Texas Two Step Taco

[Texasstar]

Was lucky running a wasted spark? (is that an induction tach?)
If not then it’s giving you double the RPM.

Awesome! Yes this was on Victoria and we were running wasted spark. Teazer gave us that tach so that is why it is lucky...our redline is 6500 on the Taco so this will work just fine! lol!


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[Texasstar]

So it looks like the Firestone 2.75 by 21.00 Ribbed Firestone is all show and no go. Looks like I need to get rid of this bias...ply! The 2.75 by 21.00 Ribbed Firestone is not speed rated and some bias ply tires are only good for 65 mph. So we have some choices and once again thankful for DTT.


https://www.bikebandit.com/tires-tubes/motorcycle-tires/avon-am6-speedmaster-motorcycle-tire/p/3324

It keeps with the vintage looks and is S rated

However we have learned that we scrubbed speed with a tire like this before when we ran a similar one on Victoria.


I am partial to this because I have AV’s on the Ducati 250. This tire is V rated and is quiet in a straight line.

https://www.jpcycles.com/product/210-230/avon-av71-cobra-mh90-21-front-tire


Maybe y’all have some other choices

The Kenda’s are appeal to my Dutch side because of price and they are H rated.

Trying to stay 80/90 by 21”

One other thing. The stock 21” akront hoop mated to the Bultaco hub is lighter than any other combination we have here around the shop.








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[Texasstar]

That sure looks like a good time to me.
If you would be interested in sketching up the old and new flywheel dimensions, i’d love to get an accurate comparison of the two inertial moments.
Only if you’re interested.

The stock Bultaco Montadero flywheel weighs 8 lbs and is 5.35 inches in diameter and the width is 2.35”

The 6 lbs. lightened flywheel is 5.13” by 1.87”


Lynn Mobley is sending me a Pursang Flywheel that is just over 3 lbs. Those measurements will be interesting.

This

will be fun to test on the dyno and look at the torque curves.

Thank you!


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[teazer]

What about something like this:

http://www.ignitech.cz/en/vyrobky/accessories/magneto/magneto.htm

https://www.electrexworld.co.uk/acatalog/STK-800.html

https://www.ebay.com/itm/Honda-Crf50-Pit-Bike-Outer-Rotor-Ignition-Stator-Magneto-BEATS-INNER-ROTOR-KIT/331263352137?hash=item4d20d59d49:g:BK8AAOSwirZTxrNH:sc:USPSPriorityMailPaddedFlatRateEnvelope!60060!US!-1

https://www.ebay.com/itm/INNER-ROTOR-KIT-CRF-XR-70-Z-50-TAOTAO-BAJA-COOLSTER-SDG-SSR-70-110-125-pit-bike/121142603046?epid=1262044036&hash=item1c34a96d26:g:iKUAAOSwpEdbUWzm

I would guess that similar units from Europe or Japan may be of better quality, but not a lot of sunk cost to try. The other thing you would have to check is the advance curve which you don't want.

Combine the ignitech magneto with an ignitech DCCDI race ignition and program it yourself with built in kill circuit........Or use it to drive an AC CDI black box of your own design.

The curve in that system from Electrexworld looks almost perfect for your application and it looks like PVL components. They have others.

Lots of choices..

 

[Texasstar]

And the winner is....the stock magneto and points or the Nova 2 electronic ignition? https://youtu.be/d9gy8bwiYEs


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[Texasstar]

What about something like this:

http://www.ignitech.cz/en/vyrobky/accessories/magneto/magneto.htm

https://www.electrexworld.co.uk/acatalog/STK-800.html

https://www.ebay.com/itm/Honda-Crf50-Pit-Bike-Outer-Rotor-Ignition-Stator-Magneto-BEATS-INNER-ROTOR-KIT/331263352137?hash=item4d20d59d49:g:BK8AAOSwirZTxrNH:sc:USPSPriorityMailPaddedFlatRateEnvelope!60060!US!-1

https://www.ebay.com/itm/INNER-ROTOR-KIT-CRF-XR-70-Z-50-TAOTAO-BAJA-COOLSTER-SDG-SSR-70-110-125-pit-bike/121142603046?epid=1262044036&hash=item1c34a96d26:g:iKUAAOSwpEdbUWzm

I would guess that similar units from Europe or Japan may be of better quality, but not a lot of sunk cost to try. The other thing you would have to check is the advance curve which you don't want.

Combine the ignitech magneto with an ignitech DCCDI race ignition and program it yourself with built in kill circuit........Or use it to drive an AC CDI black box of your own design.

