98 srx burned cylinder

U

uncletom43

New member
Joined
Jan 9, 2005
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Age
63
Location
Owosso,Mi
I wonder if anyone can help me i have a 1998 msrx 700 and i was riding in the U P of Michigan 2 weeks ago and ahve been riding for about 140 miles with out any warning the sled started to bog and it started to back fire so i shut it off but it didnt seze so i tore the head off to see what was going on and what i found on the mag side the piston was burned through the rings and the piston looked like it started to melt a hole in the side i looked it all over and i couldnt find anthing wrong so i put another piston in and drove it about 10 miles and it did the same thing the piston looks the same as the first one now im stumped any ideas? where to look would be helpful i could spend lots of $ on pistons thanks if you can help Tom
 

the cyclinder had some aluminum from the piston on it but cleaned up and yes the carbs were cleaned before i went to the U P
 
Same thing happened to mine this year, but I hadn't cleaned the carbs and had bad gas in the tank. I cleaned my carbs, and pv's, checked for air leaks the best I could and fixed it.

I have ridden aprox. 500 miles since then and haven't had even a slight hint of a problem....knock on wood....
 
if a power valve is stuck open will it make more heat in the cylinder ?and when it happened i was running at 6000 rpm about 50 mph
 
uncletom43 said:
if a power valve is stuck open will it make more heat in the cylinder ?and when it happened i was running at 6000 rpm about 50 mph
Click to expand...

IMO:

No a power valve issue would not cause this.
Holes in pistons + crown errosion is a result of excessive heat normally caused by the cylinder running WAY TOO LEAN. or ignition too advanced or a cylinder cooling problem

Possible causes:

-Dirty Carbs[most likely]
reclean those carbs, pay attention to every jet and passage, make sure you clean the little "top hat" fuel filters under the fuel inlet needle + seat

-Too lean of carb settings
make sure the carbs have not been rejetted way leaner then stock[unlikely because only one cylinder effected]

-Carb Needle Clip or washers missing or set too lean on the affected cylinder

-Air leaks
-check for cracked carb boots, loose carb boot/ reed cage bolts, torn or miising gaskets under the carb boots, air box improperly installed at the carb throat

- Bad crank seal
if the crankshaft seal behind the flywheel is leaking it will cause the cylinder to run lean

-Bad Gas
unlikely the problem this time because you were at relatively low power settings and only one cylinder is affected


JM.02c
 
sideshowBob said:
IMO:

No a power valve issue would not cause this.
Holes in pistons + crown errosion is a result of excessive heat normally caused by the cylinder running WAY TOO LEAN. or ignition too advanced or a cylinder cooling problem

Possible causes:

-Dirty Carbs[most likely]
reclean those carbs, pay attention to every jet and passage, make sure you clean the little "top hat" fuel filters under the fuel inlet needle + seat

-Too lean of carb settings
make sure the carbs have not been rejetted way leaner then stock[unlikely because only one cylinder effected]

-Carb Needle Clip or washers missing or set too lean on the affected cylinder

-Air leaks
-check for cracked carb boots, loose carb boot/ reed cage bolts, torn or miising gaskets under the carb boots, air box improperly installed at the carb throat

- Bad crank seal
if the crankshaft seal behind the flywheel is leaking it will cause the cylinder to run lean

-Bad Gas
unlikely the problem this time because you were at relatively low power settings and only one cylinder is affected


JM.02c
Click to expand...
gotta agree 100% with bob , dirty carb,air leak on the intake side or air leak from the mag side crank seal. in 60,000km's of driving and abuising my 2 srx's i've burned lots of pistons but not because of a stuck power valve .
 
I think shot exhaust donuts may cause some of that too, but I'd be surprised if it was to that extent.
 
well i removed the engine and started to tare the engine apart and i looked in the reed cage and i found some foam that was in the top of the air box on each side where the cables go through was stuck in the reed cage and thats what caused the melt down i cant belive that foam did all that damage but thats the way it goes
 
i had that foam from the airbox by the cables, get sucked into the center cylinder on my '99 srx. it just caused it to run like shit. after i got the foam out, i tore all the rest of the foam off, so it could never happen again.
 
uncletom43 said:
I wonder if anyone can help me i have a 1998 msrx 700 and i was riding in the U P of Michigan 2 weeks ago and ahve been riding for about 140 miles with out any warning the sled started to bog and it started to back fire so i shut it off but it didnt seze so i tore the head off to see what was going on and what i found on the mag side the piston was burned through the rings and the piston looked like it started to melt a hole in the side i looked it all over and i couldnt find anthing wrong so i put another piston in and drove it about 10 miles and it did the same thing the piston looks the same as the first one now im stumped any ideas? where to look would be helpful i could spend lots of $ on pistons thanks if you can help Tom
Click to expand...
Always include pics so we can be of help
Thanks
 
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