Author Topic: smoking super rocket  (Read 6166 times)

Offline mfhutchins

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Re: smoking super rocket
« Reply #45 on: 03.07. 2012 17:08 »
here is what i found on the left side.

since there were no issues with the right cylinder, i dont need to bother with it, right?

what is it exactly i am looking for?  there are little black marks on the exhaust valve and seat in the same places.  you can see in the pictures the black scoring.  i have no idea what it is or what caused it.  maybe the valve wasnt seating properly due to poor lapping?  i am on the right track?

Offline duTch

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Re: smoking super rocket
« Reply #46 on: 03.07. 2012 19:30 »
Maybe not seating due to tight adjuster?? How's top of guide/bottom of spring collar??
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
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Offline mfhutchins

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Re: smoking super rocket
« Reply #47 on: 03.07. 2012 20:16 »
after 30 mins. in oven at 215f with a light tap on each valve guide there was no movement.
the lower spring collars fell out after i turned it upside down.

can i clean and reassemble?

im thinking it was the tappet adjuster that was too tight not allowing the valve to seat completely (and bending the pushrod).
the bend in the pushrod was barely detectable. so it must have been just slightly overtight.
also, i looked at the cam lobe that probably had constant force upon it from the bent pushrod and there is no sign of wear.  it still looks brand new.

i will wait to reassemble once i get some feedback when australia wakes up.

thanks!

Offline muskrat

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Re: smoking super rocket
« Reply #48 on: 03.07. 2012 20:59 »
 Yawn, 5:30am I'm up.
Looks like the last time apart the seat was cut but not lapped. Guides sound as if their in tight enough. Put valve in and lift about 3/8" off seat, you should be able to wobble the valve fore and aft about 1/2mm, any more than 1mm is too much, valve guide liners are an alternative to new guides. Now give all the valves a lap, the bad one might take a bit. Check that all have a nice even lap mark. If the bad one's lap mark is thick then thin it's bent.
 Push rods don't usually bend by themselves. Something came into contact, either valve/piston, collar/guide. Over adjusted tappet could be at fault but not the only thing eg turning motor over with the timing marks not lined up etc. Do NOT reuse a bent push rod or valve.
The lower collars will push back on.
How do the ring gaps look?
Cheers
'51 A7 plunger, '57 A7SS now A10CR,  '83 CB1100F, .
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Muskys Plunger A7

Offline mfhutchins

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Re: smoking super rocket
« Reply #49 on: 03.07. 2012 23:10 »
Revelation! I just discovered after removing the right hand valves, that the left exhaust valve guide has been worn.  As evidenced in the attached picture, the inside diameter is significantly wider than that of the other exhaust valve guide.  Time for replacement.

Maybe this was it?

there is also pitting around the end of the guide.  not sure how that happened.  all 3 others look fine. 

Offline mfhutchins

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Re: smoking super rocket
« Reply #50 on: 04.07. 2012 00:49 »
just removed the problem valve guide and it measures .630 O.D. where it sits in the bore.  this is oversize, correct?
british cycle supply in nova scotia told me the correct O.D. is .560.

Offline muskrat

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Re: smoking super rocket
« Reply #51 on: 04.07. 2012 05:24 »
 G'day Mike,
                that sounds like a dodgy one. She must have had a problem and munched the hole at some stage. The chamber looks a little poch marked on that side, may be pinging. The alloy head should have bronze guides but have heard that BSA did use iron guides for a time.
I have the same problem with an old '54 twin carb head. Will have to make a special. When you get one made, make that bit 1 thou bigger (0.631") and the bore a tad small and ream once fitted to suit the valve. Just about any engine recondition shop would be able to do the job.
Yes that may well be the smoking problem.
Cheers
Bugga done my money on the ring theory.
'51 A7 plunger, '57 A7SS now A10CR,  '83 CB1100F, .
Australia
Muskys Plunger A7