Bubba crash at Southwick

robwbright

Member
Apr 8, 2005
2,283
0
I just watched my tape of Southwick.

Geez. That crash was awful as well.

Forgive my ignorance, but is the effect of a 2 stroke seizure as violent as that one was? I've only seized one motor in my life (on a CR80) and I didn't crash, but I don't think I was riding very fast at the time, either.
 
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SpDyKen

LIFETIME SPONSOR
Mar 27, 2005
1,237
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In MHO, it would be extremely unusual for a 2T to seize under those conditions.
Also, stopping the larger gyroscopic effects of a big 4T suddenly would have a much more pronounced effect on the attitude of the bike in the air compared to a 250 2T lockup. See http://www.dirtrider.net/forums3/showthread.php?t=135805 for more comments on this! :yikes:
 
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dirt bike dave

Sponsoring Member
May 3, 2000
5,348
3
There was a thread a long time ago about how it is possible for any engine to fail when panic revving in the air, with no load on the engine. If I remember correctly, Rich chimed in, and he explained the physics of it. I believe the failures were at the top of the connecting rod.

Looks like that is what happened to JBS. From the video it was obviously a catastrophic engine failure.

If he was revving in the air, it is because he wanted to bring the rear end down. Stopping the motor and rear wheel caused the front end to drop. Even a great rider like JBS is not going to save it when this happens unexpectedly.
 
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YZ165

YZabian
May 4, 2004
2,431
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Bubba should have read this....

http://www.dirtrider.net/forums3/showthread.php?t=130611&highlight=kxf450

robwbright said:
but is the effect of a 2 stroke seizure as violent as that one was?
Click to expand...

Weather it's a 2T, or 4T, stopping the back wheel that fast, with your nose already pointed down, is not good. Especialy when landing in soft sand. I think the speed of the back wheel at the time of the seisure has alot more to do with it than the diffrence between the rotating masses of the engines. Don't get me wrong, being a 4T didn't help, but that's not why he went over the bars.
 

kmccune

2-Strokes forever
LIFETIME SPONSOR
Jul 3, 1999
2,726
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Hey I'm all for it! :)
 
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SpDyKen

LIFETIME SPONSOR
Mar 27, 2005
1,237
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YZ165 said:
Bubba should have read this....

http://www.dirtrider.net/forums3/showthread.php?t=130611&highlight=kxf450
Click to expand...
Modern, Formula 1 inspired, extensively engineered, high-revving four stroke racing engines are truely technological marvels to myself and many others. They have their pluses and minuses, as I learned riding & racing a 1984 radial 4-valved XR200 Honda as well as seriously roadracing them for several years. I'll own another 4T dirt bike some day, for sure (maybe for Super Moto). For now, however, I enjoy, and value, the simplicity and relative reliablity of two strokes, and believe the AMA has made another in it's long list of mistakes by making it impossible to be competitive on one in professional MX racing. I think variety is indeed the spice of life and was VERY happy to see Doug Henry win a championship on a 4T. But the displacement advantage given was obviously too great, IMHO. I feel for the privateers! :(
 

robwbright

Member
Apr 8, 2005
2,283
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Okiewan said:
Here ya go ...

Yup, maybe this will convince all the pros to go back to the obviously superior 2-stroke. (yeah, that was for you Rob, lol)

http://dirtrider.net/james_wick_wav.wmv
Click to expand...

Actually my post here was more for my informative purposes - since I don't want to have a crash like Bubba's, I want to make sure my engine doesn't seize. . .amongst other reasons to not want it to seize. ;)

It appears from the posts that a small bore 2 stroke would be less likely have that pronounced an effect.

Ok Okiewan. The 4 stroke design (with an 80-100% displacement advantage) is a superior machine.

There, I said it. Oh wait - I've said that before. :nener:
 
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AXE_1967

Member
Mar 31, 2006
39
0
Where can I find the video online showing this crash? Id like to have a 4 stroke mainly because of the less demanding ride which would make it not as hard on me and my carple syndrome. After I ride I can't hardly move my left wrist on acount of using the clutch so much on my 2strokes but, it beats not having to have or adjust the valves every time you turn around.
 
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rcpilot_971

Member
Oct 30, 2002
43
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robwbright

Member
Apr 8, 2005
2,283
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Well, yea, but one of my local tracks has a jump halfway down a rather large hill - kindof similar to Bubba's BIG crash except the hill is larger.
 

AJ Waggoner

Crash Test Dummy
Nov 5, 1999
4,368
34
hey now Okie!
despite being considerbly slower than bubba ,
some of us can rival his crashes..even on a 2T
and you once had video proof!
LOL!
 

ellandoh

dismount art student
~SPONSOR~
Mi. Trail Riders
Aug 29, 2004
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nobody could possibly go as fast as the FOAT , ever , fifth gear on my as well as most others bikes is mostly for looks, and fish stories ;)
 
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SpDyKen

LIFETIME SPONSOR
Mar 27, 2005
1,237
1
Okiewan said:
It's not engine mass that caused that to happen, it's the rear stopping as fast as it did.
Click to expand...
Personally, Okie, I believe that I've noticed more frontward rotation when chopping the throttle over a jump on my buddies 4T than on my 2T. I suppose that could be attributed to increased engine braking, though, now that I think of it.
 

robwbright

Member
Apr 8, 2005
2,283
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SpDyKen said:
I suppose that could be attributed to increased engine braking, though, now that I think of it.
Click to expand...

That's what I wondered, but I guess I didn't phrase it very well.
 
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OldassKDX

Member
Nov 9, 2000
410
1
Maybe I'm missing something. The engine fried itself, it shouldn't matter 2 or 4 stroke. This wasn't engine braking, it was engine breaking. When that wheel stopped, it could care less how many strokes powered it. The wheel locked up, I can't imagine that it would have been ANY different on a 2 stroke (unless you make the argument that a 2 stroke simply wouldn't have failed)
 

kmccune

2-Strokes forever
LIFETIME SPONSOR
Jul 3, 1999
2,726
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Okiewan said:
Oh, and most of us don't have to worry about crashing like Bubba.
Click to expand...

I may not go as fast as him but I can crash as well as him... again just not as fast, reguardless of what I'm riding :)
 
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rodH

Member
Aug 17, 2005
369
0
AXE_1967 said:
Where can I find the video online showing this crash? Id like to have a 4 stroke mainly because of the less demanding ride which would make it not as hard on me and my carple syndrome. .
Click to expand...

This is true only some of the time. My 450 is sometimes MUCH more demanding, the low end torque wants to rip your arms off sometimes. I get arm pump quicker on the 4t. I think for climbing, the 4t is easier, but sometimes in other situations it is harder. Also the sudden deceleration caused by the engine braking works you arms as well.

I love me 450, but I sort of miss my 250. I wouldn't trade them straight up, as the 450 is better for me and what I ride most of the time, but I do miss how easy it is to flick my 2t around corners and jumps. I am still dialing in the handling on my 450, lowering the forks in the legs has helped, now I need to switch out my stupid 742 and see if this thing really will handle as good as a 2t.
 

YamaB

Member
Apr 2, 2004
401
0
I'm surprised that no one has accused him of riding over his head in this thread...
 

kmccune

2-Strokes forever
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Jul 3, 1999
2,726
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Well, you did bring it up sooo.... ;)
 
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ktmracer

~SPONSOR~
Aug 9, 1999
378
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I've watched the clip many times and i am still trying to decide if the bike started nosing, JS panic reved and then it locked.....or if the motor seized on its own and then nosed in.
 
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