTA to devise targets and port dimensions to match those targets.

For the street, I think an RZ or Banshee bottom end with Athena 421 or CPI top end would make a lot more power.  You need an RZ transmission though.  Banshee ratios are not the best.

Do you mean a genuine ex works 6 port with reed valves or just any TZ750 top end?  I have an early TZ750A top end on a set of RD350 cases with RD transmission and TZ waterpump and crank.  All TZ750 top ends have the same bolt pattern as an RD250/350/400.

The two holes at the top are rebound damping and most forks came with insufficient damping, so the answer was to fill one with bronze weld.  The Emulator takes care of compression damping, and that requires additional holes at the bottom of the damper rod plus on some forks the top of the damper rod needs to be modified to allow the oil free access to the emulator.

Details on the race-tech site.

Nice looking clutch rebuild.  Had to do that a couple of times on an RD and a couple of TZs which are a little different.

BTW, do not be tempted to clear coat those nice vapor blasted cases. I did that once and they looked like they had been painted and I could have achieved that same look with a 10 buck rattle can. Don't be like me..

When you press it out, check the shape of the O ring groove. It should be a square cross section to allow the round ring to deflect (squish) into the space and allow it to seal.  if the groove is round it won't seal.  Banshee inserts are usually machined correctly.

I have TZ heads with inserts and GT750 head with inserts (domes) and sealing them can be problematic. TZ is easy because it doesn't need a head gasket - just O rings.  the GT is a different story and it uses an oversized gasket that the insert fits through and seals with o rings.  best solution is BDK in the UK who do all O rings.

The second source of leaks is the same issue as here, sealing the insert against the shell of the head.  Stock heads rarely have sufficient material to seal effectively with an O ring round the dome, like that Banshee dome.  That's how Polaris and others used to seal their sled heads. And there's barely enough material to seal on teh top face of the insert against that flat surface, but that's all you have.

The reason they are a press fit in the head is probably to try to seal the head to the cylinder. They should not need to be a press fit in the head shell. Can you tell us what sort of head gasket you are using and what does the top of that insert look like?

Plug chop means chopping the throttle to get a reading that is not masked by riding back to the pits.  It does not involve cutting the plug up.  Buy a cheap plug reader.  It's a loupe with a light. I got a replacement from Summit racing after my last one died from over use.

https://www.summitracing.com/parts/nxo-00-56007

That's the one I got.  It is much better than the one I have used since Pontious was a pilot.

Triples FTW every time.  Except when I'm riding my RZ that is. 

Nothing wrong with a Suzuki or Kawasaki triple.  Well that's not 100% accurate.  I could make a long list of things that could have been improved, but let's not go there.

Twins are just a whole lot less complicated and 2/3rds the cost or less to repair, rebuild or maintain. For street riding, my favorite is my RZ350. It is infinitely (ok so a touch of hyperbole there) better an any air cooled twin I have owned or ridden.  Not as quick or exciting as a TZ but for teh street they are great.

Air cooled kawaskai triples had an evil reputation when they were introduced and that's because the rest of us were riding 30-40hp Brit bike at the time.  All that power wasn't natural and it was too much for mere humans to have to deal with. Now we think that 150-200hp street bikes are fine for learners. If you want a sweet triple try say a KH400 or S2 (350), all the sweetness and none of the nastiness

lapping the two parts is common practice.  Mark is right that if the rotor is not square to the shaft, it might be possible to make things worse, but in practice that's not a problem.

The reason to lap them together is to ensure that both tapers are exactly the same and to identify and remove any high spots caused by say loose key hammering the slot. I like to start with fie valve grinding paste and end with metal polish. With a small amount of oil on the tapers, the two parts should "ring' together and be hard to remove - even without the but on the shaft. The keyway is only there to make it easy to time.  It is not designed to hold the rotor in place.

A few random thoughts:

Anything from Frits is probably good to use.  Blair, Jennings and AG Bell all have a place to start.

For blowdown, 21 degrees is really short and it that;'s correctly measured, would explain the reverse flow in the transfers.  Blowdown time-area is a better way to calculate blowdown and allows you to take the width of the ports into consideration.  A wide exhaust will blowdown faster than a narrow one.

MOTA has a free pipe calculator.  Bimotion has a great pipe design tool but it's not free.It also has their own design plus a Blair design. 2 stroke Wizard also has a cheap pipe designer but the designs seem to be lacking something. MOTA also has a really neat pipe design optimizing tool.  You can just use the formulae and rules of thumb from any of the authors mentioned.

The data in that screenshot is a really low state of tune and if it's correct, a pipe won't make a huge difference. A modestly tuned motor should have a BMEP closer to say 6-7 and hot street would be say 8, though I aim for 10 and see what's actually possible. The higher the BMEP and HP goal, the more the important the pipe is.

For a relatively low port, low power goal, you can go with parallel header and single stage diffuser and save a whole lot of work without leaving much on the table.

   

Those look familiar.  Nice pipes.

Would you believe me if I said no? 

First thing I'm checking now though. It didn't leak before the rebuild so I figured I'd get lucky.

.  Yeah.  Right....

Do a leakdown test and see if you can detect where the leak is coming from before you tear it down. The head is easy to check. Pull the head, clean off any gasket mess left and place it on a dead flat surface.  I use a granite surface plate but a decent old thick mirror works well too. Put a thin smear of bearing blue on the head and press it down on the flat surface. Lift it and see the imprint on the plate.  Anywhere it didn't sit flat will be obvious.
   

Is it possible?  Anything is possible.  maybe an O ring is undersized or split or is out of place, but that's really unusual. If they are aftermarket O rings I guess that's possible.

That could cause a leak into the bottom end and that would be on the serious end of the undesirable scale.