Loud knock and it has got me foxed- any ideas I'm desperate!

[Rincewind]

Hi All,

My daughters wedding is coming up in early June so thought I would sort out a few things to ensure (?) reliability, so changed out timing chains, sprockets etc and checked a few things on the way. Did it all according to TH video and all went well, until i started it up and there was an almighty din, switched off immediately and went back to check everything I had done. The noise as best as I can describe is a very very loud metallic tap or knock.

TDC and cams in pretty good alignment (not more than a degree or two accross the whole lot). Chain tensioners set to about 1mm and pumping (big pool of oil on floor )

I thought I had the jack shaft a tooth out, so moved it but actually it was correct, timing is not spot on but not far off

Tried again still very, very loud tap/knock, speed dependant.

No noise on starter motor (except whirring ) so doesn't appear to be mechanical, please correct if this is a poor assumption.

When it started it was a little slow getting on to all eight, probably a bit rich from spinning over on the starter to get oil pressure, and the noise wasn't present but started to build up with the revs.

Got my listening stick out (BIG screwdriver) and the noise was loudest from the carb (Webber), couldn't hear anything from either cam bank.

Pulled each lead off in turn, no difference (except slight drop in revs as would be expected).

I checked valve clearances but haven't done anything with them so they are still the same. ( I need to do something as some are sloppy and others tight, need to wait until another day).

So, I am boogered if I know what is wrong. Anyone do house visits??

Any help or suggestions greatly received.

Keith

[singapore stag]

Where is the "big pool of oil" from? have you traced it back to the leak?.

Sukh.

[Rincewind]

Hi Sukh,

The front timing cover was off with a large rag covering the top of the sump, oil pumped out of the tensioners onto the rag then to the floor. Least that is what I believe happened as didn't see it but there was a trail on the rag, so I reasonably sure.

[Marco Polo]

My first suggestion would be to take the sparkplugs out and turn the engine over by hand to see if there are any noises or noticeable difference in torque required to turn the engine.
Regards,
Raoul

[jbuckl]

Diagnose this noise with all spark plugs out and cranking only from now on until you find the noise.

Do you know what the cranking or idle oil pressure is?

Regards
Julian

[jbuckl]

Did you turn over twice by hand b4 attempting the start?

[Rincewind]

Hi Julian Raoul,

I turned the engine over several times, than ran it on the starter to get the pressure over 40lbs before starting it. Using the starter motor there aren't any noises, only when it is running.

Cheers

Keith

[jbuckl]

good stuff, so what was the idle oil pressure?

[Rincewind]

Oil pressure is at 40lbs cold on idle. Make to much of a frightening noise to allow it to warm up!!

Brand new VR1 and filter

[RogerP]

Keith

You say you've checked the jackshaft, but what about the camshaft timing I got one out by one tooth and it made an awful noise, and I was convinced I had got it right but hadn't guess the valve was kissing the piston managed to move it round one tooth without dismantalling everthing.
The other thing you could try, and I get this every year when it's been laid up for a while it knocks like big ends or something just as bad. Take the cam covers off and put loads of oil round the buckets the back one on the left hand head is the last to get oil round even when you have got oil pressure up, this year it took a good 10 min before our's went quite.

Roger

[Rincewind]

Hi Roger,

First thing I checked as logically it has to be something I have done but it all appears spot on. I only get the noise when he engine runs, not when turning over on the starter. The is lots of oil,around the buckets and it is all collecting around the back ones, so should be OK, interesting thought though. I have listened to both cam covers and they sound normal, noise seems to be coming from the carburettor. Not sure what that means.

Thanks Keith

[milothedog]

Hi Roger,

First thing I checked as logically it has to be something I have done but it all appears spot on. I only get the noise when he engine runs, not when turning over on the starter. The is lots of oil,around the buckets and it is all collecting around the back ones, so should be OK, interesting thought though. I have listened to both cam covers and they sound normal, noise seems to be coming from the carburettor. Not sure what that means.

Thanks Keith

Kieth, does it idle OK or show any signs of a misfire. if an inlet valve had got bent you could get something like this, my next step would be to do a compression test.

Ian.

[Rincewind]

Hi Ian,

Seems to be OK, and can ' t hear a misfire above the racket. I have checked all the tappet clearances and most are either correct or a bit tight though two inlets are at 12 and 15 thou., (should be around 9 thou.) would this be enough to suggest a bent valve?

I will try my new compression tester soon.

Thanks Keith

[milothedog]

Hi Ian,

Seems to be OK, and can ' t hear a misfire above the racket. I have checked all the tappet clearances and most are either correct or a bit tight though two inlets are at 12 and 15 thou., (should be around 9 thou.) would this be enough to suggest a bent valve?

Thanks Keith

If a piston did kiss a valve, hope it didn't, it may not affect the valve clearance. it only needs a little to prevent the valve seating and allow compression to be forced back into the inlet manifold. hence the noise from the carb!!!! I would check them to eliminate it before looking further.

Ian.

[flying farmer]

Since the noise has started since you worked on it, it is almost certainly incorrect assembly. I assume you have timed the cams to the fine line scribed in the end of the camshaft, not the big notch which looks like a timing mark but definately isn't. Also worth checking that TDC is where the pointer says it is. Since the noise is coming from the carb it might suggest the inlet valves hitting the piston. I have seen this on one of the engines I stripped and a nice set of inlet valve cutouts were left in the piston crown on one bank. The timing was one tooth retarded in this case, mostly because the TDC pointer was 4 degrees out, which meant the nearest tooth to the cam timing mark was the wrong one
Neil