Relationship between Timing & tappets

[Sprunghub]

Ok - I'm going to preface this with an embarrassment warning.  I'm not an engineer, I do my best, I get by, but a lot of the time it's luck.  I have '0' mechanical "instinct".

My CB750 F1, 33,000 miles runs like a 'clock'.....which is an unfortunate analogy, because it has developed a "tick", in the last few days or, more to the point a click.....click, click & a whirring sloosh

It sounds, as best I can tell "top end"....but it doesn't sound unduly 'tappety'.....& it is the click/ticking which has attracted my ear ( I mean lets face it, it's a pretty noisy engine even when "pefect") so the slooshing, may be normal "top end" noise.

The only thing I have done to what was an otherwise sweet running, non-ticking, bike, is add the Dyna S electronic ignition & time it to perfection with a strobe light.

The question is, if the timing was slightly out before the Dyna S was fitted & the tappets set to run on a slightly "out" timing, is the fitting of the perfectly adjusted ignition likely to have induced the tappets being 'out' ?

I have double checked the fitting of the Dyna S - nothing is "catching", it does speed up with engine revs but gets pretty much "lost" in the engine noise at higher revs, on the stand or rolling & is most obvious when at low revs, low speed or static.  It's there when the engine is warm or cold ? & doesn't seem to get better or worse.  Sometimes it seems imperceptible & then like a spanner in a tin can.   

The bike is running with good power, carbs have just been set/balanced ( since the ticking started ) & touch wood nothing horrible has happened.

Any suggestions.......

[Bryanj]

Adjusting the timing can have no affect whatsover on the tappets, but altering it can make different mechanical noises appear and dissapear, check the exhaust gaskets are not blowing at the head as that can sound very much like a tappet

[SteveD CB500K0]

The tappets are set at Top Dead Centre (TDC) which is the "T" mark if you have a Honda points backing plate. This is when the piston is at the top of its throw and both valves are closed.

The timing is set "before TDC" (the "F" mark). This is a few degrees before TDC to allow the ignition a few milliseconds to fire the plug (which should happen a fraction of a second after TDC).

Hope this generic info helps.

I'll leave your other question to the 750 guys...

[Sprunghub]

Adjusting the timing can have no affect whatsover on the tappets, but altering it can make different mechanical noises appear and dissapear, check the exhaust gaskets are not blowing at the head as that can sound very much like a tappet

I wonder......in my last, re. the abortive re-fit of the exhaust, I noted & "fessed up" to the fact that one of the Motad pipes had split around the lip cum flange where it fits against the head.

I've had a 'calm' listen, tonight.......I'm wondering now if it could be coming from there.  It really is the most peculiar.....& alarming, to be honest 'noise'.  That's what made me think it wasn't tappets, it's like a szzzuzzing & a tap .  If it was likely to be a commonly found issue, I'd get a sound file & 'post' it, but it's obviously something obscure ! so there isn't much point. 

I may just hold fire & see what happens when I fit the OEM system.

[Sprunghub]

Is there anyone on the Group using a Dyna-S ignition ? particularly with the Dyna coils ??

Still trying to suss the origin of this 'noise'.

It may still be the exhaust, but I've re-bedded the rims & got them tightened down.  I can't put the 'old' set up on until the collet's arrive, but there is no sign of any escaping gas- although that still may be the issue.

In the meantime, I have set the tappets - or rather 'checked' they were pretty much perfect anyway.  Have 'tweaked' the timing chain, which again, was pretty much bang on as it was only done about 1,000 miles ago.

I'm still getting the szuzzing & 'crack'  - I'm just wondering if you get such an enhanced spark with these Dyna S systems you can hear it & if anyone who is running one can comment ?

[Yoshi823]

I wonder if the enhanced output from the ignition is causing any voltage to escape from the plug caps? The noise description might be voltage jumping to earth/chassis.

[Sprunghub]

The coils come with Dyna leads & caps.  You have to cut down & make up the connections at the coils, add screw on grommets to the plugs....just the sort normally fitted to 'plugs', & then the Dyna caps lock onto the larger connector.  I can't see any 'jumping' but I suppose if it was in the recess, I wouldn't.
Took her for a half decent run today - about 50 miles, it get's no better, it get's no worse, the performance of the bike doesn't seem to be affected........but I don't think it's "right".

Could still be that exhaust.......but instinct suggests it's not necessarily.

Frustrating............... more so, because I simply can't isolate where the noise is coming from.   

[Spitfire]

Start it up in the dark and look under the tank for arcing.

Cheers

Den

[Sprunghub]

Good plan....

[Sprunghub]

blowing at the head as that can sound very much like a tappet

Another bouquet to BryanJ  

removed the Motad, refitted the OEM with my newly acquired 'proper' collets & rear bracket, tweaked it all up & she's all purrs again
No tick's, tocks, wooshes or other odd noises, just vroom, vroooom, vrooooom.

Now then, where's that sun gone ?

8pm
Just been out for a run - first time on the OEM system......she is absolutely flying - seems to have freed up enormously after the Motad, which I presumed would have been a straight "fit" ?  
Either way up, what a  
Must get a new piccie

[Bryanj]

'Sokay, I did the tappets 5 times on a 550 i serviced regularly and was about to pull the cam when i found one exhaust gasket very slightly loose!!!