gap599
New member
Hello Everyone,
I have a problem with my sled ('99 SRX 700). I went for a ride yesterday and the sled was running perfect for the first half of the ride, on the second half of the ride the sled was doggy and I was only seeing 7200-7700 RPM.
I started digging into it today and found an issue with one of the powervalves. The cable was pulled through and the valve was broke in two pieces (where the round shaft attaches to the rectangular valve). I haven't got the broken piece out yet.
Obviously, i need a new power valve, but my bigger concern is the piston & cylinder. Since nothing was holding the valve out, could it have slid in and contacted the piston?
I did a compression test and got 105/114/114. The low cylinder is the one with the PV issues. I tested the comp at the beginning of the season and got 110/110/110 so I am thinking something is up since the one cylinder has dropped.
I have a problem with my sled ('99 SRX 700). I went for a ride yesterday and the sled was running perfect for the first half of the ride, on the second half of the ride the sled was doggy and I was only seeing 7200-7700 RPM.
I started digging into it today and found an issue with one of the powervalves. The cable was pulled through and the valve was broke in two pieces (where the round shaft attaches to the rectangular valve). I haven't got the broken piece out yet.
Obviously, i need a new power valve, but my bigger concern is the piston & cylinder. Since nothing was holding the valve out, could it have slid in and contacted the piston?
I did a compression test and got 105/114/114. The low cylinder is the one with the PV issues. I tested the comp at the beginning of the season and got 110/110/110 so I am thinking something is up since the one cylinder has dropped.
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gap599 said:
theres a stop in the cylinder so it keeps it away from the piston, if it had kissed the piston it would have taken the ring out and you wouldnt have any compression. Get the broken part out with a drill extension, put in a sheet metal /self tapping screw in there, drill it into the broken part and pull back on it, use shop vac to catch the chips if any.
on your comprerssion test, your also differnt on your other 2 cylinders, just the way you checked it, its not far off, youll be fine just replace valave and cable, reset them to correct clearance and go ride.
gap599
New member
Thanks Mrviper, I'll take a crack at it tonight and let you know how it goes.
Just to double check, all years of the SRX use the same power valves? And they are interchangeable between cylinders (i.e. a power valve from any of the three cylinders from any year will fit any sled?)
Just to double check, all years of the SRX use the same power valves? And they are interchangeable between cylinders (i.e. a power valve from any of the three cylinders from any year will fit any sled?)
viperking
Active member
Yes, all valves are the same from cylinder to cylinder and from 98-2002 as long as it is from a 700. The 600 srx valves are different
gap599
New member
Okay, I got further into it tonight. The broken PV did slide in and touch the piston, somehow the rings didn't break (see pictures). So it looks like this repait just got more expensive! I now have some more questions:
1. Piston is marked "9K STD" on the top. I am assuming this means its a standard bore, does the 9K mean anything to anyone?
2. Cylinder head is very pitted (see pics). Whats your take on this? damage from a previous blow up?
3. Right now I am debating between throwing in a new piston & PV and riding her for the rest of the season or pulling the motor and completely going through it from top to bottom to complete a proper inspection/freshening. What do you think is the best option?
Thanks again for your help everyone!
1. Piston is marked "9K STD" on the top. I am assuming this means its a standard bore, does the 9K mean anything to anyone?
2. Cylinder head is very pitted (see pics). Whats your take on this? damage from a previous blow up?
3. Right now I am debating between throwing in a new piston & PV and riding her for the rest of the season or pulling the motor and completely going through it from top to bottom to complete a proper inspection/freshening. What do you think is the best option?
Thanks again for your help everyone!
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bluemonster1
LIFE MEMBER ONLY ONCE!!!
holy man and I thought I had PV issues..Are you sure the valve touched the piston?? Should be a stop in there.What does the beveled end of the valve look like,is it chewed a bit.??
gap599
New member
yeah, the end of the valve is chewed up, i can't get it out of the cylinder. Its hard to tell from the pics, but the piston is worn wear it was rubbing against the valve.
I can definately see the wear on the side of the piston. The pitting is from the fragments of the PV and the Piston. I would pull motor and go thru it entirely. Would like to know how your PV broke. Not good.
srx steve
New member
Looks like a detonation problem to me i'm sure mr viper will chime in on this
gap599
New member
Thanks for the help so far, right now I am leaning towards parking it for the rest of the season and then pulling the motor and going through it completely this summer.
I'm really bummed about this, we have more snow this winter than any other in recent memory.
I'm really bummed about this, we have more snow this winter than any other in recent memory.
SRX_700 said:
I'd expect the piston to show the same pitting.
I'd guess the pitting of the cylinder head is from a previous melt down/failure.
gap599
New member
What would you do with the head? Replace it?
the piston has a burned off front crown from being lean, this lean condition causes heat which results in detonation and the detonation is likely what caused the valve to break.
You cant rerun that piston, at least not for very long...as once the flame front can hit the top ring(exposed by the crown edge being burned back) it will soften the ring and then bend it from being soft(it actually will turn orange from the heat)it will snag the powervalve and exh port edge and youll really have a mess then to repair.
personally at this point, I would pull the other 2 heads and see what the front of the pistons look like, if they are also burned off (rounded) your gonna need 3 pistons and rings to get going again. then find out why its lean........
ADD: the piston tops tells the story... this engine is lean, you have no wash marks, dome top is dry and not colored right, its lean!.
The head is pitted but it can be reused that really wont "hurt" it, all I would do if replacing it with another good used one isnt a option is to take some fine sandpaper and smooth it out slightly on the squishband, just remove the rough edges, it looks ugly but wont slow the sled down if its not rough and jagged edges.
on the pistons on the bottom of it, does it say 8dn?
You cant rerun that piston, at least not for very long...as once the flame front can hit the top ring(exposed by the crown edge being burned back) it will soften the ring and then bend it from being soft(it actually will turn orange from the heat)it will snag the powervalve and exh port edge and youll really have a mess then to repair.
personally at this point, I would pull the other 2 heads and see what the front of the pistons look like, if they are also burned off (rounded) your gonna need 3 pistons and rings to get going again. then find out why its lean........
ADD: the piston tops tells the story... this engine is lean, you have no wash marks, dome top is dry and not colored right, its lean!.
The head is pitted but it can be reused that really wont "hurt" it, all I would do if replacing it with another good used one isnt a option is to take some fine sandpaper and smooth it out slightly on the squishband, just remove the rough edges, it looks ugly but wont slow the sled down if its not rough and jagged edges.
on the pistons on the bottom of it, does it say 8dn?
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gap599
New member
Thanks mrviper, your advice is very helpful. I can't speculate as to why it went lean - I'll check everything (carbs, carb boots, crank seals, etc...). The only change I have made to the motor recently is swapping the stock can for a Hauck, but I checked the plugs shortly after installing the new can and the motor still appeared to be on the rich side. In your experience, will an aftermarket can affect the jetting?
no, the can wouldnt lean it out, what are the jets in the carbs?
gap599
New member
I'll pull the other two heads tonight and post pictures of what I find.
