Author Topic: valve clearance when hot  (Read 800 times)

Offline baz

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valve clearance when hot
« on: 09.06. 2012 21:22 »
further to an earlier post and out of curiosity i checked my valve clearance today whilst my engine was very hot and i found they were very slightly bigger than  when the engine was cold,i only checked the exhaust valves but i assume the inlet clearance would be bigger aswell,the engine is a 650 with alloy head and normal  steel push rods,i had always been led to believe the clearance closes when the engine heats up? ........baz

Offline muskrat

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Re: valve clearance when hot
« Reply #1 on: 10.06. 2012 02:21 »
 G/day Baz,
                I know it closes up in the cafe. My "hot" might be a bit warmer than most would get. 10.5:1, 105 octane, 2 x 30mm flat slides, straight through reverse cone meggas, 7500 rpm up Little Forest Hill. Barely made the last 1/4 mile, stalled at top. Let cool for 3 beers and she was good as gold. Did the same on way home (due to 3 beers) so I quickly took the covers off (ouch hot, ouch hot) and it took a good 1/8 turn to free the ex tappets and the inlet were zero clearance. When cold gave them an extra 2 and 4thou, not happened since. Most books will give bigger clearances for racing.
Cheers
'51 A7 plunger, '57 A7SS now A10CR, '76 XT500, '77 AG175 '83 CB1100F, '81 CB900F project.
Australia
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Offline baz

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Re: valve clearance when hot
« Reply #2 on: 10.06. 2012 02:45 »
Ive not had the chance to thrash the hell out of my one yet ive got to wait until monday when i can get it MOTd (ive only been out round the local factory estate),just fitted new rings so i'll have to break them in but then i will give it hell thats what these bikes were built for and if it goes bang i'll build it better next time i have my tappets set at 10thou in and 12thou out ,i just hope the old overheating problem has gone cheers baz

Offline duTch

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Re: valve clearance when hot
« Reply #3 on: 10.06. 2012 02:48 »
Quote
.... good as gold. Did the same on way home (due to 3 beers)

Sounds like an ad for our local midstrength??-not me.!!

  Musky, how you reckon would it be if you just set them loose-zero at hot?? (Apart from burnt fingers)
Started building in about 1977/8 a on average '52 A10 -built from bits 'n pieces never resto intended -maybe 'personalised'
Have a '74 850T Moto Guzzi since '92-best thing I ever bought doesn't need a kickstart 'cos it bump starts sooooooooo(mostly) easy
Australia

Offline muskrat

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Re: valve clearance when hot
« Reply #4 on: 10.06. 2012 05:50 »
 G'day Dutch, I would still like a coupla thou at pipe blueing hot. By the time you get it all organized it would have dropped 20-50 degrees.
Cheers
'51 A7 plunger, '57 A7SS now A10CR, '76 XT500, '77 AG175 '83 CB1100F, '81 CB900F project.
Australia
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Online Ted_Flash

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Re: valve clearance when hot
« Reply #5 on: 10.06. 2012 11:20 »
I'd guess that the major factor in differences in valve clearances as the engine heats up would the material the push rods are made of, due to their length?  So with a hot running engine you would be better off with steel pushrods rather than dural?
Ted Wilkinson, Ramsbottom, Lancashire
1950 Golden Flash

Offline muskrat

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Re: valve clearance when hot
« Reply #6 on: 10.06. 2012 13:22 »
Yes Ted your right, I use dural. Lots of other things as well, like if you used those alloy barrels on ebay would change the settings. It's a suck n see sort of thing with any motor that deviates from factory standard.
Cheers
'51 A7 plunger, '57 A7SS now A10CR, '76 XT500, '77 AG175 '83 CB1100F, '81 CB900F project.
Australia
Muskys Plunger A7

Offline duTch

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Re: valve clearance when hot
« Reply #7 on: 10.06. 2012 16:03 »
Yup Musky I guess that's kind of what I had in mind by 'loose zero'....and burnt fingers
Started building in about 1977/8 a on average '52 A10 -built from bits 'n pieces never resto intended -maybe 'personalised'
Have a '74 850T Moto Guzzi since '92-best thing I ever bought doesn't need a kickstart 'cos it bump starts sooooooooo(mostly) easy
Australia