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Valve clearances at 48k

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eternally_troubled
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Valve clearances at 48k

Post by eternally_troubled on Sun 05 Dec 2010, 10:18 pm

Bike approaching 48k, so, given the lovely weather and after tidying the garage, I made a start. Drained the coolant and removed the thermostat, then managed to get the valve cover off without any serious problems. Even managed to get the little covers off the crankcase without destroying anything!

Now, I have some feeler gauges, but (like normal) they don't have quite the right size, so given that the inlet clearane is 0.17-0.19mm I thought I'd try the 0.15mm gauge and see what happens.

Problem is, it doesn't fit! The 0.10mm gauge fits. So it sounds like by clearace is, roughly 0.10mm out!

Similar results were observed for the exhast valves and all four on the other cylinder..... (ie. all had closed up quite a lot). I'm pretty sure that I got the appropriate cylinder at TDC with the timing mark showing in the window etc

Now, I know that the whole point of checking is to detect when things are going wrong before they going *really* wrong, but it seems that all 8 of my valve clearances are too small - is this the same king of thing as other people have seen in their 48k service? or have I f*cked something up?

NB. I'm going to buy some better feeeler gauges and do the measurement again...
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johne
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valve clearances at 48k

Post by johne on Thu 09 Dec 2010, 6:02 pm

Have not checked the clearances on my CB yet but have done many other bikes with valves using shims and what you have found is quite normal from my experience, they always seem to get smaller.
Reckon you will need to take the cams out and replace the shms with ones a few sizes smaller but once they are done they are usually ok for many thousands of miles.
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Re: Valve clearances at 48k

Post by Ingah on Thu 09 Dec 2010, 11:59 pm

The valves are supposed to be done every 24K on the CB500 so if this is the first time for yours then maybe it's a good job you've got round to doing it!
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eternally_troubled
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Re: Valve clearances at 48k

Post by eternally_troubled on Fri 10 Dec 2010, 8:15 am

I've now bought some feeler gauges with more suitable sizes that allow me to meausre my clearances mroe accurately.

I'm now rather more sure that I need to replace the shims - most of my inlet valves are around 0.09mm (the manual says more like 0.17mm) and my exhaust valves are around 0.19mm (the manual says more like 0.25mm).

So it seems I'll need to get smaller shims..... something to do over the weekend!
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Valve maintenance

Post by fruitbat3 on Sat 11 Dec 2010, 12:45 am

If you look in your Honda owners/workshop manual valves should be checked at every 16,000 miles(24,000 km).
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fixed!

Post by eternally_troubled on Tue 14 Dec 2010, 12:02 pm

All done!

Got the shims out on Saturday and spent Sunday putting it all back together.... culminating in a water leak caused by my incompetance (I hadn't torqued up the thermostat housing in my haste to put the bike back together!)

Bike now runs well with a very slight valve noise, as expected now I have set the clearances rather more correctly...

Definatly worth doing myself, considering that my bike isn't worth much more than the cost of getting a garage to do it!
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Re: Valve clearances at 48k

Post by birdyboy on Tue 14 Dec 2010, 9:58 pm

WELL DONE FOR DOING WHAT YOU HAVE - I HAD THE IDENTICAL EXPERIENCE AND YES - THE CLEARANCES WILL GET SMALLER AS THE VALVE SEATS WEAR AND IN SOME INSTANCES THE VALVES THEMSELVES CAN ELONGATE SO THE GAP GETS SMALLER. MY LOCAL DEALER DOES A PART EXCHANGE ON THE SHIMS YOU HAVE TAKEN OUT SO DON'T THROW THEM AS THEY WILL TAKE THEM IF THEY ARE A SIZE WHICH THEY'VE RUN LOW ON.
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eternally_troubled
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Re: Valve clearances at 48k

Post by eternally_troubled on Wed 15 Dec 2010, 10:20 am

Yeah, my local garage did a part-exchange on the shims (which roughly halved the cost).

