Texas Two Step Taco

[Texasstar]

Welded another tab on the Bultaco M51 frame for the Aprilia 96-98 RS125 coil. This coil works with the Zeeltronic ignition and has .4ohms on the primary and 8 ohms secondary. The Speed and Sport coil was 1.2 ohms primary and 6 ohms secondary.

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[Texasstar]

Couple of thoughts:

That flywheel is a long way from the bearing and at high revs will cause crank whip which may cause other issues such as cranks snapping like carrots in the same way that TD1 Yamaha motors lost their crank mounted clutches. A double row main bearing the way that many sleds do things might help a little if that's possible to fit.

The windows look a little small unless they only connect to the boost ports. Could be an optical illusion caused by the "bigness" of that piston.

Thank you. I will raise the ports on the new piston. We will probably need to find a better solution for the rotor and machine a reluctor with it. Thank you.


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[Texasstar]

Changed the air shifter to a push so we can run the chamber outside to gain some clearance just so we can drop the bike for alternate tires and wheels. Looks more suited as a Texan longhorn. please don’t judge my wiring at this time lol!

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[ridesolo]

Gotta tell ya... I've been following this thread right from the beginning. I catch most of the posts when they're new and have been thoroughly enjoying it all. Frankly, I haven't understood much of it, the technical stuff w/ the engine building is way over my head, but I feel like I've learned much by following along. The most important thing I've learned is to leave the 2-smokers to those who know what they are doing! Build on, you're doing an impressive job.

 

[Texasstar]

Gotta tell ya... I've been following this thread right from the beginning. I catch most of the posts when they're new and have been thoroughly enjoying it all. Frankly, I haven't understood much of it, the technical stuff w/ the engine building is way over my head, but I feel like I've learned much by following along. The most important thing I've learned is to leave the 2-smokers to those who know what they are doing! Build on, you're doing an impressive job.

I am learning also so much also and only have two pistons under my belt. It is my understanding your knowledge of two strokes is directly proportional to your offering to the gods of speed on your shelf. lol! Thank you!


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[Popeye SXM]

I have also been following from almost the beginning and really enjoying the progress. I grew up racing 2 stroke MX and have tuned many of my own engines. In the 90's I enjoyed some success in the British championship. I do understand the science going on here but I am suffering some brain ache trying to keep up. Thanks for documenting and good luck. I have many pistons etc as offerings to the God of speed !!!!

 

[John Murray]

View attachment 224956

The flywheel doesn't normally sit right out there does it?

 

[John Murray]

Not really a direct comparison as this one is a little smaller than yours at 78mm, but here's a forged Wossner with pin, clips and rings

 

[John Murray]

Re the piston windows, the reason I went with a reed with the 86x64 air cooled engine was that it simply wasn't possible to get sufficient intake T/A without either making the port so big the piston would fall out of the back of the barrel or the duration unworkably long. I guess you would have been in exactly the same situation. The reed extends the port duration - and the port T/A - without either of these drawbacks. I guess what I'm trying to say is the piston windows need to be sized and positioned so as to meet this goal if you're going for top end power.

 

[John Murray]

This is my flywheel setup, like you my starter plugs into the ignition side. The flywheel tucks in fairly close to the cases, the other smaller wheel on the scales is the drive side flywheel. The starter is a geared Hilux unit attached to some bicycle handlebars with a 15/16" hex nut on the shaft that fits into the socket welded into the flywheel.

 

[Texasstar]

The flywheel doesn't normally sit right out there does it?

Here is the Pursang 250 to the left, The original Montadero with 3 lbs removed but the same width, and the one I basically halved. The mass on the crank is the same as before but the inner mass was removed.

. I think for safety sake I am going to remove the rest of the rotor and that way we can dial in the Zeeltronic in and not have that mass hanging out there. Have been practicing making reluctors on the rotary table so we can make another prototype with the mass closer to the crank. The good news is there are plenty of Femsa paper weights out there.


