hi newbie here ,ive just purchased a 05 cbf250,the problem is the engine,it sounds dredfull when started up with rattle and knocks ,but as it warms up it goes quieter but still has a grinding sort of sound,cant tell if from top or bottom,previous owner say a mechanic says its the crank bearings,im thinking of dragging it out and stripping but could doo with some serious advise on what areas I should check and how ?,on stripdown,ie top end ect,some say piston slap but how to check ? and finally is there a way I can tell when stripped down if it is the bearings,hope ive made sence,the previous owner also told me he changed the chain tensioner but seem to be better but back with avangence ??any advice really appreciated jim
Can you get a vid of the engine running so we can hear what the noise is? If your talking cam chains, then the tensioner may be the first thing to look at.
I'm not sure coz the previous owner said he replaced tensioner, I'm thinking of stripping down , I'll post video in next couple of days , it's really hard to put finger on where it's coming from , it's not a knock it's like a repeating grateing rattle sound really weird but sure it started to rev higher when warm so some people rekon that's the tapper shims need doing ??
Before stripping anything down, you need to make sure that your valve clearances are correct, carbs balanced, firing on all plugs and do a compression test. If all settings are right then you eliminate possible adjustments being the cause and can then look at what may be the problem as you disassemble. Some engines I've had have made terrible rattling noises at idle that go away when revved. After tuning correctly and balancing the carbs the noises are gone. Incorrect valve clearances will also effect running and must be set before trying to do compression testing or balancing of carbs. I have seen engines 'missing' on one plug causing the crankshaft to be 'fighting' itself and making the clutch gear rattle. Lots of different things to try before disassembly.
hi I was speaking to a top bloke last night and im stupid coz I cant find conversation for love nor money, hope he see,s this post,this is the video of noises from cbf250 on start up,it wont start on choke from cold and will only crack up if I give it a little throttle ,I cant be sure if its from top or bottom, anyway a full strip down was on the cards but am thinking top off and change the shims,any advice on how to doo it highly appreciated or anyone got a workshop manual anyway ill try upload video cheers jim ps omg I cant upload to large so made another about 5 seconds and still too large ??
hi murdo ive just posted video on my facebook jim chapman I couldn't post it on here too large , im gonna take cover off and try to get the gaps on shims ,Im not too sure on what to do next but I started up today and wouldn't start on choke,wanted air and the sound was sorta like at top so am quite sure its something to do with the rocker gaps ,and maybe a new tensioner
If you use the Tapatalk App you can upload the video from there... it compresses the video so it will fit.
I've done the top end on one of these before, really really simple you'll be right. Hit me up if you need a hand.
@Murdo - Modern CBF250s are single cylinder, so if they're not firing on all cylinders they don't start at all. Balancing carbs might be difficult too with only one! Definitely worth doing a compression test and checking valve clearances though! Also, how's the drive chain tension? I've owned two and the chains can get very noisy when they're worn.
hi murdo im gonna try take rocker cover off tomorrow weather permitting, ill have a quick look to see if I can see any wear on cams,if theres wear ill order a couple and try them but in meantime ill try get a compression tester and try that also ill try get gaps and work out what the gaps are and how to change shims ect regards jim
@Jimmycc specs will be in the manual. I'll have a look when I get home this evening if you like? Also, the workshop manual for the CBF250 is in the Resources section of this site. Access to the Resources section requires premium membership, which is only $5 a year from memory.
thanks for help lads, it was bottom end so bought a 12000 miler,all sorted,but think carb needs cleaning as doesn't need choke to crack up just a touch of throttle and wont tick over for love nor money
