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question on degreeing in a cam for a CB350

This is a discussion on question on degreeing in a cam for a CB350 within the Vintage Motorcycle Racing forums, part of the Caferacer.net Forums category; Set for centerline on the card the rest falls where it does. adjust to move the power band around after testing....

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  1. #11
    Senior Member 44dwarf's Avatar
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    Set for centerline on the card the rest falls where it does. adjust to move the power band around after testing.
    \"Smok\'in the competition NOT Tobacco\"
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  2. #12
    Senior Member craig641's Avatar
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    If the number variations are due to manufacturing tolerances as Megacycle claim, have you tried moving the rocker arms to different positions to see if your numbers get closer megacycle's card numbers? The rocker arms are easy enough to move. You may find they do in fact have different lift. My daughter lives in Annapolis but we're not going down for a visit until after labor day.

  3. #13
    Senior Member caferocket686's Avatar
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    Quote Originally Posted by outobie View Post
    did you check the other measurements or just set it to intake opening?
    I just checked the intake valve timing and valve to piston clearances. Didn't see much need in checking duration unless the engine didn't run right and I don't have an adjustable cam sprocket anyway. I may have been more curious about exhaust timing if there was an adjustment that could have been made easily but decided to just assemble the motor and see how she ran. So far so good.
    01 MZ Skorpion (No, it's not stock. It was originally designed in England, has a Japanese motor, is built with Italian components, but it's German)
    03 Kawasaki KX250 (Braaap!)
    73 Yamaha RD350/R5

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  5. #14
    Member outobie's Avatar
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    Quote Originally Posted by craig641 View Post
    If the number variations are due to manufacturing tolerances as Megacycle claim, have you tried moving the rocker arms to different positions to see if your numbers get closer megacycle's card numbers? The rocker arms are easy enough to move. You may find they do in fact have different lift. My daughter lives in Annapolis but we're not going down for a visit until after labor day.
    No I hadn't thought of that.

    I decided to just set it and see what happens. I set it exactly on the left intake lobe center. I'll run it and see what happens. Here are my current settings:
    123-40 Spec Card -11
    Open left intake 31 29
    Close 63 61
    Lobe Center 106 106
    Valve Clearance 0.050 0.090
    Valve Lift 0.381 0.375
    Open Right Intake 31 31
    Close 63 61.5
    Lobe Center 106 105
    Valve Clearance 0.050 0.069
    Valve Lift 0.381 0.371
    Open Left Exhaust 61 50
    Close 34 35
    Lobe Center 103.5 97.5
    Valve Clearance 0.070 0.074
    Valve Lift 0.360 0.359
    Open Right Exhaust 61 51.5
    Close 34 37
    Lobe Center 103.5 97.3
    Valve Clearance 0.070 0.075
    Valve Lift 0.360 0.360
    Last edited by outobie; 08-10-2015 at 08:10 PM.

  6. #15
    Senior Member Stan Lipert's Avatar
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    Make your overlap openings equal to get the best power from your cam:



    This works with whatever checking clearance you want, plus whatever checking lift, just be methodical with the dial indicator set up and that your checking clearances are the same for intake and exhaust.
    Trying to 'tune" the cam for better midrange vs. top end power is completely nonsense on these engines. The critical elements of tuning- exhaust design, porting, compression, will all make make more power overall. In other words, if you change the exhaust to make more top end power, you will get mid range as well.

    Please don't anyone badmouth Megacycle. They do an excellent job of providing cams, mostly from using old, obsolete cam templates. Megacycle has not built any CB350 engines, nor have they designed the cams themselves, so the spec. numbers were probably passed through from wherever the original cams came from.

    outobie- Who are you? I've raced at summit point from 1992 through the 2000's on CB350's. I've read through your advice on Honda Twins, and you boast of your experience, yet no name. You can add credibility to your comments if people know you as an actual person.
    monkey and Buckets like this.

  7. #16
    Senior Member monkey's Avatar
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    It is wise to not upset Stan. He has powers the are beyond the grasp of mere mortals.

    Hello Stan!!!

