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Cylinder honing piston clearance advice needed #385287
07/19/11 10:51 pm
07/19/11 10:51 pm
Joined: Mar 2007
Posts: 1,163
Winona, MN
Swan Offline OP

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Swan  Offline OP

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Joined: Mar 2007
Posts: 1,163
Winona, MN
I need to hone my cylinder to match my new .040" piston and rings. My manual suggests a clearance of .004-.006" at the bottom of the skirt. Is this correct?

I am open to any sage advice and voices of experience on clearances and grit of the final hone. I need to know what to tell my machinist.

Last edited by Swan; 07/20/11 5:01 pm.

1966 Triton
1962 BSA DBD34 Gold Star
1966 Triumph Bonneville
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Re: Cylinder honing piston clearance advice needed [Re: Swan] #385294
07/19/11 11:35 pm
07/19/11 11:35 pm
Joined: Feb 2011
Posts: 3,528
Orygone
Boomer Offline

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Orygone
Swan,

What's the make of your new piston?


Boomer
Re: Cylinder honing piston clearance advice needed [Re: Swan] #385297
07/20/11 12:30 am
07/20/11 12:30 am
Joined: Mar 2007
Posts: 1,163
Winona, MN
Swan Offline OP

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Swan  Offline OP

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Joined: Mar 2007
Posts: 1,163
Winona, MN
Wiseco forged piston.


1966 Triton
1962 BSA DBD34 Gold Star
1966 Triumph Bonneville
Re: Cylinder honing piston clearance advice needed [Re: Swan] #385385
07/20/11 2:30 pm
07/20/11 2:30 pm
Joined: May 2011
Posts: 134
Muriwai,New Zealand
L
Llewelyn Offline
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Llewelyn  Offline
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L

Joined: May 2011
Posts: 134
Muriwai,New Zealand
4 to 6 tenths of a thou may be a little tight(typo perhaps) 4-6 thou probably a bit more reasonable

Re: Cylinder honing piston clearance advice needed [Re: Swan] #385388
07/20/11 2:39 pm
07/20/11 2:39 pm
Joined: Feb 2011
Posts: 3,528
Orygone
Boomer Offline

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Orygone
Not familiar with that brand of piston. Maybe you could get the specs from Wiseco. Ron in Cal or daveNV will probably know.


Boomer
Re: Cylinder honing piston clearance advice needed [Re: Llewelyn] #385406
07/20/11 5:03 pm
07/20/11 5:03 pm
Joined: Mar 2007
Posts: 1,163
Winona, MN
Swan Offline OP

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Swan  Offline OP

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Joined: Mar 2007
Posts: 1,163
Winona, MN
Originally Posted By: Llewelyn
4 to 6 tenths of a thou may be a little tight(typo perhaps) 4-6 thou probably a bit more reasonable


LLewelyn, yes, typo, thank you. .004-.006 piston to cylinder clearance as stated by manual.


1966 Triton
1962 BSA DBD34 Gold Star
1966 Triumph Bonneville
Re: Cylinder honing piston clearance advice needed [Re: Swan] #385422
07/20/11 6:13 pm
07/20/11 6:13 pm
Joined: Aug 2001
Posts: 1,893
Elko, Nevada USA
dave - NV Offline

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dave - NV  Offline

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Elko, Nevada USA
I've not fitted a Weisco in a GS, but have been fitting custom designed Venolia pistons by Ron H. at GSR for several years. I/we fit the modern forged pistons at 3 to 4 thou clearance in the Goldies with no problems. A final hone finnish of 350 - 400 grit seems to work fine with modern nodular iron rings. I sure hope your machine shop uses a precision hone vs the POS tools some use that will give you a out of round bore with a belly. aarrgh.

Speaking of bores ... I'd heard of Bore Tech for many years but not used them until recently. The 'carbide coated' bore job they did for me on a 90 bore GS cylinder was nearly perfect. Measured with my electronic bore gauge the max error was less than 2 tenths!

If you'll notice a 'modern' piston is uses a short wrist pin and the wrist pin bosses are well inside the skirt. This reduces the skirt distortion due to the heat absorbed in the heavier wrist pin boss section. Because of this design and the high content of silicon in the alloys, the modern forged piston have much the same expansion rate as the olde cast pistons.

Last edited by dave - NV; 07/20/11 6:16 pm.

Dave - NV
Re: Cylinder honing piston clearance advice needed [Re: Swan] #385462
07/20/11 10:58 pm
07/20/11 10:58 pm
Joined: Mar 2002
Posts: 886
Earth
R
rick e. Offline
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rick e.  Offline
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Posts: 886
Earth
I used a Phil P. Weisco piston some years back and I used .0045" and all is well so far....


Now here is a bit of info that you may want to look into. Those "skinny" rings have a number on the box, something like 33485 (I'm not near the garage to give you the exact number) But after talking to Phil, It appears that this an english number when the rings are perfect round. Meaning: 33485 = 3.3485"

Now you need to do a balancing act on rings being perfect round and piston clearance. Also note those rings are really, really hard. I was lucky that at .0045" I was only .0001" from perfect round of the rings...

Yours and others piston/rings may not be the same as mine, but something to think about.

Re: Cylinder honing piston clearance advice needed [Re: rick e.] #386117
07/25/11 2:09 pm
07/25/11 2:09 pm
Joined: Mar 2007
Posts: 1,163
Winona, MN
Swan Offline OP

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Swan  Offline OP

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Joined: Mar 2007
Posts: 1,163
Winona, MN
Thank you everyone for chiming in, I really appreciate it.

Off to the machine shop this morning to have my cylinder honed.


+.040 over


1966 Triton
1962 BSA DBD34 Gold Star
1966 Triumph Bonneville

Moderated by  Rich B 


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