How important is checking valve clearances?

[SteveSmith]

I'm servicing my own bike this weekend for the first time. Everything is gong well, but when I went to remove the valve cover to check the clearances, one of the 14 bolts is rusted in place with a mangled head (the other 13 are fine). Annoyingly, it's the least accessible one, low down at the front right up against the frame. Even if I did have the tools / skills to get it out, I think I'd have to get the engine out to do so. That's beyond me, so I would be paying a garage to do it.

Questions are :

1) Is it worth it?
2) Could I tell without getting at them if the clearances were out? I've no reason to think there's a problem, but I don't really know what it would feel like if they were.

Thanks,

Steve.

[Nobby the Bastard]

Eventually the engine will stop working, either due to the valves not opening enough for mixture to get sucked in or because the valves stay open when they should be closed, losing compression (and potentially having a catastrophic encounter with the pistons)
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trevor saxe-coburg-gotha:"Remember this simple rule - scooters are for men who like to feel the breeze on their huge, flapping cunt lips."
Triumph Sprint ST 1050

[Taught2BCauti...]

It is quite important to check them regularly, so if you manage to get that dodgy bolt out, replace it with a good one and use copper grease on the threads, and don't over-tighten it.

Check again after 1,000 miles, and if no adjustment is required, check again after 2,000 miles, and so on.

Your manual probably recommends a mileage interval for checking clearances.
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[SteveSmith]

OK thanks. It's due in soonish to get the rear wheel bearings changed, so I'll ask them to have a go at it then.

Cheers,

Steve.

[STONEY!]

depends on the bike ie:

My DRZ400 has done 40,000 never checked the valves or even taken the rocker cover off, might do if it starts having trouble starting or something

My old boss's r6 had valves checked at 20,000ish then 50,000odd then finally needed adjusting at 80,000odd

however if you have something like a crf250/450 or any other harsh enduro mx bike you should check them every few hours

My road legal pit bike I had to check and adjust every ride!

[Triton Thrasher]

[Bezzer]

Take it that it's the Bandit again? "They all do that mate", common problem on the oil cooled motors you've been lucky to get away with just the one it's usually front and rear ones if the cover hasn't been touched for a while. There's a recent thread on OSS giving a few options
https://old-skool-suzuki.proboards.com/thread/4238/stubborn-bolt
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I used to be indecisive but now I'm not quite so sure.

[Teflon-Mike]

If you have a seized bolt that's stooping YOU perform a routine service inspection & adjustment... how log has it been since ANY-ONE was able to perform that routine service inspection & adjustment?

Best case, if tappet clerances are a bit wide, motor may be harder to start, will be down on power, less responsive, use a bit more fuel and probably sound like a London Taxi, as though theres a herd of ADHD dwarves in the rocker cover mining for freedom.

Worst case? Tight clerance, valve wont close; valve head gets hot n the the combustion gasses, and cant dump its heat into the seat, and melts, probably dropping the head or at least chunks of valve into the cylinder to chew piston & combustion chamber.

Often a pretty wide leeway for error on manufacturers suggested service intervals; engine thats started for times a day from cold, thrashed up ad down the gears accross town and back, will tend to suffer more 'wear' than a engine that's started once a week, warmed nicely while rider clamber into kit, then ridden for five or six hours at a stretch, at fairly constant speeds cross country or on a motorway.

BUT.. like I said if you cant get the rocker cover off to check.. how long has it been since ANYONE took the rocker cover off and checked.... and how far out of tolerance could they have gone since they were last checked? Not how far out might the go from here! That depends how far out they may be now... and you dot know

Its a piece of string question, but bolt isn't going to un-rust itself for you so you can check them next time you decide to do a service is it? And those clearances aren't going to adjust themselves to save you the hassle.
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Current Bikes:'Honda VF1000F' ;'CB750F2N' ;'CB125TD ( 6 3 of em!)'; 'Montesa Cota 248'. Learner FAQ's:= 'U want to Ride a Motorbike! Where Do U start?'

[Rogerborg]

It would really help you if you told us what bike it is, the mileage, and any evidence of them being checked before.

I skipped the 12,000 mile check on my GS because:

1) Mine is an Austrian Rotax engine, not one of the Chinese Lifans, and I'm pretty lacist.

2) There are several owners' forums reports of them being fine at much higher mileages.

3) I (with good reason) don't trust the local BMW dealer to actually check them unless I'm standing over them, in which case I may as well do it myself.

4) They're a sod to get to and I can't be arsed doing it myself. Caveat emptor, next owner.
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GONE: HN125-8, LF-250B, GPz 305, GPZ 500S, Burgman 400 // RIDING: F650GS (800 twin), Royal Enfield Bullet Electra 500 AVL, Ninja 250R because racebike

[ADSrox0r]

The valve check on the Viffer at 16k is a beast of a job, usually costs somewhere up to 600 odd quid at a Honda dealer or 400 odd indy due to the VTEC shenanigans. The flipside though is that a lot of owners say if it ain't givin you no beef, skip it.

Mine is just shy of 16k but I'll be leaving it till Spring/Summer next year to do it if at all.
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Current bikes: '08 VFR 800 VTEC(yo) , '07 ZZR1400 Winter hack: '95 Aprilia 650 Pegaso Currently lusting after: RC30

[Fizzer Thou]

If the valve cover bolt is an effort to get to,then you could tilt the engine forward in the frame in order to get better access to it.If you take the bike to a shop,this is quite likely the procedure that they will use...and charge you upwards of £55 per hour.

If you are contemplating doing your valve clearances,then the wheel bearings would be easier.With the right tools the bearings would take 10 minutes to replace.Warm the wheel hub with a hot air gun to aid removal and replacement and place the new wheel bearings in the freezer the night before.Use some good high melting point grease to lubricate the hub before installation of the new bearings.
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Always have a 'Plan B'

[SteveSmith]

Thanks everyone. Events have slightly taken over in that the bugger wouldn't start at all this morning (see separate post), so it's now on it's way to a garage. As soon as I said "valve cover bolt" on the phone he knew which one it was, so I guess it is pretty common.

From what people have said, it does sound as if they could need doing (rattly, doesn't want to start). I've asked the garage to sort the bolt for me, then I'll do the valves myself. It's an old (2001 Y) Bandit, used for a shortish daily commute in all weathers, so more susceptible to wear.

Cheers all,

Steve.