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Help FZR 250 R 3LN1 - Unusual sound and struggle between 5 to 9000rpm

Discussion in 'Yamaha 250cc In-Line 4's' started by Hk_Gks, Aug 11, 2024.

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  1. Hk_Gks

    Hk_Gks Member Premium Member

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    Hello everyone, I’m here because, since few days my bike is making a weird sound, from what I can hear coming out of the exhaust, the bike is a 1989 FZR 250 R 3LN1.

    She was running completely fine, I have it since April and done a little bit more than 3000km with it, but since 2 days, it sound weird, between 5 to 9000rpm, the sound is becoming deeper than usual, and the bike feel like it struggle a little bit, when it it the 10 000rpm, the engine goes and sound normal again, I know from the previous owner that the exup valve have a bit of play, you can here it while the bike idle or when you start to open the gas, could it be that? Or the carbs need a bit of tuning? Or is it the timing chain? When revving up at idle, it sounds perfectly normal, and the sound and struggle are not consistent.
    Other than that the bike work

    if you have any lead I’ll take it, I know it’s hard to visualise the problem but recording it is a bit hard.

    Thanks!
     
    Hk_Gks, Aug 11, 2024
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  2. an_anonymous_user

    an_anonymous_user Active Member Premium Member

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    Is it a sort of metallic rattle coming from roughly the exhaust collector? i've dealt with an FZR with a similar noise and similar power delivery issues, the issue there was an EXUP valve that rattled like hell. I'm not entirely familiar with the fixes for it but i know plenty of people have chatted about it online in the past.
    I might recommend that you try to inspect the play on the exhaust-side EXUP pulley, if it has a lot of slop side to side then that's probably your issue.
     
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    an_anonymous_user, Aug 13, 2024
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  3. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

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    It does sound like an EXUP issue - they do rattle, which isn't an issue affecting performance, it's worn bushes inside the exhaust itself and the cover plate which holds the EXUP in place on the exhaust collector.

    If it's not opening correctly then it will strangle the exhaust output, possibly causing what you're experiencing.

    There's a tang on the outside of the valve, which aligns with a 4mm (from memory) hole in the cover place which holds the EXUP - when powering on, the valve should cycle closed -> open and back and come to a stop where the tang and hole align.

    Check and adjust the cable to make sure that the tang and hole align - a drill bit works well to check.
     
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    ruckusman, Aug 13, 2024
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  4. GreyImport

    GreyImport Administrator Staff Member The Chief Contributing Member

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    GreyImport, Aug 13, 2024
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  5. Hk_Gks

    Hk_Gks Member Premium Member

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    Thanks for the answer! I’m kinda happy if it’s just that, I’m gonna check when I got time and I’ll come back here

    cheers!
     
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    Hk_Gks, Aug 14, 2024
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  6. Hk_Gks

    Hk_Gks Member Premium Member

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    Okay I cleaned the exup valve, it was really dirty, but what I noticed is that the exup valve motor sound a bit weak? Like it’s not going full power like I had before, it sound like as if there was no battery I would say

    The valve setting seems aligned

    so I guess the problem would come from the motor not following the gas opening?

    video here:
    https://youtube.com/shorts/MyL3pzc8law?si=57P7rEIoQOjUYl6X

    https://youtube.com/shorts/_DUr71-UO3g?si=LQw8F5_UpYQ7YB5u

    Don’t mind the other sound it’s the fuel pump
     
    Hk_Gks, Aug 17, 2024
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  7. Hk_Gks

    Hk_Gks Member Premium Member

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    I did a little test ride and I think I really come from the exhaust, I changed one of the cable of the exup valve, I will change the second one tomorrow, now it only make the deeper sound and struggle from ~6000 to 8000rpm (before it was between ~5500 to 10 000) and it’s not always, sometime there was nothing, then it was happening a bit, not on all gear, literally at one red light, I accelerate full power it was fine, next red light literally 200m away, accelerated and it happened. So I guess it can only come from the exhaust/exup valve?
     
    Hk_Gks, Aug 17, 2024
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  8. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

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    In the first video it looks to be opening correctly when you rev the engine.

    It's difficult to tell from the second video, however the cables can be too tight, which may be making the EXUP servo motor struggle during it's startup sequence.

    One thought: The cable that you used as a replacement, is it as flexible as the original cable, I know from when I replaced my EXUP cables, that I had to search for cable which was as flexible as the original.
     
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    ruckusman, Aug 17, 2024
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  9. GreyImport

    GreyImport Administrator Staff Member The Chief Contributing Member

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    Yes exactly what I was about to post .... tight cables

    Did you adjust the cable free play as per the info in the thread I posted earlier?

