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Hi so i hope someone will help me here
I got new engine but piston was damaged so i took old pistons., cylinder and cylinder head together without spliting heads to my new engine from the old one, now it wont start, loud big bangs in cylinder and from exhaust and my throotle body is jumping out from rubbers :eek: backfires from intake and smokes , compresion on one cylinder is out of what manual says. 1st 210 psi and 2nd 230. manual :140-215 psi, i didnt take out piston rings just turnd them like manual says, tiiming is ok
, i did it many times, valve cleariance also in range no idea whats wrong, engine turns harder with spark plugs in but i can hear air from bottom of the Engine when piston is going up or down is this normal?,, i tested new engine was starting event on 1 cylinder before so what did i do wrong that its backfiring and wont start, too much oil on pistons? In chamber? Omg help ive run out of ideas
 

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I hope you get some useful advice here but ..............
We don't really have many, if any, well qualified master mechanics who visit regularly.
I wish you luck.
 

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From what you wrote I understand you took the old pistons/heads and cylinders from your old engine and fitted them to the new engine.....Is the new engine the exact same as the old one and have the same stroke. Your compression sounds like it is way too high....even if it is close to the highest spec. Secondly are the valves the same and is the cam shaft profile the same as the old engine.

I think you may have a major problem trying to fit heads and cylinders with all the associated valve gear to an engine that sounds like it is mechanically different.....even if that is just from mods done between the same bikes a few years apart. Also are you using the same carb/injectors form the old engine?
 
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