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Author Topic: Fox MK VI question  (Read 2564 times)

Offline Brad LaPointe

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Fox MK VI question
« on: December 08, 2017, 10:09:51 AM »
It was either here or the engine column.
Recently I was rummaging around the shop and found a box with a MK (6)VI in pieces. Everything was present except the bearings . Anyone know the proper sizes?
I had sold all my Fox combat stuff years ago ,finding this was like winning the lottery!

Thanks in advance,
Brad
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Offline badbill

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Re: Fox MK VI question
« Reply #1 on: December 08, 2017, 10:14:20 AM »
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Offline Paul Smith

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Re: Fox MK VI question
« Reply #2 on: December 08, 2017, 01:13:22 PM »
Eh, tu Colombo.

So Brad is re-entering FAST as well.

Fast at the Beanfield, eh?

Henry replaced my 36 bearings at lower price than Boca.
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Paul Smith

Offline C.T. Schaefer

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Re: Fox MK VI question
« Reply #3 on: December 09, 2017, 07:37:30 AM »
Not the same as Mk7.  Maybe someone who knows can chime in.  Al?
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Offline Brad LaPointe

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Re: Fox MK VI question
« Reply #4 on: December 09, 2017, 09:59:02 AM »
C.T. I believe you are correct. The MK7 has a larger diameter crank like the Nelson . Does the 6 use the same bearings as the 3 & 4 ?

Brad
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Offline Fredvon4

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Re: Fox MK VI question
« Reply #5 on: December 09, 2017, 11:41:34 AM »
Not sure but think Fox MK III is diff

Both MK IV and MK VI use same bearings and similar crank shafts

Front was PN 13742
OD= 7/8"
ID= 1/2"
Thick= 7/32"

Back was PN 40210
OD= 1 1/8"
ID= 1/2"
Thick = 1/4"

I just measured the ones Marvin Denny sent me with some of his junk barrel engiens
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Offline C.T. Schaefer

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Re: Fox MK VI question
« Reply #6 on: December 09, 2017, 04:52:14 PM »
Brad,  The Mk6 has a 15mm crank with a 1/2" front bearing. Do not have part#'s.  Someone does.  TS
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Offline Dick Tyndall

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Re: Fox MK VI question
« Reply #7 on: December 09, 2017, 06:34:07 PM »
  The Fox MK VI Combat Special engine uses a much larger rear bearing than the MK III and the MK IV. The MK VI has a 15MM crank where the MK III and MKIV have a .500 diameter crank. The size of the rear bearing on the MK VI is: O.D 28MM; I.D. 15MM; thickness 7MM. All 3 engines use the same size front bearing. As with all of these engines the bearings came with metal tab retainers. I always changed the rear bearing with a bearing with either a plastic or a phenolic (?) retainer. I had pretty good luck boring out the MKIII and MKIV cranks to .375 ( from .312 ) and taking some weight off of the crank pin side of the crank. Opening up the crank timing to about 208 degrees total helped, also. Back in the early 1980's on a 19 1/2 ounce foamie Fast Combat airplane we could see 122 MPH pretty easy.




                       Dick Tyndall
« Last Edit: December 09, 2017, 09:25:04 PM by Dick Tyndall »
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Offline Al Ferraro

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Re: Fox MK VI question
« Reply #8 on: December 12, 2017, 08:44:58 PM »
  From Boca Bearing the front is SR6-5 and the rear is MR6902-ZZ TH9/C
Al
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Offline Lane Puckett

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Re: Fox MK VI question
« Reply #9 on: January 23, 2018, 07:04:35 PM »
Fox 25210 part number for the front bearing on the combat special  same bearing as in the rear of the Fox 25 schnuerle  I dont' recall when I last called and got some but it wasn't too long ago.   The part number for the combat special doesn't look up when you call.  you have to use the 25210 number.  I stocked up last time I called as I figured they were not going to be available.

Boca has the wrong dimension bearing for the front when you look up combat special.  There is a SR6-5(x) that is the right thickness but the one they have in their kit for the combat special isn't the right number.   I don't know about the rear as I didn't measure one but Dick Tyndal has it right for the rear.

front is 0.218 thick not 0.288 as Boca calls out as SR6-5ZZ
1/2 inch ID
7/8 inch OD
7/32 inch thick

Front bearing is generally the hard one to get.    If calling Fox doesn't exist anymore you can watch EBAY for original ones.  The original Fox part was a very high quality bearing per some very respected engine men.

The rear is easily sourced from Boca.

Enjoy,
Lane Puckett
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