SRX mid range lean condition?

[fourbarrel]

Out for a ride Saturday and it wasn't cold out,about 5 Celcius (40 Farenheight ? ),anyway put on about 25 miles,last 5 or so were slow like 40mph and only using 1/4 or 1/5 throttle. Engine was working fine and then it missed and popped and started rattling. I shut it off immediately fearing the worst,as I just got this engine back together about 2 weeks ago from last year's meltdown.

Long way round to the question but has anyone suffered the midrange meltdown Vipers are prone to?
I just finished tearing the top end off the engine and that's when I found the centre piston was toast. I checked the carb boot and it's good So I went through the carbs and I cleaned them although I didn't see anything in them to lead me to believe the fault was in them. I had about a half tank of fresh gas in it on top of the other half that was only a week old. No idea of the volume the dealer sells so I can't say if it was the freshest gas or not. From looking at the wash on the two remaining pistons I'm thinking it was running lean and the combustion chamber temp got too high for the piston. Jetting is '01 spec, 148.8-148.8-150 m-c-pto. I can't think of anything else this could be but I'll include pics so everyone can have a look see. Engine is bone stock with the exception of a can on it.Pics are centre- mag and PTO.

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[apex/viper rider]

i had the same problem on my piped viper on a warmer day trail riding then two open throttle passes on the lake smoked the center piston bent the rod and put a hole in the case beeen running this setup past three years no issues maybe the warmer day had some effect idk but i will raise my needles to be a little richer maybe you should do the same just an fyi i run non ethenal fuel always so i dont think it was a fuel problem

 

[fourbarrel]

i had the same problem on my piped viper on a warmer day trail riding then two open throttle passes on the lake smoked the center piston bent the rod and put a hole in the case beeen running this setup past three years no issues maybe the warmer day had some effect idk but i will raise my needles to be a little richer maybe you should do the same just an fyi i run non ethenal fuel always so i dont think it was a fuel problem

I always run supreme here and whether you can believe it or not but our supreme is not supposed to have any ethanol in it. I'll be raising my needles a clip to be safe because I have yet to find the cause other than fuel related. Carbs were clean,carb boot is solid and crank seals are new. Has to be the fuel or the fuel metering for the throttle amount. Too little gas going in to keep the combustion chamber cooled off.

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[apex/viper rider]

i agree

 

[Maim]

oil system is working?

 

[fourbarrel]

As far as I know it is.I bled the pump before starting it up for the first time this year,which was only 2 and a half weeks ago.There is no scuffing on either of the other 2 pistons to indicate they were as lean as the centre or lacked oil.But I will check it again to make sure.I'm kind of on the fence as to fix this engine now or wait til the fall and do it because our winter has been so disappointing this year and in order to ride I have to trailer upwards of an hour.With my work schedule and other commitments I just have a hard time finding the spare hours to get out on the sled,so it may very well be sitting til next fall.

 

[drew24]

Do you have a temp gauge on this sled? I have noticed since I put a temp gauge on mine that in warmer temps it doesn't cool very good due to the snow being thicker. My gauge stops reading at 250 degrees and it would bury it and stop reading. My temp light never came on the whole time. If there is no air leak and no carb/fuel problem I would guess it overheated.

 

[fourbarrel]

Do you have a temp gauge on this sled? I have noticed since I put a temp gauge on mine that in warmer temps it doesn't cool very good due to the snow being thicker. My gauge stops reading at 250 degrees and it would bury it and stop reading. My temp light never came on the whole time. If there is no air leak and no carb/fuel problem I would guess it overheated.

No but I've been meaning to put one on both my sleds for the last 4 or 5 years. There'll be one on it next winter though.

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[backofthepackjack]

Couple of thoughts,
I wonder if the needle clip could of come off somehow?
Iwonder if the float bowl could have went empty- stuck needle? incorrect float height?

 

[fourbarrel]

Couple of thoughts,
I wonder if the needle clip could of come off somehow?
Iwonder if the float bowl could have went empty- stuck needle? incorrect float height?

I have to adjust the clip position anyway so I'll know tonight. I had the floats and needles all out Sunday night and they were all free and clear then at least. Not saying it couldn't have stuck on Saturday but when I took them apart all was clear. Float heights I have written down but can't remember off the top of my head what they are. It's the same measurement I've been using for the past few years.

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[drew24]

I would also check the thermostat and make sure it is working properly. I am still guessing it got hot. After seeing how the engine temps are with the gauge I could definitely see it happening. The wet snow is terrible for cooling. I had 2 trips last year in that kind of snow. That's when I saw the gauge bury. Both times when I got home I noticed my antifreeze was overfull and both times I bled the rear exchanger and it went back to the normal level. I think it was boiling a little and making an air pocket in the rear exchanger. Running it at home in good snow and it has no temp problems. I would recommend ice scratchers. After using them I am a believer. This year on my trip it was cold and we had fresh snow and had no problems the first day. The second day there wasn't as much snow dust and I saw the temp start rising and it went up to 190 and I decided that was hot enough so I put the scratchers down and it instantly started going back down.

 

[brethren]

My Viper temp light has been coming on for years, and I've been dealing with it by putting snow on the running boards. We were out sledding last week and the temperature light came on again. I stopped by the Yamaha dealer and picked up a $75 thermostat. Put the thermostat in and the temperature light never came on again. I suspect the thermostat was only partially opening which was causing overheating. Also worth mentioning is it seem to be getting worse as time went on.

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