hi goodwoodwierdo:

thanks for the advice. what i noticed when i took out one by one.

1) the rear cylinder head cover: i saw the intake valve cap spring jumped off. so i thought by putting the intake valve cap back onto the spring will do the trick. BUT

2) when i took out the cylinder head, the piston is jammed onto the cylinder wall. one of the valve was broken away from the stem. i saw crack on the piston. the new piston ring came off from the side causing the jam. then the piston caliper was broken away from the piston. i couldnt find any piece of the broken metal from the piston. it's supposed to be a huge junk of metal. it could be inside the crank case.

then i noticed that when i turn the flywheel, there are some obstruction. the metal could have went into the case. the rod is bend. shit...

remedy: easy! i found another engine in germany. a used one. i trust that owner of the engine. i really hope it is just a plug and play senerio. but the engine from germany is a RD07 model where mine is a RD07A. he told me that the alternator is different.

how it happened?

the piston and cylinder:
i took the bike to austin to seek help from a friend. he is quite an expert in building up bike and has good knowledge on bikes. i had compression ratio issues and engine is burning too much engine oil. so we took out the piston ring and it is out of service spec.

we ordered a 0.25 upsize ring.

when the ring arrived, it is too big for the cylinder. we did not want to bore the cylinder as the cylinder wall is not damaged. instead, we hone abit of the wall.

since the 0.25 ring is slightly oversized, we decided to file/buff of abit of the piston ring on one end of it. we did only on the top and second ring. the rest of the lower rings are also abit big but we did not do any removing of materials. when we slide in the cylinder down into the piston with the rings, i had to squeeze in the piston ring one by one to the cylinder. i dont know if it is too tight for the cylinder.

my question: was the piston ring too tight for the cylinder? we measured it to specification. do we need to remove some materials off the lower rings also? but there isnt any specifications in the manual for the lower rings. only the top and second.

we did not change the piston holder clip. this small little clip seems ok, undamaged. the manual recommanded always replace the small clip when we took out the piston.

???


the valves:

we took the new valve stem,seat and seal to a proper machining shop. he 'cut' the cylinder to fit the new valve. paid him quite a good $ for the job. the new valve seems to fit well. i dont know what kind of specification is needed for this job. i took the manual to the workshop and the mechnic only took down some degree of angle stated in the book for cutting.

when we fixed everything in and the last thing is to do the valve clearance, there isn't any allowance to do the valve clearance. it happen on the rear cylinder. suspected that the lenght of the valve would be standard and the workshop might had took out much materials from the cylinder head, causing a overlength of the valve, we took out some materials off the top of the valve to meet the spec of the valve clearance.


the timing chain:

we turn the flywheel to front cylinder, that will be the TDC. then there is a marking on the timing chain sprocket that we have to align parallel with the cylinder head. we did it.

then we turn the flywheel to rear cylinder, that will be the TDC for the rear, again we try to align the timing chain sprocket.

but both front and rear timing chain sprockets could not be aligned. we move the sprocket one tooth to the front, it would be too much, move one tooth to the back, would be too little. meanwhile the flywheel is still in the proper position.

so we decided to make the best alignment by giving both cylinder abit off to the intake side. that is the best we could do. there isn't any 'half tooth' spacing or movement for the sprocket to get the best alignment. we also suspect that there is a elongation of chain due to the age of the bike, that is why we couldnt align it back.

this 3 elements (the piston rings, the new valve seating, the timing sprocket) would contribute to the failure of the engine.

what do u think?

goh