well today i was out with a buddy rippin around for a few hours, i mean the bike is runnin great can't complain, so we venture off further from home go into some woods play around abit on some jumps an stuff. Thennnn we leave my buddy takes off on his warrior i catch up pass him run it threw all the gears bout half throttle in 5th let off, my quad ackin like i got the breaks on i down shift gas it SH$T its not gonna go an its stallin, so roll off the road now its seized big time. get home finally tear it down pistons is melted on the exhaust side real bad rite into the second ring area an theres prestone on my reeds not sure if it came after it blew or before an during head gaskets shows some signs of failure but once again hard to tell if before or after the fact i didn't see this comin not at all, i did the head bolt upgrade did the torque sequence 4 times before i rode it an checked it twice since then the motor has just 25hrs tops on it everything has been replaced or repaired anyone have an clue as to what may have happened drop me a line or shoot me ur experience with the quad be glad to hear it thx.

 

my other zilla did the same thing just dies at the price moment i let the throttle of, took the plug out and it had blobbs of ally stuck on it of the piston, the piston skirt had snapped off as well, just part of owning a 2 stroke,[img]i/expressions/face-icon-small-happy.gif[/img] i hjad only recently aquired the quad and i didnt know how well it had been maintained so i just put it down to that,

it made me decide to get my other onee looked at and when the engine was stripped for inspection the piston was cracked and there were a few other bits as well, unfortunately i decided on a full tear down of the quad and its still a work in progress althoug im told my 2nd gear ive been waiting months for will be here this comming week,


sounds like youve been real unlucky there if youve had the engine rebuilt so recently,

 

Sounds like detonation killed another one!

Were you running pump gas? Even in stock trim, these motors are prone to detonation. Running High Octane fuel helps.
Lean jetting also amplifies this problem.

Sorry to hear about your misfortune.

 

I've read that if the base gasket starts to leak, in can suck in air and lean out the motor. Also, if you you're going full boogey and let off the throttle and coast for a long ways the piston can overheat and seize up because there's no gas or oil to keep it cool. I always "burp" my throttle if I'm slowly decelerating from a high RPM.....Just a tidbit of info I thought I'd share......

 

Good point on lettin off, makes sense. No fuel no oil. I usually give it a shot with the clutch in between gears downshifting.

Bummer it blew up this time of year.

 

nice grammar

 

Well tonite i ran a honer down the cylinder cleaned up pretty good but i'm gonna ask the shop when i order a piston tomorrow. I do run pump gas 94 oct. an i put some octane booster in the fuel i was aware of pre-detonation being a problem with them quads. I had the factory jets in the carb 420 main 30 pilot 1/2 turns out on the mixture screw, i checked my plug i normally do after about an hour of riding it looked good normal like always nice golden brown little wet i have been running amsoil 50:1 pr-mix i broke the motor in with yamaha-lube 32:1. Tonite for the hell of it i tossed my head gasket in the parts washer pulled it out after a few minutes, I noticed that theres to nice wear marks coming from the water jackets on the left leg side of the cyclinder leading towards the piston 2nd an 3rd bolt back from the exhaust. Well thats all i could find wrong other then my burnt piston, i called today for a piston an ring kit 165$ over here in canada ouch. Anyone use a different head gasket other then stock would a copper one be better? Oh an another thing i was told that this is a chrome sleeve in there should it look any different than a plain sleeze as to i've never seen a chrome sleeve before, caue this one just looks like a normal sleeve to me unless you can't tell by just looking at it. Anyways thx for your input ppl i appreciate it every little bit helps.


1987 LT500
2004 LT80
1993 RF 600
1976 KZ900
1977 Z50 <---really fast watch this one lol.

 

If the cylinder is stock then it is not chrome. Did you mic the cylinder or are you just assuming it is not out-of-round? That is a good way to end up with a ring catching a port. Boring a cylinder is not expensive but not having it done can be costly. A piston melted on the exhaust side means that you are lean. DEFINATELY pressure test the motor once it is back together (check Duncan Racing's site for an explanation of this process). Once the quad is running again, make sure you check your plug color and piston wash at various throttle openings.

BTW, there is no such thing as "pre-detonation". There is pre-ignition and there is detonation.

 

Why does it always run so good just before it blows up?? What a Beich!

 

i had my jets set to stock also and i cracked my cylender sleave yesterday .420main 30 pilot and i ran awsome yesterday but im also runing on pump gas 91 octane i bought the bike with a 470 main jet did the guy know something i didnt that i bought it from more gas or maybe it had a pipe before?but the rush is amazing that the lt500r brings on