Welcome to Netrider ... Connecting Riders!

Interested in talking motorbikes with a terrific community of riders?
Signup (it's quick and free) to join the discussions and access the full suite of tools and information that Netrider has to offer.

FZR250 Trouble with revs

Discussion in 'Technical and Troubleshooting Torque' started by AeroJake, Apr 3, 2015.

  1. Ok guys back to bother you again,
    Just after some advice on what to check/replace regarding my issue.

    Im having trouble with the revs on my fzr 250 2kr non ex-up the bloody thing wont rev past 10,000rpm and sounds like it hits the rev limiter its like this from 1st to 4th.
    In 5th-6th once over 80kmh it has trouble reving past 8500-9000rpm its like a huge flat spot and takes a fair few seconds of holding the throttle wide open to start gaining speed again then hits the limiter at about 10,500rpm but at this speed the limiter thingy makes a noticeable mettalic tapping noise presumably from the top end.

    Revs all the way to red line at idle
    and runs great just ridding around town as long as I change before 10,000rpm and dont want to go past 75-80kmh in a hurry.

  2. #2 hawklord, Apr 4, 2015
    Last edited: Apr 4, 2015
    Something as simple as a partialy blocked fuel filter will cause this.
    Start with the easy stuff.
  3. oh, and another thing, FZR250s don't have rev limiters.

    Probably not a good idea to stand around revving "all the way to red line at idle"

  4. Hahaha yeah definitely not reving it like that lol just a quick flick up to 17,000 when shes nice and warm. Yeah ill check fuel delivery, plugs, and maybe carbs need a clean. Know where I can get new HT leads ?
  5. Ok so cleaned and gaped the plugs they looked ok maybe a tad rich though, also cut 5mm of the leads and screwed caps back in.
    Now I have the carbs off and as I was removing the main jets I noticed carb 1 had no spacer under the jet and carb 4 had 2 spacers also the jets on carbs 1 and 2 were fairly clean but 3 and 4 were covered in some sort of wet black oily stuff the bowles are also heavily tarnished.
    I reckon I spent more time getting them freakin screws on the bowls undone than removing the things from the bike they set in bloody tight had to cut slots in them for a flat head and impact drill. Hope I wont be doing it again any time soon lol.
  6. Don't ever leave home without your impact drill :LOL:
  7. Anyone know of other suitable fuel filters besides the yamaha 1FK-24560 ?
  8. It's an inline filter, any filter of the appropriate inlet and outlet diameters will work. Take it along to a Repco or other car accessories place and see what they have.
  9. Ok thanks was just thinking of the filter type and thickness dont want to restrict fuel flow.
  10. The cam tensioner on my bike is manually adjusted any ideas on how I can check it?
    I found a write up for the auto tension ones but not manual.
  11. I want to check my cam chain tensioner its not a auto tensioning one.
    Is there a guide I can follow or is it fairly simple.
  12. Ok so it is auto tensioning I could pull the plunger out 7mm I think thats within spec
  13. Anyone know the float height for 2kr carbs there the stock mikuni bds-26.
  14. If you have pulled the tensioner out, there is a risk that the chain can jump a tooth on cam or crank. Should perhaps pull rocker cover & check cam timing just to be sure. 7mm of adjustment left in the tensioner is ok, though not perfect. Make sure you back the tensioner off completely before installing.

    I usually make sure the float arm is level with the surface that the fuel bowl seals on. Tilt the carbs so that floats are hanging freely, then tilt back until the floats swing back in & just close the needle valve. Float arm should be close to level with gasket surface at this point. The little metal tang which contacts the needle should also be close to level with the arm.
  15. Hey Tinkerer,
    Thanks for the reply.

    Not real keen on removing the rocker covers as I'll need new gaskets and no one stocks them locally I've never actually heard of them jumping a tooth from removing the tensioner and never had this problem with cars which I've done plenty of but I spose ill find out when I start her up,
    I am more after the height between the bowl lip and top of float when the carbs are tilted just enough so the tang is resting on but not compressing the needle valve I have them set at 14mm atm but want to make sure before putting them back in.
  16. #16 AeroJake, Apr 8, 2015
    Last edited: Apr 8, 2015
    Hey guys I have found that the hyosung gt250r uses the exact same bds26 carbs, There float height is specified to be at 17mm would this float height be the same for the bds26's in my FZR

    If this is the case then my floats were way out of spec ive had to bend the tabs a considerable amount just to get 14mm.

    Also when I first pulled the carbs I could see that the floats in carbs 3-4 where heaps lower than carbs 1-2 see pic.
  17. Ok I have found that the right setting is between 17.5mm and 19.5mm this would mean that to reach this setting I would have to adjust the floats 8mm lower on carbs 1-2 than what they originally were set at and carbs 3-4 would need 13mm adjusting as they were roughly 5mm lower than carbs 1-2.

    Is it right that my bike should have even been running with the floats being so far out of spec ?
  18. The floats only provide the fuel reservoir in the float chamber. If it is too low then you will get hesitation in sudden acceleration as the fuel reserve is depleted and before the fuel pump can refill. If it is too high you will get fuel overflowing out the drains. Too low should not affect cruising performance but will bog down when you reach for the power suddenly.
  19. well glad I didn't go and reassemble setting them at 17.5mm with the ruler method as I just found out that the 17.5-19.5mm setting is measured by using a clear tube on the drain hole measured up against the carbs when installed.
    I could imagine it would have been extremely lean lol anyhow I figured by the ruler method it would be close enough to 10mm and the 3ln's use 10.5mm using the ruler method this would be what carbs 1-2 we're at when I pulled them from the bike but 3-4 would be where my problem is.
  20. FAAARRRRR out ive just about had it with these freakin carbs now im hearing the 17.5mm should be measured using the ruler method (bowl lip to top of float) I cant seem to get a straight answer out of anyone on this matter?
    I rang the local YAMAHA dealer they said they can't service the bike because they can't read Japanese nor would they clarify were this measurement should be taken from.