R65 typ 247 1990 engine upgrade issue

Discussion in 'Airheads' started by Rasputin Saint, Sep 23, 2013.

  1. Rasputin Saint

    Rasputin Saint Adventurer

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    Dear Advriders.

    I came to purchase a 1990 BMW R65 Typ 247 with the 27hp version engine.

    The bikes serial number is 6432418 R65. It uses two 26mm BING carbs with the codes

    64/26/317 & 64/26/318, an 31/9 final drive and it runs fine in its low hp , but it is just not enough for me.

    I am thinking of upgrading the bikes horsepower and I hear a lot of different things by Greek BMW "guru" mechanics. So I would very much appreciate your professional opinion on the choices I may have considering that I would be satisfied with just a few , lets say 10 more hp than the ones I already have.

    1st choice is to upgrade the existing engine to 47 or 50 hp. What changes would I have to make in this case? I hear that I have to change the camshaft, the cylinder heads and the carbs to 32mm. Would that all be enough? What is your recommendation in this case and how much would the parts cost?

    2nd choice is to give the engine a small amount of extra hp without making engine parts changing, just some improvements in functioning such as bigger carbs, better air breathing bigger exhaust tubes and .......whatever you would recommend. Do I have any luck this way , how many hp would I might gain with minor improvements and again what would you suggest if I finally choose this option?

    Changing the whole engine with an used 50hp R65 or even to a R80 engine is not in my priorities for the moment due to cost and the leak of trust on buying a used engine with uncertain number of km in its life. But I do not completely reject that option for the future.

    Looking forward for your answer.

    Thank you forehand.

    Best Regards
    #1
  2. disston

    disston ShadeTreeExpert

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    Sell the bike. It will never be what you want it to be. It is not even the 247 type engine. We let the R65 bikes on the Airhead forum and we mention all the time that the Airjheads are the 247 type engine but the R65 is not a 247 type engine.

    To increase the HP from 27 to 47 is a doubling of HP, almost.

    Save yourself the grief and expense. Buy a motorcycle that suits your wants and needs.
    #2
  3. Airhead Wrangler

    Airhead Wrangler Long timer

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    Agreed. On both points.

    the engine is a type 248/1
    #3
  4. guitstik

    guitstik Been here awhile

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    For what it would cost you to upgrade the engine you could buy a bigger bike. Swapping a bigger engine into that frame is asking for trouble because it wasn't designed for it strength wise.
    #4
  5. Prutser

    Prutser Long timer

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    Those bikes are the same as the R80 and the R100 mono's so they are designed for the bigger engine.
    #5
  6. AliBaba

    AliBaba Been here awhile

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    Hmm, same frame was used for R65, R80 and R100: http://realoem.com/bmw/partxref.do?part=46511452025

    Sadly I'm not sure of the differences between the 27hp version and the 50hp version.
    #6
  7. 190e

    190e Long timer

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    That's entirely possible because the 27Hp model is just a detuned version of the normal R65. You have listed most of the differences, camshaft, valve sizes and carbs. In addition your 27HP engine will have a lower compression ratio. I'm not sure whether that is taken care of by the heads or the need for new pistons which could be costly. Your final drive should be OK as the same ratio was fitted to the 45Hp R65. If you did want to change it a new speedo with the correct ratio is also needed.

    So possible but sounds expensive unless suitable 2nd hand parts can be easily sourced.
    #7
  8. Airhead Wrangler

    Airhead Wrangler Long timer

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    The detuned 27hp R65 used 26mm bings while the normal ~50hp model used 32mm bings. I think I remember reading that the slides in the carbs were also limited in some way from fully openning. I've never seen them personally as they weren't sold here. I don't think the top end parts are in any way different.
    #8
  9. Prutser

    Prutser Long timer

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    The top end is different. Those heads are used on R45 models here in europe.
    It is correct that the carb body's and the cam is different too.

    The pistons used in the 27hp are not the same as the 50hp models.
    #9
  10. guitstik

    guitstik Been here awhile

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    I stand corrected, I missed or forgot that the OP's bike is a '90 model. The early R65's up to '85 used a lighter frame than all other airhead bikes so very little was comparable.
    #10
  11. supershaft

    supershaft because I can

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    R65's aren't airheads? First time I have ever heard that.
    #11
  12. DaveBall

    DaveBall Long timer

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    It does not sound like you have an actual R65.

