CBR400 Engine Noise - Help

[Hicksi]

Hey,

From my last ride and closer inspection i've noticed the motor making this noise.

http://www.youtube.com/watch?v=SE1srCq5f3A

Anyone got any ideas as to what it is? I had a thought that it might be the main bearing?

[Jakobi]

Originally Posted by Hicksi

Hey,

From my last ride and closer inspection i've noticed the motor making this noise.

http://www.youtube.com/watch?v=SE1srCq5f3A

Anyone got any ideas as to what it is? I had a thought that it might be the main bearing?

No idea. Definately increases with revs though. I know nothing about those bikes but in any case I'd be looking until I found the cause.

[Bryan]

I can't see the video at work (network police). That being said, how old is it? How has it been ridden? Has it been reved and run at the top end (such as raced)?

The reason I ask, the early Honda CBR 600 F1 was known to have some issues with the cam chain tensioner wearing. I would assume that the CBR 400 and 600 shared the same tensioner. It usually sounded like it was ticking and did vary with engine RPM.

[Hicksi]

Originally Posted by Bryan

I can't see the video at work (network police). That being said, how old is it? How has it been ridden? Has it been reved and run at the top end (such as raced)?

The reason I ask, the early Honda CBR 600 F1 was known to have some issues with the cam chain tensioner wearing. I would assume that the CBR 400 and 600 shared the same tensioner. It usually sounded like it was ticking and did vary with engine RPM.

The CBR400 is a '95 model, its done about 39K Miles. I certainly never raced her, and the owner before me had it in the garage. Its been used for commuting and the occasional sunday razz...

Thanks for pointing that out Bryan, i will check that first. Would rather replace that rather than a main bearing.

[hannesd]

could just aswell be a loose clamp of the exhaust somewhere along the line...
sounds more like a noise from outside the engine...

[Jakobi]

Yep yep! Start with the simple things. Strip her back and see if you can isolate the sound. Apply some pressure to the exhaust at certain points to see if that changes the tone/sound. Look for any obvious vibrations.

You could also use a stethiscope?? (spelling?) or a screw driver hard up against your ear on different parts of the engine to try and confirm where the rattle is coming from.

[Bryan]

Originally Posted by Hicksi

The CBR400 is a '95 model, its done about 39K Miles. I certainly never raced her, and the owner before me had it in the garage. Its been used for commuting and the occasional sunday razz...

Thanks for pointing that out Bryan, i will check that first. Would rather replace that rather than a main bearing.

Yeah, check the easy stuff first as the others say. The good news if it is the tensioner, it is relatively easy to change. The fibers slip in from the top. You do need to pull a side cover so you can make sure the cam chain does not slip a tooth (or two) while you change it out. (make sure you line up the timing marks before you start just in case the chain moves on you. It will make it much easier to get everything back in th eright place.) You do have to pull the valve cover to gain access to remove and replace. There are bolts (or dowel pin) that hold them in place in the side cover the goes through the bottom of the tensioner. (I haven't messed with a CBR since the mid '90s)

Also, the main bearings are babbit style bearing in these bikes, not roller bearings. You could have a valve that is not shimmed correctly (or loose). This bike uses shim under bucket shims and may need to be adjusted.

Here is a parts fisch for a '95-96 CBR 600 F3, it should be the same tensioner system. (couldn't find a 400 fisch)

http://www.hondapartsline.com/fiche_...1995&fveh=3044

Parts #4, 5 & 7 are the wear items. They are relatively inexpensive and they are wear items that will cause the cam chain to slap around and make noise that does change with RPM.

[Hicksi]

Guys i would really like to extend my thanks to all!

The input is greatly aprechiated, i have been out of the country for a while so appologies for the long delay in response time.

I now have some time to spend on the bike, so ill start with the simple aspects and start to try and isolate the sound.

The bike has never recived that much maintenance in terms of timing checks etc, so this could be the issue.

Will keep you posted.

Thanks again.

Hicksi

[Hicksi]

Success Gentlemen!

I had the time to remove the fairings on the CBR today.

I used a piece of wood as a make shift stethoscope, and had a listen to the motor. The noise i could hear just wasn't coming from the motor.

On further inspection of the exhaust, the sound seemed to be coming from somewhere in the middle.



The collector pipe has a plate that splits the flow, the spot welds on the top and bottom have sheered (The exhaust is the lowest part on the bottom of the bike) and thus rattles when the engine is running, and gets worse with increasing RPM.

Just need to get a welder to stick this back in place.

Thanks for all the help

Cheers

[boyscout]

Those are really cool bikes.