When I was riding home yesterday after work I realised that, yes, my bike actually runs a lot better now... I wouldn't have known it was running badly (I had obviously got used to it!).
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150k_tim
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Re: Valve clearances at 48k

Post by 150k_tim on Thu 16 Dec 2010, 7:07 pm

You're all starting to get me worried! My first CB5 did 78k and never needed any adjustment. My current bike has done 70k and the valves were ok when I last checked them at 64k.

Must admit that I wasn't too keen on the thought of having to lift out the cams to change shims (even though I'm experienced at doing my own mechanics!). Hope my clearences didn't check out ok because I wanted them to!!!!!!!!!!

Only joking, mine were definitely ok so maybe I woz lucky!
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Re: Valve clearances at 48k

Post by kungfupoodle on Thu 16 Dec 2010, 8:19 pm

Well done. I think I'm going to make a start on mine tomorrow. Been meaning to do it for the last 20,000 miles. I have measured them in the past and they're tight but not as tight as yours!
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Re: Valve clearances at 48k

Post by eternally_troubled on Fri 17 Dec 2010, 1:24 pm

150k_tim wrote:You're all starting to get me worried! My first CB5 did 78k and never needed any adjustment. My current bike has done 70k and the valves were ok when I last checked them at 64k.

Must admit that I wasn't too keen on the thought of having to lift out the cams to change shims (even though I'm experienced at doing my own mechanics!). Hope my clearences didn't check out ok because I wanted them to!!!!!!!!!!

Only joking, mine were definitely ok so maybe I woz lucky!

I didn't *want* to have to do mine either :) I was surprised at how far out they were - I suspect the previous owner(s) may not have had them done/checked.
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mark1968
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Re: Valve clearances at 48k

Post by mark1968 on Mon 20 Dec 2010, 11:28 pm

I recently checked the clearances of my low mileage, one careful owner (before me ; ) cb 500 and measured 0.15 on the inlet side and decided to leave it. I didn't have another gauge less than 0.02 so I am not sure if it could have taken a slightly bigger gauge but I think it was pretty close to the low end of the tolerance (0.16) according to the haynes manual. I was pretty glad I didn't have to change any shims but it didn't seem like too bad a job according to the manual. Well done for getting it done.
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150k_tim
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Re: Valve clearances at 48k

Post by 150k_tim on Tue 21 Dec 2010, 8:01 pm

Interestingly i've just noticed that there is a small discrepency between the Haynes manual and the official Honda workshop manual for the correct clearence.

INLET Haynes 0.16 - 0.18
Honda 0.16 +/- 0.02 = 0.14 - 0-18

EXHAUST Haynes 0.25 - 0-27
Honda 0.25 +/- 0.02 = 0.23 - 0.27

Not a big discrepency but it does make MARK1968s clearence within spec! I assume Honda allow a +/- value of 0.02 as the shims are available in 0.025 size intervals
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mark1968
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Re: Valve clearances at 48k

Post by mark1968 on Tue 21 Dec 2010, 9:44 pm

That is interesting. I noticed the difference in the clearances quoted. That makes mine within the official limit. I haven't done a lot of servicing in my life but the Haynes manual makes it easy. Mark

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Re: Valve clearances at 48k

Post by wikkadoo500 on Sun 23 Oct 2011, 7:19 pm

My CB500 has just racked up 80,000 miles and is overdue a clearance check. I've already checked them and all inlet valves are approx 0.10mm and all exhaust valves measure .20mm. Just got the task of checking the shim sizes.
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Haynes revised?

Post by dougxr on Tue 04 Mar 2014, 7:26 pm

I know this is an old thread but I'm sure I can't be the only one who finds it.
My Haynes manual says:
Valve clearances (COLD engine)
Inlet valves: 0.14 to 0.18 mm
Exhaust valves: 0.23 to 0.27 mm
So maybe Haynes have updated their manual.

150k_tim wrote:Interestingly i've just noticed that there is a small discrepency between the Haynes manual and the official Honda workshop manual for the correct clearence.