    I also lube up the motor end where the cables ride ..... and oil the cables
     
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    GreyImport, Aug 17, 2024
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  10. Hk_Gks

    Hk_Gks Member Premium Member

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    Yeah the cable are flexible, like normal cable I would say, might be a bit too tight yeah, but there 1,5mm or more of play, I’m gonna lose the cable a bit and see
    Might also lube the gears on the motors to see

    I did a little ride again today and now it’s worse, it doesn’t get high rpm properly like it really lack of power, couldn’t even hit 18500rpm on first gear and on 3-4-5 gears it would go pass 15000rpm, I guess the next concern might be the carburettors or ignition, it does stink like when it’s too rich now, which wasn’t before that.

    it’s just that is so random, sometime it happen sometimes not, sometimes more, sometime less, gonna check the spark plugs to see there, and then the carbs, think I’m gonna buy everything to make them “new” again.
     
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    Hk_Gks, Aug 17, 2024
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  11. Linkin

    Linkin The Mechanic - Moderator Staff Member Premium Member Contributing Member Dirty Wheel Club

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    More free play in the cables is better than not enough. Loosen them off more.

    Your symptoms of less and less RPM before hitting a wall indicate that it could still be the EXUP restricting exhaust flow, or that you have a fuel flow problem (aftermarket fuel filter fitted? Fuel pump still there and working?) OR a vacuum lock in the tank, which will be the drain/vent pipes being blocked up.
     
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    Linkin, Aug 17, 2024
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  12. Hk_Gks

    Hk_Gks Member Premium Member

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    I will

    and yes I changed the filter for a legit one from impex Japan, I changed the fuel pump because it was faulty, it work, the flow seems good even better than before, idk about the vaccum lock, I need to check on that.

    I’ll try to lose the cable more first and see.
     
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    Hk_Gks, Aug 17, 2024
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  13. Linkin

    Linkin The Mechanic - Moderator Staff Member Premium Member Contributing Member Dirty Wheel Club

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    When you experience the problem of being unable to rev it out, pull over somewhere, open and close the fuel cap, listen for a hiss or pressure release. If the cap is tight to lift up it is likely a vacuum lock.

    Then go and try again, if it works great but the problem returns after a while - vacuum lock caused by blocked vent hole. Inspect under the fuel cap, you can clear the vent holes with compressed air.
     
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    Linkin, Aug 18, 2024
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  14. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

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    You could also have more than one issue, EXUP not opening fully or properly, AND fuel starvation from a blocked fuel filter AND filters in the tank - need to remove the connection from the tank itself to check.

    The tip from @Linkin to check the tank vent is GOLD, it has happened to others.

    Carbs are an issue with the FZR250 - how many Kms has yours done?

    Do you know when the valve clearances were last done?

    BIG TIP - change only one thing at a time otherwise it gets messy and if you do solve the problem you know what caused it.

    My suggestion would be to work through this list in this particular order before removing and checking the carbs;
    1. Check fuel filters in the tank - clean if necessary -> test
    2. Check fuel level in carbs, this is a visual check with them attached -> test
    See this post for how to check visually with just a piece of clear tube

    https://2fiftycc.com/index.php?threads/my-fizzer.872/page-32#post-15537
    The fuel level should be 9.2mm above the casting line in the middle of the float bowl.

    hope this helps.
     
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    ruckusman, Aug 18, 2024
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  15. Hk_Gks

    Hk_Gks Member Premium Member

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    I bought the bike with ~38 200km and right now I’m at 41 200km with it

    apparently, from the previous owner, they did a little maintenance check, and I guess it was true since the bike was running very well until this problem arrived


    And yes I will do one thing at a time, I know how harder it can become without a little bit of organisation haha
     
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    Hk_Gks, Aug 19, 2024
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  16. Hk_Gks

    Hk_Gks Member Premium Member

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    Okay, little update, I loosened the cable a bit, motor seems to struggle a bit less, didn’t tried on road yet not much time, also I guess carburation is not the issue, I took out one of the spark plug and it look pretty good



    [​IMG][​IMG]
     
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    Hk_Gks, Aug 21, 2024
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  17. Hk_Gks

    Hk_Gks Member Premium Member

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    Okay, tried it, still no luck, and unlocked a new noise, idk if it’s the exup valve, seems to come from the timing chain, when in gear and slowing down I hear it, and when I pull the clutch, it stop, so it’s synced.

    no weird hiss or pressure sound when opening the fuel trap, fuel is going good.

    still struggling around 12k rpm, I can barely go above 120kmh now.

    I guess the exup valve and fuel is not the problem. What could it be now? Timing? Ignition? Carbs?

    the bike start with no problem and rev up nicely until 8-9000rpm
     
    Hk_Gks, Aug 22, 2024
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  18. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

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    These bikes are very fickle, if one or two cylinders are not firing properly, then the others won't overcome
    Work through in this order

    Timing - fixed, so rule out anything to do with adjustment.