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  8. #17
    Member outobie's Avatar
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    Hi Stan, John Knott here (Outobie). I lived in Asia (Japan mostly) from 94 to 2003. raced here and there in the states when I could. raced summit point a lot in 91 to 94 mostly on CBR600s at the time and a honda hawk NT650. did some wera endurance racing from time to time when I was back in the US for visits, entered some races out west at Willow and PIR. wasn't trying to boast. apologies if I come accross that way. overseas I raced in Japan, Malaysia and Australia, mostly on smaller bikes under 400cc both 2 and 4 strokes...did a 24 hour team event on a 50cc honda. that was the most fun ever

    the Megacycle folks are great they are always very helpful. I don't see anyone badmouthing them in this thread. I reached out in this thread since there are several cb350 racers here...I've been trying to sort out this one motor for some time now and it's been a challenge. I rebuilt it several times and can't seem to get this one to run right. I've rebuilt this one 5 times now. tried different pistons, tried different heads, tried different carbs, tried different exhaust systems, tried different ignitions. the only common factor is the cam and bottom end. I bought this motor in running condition with the same bottom end and cam with open megaphone exhaust, 66mm kawasaki GPZ750 pistons (I think) and Mikuni VM32mm carbs. it ran great and made great power. just smoked and was a bit worn out.

    now I can't get it to take throttle after each rebuild...it idles fine breaks down in the middle from 3k to 8k then runs clears out and runs to 11,500 but doesn't seem to make good power. my best jeting setting seems way lean to me with 130 mains. I'm guessing I have too little compression or the intake closing is too late pushing the charge back and forth through the carbs.

    can you PM me your phone and let me ask you a few questions about what you posted above?
    Buckets likes this.

  9. #18
    Member outobie's Avatar
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    If I understand your suggestion of making overlap openings equal properly: you'r saying I should make intake opening and exhaust closing equal.

    if that is the case, then from my measurements, I would set the cam at these numbers:

    123-40 Spec Card -8
    Open Left intake 31 32
    Close 63 58
    Lobe Center 106 103
    Valve Clearance 0.050
    Valve Lift 0.381
    Open Right Intake 31 34
    Close 63 58.5
    Lobe Center 106 102
    Valve Clearance 0.050
    Valve Lift 0.381
    Open 61 53
    Close Left Exhaust 34 32
    Lobe Center 103.5 101
    Valve Clearance 0.070
    Valve Lift 0.360
    Open 61 54.5
    Close Right Exhaust 34 34
    Lobe Center 103.5 100
    Valve Clearance 0.070
    Valve Lift 0.360

  10. #19
    Senior Member Stan Lipert's Avatar
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    John,
    A very impressive racing resume',I would be honored to shake your hand.
    Yes, the red numbers should be the same, or close. I would run the engine with numbers of 32 and 34. You would be very good indeed as a mechanic to move a cam one single degree!

    What did you do to the bike to make it run different?
    I would recommend going back to the original exhaust and jetting, to start.
    Pistons will make no difference to drive ability.
    The cam numbers are good, set ignition by strobe light at 33 degree, and verify that the timing does not jump around.
    The valves must seat, this will cause drive ability problems, also. Check by holding the chamber up to light and by looking into the ports with the valves lightly held in by hand, rotating to check for bent valves, then with a flashlight pointing into the ports and looking for light on the chamber side. Rotate the valves also.
    Head porting does not cause these problems, maybe a little loss of power if the porting is bad.

    Stan

    Cell 440-610-6187

  11. #20
    Member outobie's Avatar
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    Incidentally, I've been asking advice in several places. Here is the feedback I've received on this topic.

    Buff Harsh (email) from THR:
    "John- you only need to do the left cylinder and ideally your looking for 106... So go by the -12 setting in your chart...."
    (I took this advice to mean set the left intake according to lobe center...this is what I based my current settings on)

    Bill Moeler (phone call) from Bore-Tech:
    Bill gave me the formula for calculating lob centers and told me to "Set it by left intake lobe center and let the rest of the numbers fall where they will"
    (this seems to agree with Buff Harsh and the basis for my current settings)

    Rusty Foard (phone call) '93 AHMA championship winner and person I bought this bike/motor from
    "I always set mine to left intake closing and let the rest fall where it will"
    (my current settings are 2 degrees more advanced than this advice at present settings)

    Tech at Megacycle (phone call) didn't write down his name
    "split the difference on all measurements"
    (my current settings are 5 degrees more retarded than this advice at present settings.)

    Stan from above (if I understand properly, please let me know if I have it incorrect)
    "make intake and exhaust overlap equal"
    (my current settings are 3 degrees more retarded than this advice at present settings)

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