Project> 2001 SRX 700 W/ 1,780 miles has AAEN Pipes V Force Reeds, looks like stock clutching 144 pics on a stock proaction skid w/ aftermarket transfer rods.
1)Mag #3 cyl head had the wrong spark plug cross threaded into the plug hole, I removed and re tapped the head, OK
2)Removed the carbs, clean & inspected , OK
3)Compression test Clutch side cyl#(1) 125 psi, cyl#(2) 125 psi) Mag cyl#(3) 90 psi?
4) look in that Spark plug hole unable to see an issue
5) fill w/ fresh 93 premium fuel & new set Of BR9ECS ,starts up sounds GR8 let her worm up for a few moments shut her down fires rite up 1st pull fire her up again crack the throttle few times adjusted the idle let run on the stand the she just quit-seized.
6) tear the top end down Cyl #3 piston melted on the exhaust - front side & weakened the piston piece broke off & seized in the cyl.
Question: could the loose spark plug caused this issue or the wrong plug cross threaded in the head cause that piston to get hot on the front side of the piston which melted broke & seized? again I didn't see any issues in the carbs?
1)Mag #3 cyl head had the wrong spark plug cross threaded into the plug hole, I removed and re tapped the head, OK
2)Removed the carbs, clean & inspected , OK
3)Compression test Clutch side cyl#(1) 125 psi, cyl#(2) 125 psi) Mag cyl#(3) 90 psi?
4) look in that Spark plug hole unable to see an issue
5) fill w/ fresh 93 premium fuel & new set Of BR9ECS ,starts up sounds GR8 let her worm up for a few moments shut her down fires rite up 1st pull fire her up again crack the throttle few times adjusted the idle let run on the stand the she just quit-seized.
6) tear the top end down Cyl #3 piston melted on the exhaust - front side & weakened the piston piece broke off & seized in the cyl.
Question: could the loose spark plug caused this issue or the wrong plug cross threaded in the head cause that piston to get hot on the front side of the piston which melted broke & seized? again I didn't see any issues in the carbs?
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staggs65
Moderator
I have a bit of confusion in your time line. You're calling PTO #3 but also calling clutch side number 1. PTO is clutch side. Not a real big deal but I'm just trying to understand everything. So you're saying #3 had the cross threaded plug. You pulled that head. No piston damage at the time. Rethreaded it put it back on. Ran it on the stand and now the number 3 cyl has this damage? If I'm following it right I can't imagine that amount of damage done running on a stand. Please correct me if I'm misunderstanding so we can all help you out. I could just be reading it wrong
staggs65
Moderator
Ok. I've re-read this a few times and I think I get what you're saying. Delete the PTO thing and go ing with the numbers. 1 and 2 checked compression. 3 was low. Which had the cross threaded plug. When you say "I removed" you are just saying the plug not the head?......... now the pics. Looks like a classic lean burn down except they usually start directly at the exhaust port. Never seen it over the pin like that myself. I would say since the carbs check out it would be from the cross threaded plug. Still weird how it burnt off over the pin to me. Can only speculate its,because that's the side the air was leaking through the plug?
Hi staggs I removed the spark plug that was stripped & retapped the spark plug hole without removing the head. Used a small tube w/vacuum to remove any small metal fragments after tapping. Previous owner said plug was not in tight or torqued so it worked it's way out & stripped the threads. Then he cross threaded the wrong plug into the head. He may have driven sled for a while w/loose plug til it fell out. Maybe that caused the lean condition.
YAMMIEGOD3:16
Active member
nope, that damage was there from previous owner before you. you bought it this way. no chance that happen on a stand. tell ya thats a nice sled. this is a easy fix. 3:16x (yammie tony)
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Personally I wouldn't have messed with that head. ..get a nice usedhead on ebay or on here. Good looking sled. Do some shopping and get her right again!
toydoc
Member
IMO, the pipes / mods caused detonation. The DETO is what loosen the spark plug. The person that is tuning it after the mods keeps seeing black fuel gunk spitting from the threads of a loose spark plug. So they tighten a little more after each time. Till the tenth time of over tightening they pull the threads loose.
So the root cause was detonation eating the piston and loosening the plug. Everything else is the effect of that.
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Mac
Member
I agree that the problem was caused by the last owner or the last time you rode the sled. It may have finally broken the piston and snagged a ring on the stand but the problem is something different. The leading edge of that piston did not fail on your stand. That piston appears overheated and baked to death. Please look carefully at the piston ring orientation pin. When pistons get hot this pin can become loose and fall out. The ring then moves and gets snagged on the port. Just looking at the failure tells me the ring snagged for the final failure. Also look at the underside of the piston and it will show burnt to death ash inside under the dome.
