SRX engine experts....need help! Long!

SRXer

SRXer

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Dec 25, 2005
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411
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S Ont
OK guys, relatively new to this site, and SRX's. Lot's of good info on here, hoping someone can offer some insight. Bought an 02-700 with some miles on it, went up north, and squeaked the centre piston going across a lake at 60mph, 34*F. Take it to dealer, bad news, shrapnel got into crank. OK, so I know this guy is knowledgeable with SRX's, still rides one himself! So I bite the bullet, sled is otherwise mint, so I figure go for it. Turns out the centre power valve cable was pulled out, so I attribute the burndown to that & heavy, wet snow workin it. Ok so new crank, and new end bearings (old ones were growling a bit, must have been put away not fogged?), 3 new power valves, 3 new pistons (Yami), pins, rings, crank seals, etc.etc. Centre cylinder new as well, 2 outsides were good. All this equates to one large bill. Jetted 151.3, 150, 150 which is richer than 02 specs. Dealer runs it for like 15 min last night, and I go pick up this morning. Go for a ride with my brother, put on about 30 miles, about 28*F out, lots of snow on trail for cooling, take it fairly easy up to this point, just short 3/4 throttle bursts. Come across a sideroad, cruising about 20mph, punch it about 7/8 throttle and poof. DCS light came on, and it bogged and I knew right away. :o| Was only on the throttle about 3 seconds. Premium fuel with a small bottle of Bardahl octane boost just to be safe on the new mill. Dealer completely went through carbs (and said they were spotless). Only thing that is not stock is carbon tech reeds with spacers, which were on the sled previously, and apparently only 1 year old. I had checked plugs about 10 miles into the ride, and they were a nice cardboard brown, although it was not a full throttle chop. DCS light never activated all day up to that point. Centre plug had tiny flakes on it, and the top of the piston had tiny shiny flecks on the crown, looking thru the plug hole. Other 2 plugs looked darkish brown. Can anybody think of anything I am missing, cause I am stumped!!!! Thanks for any suggestions in advance. :die:
 
have you checked the rubber "muffers" thats on both sides of the carburators for cracks? if they are old they can crack and draw in air.. this is normaly a problem for older sleds but you better take a look at it to be sure!
 
I thought of the rubbers myself, shouldn't be the case in an 02, but hey, it's worth a look for sure. Thanks for the ideas. And I agree, it's going down in the mid, not WFO. That's kinda what has me stumped, anytime I ever squeaked one was on the big end. The carb boot thing would make sense with the same cylinder going down. Thanks for the ideas guys.
Any issued with the reed spacers. I will be the first to admit I have never dealt with them, or know the first thing about them. Should I lose them or are they a necessity with the Carbontech's?
 
reed spacers aren't usualy used with the powervalved motors, just the non powervalved. it has to do with crankcase design. most people dont use aftermarket reeds on a SRX because theres no bang for the buck. but I doubt either is causing a burn down.

look for air leaks, and rechceck the carbs yourself. got in a big pissing match with some conceted snowmobile mechanic who did carb work just before I got my sled to have it drop a piston skirt the first day of ownership. it had a 210 jet in place of a 270, a imrpoperly positioned needle, and maybe something else too. after such inspiring lines as "I didn't change them" (Did you even look at them?) "I've bean doing this for 20 years and nobody has ever acused me of making a mistake" (ya right) and finaly "thats not a lean burn down anyway" (just an unfortunate coincidence, bullshit). I endedf up fixing the sled myslef for less than $200 and have quite using that dealership.
 
Crank seals were new, as was practically everything in the engine! Also I would think a leaking crank seal would take out one of the end pistons, not the centre?
Both burndowns @ about 3/4 throttle during acceleration, the more I reflect on it, definitely not to the bar. Seems to be starving for fuel under load for some reason. During a couple short WO shots for 5 to 7 seconds seemed fine, no DCS light. I am NOT a carb expert, but if assuming needles are correct, etc, could float set too low, or stuck in the "down" position starve an engine for fuel under load? I am 90% sure the needles are set to the stock position or half a clip richer, can't remember which.
Also is it possible to check if the heads were cut, unkown to me? Is there some means of measuring this? That is another thing that crossed my mind, especially if somewhere along the line someone was racing it in a stock class, and doing a little cheating. But have no idea how to go about determining this. Thanks for the input guys. Gonna have to go through EVERYTHING with a fine tooth comb, just hope to h*ll I didn't roast the new crank!!! :die:
 
asrx600 there is a small increase in hp with the reed spacer's on the srx's.Your right on the reed's if you have a stock mototr your wasting your money.
 
