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2015 Stock Viper backfires occasionally on deceleration

H

Hibb Viper

Newbie
Joined
Jan 2, 2022
Messages
13
Age
43
Location
Wisconsin
Country
USA
Snowmobile
2015 Yamaha SR Viper
2000 Yamaha SX-R 700
2015 LTX all stock backfires or pops on deceleration when coming to a stop and letting off the throttle, but works great besides this issue. If I ease off the throttle it doesn't backfire. Has new gas and spark plugs. New ecu in 2019 with newest flash at the time (previous owner). No cracks in header pipe. Stock muffler isn't blown out and gasket is good yet. Any ideas of what to try next? Do I need a PCV to mess with fuel settings at lower rpms? Is this just the nature of the beast? Let me know what you guys think. Thanks!!
 

I had a 2016 that acted that way, and sometimes, the engine would actually die when I came to a stop. The dealer adjusted the TORS, and I never had another issue.
 
Luckily mine hasn't died yet but it is very annoying. I'll take a look at the TORS adjustment and report back. Thanks for the replies!!
 
Mine has done this for several seasons and the dealer cannot figure it out. The first time it happened I adjusted the throttle several times during the day and was not able to make it go away. The next morning we rode and it magically went away. Over the rest of the season and the next 2 seasons I have had it happen on and off. It was in again last spring and they adjusted the TORS but I am not convinced that is the issue. I will be riding for the first time this weekend so we will see. I have a theory that it only does it when it is warm out (like 32 and up) and not when it is cold.
 
SeX Viper said:
Mine has done this for several seasons and the dealer cannot figure it out. The first time it happened I adjusted the throttle several times during the day and was not able to make it go away. The next morning we rode and it magically went away. Over the rest of the season and the next 2 seasons I have had it happen on and off. It was in again last spring and they adjusted the TORS but I am not convinced that is the issue. I will be riding for the first time this weekend so we will see. I have a theory that it only does it when it is warm out (like 32 and up) and not when it is cold.
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Well, I just put mine all back together and took several runs while adjusting the throttle position, all the way loose to when the TORS starts kicking in. Still backfired the same as before. I'm beginning to think TORS isn't the problem either. I thought it only did it when it was warm as well but it was just doing it at 15 degrees today. Let me know how yours works this weekend.
 
How about a valve adjustment? I had a backfiring issue on an '05 Rx-1, which was a TORS issue. But when I had a similar experience with an '06 Apex of backfiring on deceleration or even the engine cutting out completely when coming to a stop, it turned out to need a valve adjustment. Took the dealer awhile to figure out, but the adjustment did the trick.
 
Snowaddict said:
How about a valve adjustment? I had a backfiring issue on an '05 Rx-1, which was a TORS issue. But when I had a similar experience with an '06 Apex of backfiring on deceleration or even the engine cutting out completely when coming to a stop, it turned out to need a valve adjustment. Took the dealer awhile to figure out, but the adjustment did the trick.
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I'm beginning to think it might need a valve adjustment as well. Last night I pressurized the exhaust system to make sure the header and muffler didn't have any leaks, which they did not. I'm going to put on a new header gasket and muffler gasket and try it one last time to rule out the exhaust system. Then I'll look into adjusting the valves. Thanks for mentioning it!
 
How many miles on the sled, and are you having any trouble with cold starts? My 2016 needed the valves adjusted at @6,600 miles because it had cold start issues. According to what I have read here, as well as what I was told by the service manager, that was unusually low mileage to have valve issues. This was the same sled I had issues with back-firing and stalling on deceleration, but those issues were at 1,500-2,000 miles, and were cured by the TORS adjustment.
 
Wannaviper said:
How many miles on the sled, and are you having any trouble with cold starts? My 2016 needed the valves adjusted at @6,600 miles because it had cold start issues. According to what I have read here, as well as what I was told by the service manager, that was unusually low mileage to have valve issues. This was the same sled I had issues with back-firing and stalling on deceleration, but those issues were at 1,500-2,000 miles, and were cured by the TORS adjustment.
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It has 5700 miles. Cold starts have been good since putting in a new battery. However I did notice the rpms dropping at idle during warmup. I also couldn't start it when still hot after stopping for gas last weekend. I had to crack the throttle to start (1st time I've seen this issue). All of this is still leaning me towards checking the valve clearances. I also think it is way early for valves to be out of tolerance, but might as well check since I have it ripped apart yet.
 
It’s certainly possible, and with those symptoms, definitely worth checking.
 
Wannaviper said:
It’s certainly possible, and with those symptoms, definitely worth checking.
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Well, just checked the valves. Intake are good, but the exhaust valves are definitely out of tolerance. Should be between 0.0083-0.0098 and I'm at 0.006 to 0.007. I'm guessing this might be my problem. Hopefully...
 
Hibb Viper said:
Well, I just put mine all back together and took several runs while adjusting the throttle position, all the way loose to when the TORS starts kicking in. Still backfired the same as before. I'm beginning to think TORS isn't the problem either. I thought it only did it when it was warm as well but it was just doing it at 15 degrees today. Let me know how yours works this weekend.
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I rode Friday night about 30 miles and no issues. I rode all day Saturday 175 miles and no issues until the end of the day and it stared again, the temp was only 10 F at that point so my theory about air temp is out the window. We rode again on Sunday and no issues. I like this theory about the valves needing adjustment but wouldn't think it would be intermittent if that was the case.
 
SeX Viper said:
I rode Friday night about 30 miles and no issues. I rode all day Saturday 175 miles and no issues until the end of the day and it stared again, the temp was only 10 F at that point so my theory about air temp is out the window. We rode again on Sunday and no issues. I like this theory about the valves needing adjustment but wouldn't think it would be intermittent if that was the case.
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So it sounds like yours is more intermittent than mine. Mine is pretty consistent when letting off the gas. I ended up changing the shims on my exhaust valves to get them within spec (huge pain in the butt btw) and I still have the backfire on deceleration. I also tried bypassing my tors completely and still has the issue. I might change the fuel filter and clean the injectors but then I might just run it this season easing off the gas and then take it into the dealer later and have them give it a look. Really frustrating...
 
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