Texas Two Step Taco

[Texasstar]

Wow thank you! First we will be using your engine break in procedure. We used cheap weed eater oil and pump gas (which I did not verify) last time to seat the rings but I think that was a huge mistake because even the cheap weed eater oil I have seen for sale is synthetic I want to use the KLOTZ castor at 20:1 this time.

We will also have CHT, EGT, and O2 hooked up...THIS time. EGT is going to be 7” from the piston and the O2 on the top of the belly.

Ralf said to start at 20 degrees BTDC on timing but what I have seen on the dyno we can start as low as 17. However at 17 EGT went up 50 degrees and was doing exactly what you said...rev’s went up because the rich mixture was heating the chamber changing the speed of sound so I am thinking in honor of Teazer and his Yamaha we will start at 19 degree BTDC.

Thank you for the spreadsheets will definitely use them. Paris Hilton tuning and don’t blow your load like a teenage boy. Got it.

Back to the putting on the Fritz expansion chamber my friend Michael Moore said this “Allegedly Walter Kaaden at MZ remarked that you know the 2T exhaust is getting to be the right dimensions when it can't be put on the bike without dragging on the ground, burning the rider, or requiring some major component(s) be moved to prevent the first two items.”


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[Texasstar]

Nice. Stinger length isn't very important, diameter is. Looks like you'll be able to alter the belly length easily, good work. Wondering which head you'll use for dyno testing - if it's the new one do you have some sort of plan in place to keep it cool? It'll take more than a big fan...

It would be very interesting to get a baseline for improvements so I think we will use the stock head first. Thank you.


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[Texasstar]

Thank goodness all race shops are essential services! We took the freshly bored cylinder and piston over to team treachery’s independent testing lab. We asked the machine shop to bore it to .0007” piston to wall. The results? .0074”-.0075

so we are rattlin!


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[John Murray]

Is that a cast piston?

 

[Texasstar]

Is that a cast piston?

No this is BR Bultaco’s forged wiseco designed for the Astro Flat Tracker. They run 1/2 mile WOT. Bruce Reynolds got tired of sticking the same piston we just stuck and designed this piston. It is a little heavier but has more of a taper at the top. When it quits pouring I am making a side by side comparison video. Wiseco recommended .0060” on the box piston to wall clearance but the consensus was to go .0070” this time. It is also coated on top.


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[John Murray]

Cool, looks beefy.

 

[Texasstar]

John how much lateral play does your pursang crank have with no primary attached? Both of our Montaderos have this lateral play with no primaries attached.

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[John Murray]

As they come from the factory they have quite a lot - 0.5mm or 0.020" or so but not as much as you show in the video. I reduce it to around 0.005" with the aim of keeping the rod better centered in the crank (no big end thrust washers, rod centered by the piston). The end float will increase as the cases warm up. I haven't heard of any problems arising from the factory setting, just trying to help the big end stay cool with prolonged high rpms. I'd be shimming yours to get it to a reasonable figure, but check the centering of the rod in the cylinder as you go.

 

[Texasstar]

When I put on the cush drive there is virtually no lateral play.


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[John Murray]

When I put on the cush drive there is virtually no lateral play.


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OK, I don't have any experience with the geared primary engines. So the spring pulls the shaft back against the drive side bearing? With the chain drive engines the bearings are located by the seal housings outside each bearing.

 

[Texasstar]

OK, I don't have any experience with the geared primary engines. So the spring pulls the shaft back against the drive side bearing? With the chain drive engines the bearings are located by the seal housings outside each bearing.

Your picture was a big help. When the cush spring pulls the shaft back against the side bearing you can see the crank is centered in the cases. I am curious why it is there. Both our engines have it.


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[teazer]

I think that Walter was right. I ran some numbers and there is no way this pipe will fit on any motorcycle, let alone under the frame. I'll see what happens as I slim it down a bit.

 

[Texasstar]

I think that Walter was right. I ran some numbers and there is no way this pipe will fit on any motorcycle, let alone under the frame. I'll see what happens as I slim it down a bit.

Is this the Frits chamber?


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[John Murray]

The cush spring provides the pressure that allows the cush to work as well as pull the crank up to the bearing. The chain drive engines don't have them but I kinda wish they did - these big singles can have horrendous torsional vibrations at high rpms.

 

[Texasstar]

The cush spring provides the pressure that allows the cush to work as well as pull the crank up to the bearing. The chain drive engines don't have them but I kinda wish they did - these big singles can have horrendous torsional vibrations at high rpms.

I can barely stand it at 8500 can’t even imagine it at 10500. Of course my nucleus is singing the hallelujah chorus at 8500...the best groin giggle ever!


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[John Murray]

The vibration is actually not bad at all, even at 11k. But torsional vibration - the rapid variations in crank speed that occur every revolution - can be very damaging, and that's why they fitted the cush to some engines. At present I consider the engine sprockets to be consumable items as the torsionals hammer the splines out in a couple of hours, I've had a flywheel weld itself to the crank and weak clutch plates like Barnetts are hammered to death in about an hour. Even the plates I use now start to blue after a while, even though there is no noticeable slippage.

BTW the vibration of the bike can be improved very noticeably with a good, solid head steady.

 

[Texasstar]

The vibration is actually not bad at all, even at 11k. But torsional vibration - the rapid variations in crank speed that occur every revolution - can be very damaging, and that's why they fitted the cush to some engines. At present I consider the engine sprockets to be consumable items as the torsionals hammer the splines out in a couple of hours, I've had a flywheel weld itself to the crank and weak clutch plates like Barnetts are hammered to death in about an hour. Even the plates I use now start to blue after a while, even though there is no noticeable slippage.

BTW the vibration of the bike can be improved very noticeably with a good, solid head steady.

What is a head steady?


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[Texasstar]

Ok this is on the shopping list need to sell some parts first. https://ajrmotocicletas.es/Gear-primary-drive-and-clutc


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[Texasstar]

Been doing more research on Mr. Bert Flood. My grandfather’s name was Bert. Look at the size of this chamber!

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[teazer]

Interesting bike. Pitsch/Krober tacho and lots of spark plugs to light the fire.

Call that a pipe? Mota recommends 163mm diameter.......................That's a pipe. With apologies to Mick Dundee.