Engine knocking when hot

[Beemerman59]

While I was on the Ride of Respect on Sunday the engine on my 08 GSA got hotter than normal and at these points I noticed a distinct engine knocking noise. This could be clearly heard when stationary and at a slow moving pace. When the bike had got into clear air and cooled a bit, the noise was reduced but letting the bike run a bit in the garage when I got home, the knocking returned. It's really difficult to pinpoint but seems to be coming more form the RH side, high up towards the rear of the engine, sort of between the injectors and where the cam chain is.

Now, I'm used to the bike sounding like a bag of nails at times but I am wondering what might be out of adjustment that could be causing this. It's not tappet noise I know that. I was wondering about the throttle bodies - I didn't do these at the 18K service (because all was running sweetly anyway) and now the bike's at 21K. If the sync on these were out, is it likely to cause an engine knocking which could be more pronounced when hot?


Or can those on here who regularly get hot engines due to slow traffic etc tell me this is normal? I have not ridden the bike since, but there was no sign of this before last Sunday's ride.

 

[Deleted account 210516001]

I had the same experience on the ride of respect. Cooked the engine waiting to be released onto the road and the engine sounded decidedly slack with knocking and rattles that I have not noticed before. I kept it in a higher gear than usual on the way to Wootton and it was back to normal temperature by the time I got there. It went back to sounding like the usual tin of washers and by the time we had been stopped for an hour everything sounded normal when it was started from cold. It has since done a couple of hundred miles without a problem.

I wonder if the new synthetic oil gets thinner than the old stuff when it gets very hot? It will still be doing its lubricating job but perhaps does not as good at cushioning the knocks and rattles.

 

[Deleted account 211025001]

It'll be your cam chain rattling about.

The adjuster is hydraulic and looses pressure enough to allow the chain to get noisey when very hot.

Andres

 

[Beemerman59]

It'll be your cam chain rattling about.

The adjuster is hydraulic and looses pressure enough to allow the chain to get noisey when very hot.

Andres

That makes sense except this was a definite knocking noise rather than a rattling noise.

 

[Beemerman59]

I had the same experience on the ride of respect. Cooked the engine waiting to be released onto the road and the engine sounded decidedly slack with knocking and rattles that I have not noticed before. I kept it in a higher gear than usual on the way to Wootton and it was back to normal temperature by the time I got there. It went back to sounding like the usual tin of washers and by the time we had been stopped for an hour everything sounded normal when it was started from cold. It has since done a couple of hundred miles without a problem.

I wonder if the new synthetic oil gets thinner than the old stuff when it gets very hot? It will still be doing its lubricating job but perhaps does not as good at cushioning the knocks and rattles.

Maybe, but in my case I'm running 20/50 mineral.

 

[Greg Masters]

Maybe, but in my case I'm running 20/50 mineral.

One of the real and significant advantages of fully-synth oil is that it provides a much higher level of lubrication when the engine is very hot. In oil/air cooled engines the operating temperature range is much higher than in an engine stabilised by water-cooling.

Greg

 

[Beemerman59]

One of the real and significant advantages of fully-synth oil is that it provides a much higher level of lubrication when the engine is very hot. In oil/air cooled engines the operating temperature range is much higher than in an engine stabilised by water-cooling.

Greg

That may be so, but the point is that there's two of us with what sounds like identical knocking noises due to hot engines, one uses fully synth, the other mineral. Points to the oil type not being significant as far as the noise is concerned. Agreed, wear may be a different thing all together.

 

[Greg Masters]

Agreed, wear may be a different thing all together.

.... as may be the cause of your noise. As you know, it's actually quite difficult to identify the source of some noises when you have your ear cocked to the running engine. It's even more difficult from behind a keyboard and screen.



Greg

 

[Deleted account 211025001]

That makes sense except this was a definite knocking noise rather than a rattling noise.

Maybe, but in my case I'm running 20/50 mineral.

Yup, a definite knocking noise is what you'll hear. The first time it happened to me it sounded 'terminal' it was so loud.

It happened to me for the first time after a dealer service where they put the first lot of semi-synth in so I changed back to dino 20/50 - all was well until getting caught in a Paris jam in the middle of summer where it got hot enough to do it again.

Andres

 

[Beemerman59]

Having been out tonight for a blast the bike is back to normal with general rattling rather than knocking noises so my monies on the cam chain tensioner plus I sometimes get the same on start up or after changing the oil.

 

[Deleted account 190920001]

The boxer engines are old aircooled clunkers with no real temperature control. When they get hot they knock and there isn't much you can do about it. One thing you could do is fit some fans to the oil cooler like the police bikes have. They will help keep the oil a bit cooler when your stationary.

 

[PanzerPilot]

While I was on the Ride of Respect on Sunday the engine on my 08 GSA got hotter than normal and at these points I noticed a distinct engine knocking noise. This could be clearly heard when stationary and at a slow moving pace. When the bike had got into clear air and cooled a bit, the noise was reduced but letting the bike run a bit in the garage when I got home, the knocking returned. It's really difficult to pinpoint but seems to be coming more form the RH side, high up towards the rear of the engine, sort of between the injectors and where the cam chain is.

Now, I'm used to the bike sounding like a bag of nails at times but I am wondering what might be out of adjustment that could be causing this. It's not tappet noise I know that. I was wondering about the throttle bodies - I didn't do these at the 18K service (because all was running sweetly anyway) and now the bike's at 21K. If the sync on these were out, is it likely to cause an engine knocking which could be more pronounced when hot?


Or can those on here who regularly get hot engines due to slow traffic etc tell me this is normal? I have not ridden the bike since, but there was no sign of this before last Sunday's ride.

Don't worry mate! My previous GSA did the same when it got too hot, sounded f*****g awful I pulled over, let it cool for 10 minutes which was long enough for the oil temperature gauge to drop back to somewhere near normal. I set off again riding sensibly and the temperature returned to normal, engine went back to the normal boxer sound and fine at idle speed too. As the other boys have said, these are big old engines which are never really that quiet to start with, and when the oil gets hot and thin they just sound even worse!! Funny thing is, cooking my engine made it a million times better, smoother and seemed to rev better, the heat must have helped it run in better!
It'll be fine mate, these are bomb proof Though for peace of mind you could do what I did, change the oil and filter just in case the higher than normal temperature gave it a kicking.
Rich
2010 GSA Shyyyyyyyyyyyyne yellow
Honda VFR750-FL Pro-Arm (Winter bike, now Sunday bike)