Cb400f primary chain noise after big bore kit install

[ka-ja]

The 460 yoshi kit did not alter the "sound" of my motor, but a yoshi camshaft certainly increases camchain wear rate even with a heavy duty cam chain

[Nurse Julie]

When you first started the bike after the rebuild did it have any rattles?
When the revs drop the rattle gets worse does this point to the primary chain?
I would of replaced the primary chain while it was apart but because it was quiter before the rebuild I thought it was OK, wasn't expecting it to go loud.
Would the higher compression make a rattle louder or would it make no difference?

Nope, first start up after rebuild it didn't have any rattles at all. My old primary chain had about 5k life left in it but only had a very minimal chain rattle at low revs. No idea if higher compression would make the chain rattle louder but logic tells me it shouldn't make a difference.

Hard to equate your engine with his though Julie, yours was a full engine apart strip with all the chains etc replaced IIRC, his has reused all the chains and that's where most if not all of the noise comes from.
Higher compression shouldn't alter the engine BUT if the engine wasn't running well on the old bores then fixing that problem would mean the engine balance would change, so carbs etc would be out, causing more noise as it's now unbalanced.

Yes Ken, that's why it's difficult for me to give Doom a definitive answer to all his questions. Everything inside my engine was new so I would have been most pissed off if I had any rattles of any type from anywhere.

[Doom64]

Oddjob, released the cam bolt when? I adjusted the cam chain after the kit was put in and the adjuster bolt was free.
When the new standard pistons were put in the cam chain and tensioner was replaced, also when I put it on the dyno it made 30hp at the rear wheel so it was running decent when it was standard.

[Nurse Julie]

Out of interest, what other mods have you done to the bike to make you want it dyno tested? Pods, different jets or anything like that. I still think it's the primary chain though.

[Doom64]

I dyno tested it before I put the big bore kit in it.
Everything was standard apart from a shorter silencer and electronic ignition.

[Nurse Julie]

I dyno tested it before I put the big bore kit in it.
Everything was standard apart from a shorter silencer and electronic ignition.

So is it just the big bore kit, short silencer and electronic ignition you have now?

[Doom64]

Yes I still have those and the head has been skimmed now that's the only difference.

[Nurse Julie]

So really then it most probably is the primary chain but as none of us including yourself has got a crystal ball or x-ray vision, the only sure way to diagnose the problem is to strip the engine right down. It still may be something else but you won't know until you take the engine apart.

[Doom64]

Someone else done it before and said it was within spec.
I balanced the carbs again today, took it for a spin and it does seem a lot quiter than it was before, it's back to how it was with the standard kit in it thankfully.
I will probably strip it down again winter time and do the bottom end, this was the first engine work I have done and the bottom end is a bit trickier isn't it?

[hairygit]

Someone else done it before and said it was within spec.
I balanced the carbs again today, took it for a spin and it does seem a lot quiter than it was before, it's back to how it was with the standard kit in it thankfully.
I will probably strip it down again winter time and do the bottom end, this was the first engine work I have done and the bottom end is a bit trickier isn't it?

  It's especially important with these older bikes that you learn to do the work yourself, or only entrust it to someone with plenty of experience of older Honda's. Also, as you progress with ownership, don't assume just because a part is new it can't be faulty, they can, and people spend hours chasing their own tails trying to find the problem without checking the new part is fit for purpose! Glad you got it sorted, as I said at the start of this thread, it was the most likely suspect. Enjoy riding it.

[Doom64]

Thanks for the help everyone, a lot of handy info. I have started doing near enough all the work to my bikes recently a lot of learning to do still.
About the clutch rattle I started the bike and took the oil cap off and you can hear a loud knocking from the clutch, does anyone know of anywhere you can get rubbers from apart from the ttr site?

[Arfa]

And for what it's worth I'm just in the process of running-in my 400/4 after a complete rebuild which included a Yoshi big bore kit, 455cc. I've just given it the first service. To cut a longer story short the engine was rather quieter with new oil in, and then got noisier as I made each service adjustment, bearing in mind that the tank was off so you can really hear things. I was somewhat perturbed by this as the primary noise was quite loud- lo and behold the final thing was to balance the carbs, and one (no2) was miles out on synchro and we now have sewing machine like rustling. So, from my experience balance is essential if you want a quiet engine, and on my ride earlier today, rather smoother.

I'll post at more length and include some piccies when time allows.

Regards,

Arfa.