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Reaming data for valve guides?

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Micha
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Reaming data for valve guides?

Post by Micha »

Where can I find the factory instructions for this data?
I would like to get my hands on such a chart regarding tolerances of reaming new guides for a bike that lives in a warm climate.
Is this information available at all, or does a workshop perform the reaming according to some personal knowledge?
Thanks!
Michael Steinmann
R51/3 1952
Engine Nr. 529466

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jwonder
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Re: Reaming data for valve guides?

Post by jwonder »

The info you seek is at https://vintagebmw.org/library_data/Wor ... R60S69.pdf but the real answer is it’s down to feel. My comment to you is make them looser than you would expect.

I just finished my R 50/2 a month or so ago and I measured the fit with the gauges and then made them looser. Measure with a very thin oil as well to get a good feel.
James Wonder
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Long Island, New York

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Rodolfo850
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Re: Reaming data for valve guides?

Post by Rodolfo850 »

Im 100% agree with Jwonder comments....
I rebuilt mine R60/2 LK cylinder head, but request Machinist shop the closes tolerance, to avoid burning oil.

Yesteday after 20 milles since rebuilt on my way to the Distinguished Gentelmans Ride, my engine started to sound like a typewriter and stops...

Exhaust valve sticks to valve guide......so it returns on my trailer to house...

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jwonder
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Re: Reaming data for valve guides?

Post by jwonder »

Yes, this is becoming a problem more and more and I think guide material differs greatly. I use KPMI guides all the time and their valves if I can get them.

List of KPMI components
James Wonder
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Long Island, New York

timothyferriss
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Re: Reaming data for valve guides?

Post by timothyferriss »

The factory instructions for reaming new guides for a bike can typically be found in the technical documentation provided by the manufacturer of the bike or the specific components being installed.
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Re: Reaming data for valve guides?

Post by 808Airhead »

.001-.00276” or .040-.070 mm is on the tightest end, you can go to the end of spec up to .085 mm/ .0035” or near there.
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Re: Reaming data for valve guides?

Post by flyingtpot »

Some info derived from a history on this subject:
  • Use caution when viewing listed data. 0.04mm is ~0.00157". This is a case where considering the mm->inch conversion of 0.04mm to three decimal places in inch will most probably be catastrophic.
  • When the BMW factory listed their guide reamer sizes, it was based off a supplier valve stem value that was not supposed have a significant variance, respectively for the 7mm or 8mm size. To properly process the guide ID's with the current valve supplier market, a range of reamers is required to optimize the desired stem clearance. That is, valve stems from the current suppliers (SI, TRW, KPMI, etc) vary, and and most vary between the intake or exhaust.
  • There is also tooling and material removal variance. HSS and carbide reamers can process to size differently in bronze guides, and the guide material will also have a process to sizing impact.
  • Depending on the reamer design and type used, material amount to be removed, speed & feed, etc... will determine the accuracy of the finished guide bore. Also when reaming guides, it is ideal to brush hone the bore to achieve the final required Ra finish
  • Investing in quality reamer tooling can be pricey. If only doing one pair heads, the honing process should be considered. Honing will achieve bores that are straight, sized accurately with respect to the required stem clearance and achieve an optimum surface finish. Most all quality machine shops and speed shops have a honing machine.....and know how to use it.

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