the reason viper's and srx's loose rod bearings???


mrviper700 said:
snip. Cars can spark knock and it wont do damage to soft cast pistons, because its all in differnt forms/stages, you may want to google up detonation and read about it to get a good understanding.

snip more good info


It's also my understanding that the differences in the flow of the exhaust plays a major roll in a 2 stroke's suseptability to damage from detonation.

Being the exhaust flows past the edge of the piston on a 2 stroke rather than flowing out through the port of the cylinder head (above and away from the piston), heat management is more efficient on a 4 stroke. In other words, the piston runs cooler on a 4 stroke and is less likely to build heat, that heat is passed through a much larger heat sink were as the piston in a 2 stroke only has the wrist pin, rod and to a lesser degree the cylinder wall.

O/T - Reading the crankshaft bearings is common practice when determining performance of compressed air induction engines. You can learn a lot about what's going on in the combustion chamber from the lower end as well as the valves/valve seats/pistons/rings/wrist pin.

Anyhow, thats what I've read and learned from looking over the shoulders of 4 stroke engine builders but my actual experience is limited. I was too busy putting it back together for the next round.
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snomofo said:
mrviper700 said:
snip. Cars can spark knock and it wont do damage to soft cast pistons, because its all in differnt forms/stages, you may want to google up detonation and read about it to get a good understanding.

snip more good info


It's also my understanding that the differences in the flow of the exhaust plays a major roll in a 2 stroke's suseptability to damage from detonation.

Being the exhaust flows past the edge of the piston on a 2 stroke rather than flowing out through the port of the cylinder head (above and away from the piston), heat management is more efficient on a 4 stroke. In other words, the piston runs cooler on a 4 stroke and is less likely to build heat, that heat is passed through a much larger heat sink were as the piston in a 2 stroke only has the wrist pin, rod and to a lesser degree the cylinder wall.

O/T - Reading the crankshaft bearings is common practice when determining performance of compressed air induction engines. You can learn a lot about what's going on in the combustion chamber from the lower end as well as the valves/valve seats/pistons/rings/wrist pin.

Anyhow, thats what I've read and learned from looking over the shoulders of 4 stroke engine builders but my actual experience is limited. I was too busy putting it back together for the next round.
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a 4-stroke also has more time between "power" strokes to cool down. i believe the egt temps of a well tuned 4-stroke are 200-300 deg ferenheit hotter??
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So what are the benefits of the extra material in the srx/viper cases. If it has nothing to do with oiling or performance, why did yamaha design the cases differently?
 
ottawaair said:
So what are the benefits of the extra material in the srx/viper cases. If it has nothing to do with oiling or performance, why did yamaha design the cases differently?
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Probably to limit the windage effect of the counter weights, and limit the dead space in the crankcase to keep the mixture moving and emusified at all times.
 
Yamablue said:
Probably to limit the windage effect of the counter weights, and limit the dead space in the crankcase to keep the mixture moving and emusified at all times.
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but, now on the same token, don't you think that if the mixture is hitting the counterweights like the pork chop style of a viper, that the mixture would be getting atomized and mixed more thoroughly?
 
mopar1rules said:
i'm machining my bros viper case to be similar to a sx-r case and i'm drilling out and funneling the oil holes in the case. of course those holes have nothing to do w/the rod bearings, but why not lube the main bearings a little more?

i forgot to mention that i modded my bro's viper case this weekend and we'll see if the rods live longer now. i'll keep ya guys posted.

here is a pic, to show you the sx/sx-r case to the srx/viper case
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How did this all turn out?
Its interesting that some of the most successful stock and mod engines never had the webbing above the crankshaft.
ex: VMAX4, Mach Z tripple, 800 XCR, and the current Arctic Cat 800s...things that make you go Hmmmm..
 
I'm convinced a lot of rod failure is related to heat, there's no real water jacket to wick it away from the rods others than the air fuel mix. Would you not see sings of failure in your mains from lack of oil before your rods? Maybe the needles are made of a different metal compound than the reds?
 
mopar1rules said:
I'm pretty sure I'm onto something here. I knew it wasn't improper storage, detonation, or hotter timing like a few other members stated. I knew it was something else and I was determined to find out what.
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I agree,
My viper rod bearing went and I was NOT due to not storing it properly like some people told me.
I mean, look at pics of my sled in the classifieds it's fricken clean.
That right there tells you it was taken care of.
It looks like new and it has 15,000 on it.
It's to bad I had to part it out
 
MORAL OF THIS STORIE, USE THE BEST OIL YOU POSSIBLEY CAN AND TRY AND FIND NON ETHNONL FUEL WITH AT LEAST 91 OCTANE. GREAT READ. 3:16 (yammie tony)
 
I have been running ski doo oil xps 2 full sytentic for 10 years and have had no problems ever with cranks of any bearings . It is red line oil who makes it. I am happy with the stuff it works and I am not changing.
 
We can't forget these sleds can be like 10 years old? Maybe yamaha slightly overlooked somthing when making vipers? But it was so small it just took time for it to aprear.
 
sideshowBob said:
How did this all turn out?
Its interesting that some of the most successful stock and mod engines never had the webbing above the crankshaft.
ex: VMAX4, Mach Z tripple, 800 XCR, and the current Arctic Cat 800s...things that make you go Hmmmm..
Click to expand...

Bob, everything turned out great. Sled ran super strong for a single piped viper, with ported cylinders and an opened up case. He sold the sled but never got a call saying the sled died so I assume all is well. Yeah, MANY engines don't have the webbing and they make great power. There is no real reason for the webbing to be there. Like you said Bob, look at the other engines out there that made good power with no webbing.
 
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