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Old 04-13-2010, 06:37 AM   #1
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Default Cased jump broken engine?

Ok guys this has never happened to me untill now....

Can a cased jump break an engine??

Leading the B main in the biggest race in Canada by almost half a lap i went over a double and took it a lil too easy... Knowing the "donkey kick" was coming I pinned it to keep it flat. Buggy hit chassis first on the peak and stalled... broken rod... Big flat mark on my brand new flywheel where it looks to have flattened the knurl...

Engine was running perfect around the 220 mark and nice smoke great power...

Anyone else break an engine like this? Now im paranoid!!! and sad

Any veiws on this or other experiances would ease my mind.. Thanks boys..
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Old 04-13-2010, 06:45 AM   #2
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Ya it can happen usually not that bad but get yourself a one piece engine mount like the kHz ones and that will prevent all that flex. I bet you ar using a stock 2 piece e vine mount.
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Old 04-13-2010, 06:52 AM   #3
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i done it first time racing a buggy hit hard and it stalled out but i neve brocken any rods or anything just broke the mounting all the way off funny it still would start but you could see fuell gushing out and stuff it mad me mad considering it was a brand new o.s. with eb mod but ive hears it tends to happen just rare.
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Old 04-13-2010, 06:53 AM   #4
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Originally Posted by endler View Post
Ok guys this has never happened to me untill now....

Can a cased jump break an engine??

Leading the B main in the biggest race in Canada by almost half a lap i went over a double and took it a lil too easy... Knowing the "donkey kick" was coming I pinned it to keep it flat. Buggy hit chassis first on the peak and stalled... broken rod... Big flat mark on my brand new flywheel where it looks to have flattened the knurl...

Engine was running perfect around the 220 mark and nice smoke great power...

Anyone else break an engine like this? Now im paranoid!!! and sad

Any veiws on this or other experiances would ease my mind.. Thanks boys..
Sounds like u had a freak incident, from what u said when ur car bottomed out and hit the chassis the flywheel stopped so fast that maybe the rod snapped. Going 35 thousand rpm's to 0 can't be easy on a rod.
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Old 04-13-2010, 09:34 AM   #5
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Well I just want to hear of someone else this had happened to... I know of one other instance that was sort of the same... But I just want to hear from some engine gurus or other racers that had this happen... Ben racing for alot of years... never have had this happen to me..

Motor mounts had nothing to do with something jamming the flywheel to a stop really.. I think the stock one on the D8 is pretty good?

You should see the gouge in the flywheel flattened the knurl right out still bummed.

The driver that finished 4th in the a was the first bump I had 2nd place by a half lap at the 10 minute mark grrrr... oh well thats racin
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Old 04-13-2010, 09:43 AM   #6
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Well you did pin it, so I think it's possible that when your car landed the rod just failed from revving. It could have been a coincidence that the rod failed when you landed.
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Old 04-13-2010, 10:22 AM   #7
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Well you did pin it, so I think it's possible that when your car landed the rod just failed from revving. It could have been a coincidence that the rod failed when you landed.
You see it wasnt a large jump.. I would say i throttled up about 50% power. The part I cant wrap my head around is the snapped rod and the gouge on my flywheel.. It was clear from that alone something happend along the lines of it stopping abruptly. It was a brand new flywheel and im glad it was so that I could see the gouge so clearly.. anything other than that i would have been been even more confused of why this happend.
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Old 04-13-2010, 11:28 AM   #8
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How old was the engine ( how many gallons through it ? ) ? Freak accidents do happen, but it could have been due for a new rod prior to this mishap. Does the flywheel stick out of the bottom of the chassis ?

..sorry to hear that happened to ya!
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Old 04-13-2010, 12:05 PM   #9
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How old was the engine ( how many gallons through it ? ) ? Freak accidents do happen, but it could have been due for a new rod prior to this mishap. Does the flywheel stick out of the bottom of the chassis ?

..sorry to hear that happened to ya!
It was between the 4 and 5 gallon mark.. Honesty at its sweet spot... No mechanical pinch left and all compression...

No rod slop...

Flywheel is stock D8 and the buggy is stock also. I dont think it sits to low and it definately doesnt hang out no....
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Old 04-13-2010, 12:10 PM   #10
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Sounds like you just got unlucky. I would say something like a rock caused a very sudden stoppage of the flywheel which in turn snapped the rod from impact. It is also possible that you had some crazy chassis flex that caused the flywheel to catch(though you should see markings on the chassis if this was the case).
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Old 04-13-2010, 12:19 PM   #11
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There's no doubt the sudden stop was the main factor in the failure, but the rod may have already been ready to fail and the combination of the two caused the failure. I could be way off.

I just think it's good to change the con-rod at the 2-3 gallon mark, especially if you're engine has lost the metal-to-metal pinch and is seeing higher RPM because it's running at it's optimum level. It's a little inexpensive prevention.
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Old 04-13-2010, 04:55 PM   #12
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OK so some of you have heard of this actually happening... Or your willing to put your money on it that it would be a just cause... and yes there are no marks on the chassis. I was hoping to find someone with the same experiance as me...

Not alot of rocks on the track if any, hard clay with fairly sharp peaks packed with roller...
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Old 04-13-2010, 05:04 PM   #13
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Originally Posted by endler View Post
OK so some of you have heard of this actually happening... Or your willing to put your money on it that it would be a just cause... and yes there are no marks on the chassis. I was hoping to find someone with the same experiance as me...

Not alot of rocks on the track if any, hard clay with fairly sharp peaks packed with roller...
Truthfully, I have NEVER heard of a rod snapping because of a cased jump. I have seen crankcases crack because of a cased jump, but never a rod. I really would think it was the combination of being on throttle and the flywheel hitting something that did it. Again probably a freak accident.
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Old 04-13-2010, 06:09 PM   #14
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So that's what happened. I was watching from the upstairs lounge, wondering what the hell happened. You were on fire at T-Burg. Very quick.
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Old 04-13-2010, 08:13 PM   #15
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So that's what happened. I was watching from the upstairs lounge, wondering what the hell happened. You were on fire at T-Burg. Very quick.
Ya when it came to a stop in the rollers in front of the stand i was like ummmmmm..... wtf?.... Thanks Semple I would have liked to meet you bud! Im sure ill see you around! Hope youre weekend went well!
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