mopar1rules
Active member
added a pic on the first page, to show you the differences of a sx-r case to a srx case. check it out.
the reason viper's and srx's loose rod bearings???
- Thread starter mopar1rules
- Start date
mopar1rules
Active member
modsrx said:
what's getting old? the sleds age? if so, that's not the whole issue/reason for the rod failures. the sx (red head engine) is older, and still no failures w/them. i'm still a firm believer that its the case design.
s10mike
Member
your def. onto something, better oiling=longer life. i think you already figured it out.
mopar1rules
Active member
modsrx said:
That don't matter. Poor oiling....low hp motor or not, will equal short bearing life.
If you understand how the mixture is drawn into the case and then up thru the cylinders youd then see why it makes no differance from an oiling point, because its all drawn in thru the case,then down into the case bottom where its compressed and then pushed up thru the transfer ports. There is a differance in crankcase volume, but not oiling. The crankcase volume differance is differnt because they are completely differnt engines, bore and stroke. Its still drawn in the bottom of the case the same way, the crankshaft is turning the same direction between both engines, the mixture is drawn in on the same side of the crankshaft/case, so the lower rod bearing gets no better oiling either way. The fuel-oil-air mixture being drawn in/compressed is a vapor field ,so when its compressed in the bottom it fills the entire void in the case, so it would come to reason it coats the crankshaft the very same way any 2 stroke does. The large void between the crankshaft halves is open and allows for the mixture to reach the lower rod bearing,because most all of the mixture is drawn into that void as the crankshaft spins.
There is no case flaw in a srx/viper vs a redhead engine, you simply see vipers lose the rod bearings from constant exposure to detonation. Srxs rarely lose rod bearings,unless the engine has sustained detonation damage before in its life. The vipers are just simply LEANER. Leaner coming from advanced ign timing, (advanced ign timing puts more heat into pistons). Leaner slides,needles,nozzles in the carbs, along with a higher compression ratio in the center and mag side cylinders then a srx. Along with a sub par cooling head(most all vipers lose the mag side bearing or center), all these componets combined give you the increased chance of detonation with todays lousy fuel quality.
The reason you dont see this in the redheads is simple, they for one use a differnt oilpump(richer), and they are not a high performance engine, thus they have much more squish clearances-lower compression ratios. These things simply equal= LESS HEAT, so less chance for detonation. Any 2 stroke engine subjected to detonation will fail, no matter what brand,no matter what design, the constant rattling and pounding of the bearings during detotantion simply beats the bearings to death, thus you WILL have engine failure.
There is no case flaw in a srx/viper vs a redhead engine, you simply see vipers lose the rod bearings from constant exposure to detonation. Srxs rarely lose rod bearings,unless the engine has sustained detonation damage before in its life. The vipers are just simply LEANER. Leaner coming from advanced ign timing, (advanced ign timing puts more heat into pistons). Leaner slides,needles,nozzles in the carbs, along with a higher compression ratio in the center and mag side cylinders then a srx. Along with a sub par cooling head(most all vipers lose the mag side bearing or center), all these componets combined give you the increased chance of detonation with todays lousy fuel quality.
The reason you dont see this in the redheads is simple, they for one use a differnt oilpump(richer), and they are not a high performance engine, thus they have much more squish clearances-lower compression ratios. These things simply equal= LESS HEAT, so less chance for detonation. Any 2 stroke engine subjected to detonation will fail, no matter what brand,no matter what design, the constant rattling and pounding of the bearings during detotantion simply beats the bearings to death, thus you WILL have engine failure.
03viperguy
Moderator
that makes a lot of sense Don, thats the best it has ever been explained that I have seen. glad you are back man, you just taught me something 
although I think i have not lost a rod bearing, seems like a crank bearing on mine. damn flywheel is being stubborn and will NOT get off the motor for me.
although I think i have not lost a rod bearing, seems like a crank bearing on mine. damn flywheel is being stubborn and will NOT get off the motor for me.
mopar1rules
Active member
if it was detonation that destroyed the rod bearing on my srx and my bro's viper, i'm pretty sure we would see the signs of deto in the soft aluminum piston crown, before a hardened steel bearing???? also, i understand the hotter timing, more heat, and detonation thing, but the hotter timing isn't what wipes out the rod bearing. also, my bro's viper had srx base gasket and megapower heads on it, so cooling wasn't an issue. not to mention that the oil pump had been turned up for 3 yrs. i remember preaching on here yrs back about people needing to turn up them oil pumps and they would just tell me that i'm foolish for doing so, as it will only gum up the valves sooner, etc, etc....whatever. now, if the srxs/vipers suck the mixture down into the case first, then what's the purpose of the crankcase webbing, having the ramp style shape arc to it, that directs the mixture to the bottom of the transfer runners???? not to mention, it would be pretty hard and a poor flow path IMO, for the mixture to come out of the bottom of the case, thru the slot for the rod and then around the webbing, and then finally up into the transfer runners. i'm still stuck on the case design having alot to do w/the rod bearing failures.
mopar1rules
Active member
rod bearing and crank bearings go out, due to OILING issues and not from ignition timing, head/water temp, issues.
mopar1rules
Active member
let me ask you this......what hole would lube main crank bearings better?......a 1/8" hole or a 1/4" hole? obviously a 1/4" hole. same w/the crankcase......a 2.5" opening (sx-r case) is going to allow more mixture down to the rods, versus a 3/4" or so wide slot (srx/viper).
mopar1rules
Active member
now, if all the mixture is suppose to be sucked down into the case bottom, then w/yamaha having the webbing/casting w/the arc to it, would be bad, as when the mixture is trying to get sucked to the bottom of the case, it would be having its path disturbed, from the webbing/casting w/the arc to it.
