Need help getting old CBR started

Discussion in 'General' started by USracer900, Dec 29, 2019.

  1. USracer900

    USracer900 Well-Known Member

    I bought a 1994 F2 a month ago, super clean but 40K on it. Needs a cam chain tensioner, gonna put a manual one on it, no biggie. When I went to test (ride) it, was hesitant to start. Spun over quickly but owner had to fiddle with the idle adjustment then it fired up. Took it for a quick blast and it was super smooth, pulled good, all gears were tight etc. Bike it essentially stock (shockingly), OEM fairings clean so I bought it. (I'm a sucker for these old bikes)

    Anyways, got it home and same deal, doesn't want to start. Choke doesn't help any, fiddle with idle and and it seems to help a little but still can't keep it running. If I hold the starter button for a while (20 + seconds) it will fire and sounds like it wants to run but simply won't stay running on it's own. I see some smoke from the exhaust and (I think) I smelled gas so wonder if I'm flooding it. I'm planning on pulling all the fairings, tank and digging into it, any ideas where to start first? Change plugs just for good measure? On a side note he had a battery tender on it and when I got it home the battery was dead. Replaced with a brand new battery and that went dead also after a week or so of sitting so something is draining the battery.

    Sorry for the long post, any help or advice is appreciated!
  2. Kyle Brosius

    Kyle Brosius Well-Known Member

    Easy thing to check for battery issue is pull the fuses and put an amp meter across each fuse connection. You’ll be able to tell which circuit is pulling juice with the key off. If I were you I’d replace the plugs before you do anything else. I do so on all of the bikes I buy.
    USracer900 likes this.
  3. condon66

    condon66 Member well known

    Take the carbs off and give them a proper cleaning, check float level, synch, and you'll probably see a world of difference.
  4. lee955i

    lee955i The Traveling Gnome

    And let us know how many tabs you break off removing and reinstalling that F2 bodywork....;):D
    Cannoli, SGVRider, Wheeliest and 4 others like this.
  5. Jim Moore

    Jim Moore Well-Known Member

    Clean the carbs, replace the spark plugs and air filter, and check the valves. I've had an F3 in the garage for several years. I finally got around to checking the valves at 36K miles. They were TIGHT! It starts much more easily now. When you get it back together you can jump the relay on the right side to get the low pressure fuel pump to fill the carbs. On the F3 anyway. I assume the F2 is similar. Take a bunch of pics as you take it apart. There are vacuum hoses going all over the place between the carbs and the airbox.
    SpeedyE, USracer900 and Big T like this.
  6. fastfreddie

    fastfreddie Midnight Oil Garage

    Yup. ˆ

    Before you do anything, pop the oil fill plug and take a whiff. The gas you might be smelling will create an overly rich mixture and no amount of carb fiddling will cure it. So, if you smell gas, that oil is done and you'll also want to check the fuel petcock for proper function.
    USracer900 likes this.
  7. Big T

    Big T Well-Known Member

    What Jim says
    Tight valves are probably the #1 reason old bikes become hard to start and get parked
    USracer900 likes this.
  8. DonTZ125

    DonTZ125 Purveyor of Neat Toys

    When you clean the carbs, don't waste time cleaning the pilot jets; replace them with new, they're only a few bucks. The bores are extremely difficult to get completely clean, and are so tiny that even a small amount of plaque will significantly affect the flow rate.
  9. backbone

    backbone scarred for life

    Dirty carbs are #1 reason old bikes run like crap. People tend to think old bikes ran crappy when new :)

    99.99999% of the shops/garage mechs out there don't know how to take the carbs completely apart and clean properly.

    They say just drop them in a ultrasonic with this XXXX chemical and they will work great. True, they will usually run after that but not like they should.
  10. Banditracer

    Banditracer Dogs - because people suck

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  11. turner38

    turner38 Well-Known Member

    I would start by doing a voltage drop test to the coils and on the ground side. If available voltage drops below 11v or so they stop sparking. Many old bikes see drops across kill switches, ignition switches and some times the ground cable.
    USracer900 likes this.
  12. tony 340

    tony 340 Banned

    Where are the pics..?
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  13. RGV 500

    RGV 500 OLD, but still FAST

    Sounds like the pilot jet is having a bit of a bad day. Clean the carbs fully, or have someone do it. I recommend complete disassembly of anything that touches fuel at the very least.
    ungwaha and USracer900 like this.
  14. K51000

    K51000 Banned

    Show or hands. Just how often IS the problem, a BAD spark plug? But at the first cloudy day- it's the first thing people try.
    I'm not saying don't check them for sure, and yes, relatively inexpensive, but....
    It ain't a 2 smoker, and it ran OK before.
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  15. VFR#52

    VFR#52 Well-Known Member

    you have mail.

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  16. Clay

    Clay Well-Known Member

    I admit, I'd love a clean F3. My first sportbike was a 94 F2. I'd think that finding one, a truly clean one, would be damn hard to find. Then, if you found it, they'd want a ridiculous price!

    As far as what the other guys have said, a good carb clean will probably solve the issue.
    USracer900 likes this.
  17. USracer900

    USracer900 Well-Known Member

    Wow, you guys are the best! Looks like I'm gonna be doing some carb cleaning as well as a few other things. I did change out the jets on another F2 I had 10 years ago and made a big difference, hopefully a few youtube videos will refresh my memory. I've never adjusted valves though, may have to outsource that to our local motorcycle mechanic. I'm sure it's overdue for a valve adjustment. This should be a good winter project anyways, time to put her up on the wheel stands and get to work. Thanks a TON again guys, really appreciate the time you took to offer your expertise.
    VFR#52 and scottn like this.
  18. USracer900

    USracer900 Well-Known Member

    Thanks SO much Steven for the detailed email and advice, I really appreciate the time you took. Will order some new jets and get to work, I may pick your brain a little more down the road if I run into issues. Funny you mention to get a new petcock. This one is frozen up, won't turn at all. Thanks again!
    VFR#52 likes this.
  19. USracer900

    USracer900 Well-Known Member

    IMG_3588.jpg IMG_3643.jpg IMG_3645.jpg IMG_3738.jpg IMG_3729.jpg
    Here's a few pics of the F2 in question, the red wheels will have to go, plan on having them powdercoated black which was stock for that year. Picked up the 900RR last year, had the same one 20+ years ago. Fortunately it runs well, I try to start it up every couple weeks and keep things cleared out.
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  20. fastfreddie

    fastfreddie Midnight Oil Garage

    I motion for white wheels. :cool:
    pscook, Sabre699, VFR#52 and 2 others like this.

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