Texas Two Step Taco
- Thread starter Texasstar
- Start date
It sounds so much cleaner running now and the fact that it made enough torque or power to cause the clutch to slip is a good sign that you are on the right track. Now to fix that and see it start to come alive. Any lockup clutch plates that would fit or do you have to modify a stock pressure plate (and clutch cover) to make that step?
Try longer springs with slightly lower strength so that you have lighter or stock lift pressure and more applied pressure.
John is right that the old idea was high primary compression to force gas out of the small transfers but with small crankcase volume, there wasn't much gas to squirt into the combustion chamber and as he mentioned, it tended to fly straight out the pipe. With modern pipes, the negative pressure wave "pulls" gas through much larger transfer ports and from the larger crankcase volume, so you get more gas into the combustion chamber. Some still goes out the pipe, so you design the pipe to "push" that excess gas back into the port just before it closes.
Try longer springs with slightly lower strength so that you have lighter or stock lift pressure and more applied pressure.
John is right that the old idea was high primary compression to force gas out of the small transfers but with small crankcase volume, there wasn't much gas to squirt into the combustion chamber and as he mentioned, it tended to fly straight out the pipe. With modern pipes, the negative pressure wave "pulls" gas through much larger transfer ports and from the larger crankcase volume, so you get more gas into the combustion chamber. Some still goes out the pipe, so you design the pipe to "push" that excess gas back into the port just before it closes.
John Murray
Been Around the Block
Sounds like it has a powerband now. What jet did you end up with?
Texasstar
Can't is a four letter dirty word
You were right all we had to do was watch the torque! Lol!
We never changed jets but used the 230. We are still running slightly rich on the top but are in a good place to tune the chamber. It is hitting hard at 7500 rpm and took 1/2 the time to make these pulls than Tuesday’s pulls with the longest pull being 4 seconds. As you said we will need to make longer pulls next time at least 7 seconds
We were all smiles last night and hope as Team Old Age and Treachery y’all are also. Bill says it will rev easy to 9500 but we need to pull the power band back down to where it is manageable. We may need to go to a heavier flywheel and he said lengthening the chamber header will drop the power band 500 rpms.This is still 20:1 BeNOL c12 Paris Hilton 21 degrees static. Thank you Paris Hilton and Team Old Age. Our EGT’s were down 100 degrees celsius!
Pretty sure we spun that bearing again...you can feel it in the clutch play. BB wanted me to ask you how you got your BULL to the higher Redline? Is yours 10500? Did you go down in piston size?
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Texasstar
Can't is a four letter dirty word
Ralf said, “next step lockup.” Lol! Bill said it is now all about the clutch. Zeke smiles and says, “my clutch works.”
John’s explanations gave me a great visual of what is going on and watching the EGTs is helping me see how it is pulling unspent fuel out the pipe and why we want that reversion wave to port block for us. The richer we ran the higher the EGTs and with Ralf’s head and no change in tuning we saw the EGT’s drop 100 degrees Celsius changing the speed of sound in the pipe and BAM moving the band up where you could feel it! It really is a different Animal.
I finally came clean with Ralf and sent him a picture of what our squish was last time when we melted the piston, it was .017”, and I could see his hands flailing when he texted me back and said NO NO that is too close. I told him it was a testament to how good his design is but the conrod didn’t fair too well. No beer has been consumed before any dyno pulls since then...but we popped a Baxter Brew and toasted Team Old Age and Treachery last night. Bill quipped, “take it home and let Zeke ride that!”
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John Murray
Been Around the Block
So the only thing changed was the head? That's very very odd - I don't mean to take anything away from Ralf's work at all but with such a dramatic HP difference I'd have to suspect there was something very wrong with the setup of the original head. It'll be interesting to see the number with the clutch fixed.
The air-cooled Pursang motor? It doesn't have anywhere near enough blowdown to be doing anything useful at 10500, it's all over by mid 9s. Which is a shame cos you have to try to build BMEP to make power rather than RPMs. Stock 86x64 bore and stroke but with 125mm rod.
I don't have any experience at all with the Bandido/Montadero clutches, but they appear to be just a bigger version of the Pursang etc clutch, and these can be virtually doubled in capacity fairly easily. Or maybe you could adapt a Japanese clutch..
Fantastic to see all the work starting to pay off
Texasstar
Can't is a four letter dirty word
Just working toward that T-shirt thank you and yes that original head was stock 1969 engineering. However we were making better than published Bandido power with it. Putting Ralfs head on was like time warping engineering wise forward 51 years. Now to time warp the clutch. Bill told me he has seen huge jumps in HP with a head change but the real gains will come with the chamber.
“But the engine is ancillary to the pipe.” -John Murray
Pretty sure we are going to need the straight cut gears and then we can adapt a lockup. I will get it on the stand and pull the cover later. Today is my lovely’s Bday and I was pushing it going to Bills last night
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thank you and yes that original head was stock 1969 engineering. However we were making better than published Bandido power with it. Putting Ralfs head on was like time warping engineering wise forward 51 years. Now to time warp the clutch. Bill told me he has seen huge jumps in HP with a head change but the real gains will come with the chamber. “But the engine is ancillary to the pipe.” -John Murray
Pretty sure we are going to need the straight cut gears and then we can adapt a lockup. I will get it on the stand and pull the cover later. Today is my lovely’s Bday and I was pushing it going to Bills last night
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Texasstar
Can't is a four letter dirty word
Will do. Here is the pull right before the clutch lets go at 7k. 20 ftlbs of torque 473 C on the EGT 13.2:1 air fuel and as soon as we got on the pipe it went fat. The screen you are looking at is detecting spin.
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Texasstar
Can't is a four letter dirty word
So here is the a run from 6-9-20 using the M51 old head that shows the powerband making 21 whp at 7500 rpms and then when it gets on the pipe we are making 35-36. Disregard the volt on the Airfuel that should be %
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Here is the Egt at 520 C
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Texasstar
Can't is a four letter dirty word
Plates look great but I used 10w30 conventional probably need to go to 30 weight?
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Texasstar
Can't is a four letter dirty word
Lol!!! I can’t wait to meet you someday my friend! I have 4 quarts of Honda Transmission oil that I didn’t use in my odyssey! I have been looking for use for it!
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Texasstar
Can't is a four letter dirty word
I was thinking more along the lines of ...
ATF might work though. Try it and see. It's designed for a similar sort of clutch pack, so it might be OK.
ATF might work though. Try it and see. It's designed for a similar sort of clutch pack, so it might be OK.
John Murray
Been Around the Block
No, despite being widely used by Bul riders everywhere. A few years ago I made a fixture for testing different clutch plates and fluids (I'll have photos somewhere..) and found that oils specifically designed for motorcycle engines/transmissions gave at least 15% more holding force than any of the ATFs, including the often-recommended type F.
PS. the biggest gains came from increasing the inside diameter of the outer plates so that the contact band was quite narrow; only 10 - 12mm wide. Despite the much smaller surface area the friction was greatly increased due to the larger effective radius.
