mopar1rules
Active member
BETHEVIPER said:
Very true, but if its detonation like Don believes it is, then the detonation shocks should destroy the upper bearing too I would think. I think its partially a lack of oil issue combined with ethanol in the fuel, which causes the bearing to run dry and then get hot and then its game over. Prolly a combination of a number of things. Srx's of course have this problem as well, but not so often. I have my oil pump turned up, Srx rear cooler installed, and I run Srx heads with safe jetting and so far so good.
Devilin AblueDress!
New member
mopar1rules said:
Off topic but what all did you do to run the SRX heads? I am sure carb on pto had to be re-worked. What are you running jetting wise? SRX specs?
the viper and the srx both use the same exact 8dn oilpump, the same exact crankcases.......tough to use lack of oil theory when you have the same parts.
the reason the wristpin bearing lives is its not the end of the line like the rod bearing is. The rod bearing is what takes the load, and when detonation causes the pressure waves at the wrong times it all ends up on the lower crank pin, it basicly beats the lower rod bearing to death with the pulses and jerking of the rod via the piston.
again... its the mag and center cylinder on every single blown up viper youll find, not the pto, because it has lower compression due to the head being more open. It does not detonate because it has LESS compression so the "heat" is lower, the rest of the ingrediants listed in this thread are the reason why the other 2 blow up and often.
srxs dont suffer these problems because of lower compression, less timing, better cooling system.
If the main crank bearings are bad its usually a moisture/storage problem, not detonation. if those are bad due to lack of oil then the entire rest of the crank will most likely be junk and blued as well, that would mean you have a bad non functioning oilpump,broken oilpump driveshaft,plugged oil lines,etc, very,very rare in a yamaha triple!
the reason the wristpin bearing lives is its not the end of the line like the rod bearing is. The rod bearing is what takes the load, and when detonation causes the pressure waves at the wrong times it all ends up on the lower crank pin, it basicly beats the lower rod bearing to death with the pulses and jerking of the rod via the piston.
again... its the mag and center cylinder on every single blown up viper youll find, not the pto, because it has lower compression due to the head being more open. It does not detonate because it has LESS compression so the "heat" is lower, the rest of the ingrediants listed in this thread are the reason why the other 2 blow up and often.
srxs dont suffer these problems because of lower compression, less timing, better cooling system.
If the main crank bearings are bad its usually a moisture/storage problem, not detonation. if those are bad due to lack of oil then the entire rest of the crank will most likely be junk and blued as well, that would mean you have a bad non functioning oilpump,broken oilpump driveshaft,plugged oil lines,etc, very,very rare in a yamaha triple!
mopar1rules
Active member
'98-'99 srx's had a richer oil pump than the vipers. Also, srx's have a different oil pump cable free play spec than vipers. Wasn't trying to start a pissing match Don, but it always seems you get so worked up.
yamalars
Member
Anyone tryed to back off some timing with a key on their viper? Should help with
the detonation/rod problem if you have to run lower octane gas. Maybe could try a
srx cdi if it's a stocker?
the detonation/rod problem if you have to run lower octane gas. Maybe could try a
srx cdi if it's a stocker?
mopar1rules said:
pissing match??? simply stated real facts, and not a theory...nothing more...lol.
oilpump for srx from 1998-2002 is part number 8dn-13100-00-00
same pump, same pump used on a viper. Go check the fiche.
edit add specs for oilcable:
viper 20.5mm+or-1mm, so... 19.5mm-21.5mm
1998-2002 srx 21+or-1mm, so ... 20mm-22mm
1/2 mm differance, theres certainly not enough differance in .020" adjustment!
same pump, same pump used on a viper. Go check the fiche.
edit add specs for oilcable:
viper 20.5mm+or-1mm, so... 19.5mm-21.5mm
1998-2002 srx 21+or-1mm, so ... 20mm-22mm
1/2 mm differance, theres certainly not enough differance in .020" adjustment!
