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Thread: Compression PSI on an '81R00

  1. #1
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    Compression PSI on an '81R00

    Having a valve job done. Does anyone know how much compression P.S.I. an R100 is supposed to put out ? Thanx

  2. #2
    Administrator 20774's Avatar
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    A rule of thumb is one atmosphere above the compression ratio, converted to psi. For the '81 R100, the compression ratio was 8.2:1, so 9.2 times 14.7 is something like 135.
    Kurt -- Forum Administrator ---> Resources and Links Thread <---
    '78 R100/7 & '69 R69S & '52 R25/2
    mine-ineye-deatheah-pielayah-jooa-kalayus. oolah-minane-hay-meeriah-kal-oyus-algay-a-thaykin', buddy!

  3. #3
    Administrator 20774's Avatar
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    I got my numbers from here for an '81 R100:

    http://www.bmbikes.co.uk/specpages/R100.htm

    The 9.5:1 was prior to the detuning that began in and around '78. LKChris seems to have this down cold...but I'm pretty sure they detuned the bikes in the early '80s.
    Kurt -- Forum Administrator ---> Resources and Links Thread <---
    '78 R100/7 & '69 R69S & '52 R25/2
    mine-ineye-deatheah-pielayah-jooa-kalayus. oolah-minane-hay-meeriah-kal-oyus-algay-a-thaykin', buddy!

  4. #4
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    My 1980 R100RT already has the 8.2 pistons - they stayed thru 1984 for US bikes. unless, of course, your bike is Euro, or previously modified

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