INLET   Haynes 0.16 - 0.18
         Honda   0.16 +/- 0.02 = 0.14 - 0-18

EXHAUST Haynes 0.25 - 0-27
            Honda   0.25 +/- 0.02 = 0.23 - 0.27

Not a big discrepency but it does make MARK1968s clearence within spec! I assume Honda allow a +/- value of 0.02 as the shims are available in 0.025 size intervals
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eternally_troubled
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Re: Valve clearances at 48k

Post by eternally_troubled on Wed 05 Mar 2014, 12:58 pm

It is quite possible - much as we might complain about Haynes, they do (eventually) update their manuals if errors are pointed out to them, so if you do find a problem then you should tell them!
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Re: Valve clearances at 48k

Post by HomeBrew on Wed 05 Mar 2014, 9:30 pm

Since I did the valves my bike has stopped using any oil at all. I think it is well worth doing.
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Re: Valve clearances at 48k

Post by geewhizz on Wed 05 Mar 2014, 10:10 pm

HomeBrew wrote:Since I did the valves my bike has stopped using any oil at all. I think it is well worth doing.

good to hear how long did it take you? I've been planning to do mine for the last 10k...
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Re: Valve clearances at 48k

Post by HomeBrew on Wed 05 Mar 2014, 11:19 pm

I had it in the kitchen and on the kitchen table for about 5 days. Most of that time was waiting for shims to arrive in the post. The actual spannering can be done in a couple of hours if you know what you are doing.
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@theincredibleaf
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Re: Valve clearances at 48k

Post by @theincredibleaf on Mon 19 May 2014, 11:46 pm

Sorry to resurrect this again, but Mark1968 which feeler gauge did you buy that had the correct precision to do the job.

I took the valve cover off my Mrs CB500 Cup model, only to find that the Draper gauge I had previously used to do the clearance check on my K5 GSXR 1000, was not good enough.

Any help appreciated.

Cheers.
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@theincredibleaf
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Re: Valve clearances at 48k

Post by @theincredibleaf on Mon 19 May 2014, 11:50 pm

Actually I just saw I should be directing my question @ eternally_troubled.

Thanks.
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trevor2110
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Re: Valve clearances at 48k

Post by trevor2110 on Tue 20 May 2014, 8:32 am

Is it really worth checking? My CB's done 110k now and I've never checked them, had it since 7k.
My attitude is if it aint broke...... Maybe I've been lucky Smile
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ANDYC
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Re: Valve clearances at 48k

Post by ANDYC on Tue 20 May 2014, 10:50 am

trevor2110 wrote:Is it really worth checking? My CB's done 110k now and I've never checked them, had it since 7k.
My attitude is if it aint broke...... Maybe I've been lucky Smile

The problem with direct operation valves(shim and bucket) is that as they wear the gap gets smaller and therefore quieter.
The rocker type operation or 'tappets' would get noisier as the gap gets larger.
Eventually the gap will disappear completely as the valve and seat both wear and the valve head moves up towards the camshaft.
Eventually the valve train will be bearing directly on the surface of the camlobe that is not designed to provide any lift. this will hold the valve off the seat meaning that it will not seal properly and allow the gases to escape past it.
This causes many issues such as the cam timing is all over the place.
The valves are unable to transfer the heat to the valve seat, which is what cools them and so burn out. Exhaust valves in particular.
Compression is lost and so on........
In short, there is a good reason for checking the clearance is there.
They may seem quite large with the factory settings but they have to allow for heat expansion and of course the good old slippery stuff.
Without an oil clearance the cams wouldn't last very long.

STILL THINKING OF PUTTING IT OFF UNTIL IT GETS NOISY? Shocked
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@theincredibleaf
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Re: Valve clearances at 48k

Post by @theincredibleaf on Tue 20 May 2014, 12:53 pm

Sorry but can someone recommend a feeler gauge with the correct range.

This isn't a matter of conjecture for me.

The tolerances are so tight that the bike cuts out after warming up because it can no longer breathe as the clearances become even tighter.

Thanks.

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