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Imonabuss
| | Posted on Thursday, October 10, 2002 - 04:35 pm: | 
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This is a very interesting topic, with excellent comments in many cases. Blake, three or four valve pushrod motors do very little to help, since the messy mass required for rocker arms and adjusters becomes hideous. Check out the feuling heads if you don't believe me. It will only work if you design a pushrod multivalve sytem that has pushrods about an inch long and an ultra modern rocker arm design (like the Ilmore Indy engine). XR-750s run two valves to very high rpm (although not 12,000, close to 10,000), but they require constant rebuild, and have a totally different rocker arm system. The last complete XR-750s were built in 1983, but there isn't one out there that has any of those original parts. The guys out there are still buying new parts and building engines from scratch. Definitely a cool race motor, but wildly removed from being streetable and durable. |
Benm2
| | Posted on Thursday, October 10, 2002 - 07:38 pm: |
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All things considered, back to the original question. If the valvetrain could be made relatively "float proof" by using Ti valves, heavy springs, ti keepers, etc. up to 8000 rpm, then short-stroking the motor combined with a big bore should produce a more powerful motor, with a bottom end at least as reliable as a stocker at 7000 rpm. HOW can one be built? |
Madduck
| | Posted on Thursday, October 10, 2002 - 09:12 pm: |
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Benm2,
It appears to me that you are very serious about this question. I say build one. Call Wes/Pammy at Cyclerama, Brian Nallin at Nallin racing or Hoban Brothers racing in WI. We just talk about it, They build em to suit you and will talk you out of real stupid shit. Its your bike do what you want with it, just get professional help along the way. there is a lot of fun in having a unique motorcycle, like no other. Go For IT.
I'm guessing you can do something pretty interesting for less tan $3,000.
Paul |
Blake
| | Posted on Thursday, October 10, 2002 - 11:31 pm: |
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Imonabus,
I agree. I was trying to reinforce the notion that valve float might be governed more by the valves/springs/retainers than the pushrods/lifters. Big valves need big springs and retainers that have lower natural frequencies as a system and thus lower speed limits compared to smaller valves/springs/retainers. Interesting, so to attain higher valve speeds we need smaller valves which necessitates more valves which leads to overhead cams.
What do you think about the pushrod-desmo idea? Doable? Viable? Out of my mind?
Ben,
I think Buell has just built that engine in the XB9. Add higher end valves, more spring, and a big bore kit. The stock rev limit is 7,500 rpm; 8,000 should be within reach. It just won't pass the EPA noise police. |
Benm2
| | Posted on Friday, October 11, 2002 - 08:58 am: |
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Blake:
When you're racing, no one cares how much noise you make. The Lightning races at the last FUSA event in Pocono were soul-stirring. I did think about just buying a XB motor, would it bolt up to a tube-frame?
While someday I might like to build this engine myself, my current racing budget is being consumed by tires, rearsets, sprockets, chains, stands, leathers, etc. Serious engine work is a LONG way off.
Ben |
X1glider
| | Posted on Friday, October 11, 2002 - 09:26 am: |
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Ben, "serious engine work is a long way off."
Not a bad thing you know. Paractice, practice, practice. Get the skills down and master the bike you currently have. When you have mastered it, add more power.
As a general rule, no one on the track likes a guy who has a bike he can't handle. I'm sure you are fine rider but don't allow yourself to become disillusioned in your own skill level, like some of the squids I've seen on the track this season. (it seems some have been NOT wearing their yellow jerseys as required) I became disillusioned once, on my 84 VF500F, trying to be like Fast Freddie, and it hurt, really bad. Luckily, I haven't become disillusioned on the Buell yet as I know for a fact that I suck on it. (Maybe I should put plates on the hog! ) |
Benm2
| | Posted on Friday, October 11, 2002 - 11:24 am: |
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X1G,
Let there be no doubt, my riding skills SUCK! That's half the reason I'm racing, 'cause I rode the bike in fear on the street that I might get into a situation where I'd be in over my head. I have never ridden fast, I mostly commuted on the bike. ALL my racing experience on two wheels are from bikes with pedals. Part of my motorcycle fear is based on (1) I have confidence on a bicycle that isn't matched on the motorbike, and I'm not used to that feeling and (2) I've crashed alot on the bicycle, and it always sucks. But, I have learned the golden rule of racing: no matter how much you spend, its the RIDER that determines the podium AND don't talk big & start from the front unless you know you can stay there. Otherwise, you just piss everyone off. Besides, its always more fun to start from the back and work your way up, rather than the opposite. I'd rather earn my way forward that be kicked on the way back.
To that end, I won't be making alot of motor changes starting out. But, long term, I know I won't be able to resist.
Ben |
X1glider
| | Posted on Friday, October 11, 2002 - 11:46 am: |
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Ben, one thing I feel strongly about is that those who ride in the dirt (with or without an engine) make better street riders than those who have only experienced pavement. We tend to aquire skills that a street rider would never ever dream of...crash control too! That said, I need to hit the trails again. My workaholicness and frequent preference for and engine has earned me a bit of a biker gut.
So, where are the good trails near Philly? I am familiar with the vicinity as I have lived in Philly, Bristol and Hatfield and keep a sure thing stashed away in Hershey. |
Benm2
| | Posted on Friday, October 11, 2002 - 01:09 pm: |
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Usually, I'd ride at French Creek State Park as "the regular ride". There's also some good riding in the city, believe it or not, in Wissahickon Park (although I haven't ridden there). French Creek is just a bit east of Reading. We'll see about the transfer of MTB racing skills, I guess, but I'm not sure that heaving at the top of a long climb without falling off the bike qualifies as "transferrable skill:...  |
Blake
| | Posted on Friday, October 11, 2002 - 03:56 pm: |
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I doubt seriously that an XB engine would bolt *easily* into a tube frame. I was thinking more of finding a used XB in its entirety.
X1G,
OHR is calling you. After one track session at OH on the X1, you won't ever think of putting your softail on the track again. Especially at OHR. Are you kidding me? You are joking right? Can you say "plowing up weeds?" |
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