Texas Two Step Taco

Good story, but mine came as two wheels, a frame and swingarm and forks. I bought it from a guy in MI and he got it from another guy in MI who bought it to put the motor into a hill climber or some such. I never did work out who built or raced it.

I bought s set of RD crankcases and RD400 transmission and dropped a TZ crank, and top end on it and made the back end of the frame from chrome moly. I bought a set of cones and welded up the exhaust and put on a spare set of TZ carbs and a spare Motoplat ignition, rebuilt the wheels etc. The tank and side covers are one piece carbon fiber which I made and cover a 1 gallon alloy tank that I also had to design and make.

It is very possible that it came from Alvin. The guy I bought it from is a fantastic welder and fabricator and races H2s. He showed me pictures of another RD350 which looked much more stock than mine. There's nothing very trick on my bike.

Picture one was back in the day. Pic 2 is now and picture 3 is the other bike I mentioned. His pipes are way better than my crappy welding and sectioning. I suspect he had access to a water jet or laser cutting tool to get all those sections.

There was one on ebay in march 2018 that had a first year TZ350 top end. That's picture 4.

Mine has a TZ700 (TZ750A/B - 409-00) top end. I would like to replace that with an RD400 top end with lift plate and Banshee +10mm stroker crank but I need to find a way to start printing money and take care of some other bills before I let that idea get out of hand. Maybe just get an OW31 6 port reed motor for a small fortune or get large reed boxes welded to a 3G3 6port set of barrels. Too many ideas and never enough time or cash
 

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BTW, you know that I got 52 rear wheel HP from a street RD350 last year for a client, so your full race Bultaco has to make more than that. The two are very different designs and the over square single cylinder won't make that easy, but it should be possible with enough port area.

What size is BBB's H2 motor? It must just be like three of your cylinders plus a touch of technology and years of development. Yes?
 
teazer said:
BTW, you know that I got 52 rear wheel HP from a street RD350 last year for a client, so your full race Bultaco has to make more than that. The two are very different designs and the over square single cylinder won't make that easy, but it should be possible with enough port area.

What size is BBB's H2 motor? It must just be like three of your cylinders plus a touch of technology and years of development. Yes?
Click to expand...

Dang! I will ask BB if Alvin raced H2’s. You and BB are a lot alike as far as not having anything “very trick” on your bikes.


His Pistons are only 70 mm something and his stroke is close to the Bultaco at 63. He is actually way less CC wise as the Taco is 86 by 64.

BB’s Whp was in the 50’s per cylinder for the longest time but is now way north of that. He tinkers. Nobody does more dynopulls. Just ask his neighbors lol!

Love the pictures and your RD350 is beautiful! Look forward to seeing it one day!


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Adjustments.jpg
Adjustments.jpg


BIll Baxter says, “Nothing is more motivating than success and nothing is more instructive than failure"

Speaking of nice welding...so we pulled the wristpin and it was a bugger. BB introduced me to a wristpin puller. Doug wanted us to get up close and personal where the pins were on the piston. So Doug said that once the piston rings fused the engine lost all lubrication because all the rings became oil scrapers removing all lubrication from the cylinder walls. I can now see why the lower ring needs more ring gap than the top as you can see my nice welds circled.

We also learned that this piston is a wossner design that was built to Hugh’s Bultaco specification. Good design and light.

BTW I hope you saw the Presidents press conference yesterday and all two strokes drag racers are being Quarantined in Ovilla Texas I hope you comply with the state of emergency. Big Words. Brand new 1/8 mile track a stone throw away. I was telling BB we need you around as a voice of many reasons.


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Here is why the Yamaha 760 96-97 1200 wave runner piston won’t work in the Bultaco.

Piston to deck is plus 6mm but we were planning on making a spacer.

The locator pins for the rings are in the wrong place and after comparing it to the Wossner copy we are going to back to the drawing board.
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Interesting that the piston looks worst where you circled it. That's a classic 4 corners "cold" seizure that got worse.

Those ring pegs are less than perfect but they are close to the center of each boost port and that might work. Just use a slightly larger chamfer on the top edge to allow the ends to squeeze back into place. They are best in a part of the barrel that has them fully supported, of course. Worst case is the gap right at the edge of a port leaving a long section of ring flapping in the breeze. There is more unsupported ring at the bottom of the port at BDC than I'd like, but it might work. Just carefully grind the bottom (protruding) face of those locating pins and drill it for new pins where you want them.

Pity you don't have a spare barrel to knock all the fins off. That would let it heat up and expand faster. You could always cast a new cylinder with vestigial fins and nickle plated bores. That would make a huge difference. Engines make more power when cold, but perhaps it might be necessary to warm yours up more before it undergoes the thermal stress of a run.

Does that Wiseco box say .005 clearance for a water cooled application? That gives you some idea of what your application might need and it's going to be a big number.
 
Yes that is what the instructions say on the inside. BB let me borrow a bore gauge and I have a set of micrometers to check piston to wall clearance. Rattling on...
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Measured piston to wall clearance using my micrometer and bore gauges.

My bore is now 86.08mm
Adjustments.jpg

The Hughes piston we stuck like chuck measures 85.95 mm 1” from the bottom of the skirt 90 degrees to the pin.

Making piston to wall clearance .005” or .130 mm

What was interesting is the new Yamaha 1200 wave runner piston had the exact piston skirt measurement of 85.95mm


Going over to my friends race shop who builds engines and use his expensive calibrated instruments to see how close I came and see if I get to keep my YouTube motorcycle mechanic patch.

If I am a betting man then Doug bored it originally according to the box which was .003”


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The Yamaha piston alone weighs 100 grams more than our Pro Lite Wiseco so that is another strike against this piston.

BB said they start with .0035” piston to wall clearance and when it starts getting rattley at .006-7 they replace. So that gives as a good idea on their tolerance.

As Teazer said our piston to wall is going to be a big number.






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Texasstar said:
Moonshine! One of our all time favorite memories with you my friend!


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I have no recollection of which you speak :P
There's no real Moonshine makers around here, but I'll see what I can find ;)
PM me a shipping addy.
 
Here is what we found. The Hugh’s Bultaco Piston measured 3.3834” or 85.94mm. Our piston to wall clearance after honing and brushing is .0069” I have include pictures of various measurement of piston to wall clearance. Starting top of the cylinder
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The data for the piston to wall clearance of the Bultaco cylinder after honing and brush.
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For grins we put up the cheap Chinese bore gauge (left) against the 800 buck digital right
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BB's cheap Chinese FTW.

That's a lot of variation for a low mileage bore. Hmm. Maybe the barrel distorted when everything got hot.

Any idea if those Wossner style pistons shrink after a few runs? TZ pistons used to do that, but they were cast.
 
teazer said:
BB's cheap Chinese FTW.

That's a lot of variation for a low mileage bore. Hmm. Maybe the barrel distorted when everything got hot.

Any idea if those Wossner style pistons shrink after a few runs? TZ pistons used to do that, but they were cast.
Click to expand...

There were 10 heat cycles and 2 runs. I have been given a better contact at Wiseco and will give him a call this week.

I am going to set up the bore gauge and clock the cylinder tomorrow through out the bore. Will post our video of what we did today for observation.


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