Theres plenty of animated engines online to help you understand how a 2 stroke engine works.
There is also many forms/stages of detonation, they all dont "destroy" the piston crown, its the pulses and forces (at the wrong time) from the start of detonation that beat up the bearings. You may have detonation and very well not know it, its not always audible,ESPECIALLY in a 2 stroke snowmobile application. You would need to run the engine and have a dr.s stethascope on the side of the cylinder to even remotely begin to hear the beginning stages of it over the exhaust noise alone. This is exactly how and why yamaha decided to use the DCS system for the 02 srx and later on the vipers. By picking up the various sound waves thru the coolant is as close as you can get to identifying detonation. 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.
HEAT is the number 1 player, increased combustion temps from
ethanol fuel, added timing, lean carbs,etc) increase the load on the bearings, they are all connected to each other.
Lots of "good" running sleds can have detonation and no problems will be exposed till much later in mileage or time, the very first tell tale sign is when you remove the rings. It will look like small water spots on the mainlands of the face, this means the engine/ring is expeirancing some form of detonation and the pulses are making the ring flutter up/down in the ringland groove. There will be absolutely NO visable damage to piston crowns at this stage, and will be assumed its a good running engine if you dont read the details.
The piston is connected via the connecting rod, the bearings are not meant to take shock loads,but dynamic loads, so the forces/pulses that are exerted on them will begin to weaken them over time. Now....add more heat and you have bearing failure, with a good looking piston top. This also happens when hp/load is added to a stock engine as well, so your triple pipes,more compression mega heads,porting,etc. any power adder also ADDS HEAT to a engine.
In closing, all in all it still actually comes right down to the gas quality!
simple as that.... if you run the engine with plenty of octane which in turn cools off the ign. process, the forces which wreck an engine cant work!! The problem is today you cant RELIABLY get the octane needed from the typical gas station pump for a high performance 2 stroke without added precautions such as richer jetting to defeat the ethanol blend, less compression. Ethanol is a solvent, it will diminish the bonding capability of oil to a metal object, so right off the bat your already in a uphill battle with todays fuel and a 2 stroke engine
There is also many forms/stages of detonation, they all dont "destroy" the piston crown, its the pulses and forces (at the wrong time) from the start of detonation that beat up the bearings. You may have detonation and very well not know it, its not always audible,ESPECIALLY in a 2 stroke snowmobile application. You would need to run the engine and have a dr.s stethascope on the side of the cylinder to even remotely begin to hear the beginning stages of it over the exhaust noise alone. This is exactly how and why yamaha decided to use the DCS system for the 02 srx and later on the vipers. By picking up the various sound waves thru the coolant is as close as you can get to identifying detonation. 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.
HEAT is the number 1 player, increased combustion temps from
ethanol fuel, added timing, lean carbs,etc) increase the load on the bearings, they are all connected to each other. Lots of "good" running sleds can have detonation and no problems will be exposed till much later in mileage or time, the very first tell tale sign is when you remove the rings. It will look like small water spots on the mainlands of the face, this means the engine/ring is expeirancing some form of detonation and the pulses are making the ring flutter up/down in the ringland groove. There will be absolutely NO visable damage to piston crowns at this stage, and will be assumed its a good running engine if you dont read the details.
The piston is connected via the connecting rod, the bearings are not meant to take shock loads,but dynamic loads, so the forces/pulses that are exerted on them will begin to weaken them over time. Now....add more heat and you have bearing failure, with a good looking piston top. This also happens when hp/load is added to a stock engine as well, so your triple pipes,more compression mega heads,porting,etc. any power adder also ADDS HEAT to a engine.
In closing, all in all it still actually comes right down to the gas quality!
simple as that.... if you run the engine with plenty of octane which in turn cools off the ign. process, the forces which wreck an engine cant work!! The problem is today you cant RELIABLY get the octane needed from the typical gas station pump for a high performance 2 stroke without added precautions such as richer jetting to defeat the ethanol blend, less compression. Ethanol is a solvent, it will diminish the bonding capability of oil to a metal object, so right off the bat your already in a uphill battle with todays fuel and a 2 stroke engine
SWEDE
New member
Thanks Mr. Viper, I learned something and I think I now know why my buddies zr 700 lost a rod bearing last weekend!I always thought he should be running premium fuel in that thing, but he generally ran 87.
yamachuck
New member
ride it like you stole it.blow it up and have Don rebuild it....simple
Snowsnake
New member
mopar1rules said:
Up to 10% pretty well everywhere for quite a while now.I will say I have only put on between 2 & 3 k miles in the last 3 years.Didn't ride at all last year due to a knee operation and this year was a wash maybe 700 miles.
03viperguy
Moderator
great example, thanks again!mrviper700 said: