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Discussion Starter · #1 ·
Well when we got down to the lake my brother took out our 93 340 lynx and came back about 30 mins later with 30 miles on it and said it started to die on him out in the middle of the lake so instead of stopping right there he drove it home so of course he blew it up and yes, he holds the damn thing to the bar %85 of the time. well we are sick of sending the engine to this guy to rebuild it and it just blows up 500 miles later. This is the 3rd or 4th time it has blown up on us.

anyways on to what happened to it the exhaust side of the piston on the clutchside cylinder was scored really bad and the other side of the piston seamed alright. The cylinder will need to be re nicaciled because it is scored up bad also. The mag piston and jug are also in good shape. so im thinking the seal between the 2 helves of the cases is blown around the exhaust side of the clutch side piston but i want to know what you guys think. also can someone tell me the part number for a arctic cat clutch puller for this clutch?

clutch side piston exhaust side and intake side
[attachment=59385:DSC01394.JPG][attachment=59386:DSC01401.JPG]
clutch side cylinder and head
[attachment=59387:DSC01396.JPG][attachment=59388:DSC01397.JPG]
[attachment=59389:DSC01398.JPG][attachment=59390:DSC01399.JPG]
mag side piston
[attachment=59400:DSC01395.JPG]
clutch
[attachment=59392:DSC01400.JPG]
 

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Discussion Starter · #2 ·
anyone got an opinion on whay she blew?
 

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air bubbles (massive ones) in pto cyl oil line, no premix in tank for break in,, and your brother blistering the s_it out of it with no miles on it!,,, possibly the person that did rebuild overlooked piston to wall clearances (probably not though, but have seen it happen),, if it'd been a seal, there'd be a huge amount of aluminum gone from dome also

had a reply typed up earlier, but hit wrong button and lost it (literally!)
 

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Discussion Starter · #4 ·
the rebuild had over 500 miles on it from last year and it was broken in with premixed gas and varying the throttle and all the normal brake in procedures. so you think the oil pump isnt pumping properly causing oil bubbles?
 

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possible cold seize? maybe runnin to lean due to cracked carb boot? In my opinion I wouldnt think that its air bubbles in the oil line, I have grenaded more engines than I care to remember and thats never been the cause! But hey its possible though!

Does this seem to always happen on speed runs? If yes then are you blurping the throttle while you are slowing down?

Well just my .02 hope it helps.

Tom
 

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Maybe you should think about when and where the motor blows up, is it always on the lake? possibly about the same time or in similar weather conditions? lakes tend to have frost puddles, where the temp drops down a few degrees and it could be enough to finish the motor. i have seen this happen on a lake near where i live
 

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<div class='quotetop'>QUOTE (mcc-bri @ Jan 3 2007, 08:21 PM) <{POST_SNAPBACK}></div>
the rebuild had over 500 miles on it from last year and it was broken in with premixed gas and varying the throttle and all the normal brake in procedures. so you think the oil pump isnt pumping properly causing oil bubbles?[/b]
well, after re-reading your first post, I may have taken WHAT HAPPENED out of context,, I dunno

I swear it said you'd had it rebuilt several times DURING a 500 mile period,,,, sorry 'bout that (age does that crap to ya',, stay young forever :))

as far as the pump not pumping,, unless one of the orfices are damaged or blocked off somehow, probably not,, as far as cold seizure, doesn't have that appearance either (or it'd have decent color to maybe even black on piston top), not to mention the ''4 corner'' scuffing, vs the whole exh side being as it is

it may very well be a ''SMALL'' air leak, one with just enough leanness to let these already ''jetted to the ragged edge'' fan cooled twins get too hot and start the overheating process without detonation or anything of that sorts play into it I dunno,, hard to say,, you'd think the guy will stand behind his work (maybe he does I dunno), but how many times has this happened??, with 500 miles each time??,, sounds kinda' strange to me IMO,,,,,,,, SAME cyl each time?? (then i'd definitely be searching for some type of air leak on that particular cyl as it's a single carb machine)
 

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Discussion Starter · #9 ·
well we will have a better idea of what it is when i get the crank out of it but im waiting for my clutch puller to come in beofre i tear it down.

BTW when i went to order a new piston assembly from cat for this sled tonight it wouldnt let me because they have been discontinued so anyone know where i can buy spi pistons?
 

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Top of piston doesn't look lean does it C-note? Oil or overheat????? I don't see detonation..
 

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<div class='quotetop'>QUOTE (cmscat50 @ Jan 4 2007, 10:06 PM) <{POST_SNAPBACK}></div>
Top of piston doesn't look lean does it?

Oil or overheat?????

I don't see detonation..[/b]
just from overheating as engine was overworking itself adding to frictions heat buildup

actually, I see both

neither do I
 

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Discussion Starter · #15 ·
<div class='quotetop'>QUOTE (C-note @ Jan 5 2007, 11:25 AM) <{POST_SNAPBACK}></div>
<div class='quotetop'>QUOTE (cmscat50 @ Jan 4 2007, 10:06 PM) <{POST_SNAPBACK}>
Top of piston doesn't look lean does it?

Oil or overheat?????

I don't see detonation..[/b]
just from overheating as engine was overworking itself adding to frictions heat buildup

actually, I see both

neither do I
[/b][/quote]

so you think it was from overheating?

and could the type of oil my dad uses have an affect on this. he was using penzoil sled oil at the time.
 

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<div class='quotetop'>QUOTE (mcc-bri @ Jan 5 2007, 12:59 PM) <{POST_SNAPBACK}></div>
<div class='quotetop'>QUOTE (C-note @ Jan 5 2007, 11:25 AM) <{POST_SNAPBACK}>
<div class='quotetop'>QUOTE (cmscat50 @ Jan 4 2007, 10:06 PM) <{POST_SNAPBACK}>
Top of piston doesn't look lean does it?

Oil or overheat?????

I don't see detonation..[/b]
just from overheating as engine was overworking itself adding to frictions heat buildup

actually, I see both

neither do I
[/b][/quote]

so you think it was from overheating?

and could the type of oil my dad uses have an affect on this. he was using penzoil sled oil at the time.
[/b][/quote]
just the top of damaged pistons color (or lack of it) due to additional frictions heat buildup characteristics

unless there was something in it that possibly clogged a orfice on pumps pto side, there really shouldn't have been an issue, this isn't a high rpm (higher than normal heat) engine, so i'd rule that out, it's 7200 r's max
 

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My two cents. I think it was a lean conditon. It looks like it went lean to me. Fans don't have as tight tolerences, so once it got hot enough to stick the rings that cylinder lost compression and the damage wasn't as bad as if it had been on a liquid cooled engine. Once the rings stuck in the grooves on the exhaust side the piston was in contact with the cylinder and that is why the scoring is only on that side. I think you are on the right track thinking it is an air leak, as C-Note indicated, it is a single carb sled, so ice in the carb would have leaned out both sides. I think the leak would most likely be the PTO crank end seal and not the seal on the case halves. Make sure you replace both pistons if you are not using OEM, or matching pistons to what is in there now. If you are going to split the case anyway, I'd suggest you replace both crank end seals and make sure you get the proper sealer for sealing the case halves.
 

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Discussion Starter · #18 ·
<div class='quotetop'>QUOTE (94ZR580 @ Jan 5 2007, 05:14 PM) <{POST_SNAPBACK}></div>
My two cents. I think it was a lean conditon. It looks like it went lean to me. Fans don't have as tight tolerences, so once it got hot enough to stick the rings that cylinder lost compression and the damage wasn't as bad as if it had been on a liquid cooled engine. Once the rings stuck in the grooves on the exhaust side the piston was in contact with the cylinder and that is why the scoring is only on that side. I think you are on the right track thinking it is an air leak, as C-Note indicated, it is a single carb sled, so ice in the carb would have leaned out both sides. I think the leak would most likely be the PTO crank end seal and not the seal on the case halves. Make sure you replace both pistons if you are not using OEM, or matching pistons to what is in there now. If you are going to split the case anyway, I'd suggest you replace both crank end seals and make sure you get the proper sealer for sealing the case halves.[/b]
I am planing on splitting the case and i am going to replace both seals. im also getting the crank sent into the crank shop in town to make sure everything is right and i have a fealing the clutch is out of balance and it is whats causeing this engine to throw the pto end seal. ill keep you guys updated on what i find once i receive the clutch puller in the mail and tear this thing down.
 
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