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Help fzr250 low top speed for gear

Discussion in 'Yamaha 250cc In-Line 4's' started by J127, Dec 21, 2019.

  1. J127

    J127 Member

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    I have a 1988 fzr250 (exup model), im in the process of sorting all the issues and ive come accross a problem where at max rpm bike will only do 80kph in 2nd 100 in 3rd 130 in 4th , thought this is way lower than it should be, im still waiting on exup cables in the mail so ive held the valve open to simulate how it should be for above 11k rpm, when i give it full throttle once it gets to about 12k it accellerates quickly to redline however im getting quite a low top speed per gear, i was thinking it has to be the clutch but was wondering weather anyone else has had these same problems with a different cause because clutch seems to feel fine otherwise and no clutch burning smell
     
  2. Linkin

    Linkin The Apprentice Premium Member Dirty Wheel Club Contributing Member

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    Japanese imports of this era have a speed restrictor circuit within the speedometer that will prevent you from exceeding 180km/h. They can be defeated through various means (for track use of course :thumb_ups:)

    For perspective, my Malaysian ZXR250C without a speedo restrictor was good for 210km/h indicated on the speedo with me on board. On my 3LN FZR's I had trouble exceeding 180-190km/h. All had speedo restrictors.

    The EXUP provides smooth power and better torque in low-mid range, and helps to remove the torque dip commonly found at half of peak torque in the rev range. If the valve is fully open and not shut or partially open, you should not have any restriction when revving out.

    The bike is 30 years old. They all need maintenance. I would suggest that if you are chasing the most performance, start with doing all the maintenance that has been neglected over the years... Tight valve clearances will cause hard starting, hot running and lowered compression. Properly setting the clearances is gaining free compression for not much work. Other than that, carbies.

    A compression and leakdown test will assist you in determining whether the engine is worn out or not.
     
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  3. my67xr

    my67xr Bike Enthusiast Staff Member Premium Member Contributing Member

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    You won't get a burning clutch smell on a wet clutch, but you'd definately feel it slipping if it was.

    Do you have standard gearing in it still, 17/56 ?
    The lower speed's through the gear's could be a few thing's, you are losing between 30km/h and 40 km/h out of 2nd, 3rd and 4th

    I would start with valve clearance's like @Linkin mentioned, then check out your spark plug's, coil's and carby's
    The carby's could be partly blocked through the jet's and various circuit's, or could have float height's incorrectly set.
    Intake manifold's would probably be cracked and leaking if they haven't been replaced for a while, airbox to carby boot's may have shrunk and letting in extra air too.
    Another thing that make's a difference is the air filter if it's clean or not, could also be a blocked fuel filter or pick tank pick up filter or fuel tap
     
  4. Gen

    Gen Active Member

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    I have to disagree , I had clutch slip in 5th & 6th gear on my "salt" Mc19, I rode around the slip in top, 1/2 throttle, but by the end of the timed mile, my nostrils were filled with burnt plate pong.
    At least I didn't blow it up that year
     
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  5. my67xr

    my67xr Bike Enthusiast Staff Member Premium Member Contributing Member

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    Ok you might smell it in extreme case's, would be a combination of burning plate's and gearbox oil, when i had a slipping clutch in my FZR i didn't keep the power on.
    Did your CBR slipping clutch smell anything like catfood like when a car clutch slip's badly ? lol
     
  6. J127

    J127 Member

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    Swt thanks for advice I will do a compression test and check valve clearances aswell, I already knew I'd need to check this stuff aye just thought some seasoned fizzer owners to see if there's anything else I've missed
     
  7. J127

    J127 Member

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    I think it is highly likely to be clutch , today I just held it at 14k rpm and the speed slowly climbed , I'll still do all the other maintenance valve clearances etc (was planning to do after xmas) and I'll replace the clutch aswell, I'll also chuck those exup cables in as soon as they arrive because I'm sure the instant power at 11k doesn't really help the clutch situation, I couldn't smell much just smelt a slight burning smell, probably because I was sitting up cruising at 150 trying to understand why this was my topinion speed in 6th haha
     
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  8. J127

    J127 Member

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    I kept the power on to see what it would do today, slowly gained speed sorta like the early 2000's cvt's when you punch the throttle or a carbureted petrol 4 cylinder 90's economy car
     
  9. J127

    J127 Member

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    All my filters, sparks and everythig are new , intake boots do have hairline cracks got some new ones on the way in the mail, gearing is standard I checked today, I'll keep sorting through issues when I can afford it and hopefully this fzr will be running mint in no time, cheers for the replies everyone , can always count on this forum when I need some advice
     
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  10. ShaneP

    ShaneP Well-Known Member

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    If you have a slipping clutch, one thing to look out for is the wrong oil. Car oils has friction modifiers and will cause clutches to slip. Also, avoid Pentrite oil, we (at work) have our suspicions about that one. Motorex would be my recommendation.
     
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  11. Gen

    Gen Active Member

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    Yep. Penrite fully synthetic was the reason my clutch slipped, I'm sure, previously, I'd gotten away with Penrite 10/30 mineral oil, no sign of slippage, although the bike seemed to be developing MUCH more power after changing brands of methanol the year the clutch slipped.
    Barnett clutches sponsored a full set of ultra thin Kevlar friction, and steel plates before the bank went bust & I retired
     
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  12. my67xr

    my67xr Bike Enthusiast Staff Member Premium Member Contributing Member

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    I am running Penrite 10W30 Semi Synthetic in my FZR250R, with Kevlar clutch plate's and haven't had any problem's
    SCA_519015_hi-res.jpg
     
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  13. Murdo

    Murdo The Good Doctor Staff Member Premium Member Ride and Events Crew Contributing Member

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    I use the Barnett kevlar kit in my CBR drag bike and Castrol GPS oil with no signs of slipage.
     
  14. ajb0235

    ajb0235 Active Member

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    I had a similar problem with my FZR 250. Firstly the EXUP cables were connected the wrong way round. So I had no torque at low revs and a restricted exhaust at high revs. Changing the cables over are a big difference.alsoI found that the bike was restricted. Removing the restrictors , about 17mm diameter from the inlets made another big difference
     
  15. my67xr

    my67xr Bike Enthusiast Staff Member Premium Member Contributing Member

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    Any picture's of the restrictor's? never seen them in my 2KR or any of my 3LN engine's
    There's non pictured in the part's manual's either.
    17mm is a huge restriction for a 26mm or 28mm carby
     
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