The curve in that system from Electrexworld looks almost perfect for your application and it looks like PVL components. They have others.

Lots of choices..

Talk to me about launching this Taco with a narrow torque curve. What kind of curve do we need for drag racing?


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[teazer]

If those are your choices, go with stock points. They work. That Nova module is designed for a single magnet system according to one website selling them.

 

[Texasstar]

If those are your choices, go with stock points. They work. That Nova module is designed for a single magnet system according to one website selling them.

I was just tinkering with it for fun wanted to see if it would work...The trials guys use them and an Australian company use to make the Atom https://pickersyard.weebly.com/atom-universal-electronic-ignition-module.html which had 3 different versions with different ignition curves.

I definitely think the stock points won that test. I ordered the CRF50 internal rotor to tinker with. I think paired with the air shifter it will be a fun ride.

Zeke got in the truck after school and said, “Dad guess what I learned about old people like you in Sociology class....People over 50 are bored and seek out new experiences.” I said, “Son only the boring are bored.” Lol


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[Texasstar]

It's possible that the slot is oversize already and if not, a sander will work. All it does is to locate the flywheel.

Are those tires speed rated by any chance?

Called M and H Tires technical support about their drag slick and I was wrong they are not speed rated. They told me that their drag tires are NOT speed rated but that they were the inventor of the Drag tire and we are good on a 1/8th or 1/4 mile....however they are not recommended for Bonneville. Mickey Thompson says that their non speed rated tires are good up to 85mph.


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[Texasstar]

The Bultaco’s will run on timing that is 1mm to 4mm Before TDC. I tinkered with the timing so much that I accidentally started it in reverse. Don’t do that because the Bull will kick you! This test was at 4mm BTCD. Very snappy but the plug came back a little hot. The book says it is suppose to be 3.3-3.5 for the Montadero and 3.00 to 3.25mm for the Bandido. I am pretty sure timing in the Bultaco books are like the pavement markings in Italy...just suggestions. If you read the trials forums they pretty much set them for the throttle response they want.

Interesting note the 360 Pursang is 2.2-2.4 BTDC

https://youtu.be/_gpMAY_kOCQ

I am looking forward to the internal flywheel ignition that is coming next week. Pulling off the flywheel is a pain to set the ignition.

We are taking the Taco to the dyno for the first time to see what we have. I have set the timing back to 3.5 mm BTDC.


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[Texasstar]

Do not buy this gauge to time your Bultaco you can probably get as close by holding up your thumb...

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[Sonreir]

 

[Texasstar]

No need for a buzz box to set your timing on a magneto points system for a Bultaco. You can use a test light and external battery. Disconnect ground and the lead from the coil. Attach ground to battery ground and then attach the test light to the positive. Touch the backside of your points with the test light. When points are closed light lights up and when they are open it is off.
https://youtu.be/KC67Web7Tjk



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[Texasstar]

Yes and who in the heck came up with MM BTDC instead of a degree wheel?


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[Sonreir]

That always confused me about two stroke timing as well. It seems a lot of them use a distance measurement rather than degrees. I never did figure out why.

 

[Texasstar]

That always confused me about two stroke timing as well. It seems a lot of them use a distance measurement rather than degrees. I never did figure out why.

Then try and set something to 3.3 mm with that vernier gauge? Lol!


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[teazer]

And they say that Timing is Everything.....

Just off teh top of my head:

Some motors are very tolerant of ignition timing. As a huge generalization, 2 strokes can stand way more advance at lower revs and smaller throttle openings and need a whole lot less at the top end under load. It comes down to cylinder pressure.

At low revs and small throttle openings there isn't a lot of air entering the cylinder to compress, so pressure is low and so is engine temperature. When it's on the pipe, pressure waves are effectively increasing the compression. Likewise at high revs, the throttle is wide open so it's pulling in more air.

The one situation that is often an issue though is low speed high load, where the amount of air going through the motor is low and it's not on the pipe, but load is high and that raises engine temperature to the point that it detonates.

If a motor is set up with a pipe that resonates at mid revs for good punch out of a corner but has ports that send waves out that work best at high revs, that will potentially make for a more complex timing curve. But if the overall state of tune is relatively low it may have a wide range of timing that work almost as well.

For a drag race motor you want high effective compression ratio. Some of us do that with clever port and pipe designs to stuff more gas in and some of us just raise compression. The former approach will always make more power but isn't always an option.

