Hello Honda techs or friends of them or even someone who had the same problem or has afriend who had the same problem.
my 1987 XL250R has a cold knock noise that is really starting to bug me. here are some things i've noticed:
1. it only does it when the engine is cold and rarely lasts for more than a minute. it seems to match engine rpm
2. it sounds like it originates from the top end and you can actually FEEL the knock if you touch the head area
3. when starting cold, if it knocks, and i shut it off right away, then restart, sometimes the knock will not reoccur, even though the engine is still cold. sometimes i have to repeat this procedure two or more times to get it to start without knocking. when it does start without knocking and if i rev it before it is fully warm (as in normal revs between shifts, not redlining), the knock comes back until warm.
4. not sure if this is related, but the top end seems to be developing a sort of high pitched tinny rattle noise that i can hear all the time, loudest at the head, louder warm, louder from the right (timing chain) side. this noise i think is valvetrain related but hard to prove that theory. valve clearances are ok
5. sometime during warmup the knock noise stops abruptly, rather than gradually getting quieter
6. when i was setting the cam timing, i was wondering if the chain was stretched, as the marks didn't line up as close as i would have liked, to the point where i was not sure if i was one tooth out or not. i turned it over several times on the bench to verify no interference betw. valves and piston. i've timed several DOHC and SOHC engines at work so the concept and procedure wasn't the problem, no specs available for stretch limit.
7. the cam tensioner and guide showed minimal wear and the sprockets and chain seemed to be in good condition
thats all the information i have. does this give you any ideas as to what may be happening. i have 1000km (600 miles) on the overhaul now( bored .5mm over,new piston/pin/rings, bearings and oil pump, all the rest was reused.) the knock was present prior to overhaul but seems to be getting worse. the countershaft bearing grenaded and forced an overhaul, so i figured i might as well freshen it up while i was that deep into it. odo says 35,000 buti'm a little skeptical...
Any and all suggestions welcome, but spare me the "buy a new bike, buddy!!" line, ok?
signed,
wish i had a KLR
my 1987 XL250R has a cold knock noise that is really starting to bug me. here are some things i've noticed:
1. it only does it when the engine is cold and rarely lasts for more than a minute. it seems to match engine rpm
2. it sounds like it originates from the top end and you can actually FEEL the knock if you touch the head area
3. when starting cold, if it knocks, and i shut it off right away, then restart, sometimes the knock will not reoccur, even though the engine is still cold. sometimes i have to repeat this procedure two or more times to get it to start without knocking. when it does start without knocking and if i rev it before it is fully warm (as in normal revs between shifts, not redlining), the knock comes back until warm.
4. not sure if this is related, but the top end seems to be developing a sort of high pitched tinny rattle noise that i can hear all the time, loudest at the head, louder warm, louder from the right (timing chain) side. this noise i think is valvetrain related but hard to prove that theory. valve clearances are ok
5. sometime during warmup the knock noise stops abruptly, rather than gradually getting quieter
6. when i was setting the cam timing, i was wondering if the chain was stretched, as the marks didn't line up as close as i would have liked, to the point where i was not sure if i was one tooth out or not. i turned it over several times on the bench to verify no interference betw. valves and piston. i've timed several DOHC and SOHC engines at work so the concept and procedure wasn't the problem, no specs available for stretch limit.
7. the cam tensioner and guide showed minimal wear and the sprockets and chain seemed to be in good condition
thats all the information i have. does this give you any ideas as to what may be happening. i have 1000km (600 miles) on the overhaul now( bored .5mm over,new piston/pin/rings, bearings and oil pump, all the rest was reused.) the knock was present prior to overhaul but seems to be getting worse. the countershaft bearing grenaded and forced an overhaul, so i figured i might as well freshen it up while i was that deep into it. odo says 35,000 buti'm a little skeptical...
Any and all suggestions welcome, but spare me the "buy a new bike, buddy!!" line, ok?
signed,
wish i had a KLR
