tore down the 426 today.......bad news

[underpowered]

well last week my 426ex died. made a horrible noise and locked up.

tore it down today. found the timing chain tensioner had gone bad, allowing it to jump time which let the intake valves hit the piston. broke one valve off completely and lodged it into the top of the piston. destroyed the head itself, as well as the piston.

total damage parts list:
Cylinder head (P&P)
2 Kibblewhite blackdiamond valves
1 88mm 426 piston
Timing chain tensioner
CRF timing chain.


that is all i know of right now.

on the good side of things, The piston is incredibly clean with harldy any carbon build up after 2 years of run time. gotta love spot on jetting. pics will be up tomorrow of the damage.

sounds like my brothers last motor lol it just locked up and then thatw as it tore it down there was a valve stuck all the way through the wiseco piston that was 2 weeks old. The head had gashes in it from the valve digging in and the chain dd damage to it aswell grinding some chunks out. even the flange for the cam was all bent up

[underpowered]

on mine the valve looks like it was the only thing that did any damage. If the valve had not got the valve seat, the head would actually be usable, but there is a huge dent in the valve seat. i am gonna just get a new head and P&P it. gonna go a slightly different route with the P&P this time though.

different route for porting like another company or a different style?

[underpowered]

different style.

i had the mechanic at the shop i work at port it for me. I am going to do it myself with his guidance this time. gonna try some different port shapes than he used, not go quite as big as he did either. He did an all out MX race port last time. this time i will keep it smaller, not as much top end.

[underpowered]

pics
http://img.photobucket.com/albums/v202/426EX/PICT9155.jpg
http://img.photobucket.com/albums/v202/426EX/PICT9153.jpg
http://img.photobucket.com/albums/v202/426EX/PICT9149.jpg
http://img.photobucket.com/albums/v202/426EX/PICT9156.jpg

i can match those lol

head

[underpowered]

lol thats awesome.

my brother got damage from the chain too

something went wrong lol

[underpowered]

Originally posted by FoxHondaRider
something went wrong lol

that's one i have never seen before.

[Ruby Soho]

how did the valve get like that? wouldnt it be going through the other way?

Originally posted by Ruby Soho
how did the valve get like that? wouldnt it be going through the other way?

what happens is the piston smacks the valve cracking it of and after a few more strokes the valve is rattled so the stick end is at the piston and stuck in it

[REDRIDDER]

R.I.P 426EX.....Gone but not forgotten

[underpowered]

Originally posted by REDRIDDER
R.I.P 426EX.....Gone but not forgotten

no worries mate, Dr. Frankengear will work his magic and bring 426ex back to the living. in a bigger, better fashion as well.

and as foxrider said. the valve breaks off from hitting the piston. the motor does not instantly stop. with no compression (no valve to hold compression) the engine coast to a stop allowing it to bounce around a few times, ending up upside down in the piston.

[Speedy 400ex]

OUCH:eek2: :eek2:

[gcart2]

Originally posted by underpowered
pics
http://img.photobucket.com/albums/v202/426EX/PICT9155.jpg
http://img.photobucket.com/albums/v202/426EX/PICT9153.jpg
http://img.photobucket.com/albums/v202/426EX/PICT9149.jpg
http://img.photobucket.com/albums/v202/426EX/PICT9156.jpg


look at it this way..... that piston would make one heck of a necklace charm..:devil:

[MtnEX]

Ouch....


How often should the timing chain and tensioner be checked out?

Is there ever any warning it's going south?




On a side note, do any of you guys ever use anything like seafoam in the gas to clean out the deposits?

[underpowered]

Originally posted by MtnEX
Ouch....

How often should the timing chain and tensioner be checked out?

Is there ever any warning it's going south?

On a side note, do any of you guys ever use anything like seafoam in the gas to clean out the deposits?

some things just go. the timing chain and tensioner are 2 years old, with maybe 50 hour on them i have not ridden much in the past 2 years.

warning signs are loud ticking noise, and you can hear the chain slap, a hard noise to describe.

never seafoamed a quad. good jetting should keep deposits down. i did not clean up the piston at all, it was that clean right out of the motor. usually they have a layer of carbon built up on them.

[MtnEX]

Originally posted by underpowered
some things just go. the timing chain and tensioner are 2 years old, with maybe 50 hour on them i have not ridden much in the past 2 years.

warning signs are loud ticking noise, and you can hear the chain slap, a hard noise to describe.

never seafoamed a quad. good jetting should keep deposits down. i did not clean up the piston at all, it was that clean right out of the motor. usually they have a layer of carbon built up on them.

Thanks for the info.


I had this "tap" crop up I've been worried about... and the valves didn't need adjustment.

It's a pretty singular sounding tap, like it's coming from one individual thing.... and I can make it go away by working the throttle just right.

So I'm curious about just about everything internal these days.

http://www.exriders.com/vbb/showthread.php?s=&threadid=360580

[underpowered]

it could be a wristpin knock.

also, may be worn rocker arms. your valves me be in spec, but if your rocker arms are worn it will still tick. usally you will see scarring or wear on teh cam if your rockers are bad.

[MtnEX]

From what little I could see through the valve caps, the top end looked pretty darn good best I can tell, never having seen the inside of a new one...


However, the wrist pin suggestion does make too much sense.
That you might could get to settle out and quiet down like that.

I just hadn't thought of that because the noise sounded so high.

[underpowered]

the wristpin could be worn, and it will not be a constant sound. it will come and go.

if it is the wristpin, you are riding a ticking time bomb. it could let go at any time.

[MtnEX]

Yep... might just be a ticking time bomb...

Time for my own thread I guess... good luck with your rebuild.

[JBacon]

WOW. dude thats pretty bad. Is it burning a hole in your wallet yet? lol

[underpowered]

Originally posted by JBacon
WOW. dude thats pretty bad. Is it burning a hole in your wallet yet? lol

eh, should be fixed for under $300. bought a head off Ebay, new piston, gaskets and such. the head was the most expensive at $150 for a used head.

[JBacon]

Originally posted by underpowered
eh, should be fixed for under $300. bought a head off Ebay, new piston, gaskets and such. the head was the most expensive at $150 for a used head. Oh, that doesn't sound so bad then....

[RaginRedneck]

Looks like a good candidate for the wall of shame/fame. I have quite an extensive collection

My two prize possesions are:
1) a Melted rod out of a VW that saw 13,000rpm (old school Baja)

2) a 5 inch chunk of a cam out of a 428 Cobra Jet that I destroyed.

Makes for good topical pieces :D

[underpowered]

Originally posted by RaginRedneck
Looks like a good candidate for the wall of shame/fame. I have quite an extensive collection

My two prize possesions are:
1) a Melted rod out of a VW that saw 13,000rpm (old school Baja)

2) a 5 inch chunk of a cam out of a 428 Cobra Jet that I destroyed.

Makes for good topical pieces :D

i would need a whole room of shame. i break alot of stuff.

[krt400ex]

Originally posted by gcart2
look at it this way..... that piston would make one heck of a necklace charm..:devil:


lmao. just made me think of flava flav :blah: i cannot stand the guy wit his huge clocks...hahhaa