Motors that don't rev very high such as our old GTs with mild ports, crappy cylinder head design, and no existent pipe design are remarkably tolerant of timing. High revving high HP motors are way more complex.

I'd suggest that you try a few different timings on the dyno to see what makes best HP and torque and use the least amount of advance that still gives good throttle response.

 

[Texasstar]

Why do you think they put more advance into the Montadero and Bandido engines than the rest of the Bultaco line up? Gear drives vs chains crank to clutch?


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[teazer]

I don't know enough about any of teh Bultaco line to make any reasoned response, but why let facts get in the way of a good story....

I'd speculate that it was how they were used, who they were used by. The 360 Montadero was a dual purpose bike that was a development of the Bandido and most likely would be ridden less hard than the race or MX bikes and the extra advance would perk up the mid range and throttle response. It made peak torque at a lowly 5000 rpm, so it was never designed to rev very hard.

The Bandido is a full on MX bike - again a 360 and had a reputation for melting. Much of the blame was placed on the Femsa ignition and poor metallurgy but I have seen no tests of the ignition on a jig or dyno to support those theories.

Neither model lasted very long and it is possible that Bultaco thought that the pointless CDI Femsa was more able to support more advance reliably or they just went too far in pushing peak torque and had too much advance for the motor. It's also possible that they changed the squish design on those motors. Some Bultacos has an offset squish band. The Montadero had a bath tub shaped combustion chamber with two wide squish bands at the sides of the head. Who knows what the squish band thickness was on any of those motors.

That's all based on 5 minutes of Bultaco research and a whole lot of speculation, so take it for what it's worth.

If you have ported that motor and or matched the pipe design, you will probably need less advance than stock even with a higher octane fuel. You have all sorts of scope for a better combustion chamber shape to get the squish band where you ant it in terms of width shape and thickness. Decide on an MSV value you like and design the head to generate that answer. Look at port time are and flow direction as they all impact on trapped volume/effective compression and match the pipe to the ports.

Gear drive would probably be an improvement on chain driven clutches too. In the end, you have what you have, so it's time to optimize that package and start designing a new optimized package for next year.

 

[Texasstar]

I don't know enough about any of teh Bultaco line to make any reasoned response, but why let facts get in the way of a good story....

I'd speculate that it was how they were used, who they were used by. The 360 Montadero was a dual purpose bike that was a development of the Bandido and most likely would be ridden less hard than the race or MX bikes and the extra advance would perk up the mid range and throttle response. It made peak torque at a lowly 5000 rpm, so it was never designed to rev very hard.

The Bandido is a full on MX bike - again a 360 and had a reputation for melting. Much of the blame was placed on the Femsa ignition and poor metallurgy but I have seen no tests of the ignition on a jig or dyno to support those theories.

Neither model lasted very long and it is possible that Bultaco thought that the pointless CDI Femsa was more able to support more advance reliably or they just went too far in pushing peak torque and had too much advance for the motor. It's also possible that they changed the squish design on those motors. Some Bultacos has an offset squish band. The Montadero had a bath tub shaped combustion chamber with two wide squish bands at the sides of the head. Who knows what the squish band thickness was on any of those motors.

That's all based on 5 minutes of Bultaco research and a whole lot of speculation, so take it for what it's worth.

If you have ported that motor and or matched the pipe design, you will probably need less advance than stock even with a higher octane fuel. You have all sorts of scope for a better combustion chamber shape to get the squish band where you ant it in terms of width shape and thickness. Decide on an MSV value you like and design the head to generate that answer. Look at port time are and flow direction as they all impact on trapped volume/effective compression and match the pipe to the ports.

Gear drive would probably be an improvement on chain driven clutches too. In the end, you have what you have, so it's time to optimize that package and start designing a new optimized package for next year.

This is going to be fun! That makes a lot of sense of why you don’t want the timing advanced as much on a two stroke. With the timing advance to 4mm your could hear it pre detonating at the upper end of the rpm range on the pipe. I also learned how a magneto advances timing from this guy https://youtu.be/Iw85e1a8jO4 Australians are amazing. This one has carnal knowledge of his Bultaco


https://www.2strokeworld.com/forum/index.php?topic=29087.0


Zeke and I are starting on making a new swing arm tonight. I have his Mark 2 engine out of his bike and on the bench. It has an extra plug and I have a compression release for it. Reed valve. Will disassemble and post pictures.

I have done nothing to my engine since we got it but change the crank seals. It does NOT like to be started after a good ride. I switched to a 40:1 fuel mixture


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