    The R45 came in 2 flavours. Both are 450cc. A 35HP and a 27HP model. The 27HP model could be brought up to the 35HP version fairly easily. But to go any further requires major surgery, like new pistons and jugs, new carbs, different cam, etc. Cheaper to buy a good used 650 engine.
    #12
  13. Airhead Wrangler

    Airhead Wrangler Long timer

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    Oh. Nevermind then.
    #13
  14. Airhead Wrangler

    Airhead Wrangler Long timer

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    They stopped production of the R45 in '85. From then on to meet the beginner rider requirements in germany, they sold detuned R65s making 27hp (the max allowed for a beginning rider in Germany at the time). From what I've read, all R65GSs were detuned to meet this standard except those sold to french police or the danish military. Other R65 models were sold to the public as both normal AND detuned versions.
    #14
  15. eric2

    eric2 ®egister this:

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    I rode an r65ls for 12 years and about 80k miles. Waste of time to try increasing power, and they aren't that reliable to start with. Your best bet it to get a used r80 motor.

    You won't get bigger jugs on the r65 as the opening in the block needs to be larger. Some more info below, but considering my r12gs gets better mileage and has about 3x the power, and a reliable charging system I wouldn't go back.

    http://www.chemie.unibas.ch/~holder/r65faq.html#POWER_INCREASE
    #15
  16. dudester

    dudester Dudester

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    Just got a R65 (1987 year monolever). Have an R80st and also R80g/s....bought the R65 to put and R80 or R100 engine in, but after riding it yes at higher R.P.M.s can say that it needs nothing and except for low end torque can't really feel any difference from the larger bikes.....except for pushing 6-7k rpms.

    Look for a good used R65,R80 or R100 engine for transplant. The monolevers are great bikes!

    Dudester
    #16
  17. Boxer Metal

    Boxer Metal Mad Scientist

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    Since this bike was never in the US I can only assume that you are in somewhere in Europe or beyond. It was very common for companies like Fallert, Wudo, Siebenrock and more to make kits to lower the horsepower on some models for insurance and registration reasons as well the offered kits to go the other way. Check with one of those companies for help as it looks like you are getting a lot of wrong info here:D
    #17
  18. Rasputin Saint

    Rasputin Saint Adventurer

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    First thing, thank you all for your answers, forgive my bad english,I'll try to be as acurate as possible. I'm not talking about the frame, which is the same monolener the 50 hp version uses. I attach the specs ( http://www.gobookee.net/get_book.ph...vc2hvY2sgU3BlY2lmaWNhdGlvbnMgLSBCTSBCaWtlcw== ) . The vin label on the frame is writting exactly : Typ BMW 247 649 ccm.
    As far as I know and correct me if I'm wrong, the R65 (27hp 47 hp and 50hp), R80, R100 have the exact same engine housing. The low tuned R65 uses a different degree camshaft in order not to advance, all the others R65 R80 and R100 use the same. Also the low tuned R65 engine uses cylinderheads with smaller inlet than the ones with 47hp and 50hp has lower compression ratio and smaller 26mm carbs.
    The main cuestion is, what could go wrong if changing the camshaft, the cylinderheads the pistons and the carbs. In my opinion , this would be a safe transforming the entire engine and not a dangerous experimental tuning . Plus that by oppening the engine, is a good oportunity to check and change old seal rings, gascets, beerings and whatever else is needed. In this case I think it would be an almost new engine. How about that?

    As I said before, an option is to buy a used R65 or R80 engine but it is allways a risk on what is one buying and what hidden problems the engine might have.


    P.S. How do I attach images?
    #18
  19. Prutser

    Prutser Long timer

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    I think changing the cam, heads and carbs is the best option but it might be hard to find them without the engine it self.
    And sometimes its even cheaper to buy the engine complete. Than you can still swap the parts onto your own engine.
    #19
  20. AliBaba

    AliBaba Been here awhile

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    R80 and R100 use the same housing. The R65 has a different housing (at least the angle of the pushrods are different).
    #20