    Ignition - trim the ignition spark plug leads at both ends, be careful at the coils with the small plastic clips as they are delicate.
    The plug leads unscrew from the leads, trim a few millimetres from the end and refit.

    The plug caps themselves have a resistor inside, check the resistance, there is a small brass screw, where the plug inserts, which can be unscrewed and the resistor is inside - check for corrosion and clean.

    The bike is now 35+ years old, so consider that there's likely some slight corrosion on those leads.

    Although your plugs look good, a small carbon trace can cause a misfire - worth replacing if they are not new or close to new.

    Carbs - Known issue, however check the fuel height first thing before going any further, refer: Fuel pump.
    Keep this for later - There is one known issue with carbs, and this depends upon whether the previous owner installed keyster kits.
    Note: In the keyster kits, the main jets between the inner and outer pair of carbs are in the incorrect boxes - the inner pair of carbs take smaller main jets and the out pair take larger main jets.
    If the inner and outer carb main jets are wrong, it won't rev properly past ~11K or thereabouts - because the two inner carbs are too rich and the two outer carbs are too lean - they are that sensitive.

    Fuel pump - The OEM pump is very low pressure, 1.5PSI - it's only there to fill the carbs when the fuel tank is low.
    Do you know if the replacement fuel pump is low pressure or an actual OEM pump?
    With a decent amount of fuel in the tank, it can run perfectly fine without a pump, so bypassing the pump is an easy step to eliminate it as a source of the problem.

    I am sceptical that it is carbs at this point because your issue keeps changing and it's not at idle RPM (chugging - known issue), but I do note that it didn't have this problem when you got it - correct?

    Knowing any details of work done on the carbs by the previous owner will help
     
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    ruckusman, Aug 22, 2024
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  19. Hk_Gks

    Hk_Gks Member Premium Member

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    okay I got rid of the fuel pump and put direct to the carbs, and now I don’t have that specific sound and no more power struggle, until 12 000rpm, now it struggle at that point, hardly pass it in 3rd, even in first in fact.

    https://youtube.com/shorts/LuJdAS0Pzl4?si=FcYqr8T_sa07hguW

    Here you can see it, normally at idle, it doesn’t take that much time to go high, that’s what happen, it take time to reach high rpm now, also idk if we can hear that rattle sound clearly on the video, coming from the engine.
    I’ve checked the timing chain tensioners few days ago, could it be that?

    also yeah planning to replace spark plugs, getting new ones tomorrow

    Other than that idk
     
    Last edited: Aug 23, 2024
    Hk_Gks, Aug 23, 2024
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  20. Linkin

    Linkin The Mechanic - Moderator Staff Member Premium Member Contributing Member Dirty Wheel Club

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    OK I have just watched all three of your videos.

    First one - I can hear a rattle or chatter on acceleration. It could be a lot of things.

    My suspects are:

    Chain and sprockets as the bike was in gear and on a stand. Some final drive noise is normal.

    The second suspect is that it could be the clutch basket. The rubber dampers between the primary drive gear and the clutch basket wear out and loosen, and after that the steel rivets into the aluminium basket can loosen, you will get a chatter under load at low RPM. The fix is a new basket, or if you are to repair it, it needs new rubber dampers and new rivets if they are loose/worn. It is quite a common repair done in Asia.

    Third suspect it could be the cam chain going, but this sound is a consistent rattle that gradually goes away as RPM increases, and returns immediately when you close the throttle.

    Fourth suspect, carburettor balance is way out and you will get all sorts of rattles from the engine, clutch and gearbox.


    Your second video shows the EXUP operating, and the fuel pump was screaming for mercy in the background. Was the fuel turned off or was the tank removed? If so, disregard. Otherwise, we are back to a fuel flow problem. In any case, these fuel pumps are low pressure units in the range of 1.5-3 PSI. When the carb bowls are full of fuel, the pump will click slowly or stop entirely. When fuel supply is cut off or restricted, they will click rapidly and make a lot of noise.


    Your third video - the bike has a misfire or the balance is way out. I would say misfire as it doesn't sound like it is running on all four cylinders until the revs get really high up and even then it sounds a bit poorly. The bike was running better in your first video.


    One more check to do. You will need a multimeter set to DC voltage. The battery should be fully charged first. You should measure the battery voltage with the bike idling and then held at 5,000RPM. The voltage reading should be 13.5-14.5 volts. If the reading is above 15 volts, you have a bad voltage regulator. Excessively high voltage can cause all sorts of problems, including running problems, so you should check it rule it out if you can.
     
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    Linkin, Aug 24, 2024
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