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1974 Kawasaki F7 - Can't get bike rich enough...need carb advice.

Discussion in '2 smokers' started by spectreman, May 11, 2020.

  1. spectreman

    spectreman Adventurer

    Joined:
    Aug 22, 2017
    Oddometer:
    18
    So, I just pulled out the 1974 F7 I finished last year & jumped right into the tuning of the carb.

    I have replaced all of the engine seals, and plugged the vacuum pump on the front of the case (and plugged the appropriate vacuum port on the carb. The intake boot is secure and tight.

    I'm 99% sure I don't have any air leaks, and the bike starts right up and idles great, it runs pretty good too, but I just don't have any power.

    I've been in the carb about a million times, changing pilot jet, moving the needle clip, adjusting float height and I just can't get this bike running rich. I feel like it's not getting enough gas. It's not a fuel flow issue either, as the fuel flow to the carb is strong. The spark plug is white as can be, and I can't seem to get it to indicate a rich mix, no matter what I do.

    I'm stuck, and I need some of you experts out there to throw me some knowledge. What am I missing here?

    Here is a photo of the finished bike:

    kawi74.jpg
    #1
    Westcoasthumpin likes this.
  2. mikeysduck

    mikeysduck Slow Ride to Nowhere

    Joined:
    Jan 18, 2008
    Oddometer:
    1,076
    Location:
    Acton Ca.
    Do a leak down test. Check the compression too.
    #2
  3. baloneyskin daddy

    baloneyskin daddy bikaholic Super Supporter

    Joined:
    Oct 21, 2009
    Oddometer:
    3,958
    Location:
    southcentral PA.
    make sure the airbox opening isn't blocked or the exhaust plugged up with crud from the 2 stroke oil. Did you have the rotary valve out at some point and maybe have it miss timed.
    #3
    spo123 and mikeysduck like this.
  4. bark sampler

    bark sampler Been here awhile

    Joined:
    Mar 30, 2008
    Oddometer:
    309
    Location:
    Middle of Michigan
    You have the service manual from Kawasaki? I scanned the whole shooting match a few years ago when I was working on my F9 for someone else. The carb section may be a good check to see if it’s matching original brass & adjustment ranges. Same book was for all F models. May need to give me a few days to find it!

    If that’s right, you can do the hack method of finding vacuum leaks with carb cleaner squirts at various potential leak points while it’s running. See if idle goes up.

    nice looking resto. I’m usually too old school to like black rims on vintage bikes but it looks good there!
    #4
  5. spectreman

    spectreman Adventurer

    Joined:
    Aug 22, 2017
    Oddometer:
    18
    I've done the leak test with carb cleaner, and everything checks out fine. I have the service manual, and all brass is stock and currently set at factory specs. (I swapped out pilot and main for a bunch of different values, but stock values still work best).

    I never had the rotary valve out, but that doesn't mean it's not in backwards or mis-timed - I really should check that out...but this thing idles & runs too well for me to think anything major is the issue.

    Airbox and exhaust we're fully cleaned and rebuilt, so I'm sure all is good there.

    This thing should just rip, but it's not. I can get it going pretty fast, but it does not pull when you hit throttle going say 25mph. If I hit throttle quick at that speed it revs high but doesn't pull, but if I feather throttle it moves fine...this is why I'm inclined to think it's a fuel issue. I removed the inline filter (just to see if filter was restricting), and triple checked the float, and carb is mechanically sound and fuel is flowing.

    Compression gauge is in the mail, so as soon as I check that out, I'll jump back here and update!
    #5
  6. Dave in Wi

    Dave in Wi Long timer

    Joined:
    Feb 25, 2007
    Oddometer:
    2,655
    Location:
    Madison WI (40 Square Miles Surrounded By Reality)
    That exact bike was my first bike. It’s really nice to see one of these. It was even the same color.

    I did have a problem with it when I first got it. It ran well but had very little power. In fact that was the reason that I got it so cheap. Friend of my dad’s suggested taking the exhaust off and taking it for a short ride that way. I did that and it had a ton of power. It turned out that the muffler was plugged up with two stroke oil in the packing. I took it to a mechanic who was able to cut the pipe open and burn out all of the junk and braze it back up.

    Not sure that this is your problem but it might be worth a try.
    #6
    spo123 and 2fishkev like this.
  7. Bigeyedfish

    Bigeyedfish Adventurer

    Joined:
    Aug 19, 2018
    Oddometer:
    31
    Location:
    Missouri
    You're sure it's the engine and not the clutch? If the engine is revving but not putting power to the wheel, I'd be looking at the clutch.

    I had a TS250 that got grouchy at sustained higher speeds due to lack of fuel. I had replaced an old fuel line with the cheapest line I could find on Amazon, and I'm pretty sure it shrunk and reduced flow. When I replaced that with a pricier option, the issue went away.
    #7
  8. spectreman

    spectreman Adventurer

    Joined:
    Aug 22, 2017
    Oddometer:
    18
    Yeah....nice idea. I'll pop off the exhaust and see what happens...I'll report back later!
    #8
  9. spectreman

    spectreman Adventurer

    Joined:
    Aug 22, 2017
    Oddometer:
    18
    Sorry...I should have said "bike cuts out", like it's trying to suck gas, but not getting any. I'm working on 2 bikes at the same time, so I confused the 2 for a moment.

    So to clarify my earlier post, I can get it going pretty fast, but it does not pull when you hit throttle going say 25mph. If I hit throttle quick at that speed it cuts out, like it's not getting any fuel & doesn't pull, but if I feather throttle it will move along fine...
    #9
  10. Fred Garvin

    Fred Garvin Been here awhile

    Joined:
    Jan 21, 2011
    Oddometer:
    416
    Location:
    western slope
    Make sure your fuel cap is venting properly.
    #10
  11. spectreman

    spectreman Adventurer

    Joined:
    Aug 22, 2017
    Oddometer:
    18
    OK - following Dave in Wi advice, I dug into the exhaust.

    I had re-wrapped the baffle last summer and reinstalled - looked good to me. After doing some research (online & service manual), it appears that the baffle need not be wrapped on these 70's Kawasaki bikes. The baffle just needs to be occasionally cleaned and knocked free of carbon deposit.

    I cleaned out all the matted material and reinstalled...got more power, but still not where I should be.

    NOW, I think the clutch is slipping...getting into that in the next few days.
    #11
  12. spectreman

    spectreman Adventurer

    Joined:
    Aug 22, 2017
    Oddometer:
    18
    UPDATE! Success!

    After I cleaned out the packing material from the muffler, the "cutting out" issue with the throttle stopped, and with that came a bit more power, and as as result, a very noticeable slipping clutch.

    I pulled the clutch this weekend, and cleaned up the steel plates with 220 grit emery (before/after photos below). Re-installed, and YES! Those 2 issues turned this thing from a 40 year old bike to a 4 year old. It really tears around now. It's super fun and pulls like a beast. Just want to say "thanks" to all you experts for the troubleshooting advice. The advice really helped take my focus off the carb and made me step back and re-focus. Perfect! Thanks again!

    Attached Files:

    #12
  13. Dave in Wi

    Dave in Wi Long timer

    Joined:
    Feb 25, 2007
    Oddometer:
    2,655
    Location:
    Madison WI (40 Square Miles Surrounded By Reality)
    Awesome. Glad to hear you got it going.
    #13