tolerance correction

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salvatore
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Joined: Fri Nov 09, 2018 1:28 am

tolerance correction

Postby salvatore » Fri Jan 11, 2019 9:21 am

IMG_20190111_101240.jpg


Good morning, I have to do the adjustment of the cylinders, the new pistons are 1 mm increase, which tolerance I must respect between cylinder and piston, on some manuals we speak of original pistons, for those not original no indication, you used cruizimagine which is right measure. thank you

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barney01
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Joined: Wed Sep 26, 2012 7:33 pm
Location: Prestatyn.Wales

Re: tolerance correction

Postby barney01 » Fri Jan 11, 2019 1:17 pm

I think you are talking about clearance for a rebore. I would just take the cylinder and piston to the engineer. He will know how much clearance is required. If he does not then I would go somewhere else!

teazer
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Location: Chicago

Re: tolerance correction

Postby teazer » Fri Jan 11, 2019 3:07 pm

Stock clearance is required. 0.05mm (0.002")

salvatore
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Joined: Fri Nov 09, 2018 1:28 am

Re: tolerance correction

Postby salvatore » Fri Jan 11, 2019 3:12 pm

We are talking about grinding the cylinders to adapt new pistons, having the right size of space between cylinder and piston is a start for the worker who has to do the job, these bikes are very old and workers who worked in the 70s are now retired or up there, maybe a clue to help. Thank you

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barney01
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Joined: Wed Sep 26, 2012 7:33 pm
Location: Prestatyn.Wales

Re: tolerance correction

Postby barney01 » Fri Jan 11, 2019 4:11 pm

Yes Salvador you are right. See the post by Teazer for the clearance.

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canaletto5
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Location: Derbyshire

Re: tolerance correction

Postby canaletto5 » Fri Jan 11, 2019 4:43 pm

salvatore wrote:We are talking about grinding the cylinders to adapt new pistons, having the right size of space between cylinder and piston is a start for the worker who has to do the job, these bikes are very old and workers who worked in the 70s are now retired or up there, maybe a clue to help. Thank you
You must give the new pistons and rings to the worker so they can set the right gaps. You must give the work to someone who does this work all of the time.

salvatore
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Joined: Fri Nov 09, 2018 1:28 am

Re: tolerance correction

Postby salvatore » Sat Jan 12, 2019 4:19 pm

I will bring the kit in work with the tolerance indicated by you then there will be able to adapt, something like I can do to sweeten the edges of the lights entering mixture and exhaust, this is something that the manual specifically requires, if you use a tool such as, mini dremel or fingers and abrasive paper, maybe a link or photo, forgive my asking, I have always rebuilt four-stroke engines moto morini 3 1/2

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barney01
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Joined: Wed Sep 26, 2012 7:33 pm
Location: Prestatyn.Wales

Re: tolerance correction

Postby barney01 » Sat Jan 12, 2019 5:13 pm

Hi
Yes you must shamfer the intake and exhaust ports so there are no sharp edges. I asked the engineer who did the rebore to do it.
If not just remove the sharp edge with a file but not too much or it will affect the mixture flow.
The idea is to make sure the piston ring does not catch on the edge of the port
Look here https://youtu.be/WDKiv-nQtwA
And here https://youtu.be/UK1kzEjw1Sg
And here https://youtu.be/xY1ThQIr-J8
I dont think you need to do all of this but you get the idea i hope!


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