Valve clearances and lunched motor

[ttmadness]

Has anyone ever lunched their motor from not doing valve clearance checks?

I am starting to think it's a bunch of baloney with checking valve clearances so often. Maybe it's something the manufacturers state in order to make money at dealerships and cover their backs if anything goes wrong and try to claim warranty, for example, over revving the engine and running poor oil that can cause top end damage.

Every time I have checked valve clearances they have all been within tolerances. I have had some real ''high km'' bikes too.

Another thing that adds to all this is people with ticking cam chains thinking they have bad valve clearances... you generally can never hear the difference in valve clearances!!!

My argument is that everyone keeps saying you need to check/adjust them or you will burn valves/blow your engine etc, but I have not read about the first instance of this happening. You would think that with all the undisciplined riders out there that someone would have had a engine blow that could have been avoided with scheduled maintenance.

[ttmadness]

Is it correct that if you were to actually have a case of a significantly out of spec valve clearance/clearances that your motor would be hard to start and have low power due to short valve lift duration?

Is it also correct that the most likely cause to ever damage your engine through unadjusted valves is tightening of the exhaust valves, causing excess heat?

[Brian d marge]

Japanese design thinking is for the engine to last a set km without major maintenance , the buying culture ( which is changing slightly ) tends towards selling at low ish km

the deals on a new bike is pretty good so there is no point in keeping one that needs such a check

The big 4 tend to have an inward looking design philosophy ( go china ! )

your 600 responds REALLY well to correct valve timing ( transforms them almost )

its not hard to check.

Stephen

[ttmadness]

what about modern bikes vs older 90s bikes?

[Brian d marge]

what about modern bikes vs older 90s bikes?

from memory is was about the 3rd version of the Cbr that had the jump in first service km , 24000 ?? so about the mid 90s around the fireblade coming out

I think what u are worried about is that by not sticking to the service schedule you will lunch the motor , all things being equal and with oil changes ,,, dont worry about it to much

on the bad side , Ive got it in the back of my head that once the valve tightens and lifts it runs away on itself

So a check is at least safe and sound


and on that note , the cost of a second hand engine , is almost the possibly even cheaper than a dealers valve check????

that might be worth a look into

Stephen

[AllanB]

On new Hondas they are around 24,000. That's a few years running for most riders so bloody cheap insurance having them checked for good motoring.

[Owl]

My first valve check at 17,000km had 2 within spec, 4 just out and 6 well out. All shims were replaced and set even. At 30,000km there was slight movement with the inlet clearances, but still well within spec.

The first check was noticeably quieter after adjustment.

[gammaguy]

Has anyone ever lunched their motor from not doing valve clearance checks?

I am starting to think it's a bunch of baloney with checking valve clearances so often. Maybe it's something the manufacturers state in order to make money at dealerships and cover their backs if anything goes wrong and try to claim warranty, for example, over revving the engine and running poor oil that can cause top end damage.

Every time I have checked valve clearances they have all been within tolerances. I have had some real ''high km'' bikes too.

Another thing that adds to all this is people with ticking cam chains thinking they have bad valve clearances... you generally can never hear the difference in valve clearances!!!

My argument is that everyone keeps saying you need to check/adjust them or you will burn valves/blow your engine etc, but I have not read about the first instance of this happening. You would think that with all the undisciplined riders out there that someone would have had a engine blow that could have been avoided with scheduled maintenance.

Its like a lot of motorcycles maintenance wise.

It s not what happens when you do it,its what happens when you dont.

I have seen huge damage caused by too tight valve clearances,which could have been prevented by a check when scheduled.

Unless you have X-Ray vision or super acute hearing(Hi superman)I would recommend doing them as recommended,at least until you get an idea of if and when they need adjusting,then you can modify the check schedule on that basis.

If I had a dollar for every engine I have rebuilt where the owner told me he thought the valves never needed checking,i would be a rich man

[tri boy]

Tight valves/no clearance means fucked components in the top end=$$$$$$$$
Now, ask yaself this,
Ya feeling lucky, Well are ya, punk.
(apologies to Dirty Harry)

[Mental Trousers]

If valve clearances tighten up the valves start hammering against the seats, bending things that shouldn't ever be bent. Tends to be the cause of most motors dropping a valve. Problem is it's impossible to diagnose after the motor has exploded.

