Piston slap or valves?
 

Hi guys,

My SV650 has 42k miles on the clock and I'm starting to hear a loud ticking noise coming from the front, it's definitely not normal SV engine ticking.

At first I suspected it may be time for new cam chain on the front (Rear was replaced last year). However when the engine is warm say about after 5 minutes of running and temps above 70 degrees C, the ticking is completely gone, nothing at all, just a happy sounding engine. As if it was never there. No way it can be the cam chain surely! Can't take up what sounds like a serious amount of slack with a 5 minute warm up.

When cold, the loud ticking/tapping is there and very prominent and can be heard above my baffle-less exhaust note. It's coming from the front cylinder for sure, rear is fine, bottom is fine and happy.

There are no obvious performance issues either and I'm not burning oil, it's been like this for the last 2-3K miles now I'd say.

Someone has told me it may be piston slap purely based on the fact that it goes away once engine is warm. But would piston slap sound more like a deeper knocking note than the tapping I'm hearing? I would like to get some more opinions.

I was thinking one possibility is loose valve clearances as You'd expect them to tighten up slightly once engine warms up.

Cheers!

Re: Piston slap or valves?
 

Does the noise disappear or change if you apply the clutch whilst the bike is ticking over during the warm up?


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Re: Piston slap or valves?
 

When were the clearances last checked? Over on SVRider, the greybeards there say that on the SV, the clearances actually WIDEN by one thou or so when the engine is warm. Seems counter-intuitive, I know, but that's what they have found.

Also, is the front header snug against the exhaust port? If there's a small gas leak that can make an odd sound, and that will stop when the engine warms up a bit.

Re: Piston slap or valves?
 

To me a noisy valve is a happy valve, with modern hardened valve seats ( made necessary by unleaded fuel) the valve heads do not sink into the head material anywhere near so much as engine ages ( a valve that does not close properly does not get cooled by contact with the head and will burn out ).

May be piston slap, modern short pistons are more prone to piston slap when cold - designers shortened the skirt for weight and friction saving. Pistons are actually made in a conical shape that expands to be more parallel when hot.

Having the clearance widen as the engine warms up is proper counter-intuitive unless the valve stem material has negative coefficient of expansion, or the expansion of aluminium head pushes the camshaft away from the valves.

Re: Piston slap or valves?
 

I think it's probably the latter, as the head is a big casting. As mentioned, I've no experience of this myself, but that's what a couple of owners on SVRider have reported.

Re: Piston slap or valves?
 

Here's a clip I recorded of the sound of cold startup.

https://youtu.be/_FvQY8O7JdU

Proper rattle. But as I say, completely disappears when warm and sounds happy.

I checked the exhaust header and it's perfect so it's not coming from there.

Haven't tried pulling clutch in but will have a go tomorrow, although I feel like I would have noticed as I tend to hold clutch at stops rather frequently.

In the case that it is piston slap, is that something I should be worried about? Should I expect total failure at some point soon?

Valve clearances were never checked on the front, only the rear when new cam chain was put in which was a joke cost of £700 alone!

I don't know, what do you reckon cost would be for clearance check on the front? I'm not in a hurry as I've got the Bandit now but I don't know whether I'm up for spending another £300+ trying to sort it :(

Piston slap or valves?
 

That is rather noisy. I can’t help thinking the frequency sounds slower that 20Hz, which it would be if it is coming from an engine part at 1200 RPM, in which case perhaps it could be a transmission part (like for example the clutch basket). Try holding the clutch in as it ticks over - if the noise changes it might indicate something in the transmission.
You may be able to narrow down the fault with a stethoscope.
I suspect not many SV owners ever get round to checking their valve clearances (it would be costly to get a garage to do it and most bikes won’t be worth very much by the time they get to 25,000 miles). I could be wrong about that one (but I suspect I’m not).
There is a school of thought that says the risk of causing collateral damage might be greater than the potential gain. Saying that, if you are fairly competent with the spanners it would not be too difficult to check the clearances yourself to see if the followers need shimming - even if you then wanted to outsource the shimming job to a garage or mobile mechanic (that is the more difficult bit - taking the camshafts off and making sure the timing is right afterwards).

Alan


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Re: Piston slap or valves?
 

If you don't have a stethoscope a long screwdriver is fine, put the handle on your ear and the blade on various parts of the engine to see where noise is loudest, normally piston slap is lower frequency sort of heavier than the rattle of tappet noise, and because the cam lobes operate directly on the valve cap tappet noise is not as common as it used to be ( because there are no rocker arms between cam lobe and top of valve stem ). If it goes away as soon as engine gets warm I would bet on piston slap as I do not think clutch basket noise would be affected much by engine temperature.

As said earlier a noisy valve is a happy valve, nothing more damaging than a valve gap being too tight and running the risk of burning out a valve. If you decide to try and fix it the risk of doing damage or costing a lot of money is probably greater than the risk of engine damage from excess valve clearance, and a few thou less on lift is not going to affect performance - I regularly get piston slap in cold weather on both our cars ( Honda Civic and Jazz ) neither has done excessive miles - but it goes away as soon as engine gets warm so it does not worry me, as I said modern short pistons more prone to piston slap even on New engines than with older longer skirts designs.

Re: Piston slap or valves?
 

Don’t bother checking the clutch then.


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Re: Piston slap or valves?
 

Good morn,

Just a thought. If you eliminate the clutch and transmission from the problem then the most likely culprit might be the front cylinder valve clearances. If you think that is where the noise is coming from then I’m thinking that checking the clearances yourself on the front cylinder only would not be too onerous (it is access to the rear cylinder head that takes the time stripping bits off the bike). I’ve just had a look at my bike (K6) and I’m pretty sure you could get away with just taking the radiator off (5 minute job, drain half the coolant, one electrical connection, 2 bolts and 2 clips) then you should get clear access to the cam cover. Remove the inspection plug so you can see the timing marks then get the feeler gauge out. All that you could do with some basic tools with a little knowledge and at no cost.
Once measured you would either find it is okay (in which case the hunt for the cause continues elsewhere) or the shims need changing. If you are not confident you might want a mobile mechanic to come and do that bit for you, but you could work out the shim sizes and get them ordered first, so it would probably only take an hour’s labour to change the shims and put everything together. I suppose that might cost about £100 with some gaskets.
Just a thought - now it is time to walk Bob the dog.
AO


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