336 cam 81 R100RS Euro

Discussion in 'Airheads' started by Eduardocastrejon, May 17, 2019.

  1. Eduardocastrejon

    Eduardocastrejon Been here awhile

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    hi,

    please help me with this:
    I want to install a 336 cam on my 81 r100rs (32/11)
    I already purchased the 336 cam ,lifters, sprocket timing chain kit, head gaskets and cylinder orings,coils springs
    the cam was purchased today at bmw dealership, came from germany hope is not an old stock with failure, but I will measure at soon as arrives.
    i know that exists the 320 cam (not swiss bmw) from motobin or siebenrock but I already bought the 336 cams and light valvetrain parts but are expensive !

    some body have the specs on this cam ?, some posts says that have more duration 336 vs 308 but with same lift
    other posts says have more lift and have valve hitting pistons with oem pistons
    i supose have more duration and lift

    My motorcycle came from factory with 9,5 cr, I want to shave to obtain 10.0 cr but if exist posibility of valve hit I will suspend this until measure.
    l will not install a second plug, I dont want to raise too much the cr but I live at 7500 feet elevation , raise a bit the cr will be a good idea, at this moment i dont have pinging problems with 87 octane fuel but normally I use 91.
    bigger cam decrease dynamic cr.

    this is not a racing project, I only want more mid and high revs punch, Im not installing lightweight parts and Im not porting the head or installing dellorto carbs.
    but from factory my model have some good stuff like 9.5 cr, 40mm bings, big valves, lightweight flywhhel (clucth assembly), electronic ignition, dual pipe header, no smog device.

    I want to change this cam several years ago, but I read a lot of horror stories. but I never really believe half of this.
    most of the guys that installed this cam are happy, most of the persons that wrote horror stories appears that never installed the cam and only reads about it

    timing
    im not sure but I read that flywheel timing marks at 81 are retarded and I read that later 336 cams are advanced 6 degrees for emissions
    dual plug solves more less this issues but I will keep 1 plug
    what is the correct way to set the timing with this parts ?
    i supose the difernt parts numbers on thi cam is the way that bmw adjusted for each individual year model to still corectly use the flywheel marks. (but i will check, tdc mark when installed)
    what about the springs at can , mine is electronic, still have the springs ?

    jetting
    i already have some main jets but what about idle jet
    some says that this cam uses smaller idle jets ?, let me know your

    questions

    1.- 336 cam specs
    2.- can I shave .020 inches to raise to 10.0cr the heads without hitting valve issues ?
    (increse valve pockets, valves cutting needed if I keep oem 9.5cr ?)
    3.- timing, how to set properly
    4.- jetting with bings
    5.- valve clearance calibration ? same as with 308 ?

    thanks in advance for your help
    #1
  2. Eduardocastrejon

    Eduardocastrejon Been here awhile

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    I recently found this cam installation instructions from mattcfish
    http://bmwmotorcycletech.info/336-cam-factory-literature.pdf
    that says that I need to modify valves and valve pockets

    at the other hand I like the idea to not modify like another member posted
    supershaft
    I have a 336 and 9.5:1 pistons with .025" off the heads and I did not need to deepen my valve pockets. .050" off for 10.5:1 CR and you might have to. The 336 is a great cam and they are great for street bikes. Some say other cams are better but what they say about the 336 in comparison is far from what I have experienced with them. IF a 336 was as bad as some say they are, I would be running a different cam too! BUT they are not as bad as some say they are. Not even remotely in my experience and others' experience that I know of. I think they are awesome street bike cams. Tons of midrange and a stronger top end too.
    Run titanium retainers and stock springs with the 336. Maybe a thin preload washer? I run stock springs, no preload, and rev mine up past 8k rpm according to my tach all the time. for over 70,000 miles now!
    A 336 and titanium retainers was the FIRST thing I did to my bike. Since then I have added Staintune Sport mufflers, 38mm Dellorto's, 44mm intake valves, 4130 pushrods, 9.5:1 pistons, balanced top end, .025" off the heads, dual plugged, remapped ignition curve (bean can), extensive port work, and extensive airbox and velocity stack mods. The 336 made the biggest difference. Same here, I was amazed at all the extra power all through the rev range. My ex noticed right away that because of the cam I was shifting a lot less for all the extra torque. One hell of a paper weight I guess? Mileage? I have got my all time high mileage WITH the 336 and Dellorto's: 42mpg.

