Messages

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.   

It's chappy red for sure.  Which year/model are you looking to paint or copy?

It's a beautiful bike and reminds me of a V twin TZ but I don't suppose any parts would cross over even if they were available.

That looks like the skirt has impacted the bottom of the intake port.  Check the barrels to see if there's any damage there and check that there is a generous chamfer on the intake floor.  And wrt the prior post, check for clearance piston to bore.  If it's excessive it may allow the piston to rock too much

What it comes down to is whether there are signs of detonation.  If not, pump gas is sufficient.  I ran the phat trakka at 165-170psi on 91/93 octane with no problems.  In a TZ or TD race motor that gets heat soaked at full power, 100 octane was more than enough to keep it safe.

You can mix two lots of gas with different octane ratings to get something between but it's not a straight average.  Octane rating is simply a measure of resistance to detonation. Higher octane does not equate to more power until the motor is at the limit of detonation.  On a street motor that's rare unless timing or jetting are way off. And if they are, fix it...

Holy cow, that's bat shit crazy.  Would love to see it run though 

That mixture ring looks a little wide - assuming it was a real chop. Harder (cooler) plugs will by design, run cooler and that causes them to look rich. So you could jet with 8's in and the switch to 9s to create a margin of safety.

FYI on TD/TR and TZ's we were usually in the 280 (hot low density) to 320 (colder more dense air).

I found the most critical on a street bike is mid range ridden "softly" to not draw attention,  where most of the running typically is at 1/4 to 1/2 throttle cruising and that's needle and needle jet territory.

IIRC, RD250/350/400 A/c or W/c all had fairly small reeds and cages. The LC250 has decent transfer ports and can make almost as much power as a 350, so you might want to check out YZ85 cages.  They flow more that TZ750 or RZ350. If your motor doesn't need the reed area, don't worry, the reeds only open as far as they need to so you won't lose much low end if any.

very nice.  great choice of exhausts.

What tires did you go with and how do they feel so far?  I think it may be time for me to replace the set of Comp K Metzlers that I fitted just after I bought the bike in 93 or thereabouts.

Nice bike.  How did you adapt the clutch cover to take the water pump?

Those look like Swabrick pipes.  If so be sure to reinforce the stinger to avoid the mufflers falling off. We lost a few that way.

Devcon F is ideal for repairing crankcases on TZ or RD motors when a rod punches a hole in the bottom end to let all the big end rollers out. 

And no sign of it going soft or leaking years later. It's a great product but not for exhaust ports. I went through my stock but didn't find a stock L or MAB set of barrels.

I would try JB Weld 37901  High Temp which is also rated to 1000F and is cheap. They claim it is good for exhaust manifold repairs.

B7?   

ok to warm it up but maybe 10s for when you ring its neck.