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mopar1rules
Active member
mrviper700 said:
Don't cars what the fiche says for part numbers. '98-'99 srxs always used more oil than the '00-'02's. And .020" of cable play adjustment will make a noticeable difference. Its easy to see in the amount of oil consumption at the end of a days ride.
the fich could be wrong...
it says the srx and viper powervalves are the same part numbers
it says the srx and viper powervalves are the same part numbers
O2viper700 said:
nah, your mistaken a srx exh valve is: 8dn-1131A-00-00
viper is 8ek-1131A-00-00
the differance is the prefix, just because the rest of the numbers are the same does not mean its the same part number. youll aso find this on alot of other parts, its the prefix and even the last 2 digits can be a 01 instead of a 00 and thats the differance.
also, viper is already set richer on the oilpump cable then the srx is....
98-99 didnt use a differnt oilpump. I even gave you the benefit of the doubt and went and looked up in the 2000 tech update book to see if they revised the oilpump on the 2000 srx from 99....nope.
the oiling problem theory just isnt holding any water under the fact check as you can see.
VMAX535
New member
Viper Crank Meltdown
Hi, most of you don't know me because I'm a Vmax4 guy. I surfted around and found this thread and wanted to share what happened to a Viper in my corral. This is the second time. What we have:
*2003 Viper
*Air box gutted
*Carbs (Stock bore), 50 pilots, 160 MJ, stock tubes, 3rd clip on needle, maybe 4th?
* Bender Head, Peak Perf with low comp domes
* Last rebuild including CV-Tech Crank and Wiseco ProLite SK1325 Kit, 800km ago
* New carbon Fiber Reeds and spacers
* Heel Clickers
Last weekend blew the crap out of middle cyln. same failure as 800 km ago including the big end rod bearing. It appears that the motor detonated then the big end crank bearing let go, shot crap up through the transfers and seized the rings/piston. Amazingly enough the cylinder was salvageable.
Detonation instigated this again even though it is jetted high. I think it happened in the mid range, Has anybody put bigger tubes in there carbs. Maybe Q8's.
Hi, most of you don't know me because I'm a Vmax4 guy. I surfted around and found this thread and wanted to share what happened to a Viper in my corral. This is the second time. What we have:*2003 Viper
*Air box gutted
*Carbs (Stock bore), 50 pilots, 160 MJ, stock tubes, 3rd clip on needle, maybe 4th?
* Bender Head, Peak Perf with low comp domes
* Last rebuild including CV-Tech Crank and Wiseco ProLite SK1325 Kit, 800km ago
* New carbon Fiber Reeds and spacers
* Heel Clickers
Last weekend blew the crap out of middle cyln. same failure as 800 km ago including the big end rod bearing. It appears that the motor detonated then the big end crank bearing let go, shot crap up through the transfers and seized the rings/piston. Amazingly enough the cylinder was salvageable.
Detonation instigated this again even though it is jetted high. I think it happened in the mid range, Has anybody put bigger tubes in there carbs. Maybe Q8's.
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Devilin AblueDress!
New member
May want to start your own thread for higher/better response. I picked an 04 Viper S late last season but have had a fleet of SRX's for a while. When I picked up the Viper I read a crap load of threads for "homework" LOL! Are you running a rear cooler? Common advice is to raise needles to 3.25 for normal riding or 3.5 for putt putt (don't sound like this one putt putts) As far as your Q-8 question, you should already have a Q8 in PTO and Q4 in the others right? (stock specs) I have read of guys running SRX carbs/tubes (most in my experience are Q6s) but poster did not specify.
viper has WAY MORE ignition timing then a srx does
viper has LEANER needles and nozzles in the carbs then a srx does
lean settings and more ignition tiing with low octane fuel equals detonation, which then equates into bad rod bearings.
best thing to do is to use srx carb rack on it or at least switch over to srx needles and nozzles. Run 93-94 octane fuel only and add booster at every fill up. (you didnt mention what cc domes are on it in the peak head).
more ign. timing in a 2 stroke sled puts more heat into the piston.
VMAX535
New member
I did do a little homework, this how I ended up on this thread. Thanks for the additional information.
/Dan
VMAX535
New member
I will look into switching the needles and needle jets to the srx version. The domes are 23cc. Thanks for the input. ?Dan