Author Topic: hot exhaust valves  (Read 1404 times)

Offline Dynamo Regulators Mike

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hot exhaust valves
« on: 31.05. 2013 10:08 »
Hi all

Yesterday I was assisting a mate whose A65 partially seized on the way up to the BSAOC Open day last weekend. Engine locked up then freed after a short while, and as we were still close to home it was clearly better to reduce losses and return the bike home.

So head and barrels off to find a modest seized area on RHS piston just behind pin on flywheel side. Plenty of oil around. The engine had been playing up occasionally losing power and misfiring for a few weeks previous but nothing could be found wrong, plugs looked good colour, timing ok etc. But both exhaust valves are a striking pale brick red colour such as I have not seen before. Strikes me that it could be the result of running overly hot, and perhaps related to any abnormal conditions leading to the seizure.

Sorry no pictures as we were a little against the clock and pressing on. Pistons are GPM and seemed a little lightweight compared to other makes. Bike is early A65 Star single carb, not used particularly hard I would say.

Would value any opinions and insights into what would lead to mysterious Martian red exhaust valves.

cheers, Mike
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Mike Hutchings
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Director, DRL www.dynamoregulators.com

Online BSA_54A10

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Re: hot exhaust valves
« Reply #1 on: 31.05. 2013 10:22 »
Exhaust valves run red to yellow hot.
Inlet valved run just barl dull red.
Did he buy good quality valves from a reputable dealer with a real street address or the cheapest he could find on evilbay.
Won't be the first time some idiot sold a cheapskate inlet valves in place of exhaust ones as exhaust valver are a much more expensive alloy.
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Offline Topdad

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Re: hot exhaust valves
« Reply #2 on: 31.05. 2013 11:54 »
Good morning Mike , I concur ,after googling the question a couple of intersting pieces about this colour and ex valves showed up seems red is normal and means cooler darker to black means hot which equals pos burning ,pre ingnition and even more heat . I'd have a look  and have a read. It will ,hopefully,answer the question regards BobH
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Offline Dynamo Regulators Mike

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Re: hot exhaust valves
« Reply #3 on: 31.05. 2013 13:07 »
Thanks for your replies Trevor and Bob

Yes exhaust valves run very hot. The engine was last touched valve wise a good many years ago, before flea-bay got into its stride. Valves were fitted by my mates father, an ex RAF trained technician who I believe was a most fastidious mechanic. Probably done about 20 k miles since then so material is not too bad.

But in the extremely unlikely but not impossible event that the exhaust valves were really inlet material would this explain a light red crust over the steel of the valve head?

Bob, do you have a reference link? Sounds like you may have found something relevant!

Must admit we were expecting this to be blamed on ethanol in the fuel, though personally I think it may be down to international terrorism or the new world order. *conf*

But seriously there are one or two mentions of manganese additives specifically causing the red colour. Then I got to thinking that I commented when stripping down the engine the oil had a strong smell (akin to the sulphurous pong of gear oil) but the bike always runs with Silkolene mono-grade. Curious.

Any other ideas folks?
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Mike Hutchings
A10, B50, T800; 1,2,3 (& DVR2)
Director, DRL www.dynamoregulators.com

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Re: hot exhaust valves
« Reply #4 on: 01.06. 2013 09:05 »
And it could also be some thing simple like rust.
Alloy steels can have some very funny rust colours
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Online TT John

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Re: hot exhaust valves
« Reply #5 on: 01.06. 2013 19:27 »
Hi Mike .
Glad to see you all got back safe from our Open Day. Has Andy got elecrtronic ignition on his A65, just a thought as to whether the timing had slipped causing it to run hot, as you say theres plenty of oil around, the only other thing I could think of was oil feed to the rocker arms & valve guides. Its always more diffecult to diagnose on a key board, I'm sure that a beer or two will help.   *problem* *beer* *beer*

TTJohn
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Offline Dynamo Regulators Mike

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Re: hot exhaust valves
« Reply #6 on: 03.06. 2013 10:38 »
Hi John

He's got a Boyer fitted, want to strobe it with him, as to be honest I do not have complete faith in the thoroughness of the bloke who fitted it to have done so with accuracy. Anyway the book figure can only be taken as a starting point after 50 years of changes under the bridge.

Andy has now had a look at the valve seats and they seem good as far as he could tell, which seems to concur with valves running at normal temperature after all. As for red deposits 'computer says' this is not uncommon and probably due to some sort of additive. Main thing is getting it all up and running again for la bell france (luc-s-mer) later in June, or Debs will be looking for a pillion.

Good weekend just gone but not as many beers as the previous Open Day one.

Cheers
Mike
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Mike Hutchings
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Director, DRL www.dynamoregulators.com

Online Brian

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Re: hot exhaust valves
« Reply #7 on: 03.06. 2013 10:59 »
Hello Mike,
               I dont have an explanation as to why the valves could look red but I have pulled a few motors apart that have had this appearance.

I have never seen it cause any issues so can only assume it is something to do with addatives in the fuel. I wouldnt worry about it.

ps. All my belt drives and DVR2's are working perfectly.

Brian.
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Online TT John

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Re: hot exhaust valves
« Reply #8 on: 04.06. 2013 09:36 »
Mike.
I believe that Andy is stealing army fuel, they are the ones that put red dye in the petrol etc,  tell him to start buying it like we have to.

I think the only reason you did not drink so much is because Alison wasn't there, I did notice there were quite a lot of lightwieghts, including Clive & Bob. You will have to go into serious training before Wiltshire camp & yours.

 *beer* *whistle*

TTJohn
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