Author Topic: why have my tappets gone tight?  (Read 264 times)

Offline mikeb

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why have my tappets gone tight?
« on: 20.07. 2019 04:08 »
doing some maintenance on the super rocket *eek*....
about 500 miles ago i re-torqued the head and set the tappets to 8 thou in, 10 thou ex they are now all much less than that... maybe 4 thou  *conf2*
the motor is 3000 miles plus since a rebuild so its should have all settled in ages ago..

why could my tappets have tightened? any ideas?
thanks
New Zealand
'61 Super Rocket  - '47 B33 -  '18 Triumph Street Triple RS

Online RoyC

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Re: why have my tappets gone tight?
« Reply #1 on: 20.07. 2019 07:32 »
Valve seat wear maybe.
Did you recheck clearances at the same temp as they were originally set to 8 and 10 ?
Head gasket compressed a little since re-torque.
My bike is a 1958 A7SS
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Online JulianS

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Re: why have my tappets gone tight?
« Reply #2 on: 20.07. 2019 09:44 »
Thick composite rockerbox to head gaskets will settle/compress tightening the tappets.

Copper rocker gaskets dont settle and usually the clearances stay the same.


Online Triton Thrasher

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Re: why have my tappets gone tight?
« Reply #3 on: 20.07. 2019 10:44 »
Cylinder base gasket and rocker box gaskets settle as well.  That’s why we check tightness.

Offline mikeb

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Re: why have my tappets gone tight?
« Reply #4 on: 20.07. 2019 10:54 »
it is a solid copper head gasket and i did check the clearances then and now when cold. the weather is 10 degrees C colder now but that would be a minimal difference. actually the clearances when i checked today were near 0 on all 4 valves.  *eek* scary. i would have thought it unlikely for all 4 valve seats to wear as such over 500 miles, and other settling should be well over in the 3000+ miles since reassembly... yes?.

TT i guess the rocker box gaskets could be a suspect... i replaced them with new thick ones (srm?) and the rocker box was maybe a bit loose when i checked it today- I'd say that's the best theory yet. but 8 thou? Has anyone else had this happen?

all the tappet adjusters were done up tight but.  I haven't removed the rocker box but cant see any reason to assume the head is loose (and if it was the tappets would open). basically i re-torqed the head etc before either a rally in march or a rally in May (memory fails me). the bike was running well but on the ride back from the May rally started spluttering especially on the left, under load or cold. I've ridden the b33 in between and finally got around to sorting the a10 and have been working through the various options. I thought it was a bit easy to kick yesterday hence checking the tappets. ARRG!

easy to reset them but what worries me if why this happened and the chance of it happening again...??

all theories welcome
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'61 Super Rocket  - '47 B33 -  '18 Triumph Street Triple RS

Offline Swarfcut

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Re: why have my tappets gone tight?
« Reply #5 on: 20.07. 2019 11:46 »
 Mike    By my reckoning a Super Rocket will have an alloy head fitted with hardened valve seats capable of dealing with  lead free fuels. Can't say about the valve material, but even so I would agree that erosion after such a small mileage is unlikely.
  So in the meantime it is a case of setting things up, and keeping a regular check on the clearances. As the motor settles you should find they will stay the same. If they continue to close up, it's a case of top off for a looky look.
 Worst case scenario is a bit of top end reconstruction and re-assembly, if you are extremely unlucky, which I very much doubt. It will take a good few cycles  of use for the gaskets to settle and as long as you can maintain the clearances, don't worry, just do a regular check.
 We assume you set the cam in the same place each time, but having got it wrong a few times myself, I know takes a bit of skill to get it set up right.

Swarfy.

Online chaterlea25

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Re: why have my tappets gone tight?
« Reply #6 on: 20.07. 2019 21:11 »
Hi All,

Quote
the motor is 3000 miles plus since a rebuild so its should have all settled in ages ago

I have found that the mileage needed to finally settle things down is a maybe 2 x above

If all 4 valve clearances tighten up then it's down to re torquing

Inlet valve clearances tend to close up for a while on rebuilt engines

Thick rockerbox gaskets, = PITA

John
1961 Super Rocket
1963 RGS (ongoing)

Offline muskrat

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Re: why have my tappets gone tight?
« Reply #7 on: 20.07. 2019 22:14 »
G'day Mike.
I agree with John. Alloy heads take quite a few heat cycles to settle. Keep an eye on it.
Re-tension of the base nuts will also affect the tappet clearance.
Cheers
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Offline mikeb

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Re: why have my tappets gone tight?
« Reply #8 on: 21.07. 2019 02:40 »
thanks everyone for your comments. i'm going to conclude its probably due to the thick rockerbox gasket compressing and maybe a bit more settling all-round.

which brings two more questions:
1. how often do you actually check your tappets? i was assuming 1000 miles would be fine (fastidious by my standards), especially after the first 1000 miles from rebuild.
2. where do you get decent rocker box gaskets? previously i've bought thin paper ones that didn't actually fit (too small) and i liked the idea of thick ones to control leaks. but not any more if they compress that much. i'm very unlikely to make my own.

cheers
New Zealand
'61 Super Rocket  - '47 B33 -  '18 Triumph Street Triple RS

Offline muskrat

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Re: why have my tappets gone tight?
« Reply #9 on: 21.07. 2019 09:28 »
G'day Mike.
If the head and r/box mating surface have been machined/ground/lapped flat I've had good results from solid copper gaskets. Most don't check the head surface as it needs the valve guides removed. The copper gaskets can be bought in varying thickness to account for r/box and or head machining to bring the rocker/valve geometry back to std.
When I do use paper gaskets I make my own out of 0.8mm and re torque at 100, 500 and 1000 miles.
Cheers
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Online Triton Thrasher

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Re: why have my tappets gone tight?
« Reply #10 on: 21.07. 2019 09:52 »
thanks everyone for your comments. i'm going to conclude its probably due to the thick rockerbox gasket compressing and maybe a bit more settling all-round.

which brings two more questions:
1. how often do you actually check your tappets? i was assuming 1000 miles would be fine (fastidious by my standards), especially after the first 1000 miles from rebuild.
2. where do you get decent rocker box gaskets? previously i've bought thin paper ones that didn't actually fit (too small) and i liked the idea of thick ones to control leaks. but not any more if they compress that much. i'm very unlikely to make my own.

cheers

I retorque the head after the first time it gets hot, then head, barrel and rocker box after 50 miles and 200 miles.  Checking the valve clearances after each time, obviously.

Your thick rocker cover gaskets should stop compressing eventually. Maybe they have now.

What’s stopping you making gaskets?

Offline mikeb

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Re: why have my tappets gone tight?
« Reply #11 on: 21.07. 2019 10:06 »
Quote
What’s stopping you making gaskets?
general laziness and attention deficit. i've make a few but the rockerbox is a bit fiddly. i guess it would be feasible to make it in two halves, tho maybe then even trickier to fit?
New Zealand
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Re: why have my tappets gone tight?
« Reply #12 on: 21.07. 2019 10:48 »

 
Quote
.......What’s stopping you making gaskets? 
Quote
....general laziness and attention deficit. i've make a few but the rockerbox is a bit fiddly..........

 Not so hard a tall actually- I haven't needed to for a while but working up tuit and/but because the interfaces are so narrow, I make them oversize and trim the outside when I get a round tuit  *smile*...can't rush some things

 
Quote
..... i guess it would be feasible to make it in two halves, tho maybe then even trickier to fit?...

 am I missing something?  *conf2*
      They're in three pieces anyway so no more fiddly whether you've made them or bought them  *conf2*
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