TRX250r.org

Author Topic: engine failure  (Read 13352 times)

Offline udontknowme

engine failure
« Reply #15 on: May 27, 2014, 01:36:48 AM »
Quote from: johnny22;35006
So both of those are definite upgrades over the pro x rod that was in there?

prox rod is good stuff so i dont think its a qaulity issue here. maybe you just exceeded its breaking point some how or possibly something went wrong with the wristpin bearing. ktm parts wont necesarrily be better qaulity than prox i dont think, but the beam and small end may be alittle thicker for more strength
to much power is almost enough

Offline johnny22

engine failure
« Reply #16 on: May 27, 2014, 02:36:39 AM »
OK I get what you're sayin. I will probably just end up goinf with the same rod and same setup basically then, probably on alky though. from the looks of it and after talking to a buddy of mine he have me his opinion because he saw how many passes I make at once and it made sense. I ride it pretty hard most of the time and it may have just gotten too hot especially since I went down in jet size per someone else's advice. Don't really want to put any names out there since it's no ones fault but mine

Offline udontknowme

engine failure
« Reply #17 on: May 27, 2014, 03:10:43 AM »
well it might not hurt to look into a beefier rod. i think theres atleast 3 different ktm rods that might fit but i dont have their dimensions off hand to see how they compare to your rod. . i have a 380 rod if you need to know anything about it but i dont have any info on the 129 and 132. you might check prox site and see if they list the specs on them rods
to much power is almost enough

Offline Jerry Hall

engine failure
« Reply #18 on: May 27, 2014, 03:58:52 AM »
I use after market rods as a last resort when I cannot find the dimensions I am looking for in an OEM rod.  I have seen too many of these types of failures in aftermarket rods.  Years of observations of hundreds of related failures points to poor designs, substandard metallurgy and quality control in the aftermarket connecting rods and cranks. Wrist pin bearing failures will not usually cause the rod to break like the one pictured unless you are drunk and completely oblivious to the noise the engine was making.  These types of failures are the result of running a piston that was much heavier and at a much higher RPM than the rod was designed for or the heat treat was not right or they drilled the oiling holes in the side of the rod right where the stress is at a maximum.  I think that being a mechanical engineer often gives more insight to the understanding of where stresses are located and if failures occur in those areas.  Did the rod break through the oiling holes?

The quality control is higher in OEM parts. Engine manufactures have a lot more to loose when they produce the whole engine.  Anytime I have ever had a problem like the rod pictured, the aftermarket parts manufacturers ALWAYS point the finger at the engine builder or the operator. They are sometimes correct when they point the finger at the crank builder, especially when the crank builder grinds the outside of the big end of the rod for case clearance for a stroker crank.  

The price of an OEM rod could have been a big savings when you have this type of rod failure even if the OEM rod cost $500.00.  

I am not saying that an OEM rod could have prevented this failure especially if the engine was over-reved with a big heavy piston.

Offline seanoktm

engine failure
« Reply #19 on: May 27, 2014, 09:37:43 AM »
Hot rods now makes the 132mm ktm rods. You could even go to a yz490 rod its 137.5mm would need the right spacer. The yz490 you can only get through Yamaha so there not the cheapest. But the hold up well in my puma.
JDI Racing

Offline johnny22

engine failure
« Reply #20 on: May 27, 2014, 11:50:12 AM »
Its hard to tell where it broke jerry. I havent found the other pieces of the rod and where it broke it hit something more than once so it doesn't show it. It doesn't looks like at broke at the holes though

Offline johnny22

engine failure
« Reply #21 on: May 27, 2014, 11:51:21 AM »
I never knew that you could run all those different ones. That's interesting

Offline johnny22

engine failure
« Reply #22 on: May 27, 2014, 01:07:29 PM »
****
« Last Edit: May 27, 2014, 01:08:25 PM by johnny22 »

Offline udontknowme

engine failure
« Reply #23 on: May 27, 2014, 07:43:38 PM »
490 rod uses 24mm lower and 18mm upper pin ?  thats weird. normally the bigger engines use larger pins. but anyways at 137.5mm im not sure what plate you would use. maybe the .5" (12.7mm) thick and machine it down ?  135 rod seems alittle more straight forward. .375" plate which actually will measure closer to .385" then a .015" gasket on each side of the plate and you should be back  to a pretty good cylinder height but you can always fine tune it with different thickness gaskets. id like to see the 129 and 132 rods. that might not be a bad choice either depending if theyre heavy duty enough. but which ever direction you go, i dont see one good reason to stay with a short rod.
to much power is almost enough

Offline seanoktm

engine failure
« Reply #24 on: May 27, 2014, 08:27:12 PM »
Here is a 132mm Ktm rod on the left next to a pro-x honda rod. I am not sure what set-up you go with in a 370 with the yz490 rod. I am pretty sure bubba Ramsey runs a 490 rod in his wife's 370. The 132mm ktm rod is pretty beefy.
JDI Racing

Offline udontknowme

engine failure
« Reply #25 on: May 28, 2014, 12:10:47 AM »
one on the left looks more sturdy for sure. so that 132 is pretty much a direct replacement for the 250r rod as far as the big and small end widths being the same so theres no machining needed to the rod or crankwheels ?  whats the deal on the 490 rod. is it a direct replacment as well with no machining needed ?

check this out since were talking oddball projects. fitted a 144 honda rod onto ktm crank. originally it used a 140mm but it didnt seem up to the task :welcoming:



to much power is almost enough

Offline seanoktm

engine failure
« Reply #26 on: May 28, 2014, 09:48:09 AM »
My buddy dose all my engine work. He put a 132mm ktm rod in my polonda i dont think he had to do much machining other them the oil groves. To put a yz490 rod on a 250r crank there is a good amount of machining you have to do to the rod. But i do t think you do anything to the crank wheels.  
 Here is a new 490 rod then others pictures are going through machining next to my old rod off my puma.




JDI Racing

Offline Pumashine

engine failure
« Reply #27 on: May 28, 2014, 10:01:05 AM »
Quote from: seanoktm;35129
My buddy dose all my engine work. He put a 132mm ktm rod in my polonda i dont think he had to do much machining other them the oil groves. To put a yz490 rod on a 250r crank there is a good amount of machining you have to do to the rod.

Some builders do machine the KTM rod for clearance even though it fits without hitting. Maybe its the 4 mil I am thinking of. I have made many 2mm spacer plates for the use of the KTM 132mm rod.
Puma 408, Puma 431,  Pilot 412, Puma 431, Mini-tooth 486 Trx450r
89mm  Mini tooth Shearer in frame pipe chromed! With Cascade  Q

Offline seanoktm

engine failure
« Reply #28 on: May 28, 2014, 01:10:18 PM »
You may be right tony on the 4mm. Mine is on a stock stroke crank and I don't think James did much machining on the big end. It may have been narrowed a little but can't remember.
JDI Racing

Offline udontknowme

engine failure
« Reply #29 on: May 28, 2014, 09:09:11 PM »
stumbled upon this today. figured some of you want want to have a look


[video=youtube;fjgKtaX54gE]https://www.youtube.com/watch?v=fjgKtaX54gE[/video]
to much power is almost enough

 

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