VH metallic tapping noise at TDC

[Les H]

I was just going over everything on a newly acquired 58 VH. I noticed that if I slowly positioned the piston near TDC with the kickstart and prodded the kickstart to rock the piston on the compression there is quite a loud metallic clicking noise seemingly coming from the top area of the engine. If I remove the spark plug no noise is created, only when the piston is at TDC and compressing the gas but not actually going fully over and down...just rocking under compression. I imagine this must be the piston rattling with excess clearance?...I was wondering if any other owners of VH bikes have noticed this phenomena....OR do I have a very badly worn bore?...Compression seems OK though ...Hopefully someone will tell me this is normal

[will_curry]

Les,

I assume this is the bike with the painted alloy head?
Alloy engines seem to make more mechanical noise that their all-iron
counterparts but I don't recall any of mine make a noise such as you describe.
Does the bike knock when the engine is running?

Any chance of a picture or two?

[Les H]

Hi Will. yes it's the one with the painted head ...Although now most of the very thin paint has been removed by me with a green abrasive dish washing scouring pad...most of it has actually cleaned off quite easily and no hidden horrors have been revealed...phew!... I was thinking I would film it with sound and put it on YouTube for anyone's interest. I haven't ridden it much so far but I noticed the ignition is way too advanced as the engine slows past the optimum magneto setting of about half way on the lever. When it slows the engine does become much harsher and clanks quite a bit... so either massive piston slap or the big ends are worn possibly OR Ok with the correct ignition setting...The noise this post is about is not with the engine running though, just rocking the piston at TDC and letting it "bounce" on the compression at this point....it clicks quite loudly and metallically

[Brian_Walker]

Could be in the valve train, when the inlet valve closes if the pushrod is bent or not lined up it may make a noise at the finds its correct seat.
The rods may not be sitting on the tappet adjusters properly due to cam followers shifting around too much or the springs are snapping back after being compressed.
Not sure I would be running it before at least checking the valve clearances, with the caps off and without the plug you can turn the engine over slowly with a finger on the top of the tappet, as it gets towards the top of the lift it will be quite hard to turn (with the clutch cover off it is hard to move by hand due to the valve spring tension. If it goes clunk at this point as it rolls past the top of the lift it could even be the inner valve spring binding.
Question from Will should give us more insight.

[will_curry]

I'd expect both valves to be properly shut if there is compression
and so they wouldn't contribute to the noise.

If there was enough clearance between the bore and the piston
to be heard turning the engine over by hand I'd expect a lot of
piston slap when the engine was running. There can a lot of
clearance between bore and piston with the compression still
good as it's the rings which make the seal, not the piston.

Also, if the ignition was so far advanced as to slow the bike down
I'd also expect a lot of knocking. Are you sure you're working the
ignition control the right way? With the control cable attached to the
right side of the magneto when looking at the points the wire has to
be tightened to advance the ignition.

[Les H]

Thanks for your suggestions. Re Brian: At first I thought the same as you Brian, it did sound like a pushrod was either catching or finding its way into its position at the rockers. However I have set the clearances accurately and even kept my finger on the rocker arm to feel if the clicking was coinciding with any feeling being transmitted to the arm but nothing. To also eliminate the valve train possibility, I removed the spark plug and spun the engine over and over with the kick-start but total absence of any clicking, just slight chain and gear noise. Re Will: Yes it has good compression (not measured but feels good and holds well) As far as slapping when running I will have to do that a bit later as I am in the process of doing some tidying work before taking it properly on any run. The situation of the engine being stone cold is that any piston clearance is at maximum and devoid of oil, I was just interested to know if anyone else with a worn engine can get the same clicking noise by doing the same "test" at TDC IE: rocking the piston but stopping just short of allowing the piston to actually pass by and down the bore. Regarding the ignition timing: Yes I'm pulling the lever back which causes the engine speed to rise (at tick-over) until about half way and any further advancement, the engine slows and becomes harsh and noisy. The actual timing will be checked and adjusted soon. Its 0.5" BTDC fully advanced?. Coming back to the clicking. Once I get the bike rideable again I'll know if I have a problem that does have to be fixed...I really hate piston slap

[Les H]

Well I spent all day on it today but really I should say I wasted a whole day on it I spent a lot of time making sure the ignition was set accurately plus cleaning up and other improvement jobs. Well it started but just like before, it slows down on full advance at tick over. The other thing that is VERY odd is that the pilot jet on the Monoblock needs to be out about 5 turns to get the best idle with the ignition set at about half max advance or it conks out.. It just does not like running with full advance. Then the metallic clattering sound confirms this engine is possibly a pile of junk. I'm really peed off with it. I do know what I'm doing as I have 55 years experience but this needs a total rebuild I reckon. However I really would like to compare this bike to a known excellent example of a VH Ariel just to know what I could expect to achieve or maybe ALL VHs make a lot of mechanical noise...Please let me know your views. I would be most appreciative. Thanks PS I'm thinking maybe the valve timing could be wrong apart from any other rattle producing wear ...PS: I'm thinking maybe it has a high comp piston?

[will_curry]

I'm sorry to hear that you're not happy with your Ariel. Whereabouts are you?

For what it's worth, none of my singles will tick over on full advance. I wouldn't
describe any of them as being in excellent condition either and they've all been
in my possession for over 40 years and two for nearly 60. They all rattle to a
degree which now I've come to accept as 'usual'.

You've no way of knowing what injustices previous owners may have
committed to your bike.

[Les H]

Hi Will. Thanks for letting me know about ignition setting at tick-over. I did have the suspicion that full advance at tick-over seems too much for any engine to handle. The handbook however says as soon as you start you should leave the ignition on full advance but this seems difficult to understand as the slow piston speed would give too much time for the burn to push back the piston. What you say makes me feel better and I might be able now to continue the search for getting the bike to run correctly. I was also thinking that maybe the air filter is restricting the air flow which is why the idle air screw needs to be nearly all the way out...or maybe the pilot jet is too big or not screwed in and leaking? PS I live in West Somerset...it would be nice to know you do too. But I bet you don't

[will_curry]

It would be too easy if I lived in West Somerset. I live in the wilderness north of Luton but
there are a number of very talented Arielists who live in your part of the world. It may well
worth your while joining the club.

As you must appreciate modern petrol is nothing like what was available in the 50s and
for that reason alone a lot of what is in the factory documentation is now inappropriate.

If you're happy the ignition is correctly set the carb is a good place to start next. A worn
slide can make a mockery of setting up the pilot as can an incorrect fuel level caused
by wear on the float. The fuel and mixture passages for the pilot are easily blocked so
a complete carb strip and clean in an ultrasonic tank are the first step.

It would be nice to see some pictures too.