I'm no expert but I know a little about the dcs. I don't think it would let the engine burn down in 3 seconds.. This may sound very stupid but have you checked the carbon tech reeds, I have heard of cases where aftermarket reeds chip and ruin the engine.
That being said, I will lean towards the leaky boot theory. If it is leaky, and you jam it, I think it may create a very hot flamefront against the piston.. Does this make any sense? But what really puzzles me, is that if the boot was leaky, why didn't it activate the dcs earlier in the day? This may also sound stupid but, as you say, something got into the crank, maybe it made a groove in your crankcase?
 
As I said the crank seals were brand new, along with the crank, and duplex bearings, so I can't see the seal being the problem. I made a concious effort to watch for the light whenever I was "on it", and I don't understand why it never flashed either...ever. It did come on just as it locked up, but that was the first time. The carb boots will definitely be getting some attention tomorrow! As will the #$%&* centre carb...
So does anyone know a way to check if the heads have been cut?
And for anyone with an 02 SRX, what are you running for needle postion/ main jets?
Thanks for the replies.
 
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its not the crank seals if its the center cyl., things to look at:

1.) carb boot, reed spacer air leak, with a spacer, theres another splice and another joint to leak. spacers are of no gain on a srx/viper engine, especially stock.

2.) if you have never checked the carbs yourself ,thats where you need to look, wheres the needle at? wheres the shims placed at? is it the correct pilot jet?

3.) is it the correct spark plug heat range?

4.) the head would have to be considerbly cut to do this, it would have well over 150+psi in the cylinders to detonate on reg gas in such a hurry.
 
where does the fuelpump pulseline go-if its to the center on the crankcase id check that one for cracks too,i have never checked where mine is attatched so i cant tell for sure.
 
I've had this problem with a srx before...everything gets done by the dealer...yet he never checks the carb on the burndowned cylinder....just changed the burnt parts...not solving the cause....a leaking carb boot or even
if spacers are used without gaskets...might be leaking air there?
as mr.viper700 illuded to:something out of spec,an air leak somewhere,a dirty or damaged main jet or a wrong needle position or a plugged or crimped ventline to that carb.. leanout at the wrong time...burndown! as to the plugs...I've ran br9es's before with no problem as long as I kept the throttle away from the bar..
AS TO A BROKEN REED ....has anyone heard of a machine buring down from a broken carbon fiber petal?...I havent..and the chances of it happening twice..I dont think so..
if ALL the above is right on,undamaged,not obstructed and clean......it's an air leak...
as to the heads being cut...all would be and one wouldnt be reacting that way...what's most important there is your compression and squish...compression is easy enough to check...theres a post in tech right now on the protocol...I've checked squish with some soft lead solder(thick stuff) and stick it in til it hits the side...and gently rotate the engine(with the kill off) around the piston will smash the solder....then mic the thickness
 
Things to check on the carbs.....

Take the rack off, and totally rip that center carb down! Pull the float off,, and blow threw the seat with a rubber tipped air nozzle. Then tap out the jet needle, you need to have the slide removed to do this. This is the part the main jet threads into, screw in an old jet to tap on. They can become very crappy inside, clean/look for particles trapped inside. Last I can think off, make sure the carb top (held on with two screws) has all of the gasket material in place, a chunk of gasket missing can make the thing act funny. If nothing is found, you may want to start looking at the fuel pump/fuel line?
 
I didn't say it burned down due to the reed, I just suggested that a broken chip got into the engine and destroyed the piston. As I said, a stupid guess, but a stupid guess is better than no guess at all in my opinion!
 
Well thanks for all the replies guys, ;)! some real good ideas for oddball stuff put forward, that could be potential problems for sure. As it turns out, it looks like that crank was the culprit, :die: taking out the piston as a secondary issue, caused by the crank. I had never seen aluminum on a piston look the way this one did, and as it turns out it was probably shrapnel spattering off the top of the piston as opposed to being melted off, giving the plug the odd look. The pieces were very small, much smaller than I'd ever seen from pre-ignition or meltdown. And this was the second crank, UPS dropped the first one and bent # 3 rod. Well maybe the third one will be the charm??? I have no idea what would take that centre bearing out, aside from just being defective somehow, the crank checked out perfect in the v-blocks. Hopefully the dealer will go after the crank rebuilder, and I can finally get to ride this thing before the snow is all gone! :o|
 
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