cb 400 engine knocking then dying

this one shows the moments before the dying of the engine. it also shows the irregular knocking sound. once again i am looking for a diagnosis of the problems so if you can help please reply.

Category:

Autos & Vehicles

Tags:

• cb400t
• cb
• 400
• cb400n
• honda
• problem
• mechanic
• repair
• help

[scott93257]

Could be clutch noise...the Old Honda's are notorious for that. I had a CB750K, a CB900 Custom, and a CB650K...All of them had clutch lag like that.

[007wolfen007]

i think its just old age but you could be right especially as you have more experience with the cb range than me. the noise did appear to come from the cylinders at idle but she does suffer from really bad vibes so its really hard to be sure. i may redo the whole internals as a project as soon as the vfr is roadworthy. the main reason for me wanting a new bike is the harsh vibes at anything over 5k, never really found a solution for that problem. anyway thanks all again for the help and advice.

[scott93257]

Glad to be of service my friend..and good luck on the rebuild project... Another thing on the older CB's is that sometimes the cranks were manufactured slightly out of balance.. So that would probably be why the racket gets louder above 5K.. There is one bike that I forgot that I had that might be of interest...I actually had a CB350 Four...Yep a 350cc four cylinder...It was the coolest little thing..

[007wolfen007]

i honestly didnt know they existed. its like a miniature cb400 - the engine seems a good bit smaller. it looks like a cool little bike, in fact it looks very small. i prefer the fours over the twins and even the triples.

thats an interesting thing to know about the crank, i can check that out when shes in bits. you wouldnt happen to know if a cb250 crank is interchangeable do you? i have an old cb250 engine being used as a donor and most parts seem to be compatible but not sure about the crank.

[007wolfen007]

she is a noisy beast but i had to do the clutch as well when i noticed theres a second tensioner inside. when i slacken that it kills the noisy slap completly. i have a spare set of barrels and pistons anyway but i have had enough of the problems with it so i bought myself a vfr400. it only needs a new rear tyre, fork seals and levers + carb cleaning and new juice. once im happy with my vfr ill probably pack the cb400 away for emergency use.

thanks for the help and advice anyway.

cheers,

steve.

[fontheking3]

Honda is a piece of shit

[007wolfen007]

well the bike is almost as old as i am - nothing lasts forever. but true i have had more than my fair share of trouble from hondas.

[klozedbeataofficial]

@natureboy602

Its a bit late for a response, and the bike probably hasnt ran after this video, but.

Cam chain noise on a cb400f sounds different, its more of a rattling noise rather than a knocking sound.

And, adjusting rarely ever helps if the engine hasn't been rebuilt. this is because of the design of the tensioners, they just jam. Thats why 90% of the old Honda CB's have a rattling cam chain.

[gyroerror75]

@007wolfen007

The second tensioner you are talking about is the chain for the balance shaft which also runs from the centre of the crank. If someone split the cases & didnt time the balance shaft properly or the chain jumped a tooth the engine will vibrate a lot and not run till higher revs.

[BlackLabel7345]

if your PCV valve is not connecetd to the airbox it will sound likle a worn bearing or other random engine noice

[natureboy602]

That knocking noise, it sounds like there is a little bit of slack on the timing chain. Maybe you should adjust to take away the knocking noise.

And also a thing to look out for on these CB400 is piston slack, and you don't want piston slack as it will make your barrel egged shape.

Hope you work it out and get it fixed,

Maybe you would have more luck with my Yamaha YTM200 3 wheeler it just needs a centrifical clutch, sump plug and side casing bolts.

Anyways have a good one.

Cheers Matt