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

mopar1rules

mopar1rules

Active member
Joined
Jan 30, 2006
Messages
3,198
Age
40
Location
manitowoc, wisconsin
well guys, after hearing about all the people loosing rod bearings within the last 3 yrs on their vipers and srxs, and including myself this year, i was determined to find out why the vipers and srxs are affected, but not the red head sx-r's. well, i bought a sx-r 700 crankcase, and started comparing it to my viper/srx crankcase. right off the bat i thought it might be something w/that oil line that goes to the bottom of the lower case, for the pto cyl, cause its never a pto cylinder that goes down, its a center or mag. well, it can't be that, cause both the srx/viper and sx-r crankcases are the same in that respect. now, what's really different between the 2 cases and what i truely believe is the reason that vipers/srx lose rod bearings and sx-r's don't, is that the sx-r case has a "open" design, in the area after reed cage area and under the piston. now, on the viper/srx case, its got that radiused shaped casting/webbing, under the piston at bdc and the rod has to stick thru that like 19mm gap. know what i'm talking about?? i feel that its too hard for the oil/fuel mixture to get down to the rods, expecially when the engine is running at 9000+. what little bit of oil that goes down to the rod bearing, gets washed away from the poor ethanol fuel now a days. not to mention that there is "ramp like" protrusions of casting, that direct the oil/fuel mixture up to the bottom of the transfer runners, where it doesn't even hit the rod bearing. with the large "open" design like the sx-r's, the oil/fuel mixture gets down on that rod very easily, as the mixture doesn't need to go thru a 19mm or so slot. follow me?? i never really hear of a rod bearing going out, on engines w/"open" case style designs. i have a pic to post, to show the differences to those confused. also, i noticed that the oiling holes for the main bearings in the case, are .017" larger on the sx-r than on the srx/viper case. not to mention, that the oil grooves in the case, that's fed from the oil hole, are deeper in the sx-r case, than on the viper/srx case. so, 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
 

Attachments

  • crankcase comparo pics.jpg
    crankcase comparo pics.jpg
    67.6 KB · Views: 74
Last edited:

I had friends that owned the mid '90's Polaris 600 triples that had similar problems. They had a similar "closed" lower block design and only a 3-stage oiling system. When they lost their crank bearings they took their cases to an enginer builder that then outfitted them with the 4-stage oil pump system from the 800 triples which directly fed the center bearings better. After the mod they never had a problem again. So, I would support your theory based on another brand with a similar design that experiance similar problems.
 
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.
 
Probably better to adjust the pump to add a little more oil than the 50-1 that most people are set up for. A little extra oil won't hurt anything you actually make more power with more oil anyway providing your jetting is on.
 
Bluemonster2 said:
Probably better to adjust the pump to add a little more oil than the 50-1 that most people are set up for. A little extra oil won't hurt anything you actually make more power with more oil anyway providing your jetting is on.
Click to expand...

i already did that yrs ago, as well as others, and the rod bearings still let go.
 
staggs65 said:
i was kind of wondering since the ethanol seems to wash oil away more then the older fuel if it would give false piston wash readings. just a thought
Click to expand...

actually staggs, i've noticed more oil deposits (lean wash) w/running ethanol fuels, versus non-ethanol fuels. my theory on that is, if the ethanol is washing the oil off the bottom end, then its allowed to be sucked up thru the transfers and then allowed to be burnt to the piston crown, instead of staying down on the rod bearings, etc.
 
Not disagreeing with anything that's been said,but if it is basically a design flaw in the block how would you explain the fact that there are lots of these motors around with a ton of miles on them without being apart.Motors like mine(bone stock) that have ran regular(87) fuel as often as good fuel,cheap oil(Yamalube & BRP) and had the crap ran out of them.15,081 miles and counting.Just wondering.
 
I am in the same boat. 9k miles and dead, cheap gas and mostly cheap oil. amsoil interceptor the last few seasons, and they were low mile seasons with a lot more frequent valve cleaning. point well taken from you :) I was planning to ride the crap out of mine for a while like you have, just no such luck :(
 
I was going to run it until it scattered,but 3 crap winters in a row here so I don't want to be bothered dragging it out and getting it ready to ride next year.That on top of a $210(early purchase)trail pass and insurance to ride 5 or 6 times.Hopefully it will be in someone elses garage with-in the next couple of weeks.
 
Guess I should count my blessing on a $35.00 trail permit, and Insurance isnt mandatory. We have to regiter at D.M.V 6% sales on sled price and renew every 3 years, I think it was $22 for 3 year renew :letitsnow :letitsnow :letitsnow
 
Snowsnake said:
Not disagreeing with anything that's been said,but if it is basically a design flaw in the block how would you explain the fact that there are lots of these motors around with a ton of miles on them without being apart.Motors like mine(bone stock) that have ran regular(87) fuel as often as good fuel,cheap oil(Yamalube & BRP) and had the crap ran out of them.15,081 miles and counting.Just wondering.
Click to expand...

87 octane is fine in a stock viper. the fuel you run, does it have ethanol in it?
 
mine has been ethanol the last few years regardless of octane rating. tats been MY experience at least
 
03viperguy said:
mine has been ethanol the last few years regardless of octane rating. tats been MY experience at least
Click to expand...

and its my gut feeling that the ethanol, combined w/the crankcase design is what did it in.
 
i def. agree with mopar, ethanol is bad for a 2 stroke. although alot of car guys love it for its cooling aspect combined with boost. alcohol is fun to drink though. i'm just guessing here but, are you trying to squeze every pony out of them srx's? = lean? = boom?
 
s10mike said:
i def. agree with mopar, ethanol is bad for a 2 stroke. although alot of car guys love it for its cooling aspect combined with boost. alcohol is fun to drink though. i'm just guessing here but, are you trying to squeze every pony out of them srx's? = lean? = boom?
Click to expand...


Not sure what to think with regards to ethanol. We've had E10 in Michigan since my '01 SRX was new and I'd guess it's been run 80% of the time with E10. I can say for sure it's seen nothing but E10 the last 5 years. FWIW - stock jetting and low miles and fogged heavily.

Ethanol is typically more volatile and will flash sooner than other oxygenates so I'd expect it to have less of a solvent/washing affect.

I do think Mopar may be on to something regarding the differences of rod bearing exposure between the redhead vs PV.

I never had issues with my monoblock 600 either and spun it at 9200 for 8k trouble free miles.

Dunno.
 
You must log in or register to reply here.


Back
Top