Texas Two Step Taco

Texasstar

Can't is a four letter dirty word
Data is good. Now to put that back into context, a high performance two stroke should have a BSFC around say .65 or half the number I used earlier for that simple illustration, so it should burn through 32.5 pounds per hour or around .5 pounds per minute. That's more or less 225cc per minute, so it looks like you have more than enough flow under any of those conditions - cap on or off, but get rid of the filter.

Race fuel is much cleaner than street gas and I'm sure you use a clean ratio rite or Accu-Mix jug and a clean filler funnel.

That leaves us electrics and or jetting. I think I covered both of those, but I am more inclined to think that it's a sticky switch or maybe a thumb stuck on a switch perhaps.
I am all thumbs lol


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Texasstar

Can't is a four letter dirty word
I ordered a pingel momentary switch to replace the 9 buck one off Amazon with a 3 1/2 star rating. ;)


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Texasstar

Can't is a four letter dirty word
Little side note. The clutch has been holding for 3 passes! Remember our little bearing problem in the clutch basket? It was pushing out of the basket? Well a fellow Bultaco friend has a service manual for the Bandido and sent me a note. The bearing in the clutch basket is suppose to be 15mm wide but both of the clutch baskets I have the bearings are 14mm wide.


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teazer

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It's a process of elimination and it just takes time to get everything working just so. On our first few runs with the Yamaha I couldn't work out why we had a similar problem and so I just swapped out the whole air/electric kill switch. When I got home I tested it and it was just a sticky switch. No idea why but after cycling it a few times, it seemed OK, but not work the risk, so I bought a couple of spare switches and threw the old one away. For 13 bucks, it's not worth it to hang on to crap.

With push buttons, some cheap ones work fine and some are too sticky and the button is too low to hit repeatedly, or it sticks ON for a moment too long. I have some MPS buttons and the mounts are big and ugly, but they work all the time every time. One problem at a time.
 

Texasstar

Can't is a four letter dirty word
It's a process of elimination and it just takes time to get everything working just so. On our first few runs with the Yamaha I couldn't work out why we had a similar problem and so I just swapped out the whole air/electric kill switch. When I got home I tested it and it was just a sticky switch. No idea why but after cycling it a few times, it seemed OK, but not work the risk, so I bought a couple of spare switches and threw the old one away. For 13 bucks, it's not worth it to hang on to crap.

With push buttons, some cheap ones work fine and some are too sticky and the button is too low to hit repeatedly, or it sticks ON for a moment too long. I have some MPS buttons and the mounts are big and ugly, but they work all the time every time. One problem at a time.
I looked at the MPS but they were ugly. I have a pingel deadman switch and it works every time. The airshifter is pingel so I am sure they will be compatible.

Joseph is trying to talk me into methanol. I am almost out of c12 and we are ready to rejet for the u4.4 I have. Btw BB goes to the mancup this weekend to go after the 7.77 record. Fuel injected with a new dry clutch. It is only money ;)


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teazer

Over 1,000 Posts
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We ran road race bikes on Methanol is Australia and it has some huge advantages. It will make around 17% more power when you increase jetting by a factor of 2.3 IIRC so if you have say 300 main jet now you will be using around 700 main jet with methanol. You will need a much larger float valve, needle jet and skinny needles. I used to copy AMAL Z (alcohol) profile onto Keihin needles when I set up CB77s with CB750 carbs.

Beacuse you jet so rich and it has takes a lot of heat to vaporize, it keeps a motor cool. And it is rich tolerant, so a little too rich, no difference.

It does have a few minor annoying disadvantages though. It can be hard to fire up on a cold morning. It burns with a colorless flame, so when the bike catches fire you can't see the flames until the bike itself is burning oh and it's poisonous. It can be absorbed through skin as well as through breathing it. With a nice rich mixture, the unburned methanol in the air can literally bring you to tears.

But for HP it can't be beat.

But why go to methanol when E85 is available and contains 85% ethanol which, as a fuel, is very similar to methanol in many ways...... But to get the most out of any alcohol fuel you need a lot of compression compared to gasoline. 14 or 15 to one or more will work.
 

Texasstar

Can't is a four letter dirty word
We ran road race bikes on Methanol is Australia and it has some huge advantages. It will make around 17% more power when you increase jetting by a factor of 2.3 IIRC so if you have say 300 main jet now you will be using around 700 main jet with methanol. You will need a much larger float valve, needle jet and skinny needles. I used to copy AMAL Z (alcohol) profile onto Keihin needles when I set up CB77s with CB750 carbs.

Beacuse you jet so rich and it has takes a lot of heat to vaporize, it keeps a motor cool. And it is rich tolerant, so a little too rich, no difference.

It does have a few minor annoying disadvantages though. It can be hard to fire up on a cold morning. It burns with a colorless flame, so when the bike catches fire you can't see the flames until the bike itself is burning oh and it's poisonous. It can be absorbed through skin as well as through breathing it. With a nice rich mixture, the unburned methanol in the air can literally bring you to tears.

But for HP it can't be beat.

But why go to methanol when E85 is available and contains 85% ethanol which, as a fuel, is very similar to methanol in many ways...... But to get the most out of any alcohol fuel you need a lot of compression compared to gasoline. 14 or 15 to one or more will work.
Zeke asked me the same question. Why aren’t we running E85? It’s my kinda fuel! It’s cheap! We are 14:1.

Is the prep the same as methanol?


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teazer

Over 1,000 Posts
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In principle yes, but check the lower heating value compared to gasoline and the stoichiometric ratio to work out how much to increase jetting. Jet up by 40% for E85 and leave timing alone to start with. It should run ok on the same compression ratio as now.

Try it on the dyno and see. You may need a slightly larger pilot jet and needle jet. start at 35% increase in flow and work from there.

Why did I say 40% on main and 35% on others? In theory the increase you need is 34% - or so I read - so I play safe on the main jet which is where you will be running. You can jet down as you get closer to max power/torque.

You could get a knock detector and conditioner with LED to watch on the dyno just to be safe. http://www.ms2tuning.com/products.html plus https://www.walmart.com/ip/HQRP-Kno...=sem&msclkid=05b45fa884e71370b0ac001d14457755
 

Texasstar

Can't is a four letter dirty word
The motorcycle parts distributor Western power sports is about 5 miles away and I typically get parts delivered to my door in a day. This is a Shinko 712 110/90-18 tire. Weighs 11.2 lbs. Many big bikes use the Shinko hook up. Zeke has taught me how to read the stamp on the tire and this is a 2020 tire. The review said it was a soft compound tire. At 55 dollars on amazon we will give it a try. This is a rear tire but we can go to a front tires should be lighter. We can test 3 of these tires to 1 slick. I chose this tire because it is 25.7” in diameter and our current slick is 26.6”
IMG_1405.jpg



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Texasstar

Can't is a four letter dirty word
The rear wheel.

When I hung the bike from the trolley the rear brake was dragging bad and the wheel was not rolling free. I had used a bolt hole that was for mounting a brake rotor mud guard as a stay bolt. That stay was putting the brake in a bind. The original design had the stay floating but there was a notch coming out of the swing arm. As soon as I removed the bolt the wheel spun freely. After removing the bolt Zeke still thought it was the bearings so I removed the brake and mounted the wheel with a spacer and torqued it down and it spun freely. Bb is right with an 1/8 mile run out on this track you don’t need a brake but I want one in case I’d a wheelie. We really don’t need the wheelie bars either and that saves 10 lbs.


We were running 15/45 sprockets. When I changes to a 13 tooth front sprocket last time we picked up .3 in our 60’ so I am changing to 13/45 for our next runs. We had 2.16’ in 60’


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Texasstar

Can't is a four letter dirty word
Here are Zeke’s times on his 900ss and my one time slip from last Sunday
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Texasstar

Can't is a four letter dirty word
-1.4 lbs off the rotational mass. Brake drag is fixed. 13/45 gearing. 1” clearance beneath the chamber to the ground. Waiting on UPS.
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Texasstar

Can't is a four letter dirty word
Teazer,
I have the 708 pingel air shifter. The directions say the hose to the air cylinder needs to be 8-14 inches, mine is 12. The hose running from the same t fitting to the cut off box needs to be 6” longer that tree hose to the shift cylinder. It gave no maximum length so mine is 19” long.

Will this effect the shift kill time? I thought I read somewhere that it may but I can’t find it.

On the MPS unit that looks exactly the same as the pingel unit it says you can drill out the hole to shorten the shift kill time.




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teazer

Over 1,000 Posts
DTT BOTM WINNER
Rear end is much lighter so that's good.
Zeke's times are not far from mine on the Phat Trakka. Don't encourage him to practice, because those times have room for improvement...
Your time slip is interesting. I compared that to our RZ350 and the 60' is similar but speed at the 1/8 is significantly lower and it's almost a second slower for the 1/8th and that talks to power. I only had the RZ on a dyno once and that was years ago, but it made about 56 at the rear wheel IIRC.

