blew up middle cyl 3 times wtf

regert

regert

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Sep 10, 2007
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What would be the problem 01 srx 700 blew up middle cyl 3 times in 2000km. Looked at carbs, seals, base gaskets???? Could it be a cank seal messing up the middle cylinder??? need help on this asap going on a trip this weekend.

Thanks Regert
 
Info

WHat do you mean blew up..melted down?? DO any mods, or all stock? Plug color?
 
regert said:
What would be the problem 01 srx 700 blew up middle cyl 3 times in 2000km. Looked at carbs, seals, base gaskets???? Could it be a cank seal messing up the middle cylinder??? need help on this asap going on a trip this weekend.

Thanks Regert
Click to expand...
Not to be a smart-aleck, but failure to determine the root cause seems apparent. This is why I stress finding the root cause before you completely tear it down and rebuild it.

I would just go through the whole air/fuel supply process carefully. Not enough fuel to keep the piston cooled is the likely culprit. It is simply an air pump that needs to take a certain amount of fuel along with the air. So something is either limiting the fuel or allowing extra air into the process.

Fuel pickup / filter, fuel pump, pulse line, carbs, intake boots, crankcase seal, crankcase ventilated or perforated, exhaust restriction, etc. are all possible problems.
 
piston melted on the exhaust side all 3 times, plug color seems to be good. I will try to get some pic's up of plug and piston.

Is it possible if the crank seal is leaking that the middle cyl would have problems but the outside cyl wont????
 
I don't see how . . .

Check the whole intake for that cylinder very carefully.
 
We checked the carbs, carb boot, base gasket, block. didn't look at the fuel pump or pulse hose tho will look at those tonight.

If it ran lean why would it melt the exhaust side of the piston? Wouldn't there be melting on the top???
 
it will melt the exhaust side ...gaz cool down the exaust temp....what size jet are u running ???pilot .and needle clip..do u have stock air box ????
 
did u put a new base gasket last time u fix it ...in someway u have a air leak ....boot,reeds,air box not seat correctly ,or dirty carb ...maybe it run at higher temperature with that track do u have a temp gauge ???
 
no temp gauge, have 2 other sleds have same set up one is stock and one is geared and clutched and no issues, this one melted down the first time withh the 121 on it still and 2 times with the 144 set up
 
then try to have a look to everything ....oil line ,gaz line ,carb boot,reed booth to base ,.... does it burn running midrange,full throttle ??..
 
not sure when it burnt, not my sled it's a buddies. one time I know he was running about 70mph on the lake, and the last time he was running in some small powder. The 1st time it burnt not sure what he was doing.

I think he is feathering the throttle but would have to ask him and get back to you
 
Lean

Sounds like your lean and mean. I stepped up 1 size on my main jets, id rather spend a few bucks on fuel then wrench. I also run my carb heaters on at all times, unless its 30f+ Why not install a temporary egt in there or get a kit for all three. A single probe setup is still cheaper than 1+ pistons.
Some where some how its lean. Is the air box modded up or cracked? Sometimes boots look good so really examine them....its not being ran with a huge exhaust leak is it?
For gods sake dont run it so hard it melts down again. Pull the plug then get a super good light so you can see the pistons top for wash, or pull the head.
 
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not sure jetting will solved the problem if he burn the sled on midrange and never run full throttle thats why u need to figure out where it turn lean
 
I will see the sled this weekend and hope to find the problem with it if my buddy doesn't find it. If you could think of any other places i could look please let me know.

Is there a way to test the fuel pump with out pulling over the engine as it is apart already???
 
if no air leaks anywhere.....

90% of burn downs happen at mid range cruse speeds(needles)your just to
lean in carboration settings and probably bad crap fuel,check jetting settings clean carbs and use GOOD premium 93 or higher octane,watch plug color close through out all carb circuits low, mid, top..
 
on a 01 srx what should the needles be set at and what should the jets be? for a stock engine?

still need to know if there is a way to test fuel pump on the bench? is there a way to mimic the pulse ther engine creates with blowing air past the whole and pinching the line quickly?????
 
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