engine rebuilt summary and.......

dear friends,

here is a list of what i did to my engine when suddenly stopped working properly(mixture seemed to get really lean when the bike got hot) and smoking real bad:

the first day i found that...

1.broken needle circlip,carb worn(vhsb38) - bought new phm 40
2.unscrewed sem - bigger threads new bolts+loctite
3.broken woodruff key - new one from a yamaha

after these repairs nothing really changed so i split it.....

for the next 3 months.....

4.very worn piston rings - bought new piston
5.worn cylinder - had it electroplated
6.broken reed valve - a new one was installed
7.worn exhaust valve guides - put new guides, new seals, treated and aligned all valves
8.cylinder and cylinderhead combustion surfaces found to be not entirely flat - had them treated so as to match perfectly and put new gasket

after all these repairs nothing changed too !!!!!

oil consumption is about 1 liter at 100km, scary isn't it 8O

here some scrappy cellphone pics when i last split it few hours ago:




note the mysterius oil remains above the upper exhaust valve

when i assemble it i applied some red hi temp sealant on the cylinder and cylinder head surfases (the cam chain side) so as to locate any leaks from there.










cylinder and piston are rectified by a specialized shop, gaps and play are re-checked by me before install and found to be factory. no matter though since the smoking effect did not changed a bit after putting the new piston and cylinder...





what do you boys see/think that i don't :?:
there must be something very wrong, but what?

wtf

thanks for the reply mr Dale,

as for the crankcase, the main bearing seal is in place and when i removed the cylinder oil level (inside crankcase) was low as it should be and piston skirt had only a thin film of oil on it(opposed to what i saw when i discovered the broken reed valve-crankcase filled with oil and piston soked in oil).

i will double check about any blocked bypass though (there is reed valve and the oil filter-there is no other bypass to check right?)

i even consider the possibility that there is a crack at the cylinder head which is not noticeable and the oil + some air find their way through it.

in the following picture, the oil remains between the upper left exhaust valve and the cooland bypass are there in the same place each time i open it, this indicates something but i don't now WTF it is !

smokind like a train

hi all and thank you for your valuable help :wink:

i did some digging lately in my engine, i split the cases and dissasembled it completely.

there is not any missing case parts (i mean broken) or seal missing to result oil entering in the crankshaft chamber.

the whole area seems perfect.

the only thing that was a bit odd is that the right case screws (the flywheel side) were quite loose, nothing else. i don't thing that it means anything.

on last sunday i spend 2 hours checking my cylinderhead for cracks and i only noticed one or 2 pores at one of the intake valve seats.they are tiny and they seem to be nothing special+they don't seem to lead to anywhere. even though i warmed it up, no crack was noticeable. i also concluded that (as also mr dale pointed out) even if there was a crack it would be quite impossible for oil to go through as the combustion chamber and the cam shaft area are separated by cooland passes.

this week i will assemble my engine carefully with a husqvarna/husaberg specialized engineer (which happens to be my friend). during the assembly we will examine all the engine parts one by one for any abnormalities.

please excuse my poor english but i don't quite understand when you say camchain cavity. is it the passage of the camchain from the crankshaft camchain gear to the camshaft gear, isn't it ?

dsducati wrote:From all this shock, heads can end up broken and rods ever so slightly bent.

do you suggest that a slightly bended rod could cause piston not to seal enough at some point of its travel, or i just have missunderstood ? (piston and cylinder "wear" after 100 km of testing seem symmetrical and normal)

you all seem to be extremely qualified and experience engineers and i am really thankfull to you for your even bothering to help me solving my problem out.

as for nsman mention that it is quite a puzzle, man i am a really great puzzle and riddle solver but this.............. :evil:

some time ago oyk wrote:

the only thing that was a bit odd is that the right case screws (the flywheel side) were quite loose, nothing else. i don't thing that it means anything.

guess what...........it meant EVERYTHING :evil: :evil: :evil: :evil:

hi all gentlemen,

me and my pal (husqvarna/husaberg specialized mechanic, more than 20 years on and in these bikes) performed many pressure tests to ensure that the cylinder + cylinderhead were ok, then i decided to split the cases and on the way i noticed that the main case screws were so loose that you could unscrew them by hand. i didnot pay much attention to this at first but after some thinking i reconsidered...

so primary trouble found to be the main case screws and the fact that they became somehow very loose.
on the way to TDC oil was entering primarily through the case ''walls'' right from the gearbox and secondary through the oil filter.

total amount of oil in to the crankcase cavity was so much that the poor reed valve could not get rid of it entirely when piston was moving to the lower point of its travell.

the result was piston rings to be over loaded with oil which later after caused the smoking effect.

of course, when i left the engine to cool down few hours so as to remove cylinder to check it (after i replaced my broken reed valve) the oil had enough time to go back in to the gear box through the reed valve-so when i did open it i could not spot any excessive amount of oil, even piston skirt seemed dry enough.

mr lineaweaver the problem is now fixed, but as you have much more knowledge and experience on these engines i would like to know if there is something wrong in my above explanation.

and NO, i don't thing that any other berger will ever come up against such a problem. ONLY ME

any comments are welcome :wink: