1995 VFR 750 Engine noise

Hi all,

Realise that the video isn't great but wondering if anyone can diagnose this.

DSCN0300 - YouTube

Its a 1995 model, done 36k. The noise I hear is a tapping that sounds like a knocking big/small end.

However, it comes and goes. I went for a 30 mile ride yesterday and I didn't hear it once. Started the bike up today and it happened straight away. The weird thing is (as I was demonstrating in the vid) is that if you tip the bike to the right, it goes away.

Carbs are balanced, engine oil was changed 1500 ago and the old stuff was clear of swarf. I can't get rid of the noise by putting it in gear, pulling in the clutch etc. However, I cannot seem to get the bike to make the noise either. It just happens when it wants.

Bike is slightly buzzy through the bars over 7000 rpm. This is the first VFR I've owned so don't know if that's normal.

Noise is as loud on the other side. Valves done recently, no other issues as far as I am aware.

Thanks for any useful input.

Chris.

 

It sounds like it might be your clutch basket.

 

In what way? Worn ears? Shock absorber springs?

I did wonder whether it was the release bearing - can anything go screwy with the actuation mechanism on the left hand side of the engine - where the clutch hose goes to?

Thanks.

 

There is a thread here somewhere, where it's explained really well. Something about a conical washer/spacer that keeps the clutch basket under load when the bike is in neutral, when it gets buggered the basket rattles (I think, will try track down the original thread, may be on VFR Club or VFRD though)

 

Thanks, any help would be great.

Not too afraid to pull the engine but if it's confined to a clutch only job that would be great.

 

I'm starting to suspect it is this -

Rattle/knock in engine. Possible starter clutch problem? - Third and Fourth Generation VFR's - VFR Discussion

I have certainly some symptoms and after listening to the engine again today it definitely seems to be coming from the rear top end of the engine.

Has anyone ever drilled their cam caps themselves?

 

The bike I sold to Cundalini had a problem like this when I bought it. One of the starter clutch bolts backed oot and would just touch the clutch cover when tilted to one side. I would pull the clutch cover and inspect all with a very close eye.

 

This is certainly counter-intuitive to me.

So according to the TI in that post, if the camshaft journal diameter is close to the upper limit value, then the camshaft will incline or tilt during valve actuation and the cam sprockets generate an axial thrust force on the camshaft that causes the knocking sound.

Looking at the hole-drilling pattern on the TIB from Honda Europe--what does this really do and what do they think this will solve?

It appears to be adding a bleed-off hole in the oil supply channel to the camshaft bearing journals--so is the oil pressure too high? And how will reducing cam journal pressure affect cam bearing wear and life over time?

It seems to me that if the journal diameters are too big (at the upper limit) then the camshaft is free to flop around and bang the bearing surface. And in a hydrostatic oil-film bearing the solution would be to increase the journal oil pressure, not reduce it.

Or replace the worn out journals with a new tighter-fitting bearing. i.e. new cam holders

Plus how do the straight cut gears generate axial thrust? i could see it in a helical cut gear, but that's not what we have in the VFR.

Maybe drilling holes works okay? Maybe it's PFM?

 

kennybobby - When you put it like that, I agree with you. It doesn't make much sense.

Less pressure / oil flow should make the tolerance more prone to noise, unless I don't understand fluid dynamics very much.

I'm curious as to how this only seemed to affect 95 - FS models.

What happened on the 96/97 engines.

Did they come pre-drilled?

Or something else like a tighter tolerance?

 

i went to look in the FSM for more info and details on the cams. Maybe i was a little rough on the beaver...

Now i can see that the hole to be drilled is ONLY on the interior end of the cam holders--towards the gear. So it may be possible that these act as a thrust bearing to push axially on the gear from both sides and hold it in position, although it's not clear what keeps the oil in place if there is no pocket to hold pressure. Likely it's just a high-pressure jet of oil squirting out and hitting the flange of the gear from both sides--just enough to keep the cam centered or keep it from floating axially and making the noise.

The holes are a small orifice at 0.6mm (0.024") diameter, that would be a #73 drill bit for me. Looks like a lot of work. If the journals really are too large, and the noise is too loud, then i would consider replacing the cam holders and then drill them before installation, rather than take it down just to drill worn-out holders.

i have a '96 and will try to look next time i'm in there, but it would require pulling a cam holder to inspecticate it...

 

Thanks.

Yep, looking back through the TI it only mentions cam cap #8. I'm guessing as you've described it that is the one closest to the gear.

So the oil pressure through the drilled hole pushes the camshaft hard to the right? Which would explain the noise going away when I tip the bike to the right at present?

Why is it a lot of work just out of interest? I was just thinking it through - pull cover, loosen cam covers for that camshaft and pull out and drill the hole.

I've not done the valves on mine - this is going on what I'd have to do to the Hawk I've also got in order to do the VFR.

Thanks for your input - least feel like I'm getting somewhere.

BTW - it looks like it might affect 96's as well - it mentions FS and FT.

 

It is a somewhat unclear document, but appears to say do it to all 8 holders, one at a time.

Not a difficult or hard task, just time consuming--remove seat, rear fairing, tank, middle fairing, airbox, carburetors, radiator, thermostat housing, spark plugs, cam cover, cam holders (1 at a time), drill tiny hole without breaking bit, clean out swarf, etc...If i got into it that far i would be wanting to pull the cams and measure the cam and journal diameters.

Sounds like you are ready to do it so let us know how it goes. Good luck and have fun.

 

Well, to cut to the chase, that seems to have fixed it.

As the noise was only coming from the back two cylinders, thats all I looked at and that was enough.

I drilled all 4 cam caps (one at a time) with a 1mm drill as per the tech document. The noise has gone away completely.

It was quite easy as all I had to remove was the tank and rear rocker cover.

Nothing was stuck and despite breaking the first drill from rushing it all went smoothly.

 

Great work man, that is Exellent news--love a happy ending!

 

Anyone care to resurrect an old thread?! I think I need to do the mod, but can't find anything specific, as far as where to drill, etc.
Help a brother out!!