    I run my engine through a stock BMW late model clutch and a BMW close ratio gearset mated into a late model 17.5 degree pressure face angle gearbox with the later much beefier input shaft cush drive. My FD ratio is 33/11. Plenty tall enough for me!! I have yet to see what it will pull in top gear. After I just cammed and carbed it, it use to pull 8k rpm in forth pretty easily but since I raised the CR and ported it it will pull 8k rpm from a dead stop up a steep up hill on ramp by the time I am up the hill and next to the interstate! I am now pretty sure it will pull that in fifth on level ground but I will probably never find out.

    posted https://advrider.com/f/threads/336-cam-in-a-mono.878315/page-2


    mattcfish
    I've got a 336, 9.5:1, 1000cc Siebenrock jugs and pistons, balanced top end, dual plugs, titanium retainers, 38mm Dellortos, 2 into 1, post 81 tranny and clutch gear, 32:11 rear, and a crank mounted ignition. The 336 was the last Mod and made the biggest difference. I was surprised how much more power was available throughout the rev range. No down sides except for a slight loss in MPG...mostly because I can't stay off the throttle......still can get over 45mpg if I granny ride. Never tried the other cams, but I can say, if your bike is set up right, the 336 is the"Bees Knees".
    #2
  3. Disston

    Disston ShadeTreeExpert

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    I've thought about using another cam on my bike but because of various factors it never gets much above thinking about it for me. Most of us would like more power, performance...etc, etc...To do it right the system would have to include a different cam shaft. Be thinking about the whole system, exhaust, carbs, compression..cam...and cam timing. BMW changes the timing on the cam shaft at some point. Not easy to go against what they do.

    I'm sure some riders here have done the 336 and maybe some of the other choices. But from BMW the 336 is it isn't it? I think most of the bad press concerning the 336 came years ago from the Airlist. I no longer belong to that forum but I remember some years ago that the subject could not be raised without the most vial statements being made concerning the 336.

    I've heard a few bikes running the 336 and they sound good to me.

    I know some riders here run it.

    So good luck with it and I hope you post your experiences here.
    #3
  4. Kiwiabbo

    Kiwiabbo Been here awhile

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    I think also some of the bad press has come about recently cause people have actually done tests on cams. There are places out there doing a range of cam profiles now. 336 was the origonal BMW hot up cam but there are a lot more choices now depending on what, where and how youwant your power and what other mods you are planning. I’m going thru this at the moment, and once you start down the track you just seem to want to keep playing. It can get expensive, :-)
    #4
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  5. Jim K in PA

    Jim K in PA Long timer

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    What Charlie says is good advice. Changing just the cam will change the power characteristics, but maybe not the way you want. Look at the system. Measure, don't guess.

    Are you sure your '81 is 9.5:1 CR? A cam with more duration and overlap will need more static compression to compensate for the reduced dynamic compression. Verify the factory "spec".

    Jetting is the least of your concerns if you want to upgrade the engine.

    My 336-cammed '79 will be fired up soon. It also has custom pistons and some other upgrades. I'm looking forward to hearing it bark. :D
    #5
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  6. chasbmw

    chasbmw Long timer

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    Supershaft had a very fixed view that the 336 was the only sports cam to use in an Airhead.

