piston chewed

mattysmith440 said:
so i hauled my motor apart. the mag side, which i knew was shot, was chewed to pieces, with half of the top ring not even there, and the cylinder mangled. took off the middle cylinder and everything seems fine. so i take off the pto side cylinder and to my surprise the top of the piston is burned down on the exhaust side, almost to the top ring. so what could cause this? the only thing thats changed is my pilots. they were 45 and i changed them to 42.5, and i took my bender can off and put a mbrp race can. it has fresh 91 octane, with a new filter and carbs thoughrouly cleaned numerous times. im running yamalube. i havent had a temp light come on.... i need to figure out what cause it before i spend money to put it all back together, stock or big bore.
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well, its been run lean over time, the piston edge errodes and then exposes the ring to the flamefront, where it becomes soft and molten from the heat, then snags the exh port and makes deep gouges in cylinder.

45 pilots are usually used when someone has aggressive clutching, it makes the sled richer in the low speed area, not leaner. So going back to 42.5 pilots you leaned out the low speed operation although this was not what caused your burndown. 2001 srx used 40 pilots so with 42.5 your still richer then stock. Most likely you or the person before you had low octane fuel and a big lake to hold it open on, and you just got lucky enough it went out on you if the damage was done before you got it.
Sideshow Bob gave you a very informative list to go over to make sure when you repiar it, it doesnt happen agin. I would check off every item he has listed there!.
 

the piston in the pto side is the one that eroded, but that one caused no damage to the cylinder. the mag side piston wasnt eroded at all, it just looks like someone smashed it with the claw of a hammer and most of the top ring is nowhere to be found, that the one that has the cylinder and head very damaged. im after putting 1000 miles on the sled since i bought it, and have had clean gas in it since the day it came from new brunswick. the only thing i didnt check off his list yet is the crank seals. 40 is stock for 2001? my manual and the tech section on here says 42.5 ? i want to big bore it but ineed to figure this out before i spend the money on that! by the way mrviper i heard you were the man to talk to when it comes to big bores, wanna pm me some info on them /pricing/availability ? i wanna get this thing back on the snow, i think im just gonna turn it into a race sled, and keep an eye out for another srx for the trails. infowould be greatly appreciated! thanks in advance!
 
I just went through the same thing... bought the sled last year cleaned the carbs and only rode it a few times then BOOM. So tore it apart last month and same thing both outside pistons and cylinders were shot. What I found was both crank seals were gone and 1 bad exhaust doughnut. I also have a set of stingers on it but I think im done with them. So now its all back together and I have a fuel delivery problem, when I open the choke no fuel is geting to the cylinder, dump a little down the cylinder and she fires right up and stays running so I dont think its the fuel pump, vaccum leak??
 
That is a very good point about the condition of the exhaust donuts and the retainer springs. At the start of last season I replaced all three exhaust donuts and coated them with a thin layer of the red high temp. silicone sealant. When I reinstall the engine after rebuilding it, I'll use the new exhaust donuts with the high temp. silicone and new exhaust springs. That is a critical seal in the exhaust system.
 
Engine burn downs

There have been a lot of folks having engine failures on SRXs and Vipers over the past couple of years due to detonation or lean burn downs. I try to keep up with all the posts in this section and I do not believe I have seen a single posting by an owner of a 2002 SRX whi has had an engine failure of this type. If this is true, it shows the DCS system is doing a good job. Anyone notice the lack of engine failures on the 2002 SRX model?
 
actually true.I don't remember anyone with a 02 SRX burning down to my knowledge.I believe the DCS is doing its job.I run my SRX hard and do a lot of 1 mile and longer wot pulls and never had an issue come up.,light stays off.That is why I waited until I could find an 02 SRX instead of the earlier ones.Almost bought a 98,glad I didn't.
 
ya i wish mine had dcs, i most likely wouldnt be in this situation right now! 60 cm of the white stuff forecast for today, and my poor girl is sitting out in the backyard getting buried :(
 
I don't think I would ride my SRX in 60 cm of fresh snow..I would get stuck just leaving my garage.You need one of them dual track Ski-doo's to make tracks instead out there..way to much snow for my liking.We would be flooded out every Spring if we got snow like that..
 
mines pretty good in the snow with the 1.75! well our annual snowfall is between 16-18 feet. we get from the end of october until the end of april in which we can leave our driveways and go. then all of may we need to trailer our sleds out of town to the trail/lake systems so its pretty good in that way, when you own a running srx lol
 
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