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[Texasstar]

Thanks John what is the diameter of your fly wheel and have you experimenter with different diameters and masses? BTW I want you to know and everybody needs to know that you have HUGE balls as we say here in Texaa. It is one thing to seize a piston on the dyno it is another thing to do it at 160 mph and not go down.

Nice remote starter! I like the idea of using the socket reversed! Brilliant! Are those bultaco handle bars? I want to make one like yours and have a twist throttle lol!


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[John Murray]

The current flywheel is 110mm dia and is too small I think. Like everything on the bike I'm up to about version four I think. I originally used a small KX250 wheel which was waaaaay too light. Next I went to the one pictured, but without the holes. It was much better but welded itself to the crankshaft so after that I drilled it out to get some weight out of it. It worked fine after that but I got fed up with magnetic pickups and Hall Effect sensors and their susceptibility to EMI so then switched to an optical trigger and the current flywheel. It's pretty good as is but I think I'll add another 20mm to the diameter.

Thank you for the kind words, to be honest though big balls aren't a requirement. Seizures aren't instantaneous and if you're paying attention - and you should be - there's time to pull the clutch before it locks up. And besides, the little bike is beautifully stable even when it's spinning the wheel, it's really not hard to ride.

Will the Pursang flywheel and stator fit? If so it'd be a quick and easy way to get it onto the dyno without the distractions of the Zeeltronic setup. If you use the Zeel I'd be inclined to just set it up for a fixed or straight line timing curve. A curve will make hardly any difference on the strip and will just take your time and attention away from more important things.

 

[Texasstar]

The current flywheel is 110mm dia and is too small I think. Like everything on the bike I'm up to about version four I think. I originally used a small KX250 wheel which was waaaaay too light. Next I went to the one pictured, but without the holes. It was much better but welded itself to the crankshaft so after that I drilled it out to get some weight out of it. It worked fine after that but I got fed up with magnetic pickups and Hall Effect sensors and their susceptibility to EMI so then switched to an optical trigger and the current flywheel. It's pretty good as is but I think I'll add another 20mm to the diameter.

Thank you for the kind words, to be honest though big balls aren't a requirement. Seizures aren't instantaneous and if you're paying attention - and you should be - there's time to pull the clutch before it locks up. And besides, the little bike is beautifully stable even when it's spinning the wheel, it's really not hard to ride.

Will the Pursang flywheel and stator fit? If so it'd be a quick and easy way to get it onto the dyno without the distractions of the Zeeltronic setup. If you use the Zeel I'd be inclined to just set it up for a fixed or straight line timing curve. A curve will make hardly any difference on the strip and will just take your time and attention away from more important things.

I have a magneto that we have been running and we can always use it on the track. The Zeel gives us so many options on the dyno to get to a fixed tuning and has a rev limiter and a cool shifter light option. C’mon John you need more Zeel in your life


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[John Murray]

Don't worry I've tested plenty of motorcycle "performance" ignitions, every one of them feeble compared to automotive boxes..

 

[Texasstar]

Don't worry I've tested plenty of motorcycle "performance" ignitions, every one of them feeble compared to automotive boxes..

But then there are the aircraft ones...and pretty soon 3 spark plugs...I want to know the story behind the engineers at Rotax.


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[John Murray]

I have a magneto that we have been running and we can always use it on the track. The Zeel gives us so many options on the dyno to get to a fixed tuning and has a rev limiter and a cool shifter light option. C’mon John you need more Beer in your life


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Fixed it for ya

 

[Texasstar]

Fixed it for ya

Cheers ...hold my beer watch this! Lol!!!!


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[Texasstar]

Reduces the overall diameter to 108mm and 1294 grams

A comparison

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[John Murray]

I think you'd get away with that, though it'd be nice if the reluctor and pickup didn't force the wheel so far out.
An earlier version I used on my Metralla had the pickup mounted outside the case, sensing a notch in the periphery of the flywheel.