    Personally I used the Seibenrock asymmetrical cam in my 1070cc 1982, twin plugged and it’s still a good performer (according to the guy I sold the bike to)

    Back in the day the 336 had a reputation as being a high RPM performer, but for a many people lost too much drivability at lower revs.
    #6
  7. Eduardocastrejon

    Eduardocastrejon Been here awhile

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    Thanks for your answers
    R100rs 81 euro version - nikasil cylinder 94mm 9.5cr piston
    Like I wrote , I know that exists other cam option but I already bought this.
    This will be my first hot cam on airhead but not my first hot cam.
    I bought a 11312365168 cam
    Suposed that is 6 degree advanced
    Yes I need to measure and check .
    But Im opened to every advice of members that alteady installed 336 cam with oem 9.5cr pistons .
    #7
  8. Arktasian

    Arktasian Lets call it Naturalized

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    I gained a lot more power with the stock cam and several adjustments. :hide
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  9. bmwrench

    bmwrench Long timer

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    I asked Siebenrock for specs on their "asymmetric" cam. What I got was useless. I'd love to measure all the cams available.

    BMWNA once called me for specs on the 336!
    #9
  10. Lornce

    Lornce Lost In Place

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    You've already got the cam and associated parts. It's been a proven piece for over 45 years.

    I think you'll be okay to run it. :thumb



    :beer
    #10
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  11. Jim K in PA

    Jim K in PA Long timer

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    You, sir, are what we call an "outlier". :lol3
    #11
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  12. Arktasian

    Arktasian Lets call it Naturalized

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    That smacks Jim, of excommunication from the fold. Have I been flying too close to the sun?
    At least I can remain a lert.
    #12
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  13. mattcfish

    mattcfish R90X Supporter

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    With the 6 degree advance 336 cam, you only need to modify the intake pockets on the pistons, especially if you shave the heads. Do a clay or solder test to verify you have enough valve clearance. The old bulletin says to increase the pocket radius by 1.6mm. I deepened mine as well, but I wasn’t using OEM pistons. There is a lot of debate about what minimum clearance should be.
    I ended up with way more than enough. You may not need to modify, but you must verify that.
    Big valve heads may need modifications to the valves as well, according to the bulletin.
    All this said, I had a friend with a stock 77 r100s who just dropped the cam in and drove. That bike ran like a champion.
    #13
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  14. mattcfish

    mattcfish R90X Supporter

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    From what I’ve gleaned, the 7rock asymmetric is a 320 exhaust and a 324 intake. The 324 has the same lift as the 336, the 320 is slightly less. Lobe center are the same at 106.
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  15. mattcfish

    mattcfish R90X Supporter

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    324= 7.7 lift x 1.39 ratio=10.7 mm lift
    320= 7.18 lift x1.39 ratio= 10 mm lift

    Attached Files:

    #15
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  16. Jim K in PA

    Jim K in PA Long timer

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    I won't belong to any "fold" that would have me as a member. :D You are welcome to a cold one in my shop any time, Lorne. :thumb

    Watch out for the lert traps. :lol3
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  17. bajaburro

    bajaburro Ancient Adventurer

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    I have the 336 bmw cam in my 91 GSPD.The bike will come on the cam @4500 rpm and makes the bike much more fun to ride.At the time I put the cam in I also switched from stock 8.5 to 9.5 BMW pistons.Went from 135 psi to 165 psi.Also with a larger BMW intake valve.Its been about 45,000 miles since then and all is well with the mods.Good luck with your cam.
    #17
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  18. mattcfish

    mattcfish R90X Supporter

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    It would be invaluable to have a pro measure all the cams and produce the results in a standard format that we could all understand. In the Famous 336 bulletin the cam is measured at 2mm lift, which doesn’t correspond at all with Schleicher’s measurements. US cams and cams available in the VW world are measured at a different starting points as well. Hard to understand why this can’t be standardized.
    #18
  19. bmwrench

    bmwrench Long timer

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    Then there's the lobe center specs, lobe separation method...all of which get to the same point. The Triumph Triples guys are looking at lift at TDC.
    #19
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  20. Eduardocastrejon

    Eduardocastrejon Been here awhile

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    who sell the titanium retainers ? worth it ?

    500RPM More than stock before valve floats ?
    #20