[pete376403]

If valve clearances tighten up the valves start hammering against the seats, bending things that shouldn't ever be bent. Tends to be the cause of most motors dropping a valve. Problem is it's impossible to diagnose after the motor has exploded.

I've always understood that hammering seats, dropping valves is more a result of floating the valves from over-revving, with poor quality valve springs not being able to keep the cam follower accurately following the cam profile.

Tight (ie insufficient) exhaust clearance will eventually result in burnt valves as the valve head cannot transfer heat to the seat. Once the valve head is burnt the seat will probably go as well as there is a flame path across. Tight inlet valves are not such an issue, apart from the resultant lack of compression.
Valve clearances usually close up over time as the valve head sinks (wears) into the seat, more the case with old motors and unleaded

[Brian d marge]

Im stopping the gasoline causing the problems type of argument right here ... Never heard gasoline blamed for so much stuff until I spent some time in NZ ( yes there was one batch from Singapore that melted some escort drivers oring ,,,,,

anyway You don't have to be anal about checking , ,,I mean think about it , a brand new bike fresh from the factory , doesn't need a valve check for 24k , and to be honest I would be surprised if they were out ... ( the unscrupulous dealer in me coming out now )

but what are the service intervals . 6000km with the valves every second one ??? ( off top of head ) . if you just flicked the gauge under them once a year , you might notice the middle exhaust ( Im doing this from memory so please forgive ) tightening slightly

Your call on how anal you want to be


Oil

its amazing how many Kilometers this new stuff can do ...........

Stephen

[Brian d marge]

If I had a dollar for every engine I have rebuilt where the owner told me he thought the valves never needed checking,i would be a rich man

Can beat that

Hondas larges warranty claim , Honda 50 , for ,,,,no oil ( didn't think it needed it )

Oh they are out there all right , they may be your neighbor

or at the movies ,,,with your sister

Stephen

heard that a long time ago so with a pinch of salt ,

[jonbuoy]

Has anyone ever lunched their motor from not doing valve clearance checks?

I am starting to think it's a bunch of baloney with checking valve clearances so often. Maybe it's something the manufacturers state in order to make money at dealerships and cover their backs if anything goes wrong and try to claim warranty, for example, over revving the engine and running poor oil that can cause top end damage.

Every time I have checked valve clearances they have all been within tolerances. I have had some real ''high km'' bikes too.

Another thing that adds to all this is people with ticking cam chains thinking they have bad valve clearances... you generally can never hear the difference in valve clearances!!!

My argument is that everyone keeps saying you need to check/adjust them or you will burn valves/blow your engine etc, but I have not read about the first instance of this happening. You would think that with all the undisciplined riders out there that someone would have had a engine blow that could have been avoided with scheduled maintenance.

This has to be a joke? I guess you don´t need to change the oil either - never looks that bad when I drain it You might not hear a tight clearance but you´ll burn out the valve if it can´t close when the big bang happens - the valve seat and cylinder head acts as a heat sink transferring heat away from the valve itself. A loose clearance you will hear less dangerous to your engine unless its real sloppy and slappy.

[Mental Trousers]

I've always understood that hammering seats, dropping valves is more a result of floating the valves from over-revving, with poor quality valve springs not being able to keep the cam follower accurately following the cam profile.

As I understand it, that happens a fair bit but usually only on motors that are a bit tired already or have been fiddled with.

Most bikes have their rev limit set comfortably below what they can actually do. For instance, from the factory mine is set to start reducing petrol @ 13,500rpm (it doesn't cut the ignition and is a much better way of doing things if you ask me) and completely cut it at 13,900rpm. Whereas these engines are perfectly capable of going until 14,500rpm before totally cutting the petrol delivery.

On modern bikes dropping a valve due to over-revving isn't such an issue because they already do lots of revs.

I could be wrong of course.