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Author Topic: Sound advice please!  (Read 2715 times)

Offline crazypj

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Re: Sound advice please!
« Reply #60 on: Jul 21, 2017, 22:17:46 »
You don't use platigauge on pistons, Plasticine or Play-Doh works fine.
Are you going to use it on crankpins to make sure big ends don't have too much clearance?
 Just remembered, you can also use soft solder in smaller diameters (not silver solder), plumbing solder is mostly tin but diameter is too big. you can carefully thread it through plug hole and check without pulling head (although you may need to after checking)
« Last Edit: Jul 21, 2017, 22:23:54 by crazypj »
'you can take my word for it or argue until you find out I'm right'
I gave my girlfriend an orgasm the other night, but, she spat it back at me
 Some humans would do anything to see if it was possible to do it. If you put a large switch in some cave somewhere, with a sign on it saying 'End-of-the-World Switch. PLEASE DO NOT TOUCH', the paint wouldn't even have time to dry
 It’s not worth doing something unless someone, somewhere, would much rather you weren’t doing it  (Terry Pratchett)
CB360's,  http://www.dotheton.com/forum/index.php?topic=11736.0
XS650,  http://www.dotheton.com/forum/index.php?topic=11922.0

Offline quadracer351

  • Posts: 522
Re: Sound advice please!
« Reply #61 on: Jul 22, 2017, 04:18:39 »
You don't use platigauge on pistons, Plasticine or Play-Doh works fine.
Are you going to use it on crankpins to make sure big ends don't have too much clearance?
 Just remembered, you can also use soft solder in smaller diameters (not silver solder), plumbing solder is mostly tin but diameter is too big. you can carefully thread it through plug hole and check without pulling head (although you may need to after checking)
Was going to use it to see what the Clarence is at the top of the piston and figure out was gasket thickness to get.

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Offline crazypj

  • Posts: 12464
  • Split personality, I fake being smart
Re: Sound advice please!
« Reply #62 on: Jul 22, 2017, 14:44:09 »
As the pistons touch the head when running, you have zero clearance so just add 0.038" to whatever the base gasket thickness is at present. Your complicating what is really a simple jpb. You can check total clearance with thin solder after you do a test assembly, twist 2 strands together so you have over 0.040" to 'squish'
'you can take my word for it or argue until you find out I'm right'
I gave my girlfriend an orgasm the other night, but, she spat it back at me
 Some humans would do anything to see if it was possible to do it. If you put a large switch in some cave somewhere, with a sign on it saying 'End-of-the-World Switch. PLEASE DO NOT TOUCH', the paint wouldn't even have time to dry
 It’s not worth doing something unless someone, somewhere, would much rather you weren’t doing it  (Terry Pratchett)
CB360's,  http://www.dotheton.com/forum/index.php?topic=11736.0
XS650,  http://www.dotheton.com/forum/index.php?topic=11922.0

Offline datadavid

  • Posts: 1066
Re: Sound advice please!
« Reply #63 on: Jul 22, 2017, 17:14:55 »
Yes plastigauge is used for checking OIL FILM clearance. You use Play Dough to establish squish clearance. Good luck with this engine, god knows i did and still do fucked up shit to my engines, this one still has a chance!

Offline teazer

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Re: Sound advice please!
« Reply #64 on: Jul 22, 2017, 17:55:26 »
The problem is that the piston crowns are the wrong shape and don't match the combustion chamber shapes.  Adding thicker gaskets is not a very good solution to that.  better to rub bearing blue or even thick grease over the piston crowns and put the head on and turn it over to see where it is making contact and then machine teh pistons or head as appropriate to fix the problem.

You are looking for zero clearance without a head gasket and .040' with a gasket.  So test it without a head gasket and massage metal until it turns over without a clunk at TDC, then clean it up and fit a head gasket.

Offline datadavid

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Re: Sound advice please!
« Reply #65 on: Jul 22, 2017, 18:24:41 »
Btw im not a mechanic, just learned this shit by lifelong exposure to my dad who indeed is.

Offline teazer

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Re: Sound advice please!
« Reply #66 on: Jul 22, 2017, 18:32:10 »
Your dad is right. modeling clay is ideal for measuring piston to valve and piston to head clearance - as long as there is clearance.  While he has "negative clearance" he needs to see where it is hitting and simple bearing blue or grease shows that very clearly. 

Offline datadavid

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Re: Sound advice please!
« Reply #67 on: Jul 22, 2017, 18:58:50 »
Your dad is right. modeling clay is ideal for measuring piston to valve and piston to head clearance - as long as there is clearance.  While he has "negative clearance" he needs to see where it is hitting and simple bearing blue or grease shows that very clearly.
If its clanking there will be evident rub marks to begin with, not to mention possibly rod and main bearings hammered to shit in the minutes its been running.

Offline datadavid

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Re: Sound advice please!
« Reply #68 on: Jul 22, 2017, 18:59:50 »
And gudgeon pins. And small ends. Dont try this at home kids, the sound of failure is green burning.

Offline teazer

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Re: Sound advice please!
« Reply #69 on: Jul 22, 2017, 20:12:19 »
If its clanking there will be evident rub marks to begin with, not to mention possibly rod and main bearings hammered to shit in the minutes its been running.

probably but not necessarily.  Witness marks are not always easy to identify.  Agreed that running it with interference could easily cause damage to many internal components