It's unlikely that the Bul will make that much power, but I would have expected a slightly higher speed and lower ET, so there's some more work to be done there over the winter.

I hadn't really thought through the shift timing before, but here's today's thoughts:
I use the same Pingel switch on the RD350. In theory at least, it's air pressure that activates the ram and kill switch, and whatever speed it travels at, a longer tube will always take longer for that pulse to reach the other end. For us mere mortals, that seems like it's instantaneous, but it does take time - albeit not a lot. at say 1000 ft per second in cool air, that pulse will take 1/1000 of a second to travel 1 foot and 2/1000 sec to travel 2 feet. Doesn't sound like a huge difference if the kill switch kills ignition for say 50 milliseconds which is 50/1,000 sec.

But that's the time the ignition remains off to allow the shift to complete and will all that heavy metal to move, that sounds reasonable.

The idea behind a shorter run to the ram is that you want it to start moving before the kill happens. So the air pulse travels to the ram which reacts and starts to move and take up slack in the linkages. If the ram is attached a long way from the shift shaft, it will have to travel further to make a shift and if the ram is attached closer to the shift shaft (shorter lever so less leverage but also less distance to move) it will start to move the shift mechanism earlier.

Our old fashioned shifters have a lot of movement from the shift mechanism (claws/pawls etc) to play between the shift forks and the rails and shift forks to the gears and the distance the gear have to move. And that's before the gears start to move. All that mechanical mayhem takes time, so we need to initiate the mechanical part as far ahead of the kill as possible. There's work to be done and it takes time.

So mount the solenoid as close to the ram as possible even if the gear shift has very little latency.

OR... Fit what is known as a window switch that will shift automatically at predetermined revs, then redesign the whole transmission and have the dogs cut for auto shift - basically a ramp on the engagement side of the dogs so never ever down shift or close the throttle. Then take the shift forks and measure the free play and build the ends up with hard weld and grind back to minimal side play and shim the gears and so on. But I'd just shorten the one side for now. Mount the solenoid on the shift ram if possible and see how that works.

Or fit a modern Ignitech or MSD ignition and adjust shift delay with a laptop.

BTW, my best time was set after I almost ran out of expensive race gas and tipped in some 93 octane street gas...... May be a coincidence, but who knows. I find C12 to be sluggish maybe because I need more compression to get the best out of it and U4.4, which we are not allowed to run has the best throttle response but I have not dyno tested different fuels back to back. On our Honda CB160 race bikes, they made more power with 89 octane street gas than with C12 - not by much but it was measurable (just).

So in summary, it's time for a Rotax top end with new design of transmission, thin wall frame, and titanium everything coupled to space shuttle level electronics and rocket fuel... :)

It all comes down to how badly you want to beat Zeke.
 

Texasstar

Can't is a four letter dirty word
Rear end is much lighter so that's good.
Zeke's times are not far from mine on the Phat Trakka. Don't encourage him to practice, because those times have room for improvement...
Your time slip is interesting. I compared that to our RZ350 and the 60' is similar but speed at the 1/8 is significantly lower and it's almost a second slower for the 1/8th and that talks to power. I only had the RZ on a dyno once and that was years ago, but it made about 56 at the rear wheel IIRC.

It's unlikely that the Bul will make that much power, but I would have expected a slightly higher speed and lower ET, so there's some more work to be done there over the winter.

I hadn't really thought through the shift timing before, but here's today's thoughts:
I use the same Pingel switch on the RD350. In theory at least, it's air pressure that activates the ram and kill switch, and whatever speed it travels at, a longer tube will always take longer for that pulse to reach the other end. For us mere mortals, that seems like it's instantaneous, but it does take time - albeit not a lot. at say 1000 ft per second in cool air, that pulse will take 1/1000 of a second to travel 1 foot and 2/1000 sec to travel 2 feet. Doesn't sound like a huge difference if the kill switch kills ignition for say 50 milliseconds which is 50/1,000 sec.

But that's the time the ignition remains off to allow the shift to complete and will all that heavy metal to move, that sounds reasonable.

The idea behind a shorter run to the ram is that you want it to start moving before the kill happens. So the air pulse travels to the ram which reacts and starts to move and take up slack in the linkages. If the ram is attached a long way from the shift shaft, it will have to travel further to make a shift and if the ram is attached closer to the shift shaft (shorter lever so less leverage but also less distance to move) it will start to move the shift mechanism earlier.