So once you rebuild and replace cylinder, piston, head your gunna need to solve why it burned down and ran lean. Air leak, bad gas, incorrect jetting, clogged pilot and many other reasons. ---mac---
So once you rebuild and replace cylinder, piston, head your gunna need to solve why it burned down and ran lean. Air leak, bad gas, incorrect jetting, clogged pilot and many other reasons. ---mac---
yamahamark
Member
Nice sled!! But yeah that piston has been toasted for a while to look like that.
Yammigod, I agree it definitely happened on the previous owners last ride with the sled, before i bought it.
Mac, the piston ring orientation pin still in the piston, correct looks like the piston melted so bad that it weakened the piston and broke apart and siezed, took a picture of the underside of the piston dome not that badly burnt or ashed.
Pics from the under side of the piston, checked the carb jetting #1 carb Clutch side 152.5 main 42.5 pilot & 1 turn out
#2 carb CTR 152.5 main 42.5 pilot & 1 turn out
#3 carb MAG153.8 main 42.5 pilot & 1 turn out
may have to call AAen and ask what the jetting is for there pipes?
#2 carb CTR 152.5 main 42.5 pilot & 1 turn out
#3 carb MAG153.8 main 42.5 pilot & 1 turn out
may have to call AAen and ask what the jetting is for there pipes?
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staggs65
Moderator
Ah yes. I can see the pics better now with both eyes open. Like Mac said, the piece over the pin is broke off. And it's eroded at the exhaust port where one would expect.
took a close look @ the air box gutted and has holes drilled in it may be an issue?? i will post some pics tomorrow
toydoc
Member
IMO, it wasn't lean. The top and sides are to clean. Even the top of the burnt piston that didn't get eaten still has alot of wash on it (rich).
Lean wont loosen a spark plug, detonation does. Detonation blows the protective top layer of fresh charge off the piston edge (like taking off cool padding).
That will expose the piston edge to all the force and heat of the CORRECT time explosion without it's natural gas protection.
Lean expands parts and makes abnormal shapes.
Detonation just plane eats parts / brakes parts
You have timing or fuel quality issues or both
Lean wont loosen a spark plug, detonation does. Detonation blows the protective top layer of fresh charge off the piston edge (like taking off cool padding).
That will expose the piston edge to all the force and heat of the CORRECT time explosion without it's natural gas protection.
Lean expands parts and makes abnormal shapes.
Detonation just plane eats parts / brakes parts
You have timing or fuel quality issues or both
True, detonation eats things, but it'll eat a hole right thru the center of the piston, not the edge. At least everyone I've ever seen. I believe that damage was from a lean condition. Who knows from what or when.
jetting on the mains look good maybe a little rich dont know why mag carb #3 mAG had the larger jet 153.8 maybe because the heat from the aaen pipes run close to that cylinder?? took a closer look @ the box has a few holes drilled in it and no dividers inside?? Any Ideas? 
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toydoc,
its possible he got a bad batch of gas? your rite the rest of the piston looks good , even the head dosn't look that bad, would like to id the issue before I builder back up.
its possible he got a bad batch of gas? your rite the rest of the piston looks good , even the head dosn't look that bad, would like to id the issue before I builder back up.
Mac
Member
Pic number nine out of ten shows the exhaust side of the piston had heat related failure because the leading edge of exhaust is burned so badly. Once the ring becomes exposed its then snagged on the port and seized. I doubt timing because the timing is fixed unless someone modified the stator.
Remove the flywheel and inspect for an offset key-way.
Also look for modified stator that would make it adjustable.
The holes certainly would allow for more air and a leaner setup. It almost appears if the thought was to provide more air to individual cylinders to even out the state of tune. I cant imagine what else the holes were for?
If you can..... provide a closer more detailed pic of the leading edge of the broken piston. Also the entire piston crown. Deto normally looks like a flat pic or very small hammered marks all over the crown and not localize to only exhaust.
Remove the flywheel and inspect for an offset key-way.
Also look for modified stator that would make it adjustable.
The holes certainly would allow for more air and a leaner setup. It almost appears if the thought was to provide more air to individual cylinders to even out the state of tune. I cant imagine what else the holes were for?
If you can..... provide a closer more detailed pic of the leading edge of the broken piston. Also the entire piston crown. Deto normally looks like a flat pic or very small hammered marks all over the crown and not localize to only exhaust.
staggs65
Moderator
2000 up don't have dividers in the airbox