400->470 failed, need help

I wonder what would happen if you milled a few thousands off the top of a new piston. Just a thought.

artus good photo! The same thing happened to a stock 04 fe 550 from wyoming
no other damage anywere. I have only seen this on bikes that had been run in baja
2 went down to pre run in 1998 on 400 ktm's . Bikes smoking badly but still able
to run sort of.Compression to high? Bad gas? I repaired both bikes & ran fine in the
states for as long as they were around for me to see. Maybe this is the price one
pays for a high end race bike? Dale lineawever & some others may be able to shed some
more light on this?

All I did was richen the bikes up for them before they left for eastern oregon 4 hours
from the shop.

berger, don't you think the piston is already somewhat of a week link?
I would try a small base shim ,or remove a little material from head?

Or get a new piston to compair with the old one?

hi artus

this has been known to happen on several husabergs i'm afraid. the crack goes in the same direction on all of them which should tell you that its a manufactureres problem. not your fault.

firstly, the pok marks are just the general dust and dirt that somehow gets in, bits of carbon that harden then break off and pock-mark the piston so no problem there.

the piston has been missing the head otherwise it REALLY would have a SHOT BLAST look over the left and right extremes you can see (behind the valve cutaways left and right) so there's nowt wrong there. looks like you have a very good squish. when you rebuild - WATCH the little end for spreading and replace if this happened.

all i would do is make sure that the squish area is no wider than 8mm and then machine a step in that is 1mm off the head. so what i mean is, where the piston is near the head is the squish, measure from the outside edge and go 8mm and scribe a line. any squish inside that ring should be less so 1mm (.040") should be say 1.5mm. this is very easy at the exhaust end and not so easy at the inlet end but should be ok.

the elko piston has the same centre crown as yours but is 2-3mm higher around the outside edge so you are no further forwards.

the small valve heads only restrict power a little this is all and the only damage would be to the exhaust valves themselves. remember that all husabergs now come 35/30 and you have 35/27s fitted. i may have some 30s, i'll look. however i fitted 29s and ported the exhaust ports very heavily (lots out). to do this on yours would make a fantastic difference!

for a similar photo check the gallery of

UNO (old posts maybe)
Dr_C

your fuel in germany is also very good so no problem there.

here is what i suggest. find the real TDC of your engine and then rescribe. the days of 'maybe' are gone. finished. ALL THE FLYWHEEL MARKS ARE OUT. FULL STOP. i can tell you now, before you even check it that the correct mark will be equadistant to the right of the first two.

i would then strobe the ignition timing at 36d BTDC. i would also pick a very good plug because you may be getting a rogue spark. i swear totally by the IXU24 plug. simply brilliant and if you look in the doc you can see it gives a great spark.

i would also look at the carb as well and get a DR272 atomiser, a fresh K51needle, 40 choke jet and i would even consider doing the drill mod that dale used to do to all bikes.

regards

Taffy

Hey the parts are able to be installed but your head is different from the others
in that year as well as valve's! you may want to cc your head & compare to 470.

This failure should not occure in this time frame. Or at all. Also your headers are
smaller so heat may also be a factor? The small poc marks are of concern as well!

Artus, what is sv head ? & both intake & xhaust valves are smaller than disigned
for! you have too hot of an oven, go back to stock or get ready for melt down!

Nice to see guy's looking for an edge though

Artus, fyi those poks on the piston to me say problems! You will find that you have

most likely lost a bearing, if you do not use an air filter this could be the reason for

such marks, carbon will not make those marks ! A tear down is in order asap!!

lots of good advice here .... you have to respect people who pay to maintain the site and offer free professional advice . [ i exclude myself ]

I'll probably get shot down, but is it possible the piston has hit something between its fore and aft areas on the crown and the head? The machine marks are worn off around where the pits are. To me the pits look like impact marks.

This would tend to cause it to break in bending along where the crack is because the piston is so short and so has minimal strength in this direction.

I would have thought if this was the case you would have heard it hitting when it was running.

well i won't repeat myself for fear of a war but i will add that your squish is close and i would think the little end is worn as well.

boss mentioned headers. the headers from the 470/501/550/650 are the same as each other but bigger than yours from the 400! these you should change.

2001 -03
400 = 35/27
470/501/550/650 = 37/30

2004 to today
all models
35/30

your seats won't take a 30 but they will take a 29!

the problem is the piston.

they used to quote a number for a thicker headgasket (the doc/engine tuning). i would try and get one if i could just to be safe. cometic in the USA make them.

they now run 35/30 and you have a 30/27. even though back in the day it would have had a 37/30 head which reduces the compression by 10cc.

as boss says - a compression test. actually measured and not theory. you should block that crack with some s....t! and smear vaseline around the circumference of the piston edge to stop fluid going down the bore, even put some vaso around the valves. with it at TDC and then using a syringe: squirt white spirit/kerosene/paraffin in. i would think the compression is very high indeed. almost high enough to snap the crankshaft!

if the engine has not been rebuilt since new and considering the compression you're running - i think you need to consider a rebuild with a new rod kit. i have rod kits at 50% off OEM price.

come back with the cumbustion chamber CC measurement.

i'll give you the compression ratio. the paraffin should stop at the first thread coming up the plug hole. the engine layed over at an angle on the bench so that the plug hole is the highest point.

regards

Taffy

Artus,those pics are better.You really do have a bearing coming apart!

thinking about this, if the compression is VERY high you and you have to have a rebuild, i would consider the 450 rod which has 117mm centre-to-centre. this 3mm off will let you use the elko piston.

regards

Taffy

12.5 to 1 isn't too bad and i don't think its your big end that would cry enough. main bearings are the biggest bugbear with husabergs.

they can go at any hours especially as that first rebuild was because something was wrong (and you still didn't cure it).

incase we don't see you too often again, please make sure that you do the balancer bearing (go to double row with the special bearings i have had made) , the intermediate shaft inner bearing (with the 2 rubber seals) and the cam bearings as well.

your bike is like me...."at that age now"!!!!!!

regards

Taffy

BOSS said:

berger, don't you think the piston is already somewhat of a week link?
I would try a small base shim ,or remove a little material from head?

Or get a new piston to compair with the old one?

Click to expand...

I have had to take off 60 thousands out of the valve pockets on a 470 in order to run Dales LX1 cam. I dont think a few thousands off the top will hurt much. It should get the piston a little closer to deck heighth and lower the compression alittle. That should help with the detonation.
Just a thought to be taken with a grain of salt.

artus said:

BOSS said:

You really do have a bearing coming apart!

Click to expand...

what do you mean? a engine-bearing will fail soon? the big end?

taffy, 30h before we did a complete engine rebuilt with new piston, cylinder, conrod and all bearings and bushings. the head was adapted to the 35/29 valves. combustion chamber was enlarged a little bit at the sides.

we tested the compression (12,5) an other way but it is not correct enough i think. tomorrow we will do it again like you it describes. then i will tell you ...

headers means the exhaust pipes? yes we took the big ones and an FC-muffler .

Click to expand...

Did you have 12,5 to 1 with 92mm bore?Then you probably will have way to high compression when you increase the bore.The detonation marks on top of the piston may be a result of too high compression ratio