Our old fashioned shifters have a lot of movement from the shift mechanism (claws/pawls etc) to play between the shift forks and the rails and shift forks to the gears and the distance the gear have to move. And that's before the gears start to move. All that mechanical mayhem takes time, so we need to initiate the mechanical part as far ahead of the kill as possible. There's work to be done and it takes time.

So mount the solenoid as close to the ram as possible even if the gear shift has very little latency.

OR... Fit what is known as a window switch that will shift automatically at predetermined revs, then redesign the whole transmission and have the dogs cut for auto shift - basically a ramp on the engagement side of the dogs so never ever down shift or close the throttle. Then take the shift forks and measure the free play and build the ends up with hard weld and grind back to minimal side play and shim the gears and so on. But I'd just shorten the one side for now. Mount the solenoid on the shift ram if possible and see how that works.

Or fit a modern Ignitech or MSD ignition and adjust shift delay with a laptop.

BTW, my best time was set after I almost ran out of expensive race gas and tipped in some 93 octane street gas...... May be a coincidence, but who knows. I find C12 to be sluggish maybe because I need more compression to get the best out of it and U4.4, which we are not allowed to run has the best throttle response but I have not dyno tested different fuels back to back. On our Honda CB160 race bikes, they made more power with 89 octane street gas than with C12 - not by much but it was measurable (just).

So in summary, it's time for a Rotax top end with new design of transmission, thin wall frame, and titanium everything coupled to space shuttle level electronics and rocket fuel... :)

It all comes down to how badly you want to beat Zeke.
The taco on that pass was only at 7500 rpms. I kept it at the shift light the complete run. I was reviewing my runs from when I raced Zeke and my 60’ and 300’ improved dramatically when I changed to a 13 front sprocket. So we are going to the 13 from the 15.

I am going to set the rev limiter 200 rpms higher to 9k. The shift light to 8k.

At 9k we have the ignition retarded to 17.5. At 8k we have the ignition at 19. Going back to the track tomorrow if it doesn’t rain.


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Texasstar

Can't is a four letter dirty word
This is with the shortened tube but with the Chinese momentary switch. I am sure it is different under a load.



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Texasstar

Can't is a four letter dirty word
Was over revving. Watch my throttle hand and this is the shift light set at 8k. I really don’t get it...we are barely opening the carburetor.


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Last edited:

John Murray

Been Around the Block
Was over revving. Watch my throttle hand and this is the shift light set at 8k. I really don’t get it...we are barely opening the carburetor.


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That's normal - there's insufficient load. Wouldn't it make sense to make a run or two with a conventional shift lever and the air-shifter disabled if there's any doubt over whether it's working properly? You seem to be continually distracted by peripherals... I'd be focusing on tuning the engine first; the dyno settings are a good starting point but you almost always need to make some changes at the track. It might be a good idea to leave the air-shifter disconnected while you do this just to eliminate one more variable while you dial in the jetting and timing.
 

Texasstar

Can't is a four letter dirty word
That's normal - there's insufficient load. Wouldn't it make sense to make a run or two with a conventional shift lever and the air-shifter disabled if there's any doubt over whether it's working properly? You seem to be continually distracted by peripherals... I'd be focusing on tuning the engine first; the dyno settings are a good starting point but you almost always need to make some changes at the track. It might be a good idea to leave the air-shifter disconnected while you do this just to eliminate one more variable while you dial in the jetting and timing.
John have you had any problems with the old Bultaco kill switch?


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John Murray

Been Around the Block
John have you had any problems with the old Bultaco kill switch?


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I haven't used a Bultaco kill switch for maybe 40 years or more, they were pretty poor quality. If there is any doubt about the switch just swap it out. Looking at the wiring diagram for the Pingel air shifter it appears to be set up for an inductive ignition system. It might work with a CDI (which I assume the Zeel is) but it wouldn't be good for it - there would be spikes in the primary circuit as the output to the coil is broken during shifts. The Pingel switchgear would subjected to some pretty high voltage as well. If you really must use the Zeel I'd set it up so the primary side is grounded rather than broken during the shift.

I know I've said this a hundred times but I'll say it one more time then I'll stay out of this altogether - you're making this much harder on yourself than it has to be. Take anything off the bike that isn't absolutely necessary or disconnect it until you get the engine tuned. Once it's running strongly and consistently you can add the trick stuff one piece at a time, so if any problems appear you'll know what's the culprit. I'm trying to help you but feel like I'm wasting my time.
 

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