Solved: VFR750F 1988, (I thought) clutch was sliding after oil change

Discussion in 'Mechanics Garage' started by Dennis Micky Jensen, May 28, 2020.

  1. Dennis Micky Jensen

    Dennis Micky Jensen New Member

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    Hi guys.

    I just changed oil and oil filter on my VFR750F from 1988. Since I bought it 2 years ago, I've never had any problem with it.
    Now after oil and filter change, I did a 150km run in southern Sweden, and the clutch is sliding whenever I accelerate.
    So it's like, whenever I accelerate above 4-5k RPM (I think), it's like half a second of acceleration and then half a second of much less acceleration. It doesn't sound like engine is over-revving much. Does that make sense?

    There is a few pointers in the manual regarding clutch sliding, but it just seems coincidental, that this happens on my first proper ride after oil change. Not sure if it's worth sharing, but this is the first oil change I've done on the bike since I got it (yes I know, I should have done this every year).

    I spoke with a friend of mine, that I deem know a bit about MC and a bit older ones, and he said, that it could be the oil brand and the viscosity of it, that might be the case. That perhaps it's a bit too thin or the actual composition of the oil.

    Another thing: I actually did put on too much oil on the bike. Above the MAX on the pin when checking. I have after experienced this issue, tapped the excess oil from the bike. I haven't tried driving with that yet, but it was just to rule that out.

    So a few facts:
    • Bike has ran 54k kilometres
    • I don't know what oil or when it was last changed
    • I put on 3,8 litres of Castrol 10-40 semisynthetic oil

    I hope someone has a few pointers on what I can do and perhaps whats wrong.

    Also, I was planning to go on a ride today: Will that be safe, as long as I don't push it to when it starts sliding?

    Thank you on beforehand!

    VFRF for life.
     
  2. raYzerman

    raYzerman Insider

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    With that low mileage I would not expect the clutch plates to be worn out. Was the Castrol a motorcycle specific oil, JASO MA, or an automotive oil with energy conserving additives (what does the label say).
    The viscosity is fine and a little overfill is OK, neither should have caused your issue.
    Has the bike been sitting not ridden for some time?
     
  3. Dennis Micky Jensen

    Dennis Micky Jensen New Member

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    It was quite a lot of overfill (I think) actually.

    The bike has been standing still over winter in my heated garage. And I've probably had 500km this season since march with no issue, and I was riding all last summer.

    I'm at work now, but this is the oil I put on:

    [​IMG]
     
  4. raYzerman

    raYzerman Insider

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    I should say I've never had a VFR750, what is the oil capacity specified with a filter change? The only danger with overfilling too much is the oil level can get to the bottom of the crankshaft...
    The oil looks to be a motorcycle specific oil, would need to confirm with the label on the back. If so, for the moment, go for some more rides and see if the situation improves as the new oil gets into the clutch plates. It may or may not improve, but it may if the bike was ridden more.
    Does the bike have a hydraulic clutch? If so, ensure it is flushed and bled, not sticking. If cable, ensure clutch is not partially disengaged when lever is fully released.
     
  5. Dennis Micky Jensen

    Dennis Micky Jensen New Member

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    It is hydraulic... I haven't bled or flushed the clutch before, and looking at it now, it looks like the fluid level is pretty low actually.
    Is it possible to bleed/flush/refill the fluid without any special tools?
    My apologies if the question is dumb. I'm kind of a rookie when it comes to this,
     
  6. Captain 80s

    Captain 80s Member

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    "Bike has ran 54k kilometres"

    This is about the time that I do start wondering about clutch life. Plus you don't know how the clutch was used (or abused) for it's entire life not being the original owner.

    The hydraulic components won't make it slip unless the clutch lever is incorrect (I doubt it). That oil looks perfectly suited. Slightly overfilling won't make a clutch slip. Sometimes changing to a different type of oil that what it was used to can make symptoms of a higher mileage clutch appear sooner.

    Sounds like you need a new clutch. Don't forget to inspect the metal plates (which are probably fine) and definitely replace the springs. Easy job. And don't over tighten the clutch spring bolts.

    Bleeding a clutch is pretty much just like bleeding brakes. Same system components, think of the slave cylinder on the engine like a brake caliper.
     
    Last edited: May 29, 2020
  7. raYzerman

    raYzerman Insider

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    Clutch shouldn't be done at 54k kms I wouldn't think, I got shoes older than that, LOL. Clutch should go double that if not abused.
    However, a good cleaning of the clutch plates might be in order, along with a 5 minute soak in fresh engine oil. Check for weak springs while you're in there as weak springs can contribute to slippage. Measuring plate thickness will tell you if they are worn beyond limits.
     
  8. Captain 80s

    Captain 80s Member

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    "if not abused". No idea what life it had. If I'm taking the cover off and scraping gaskets, there's a new clutch going in at that mileage. Never have to worry about it again. And EBC springs are $10 free shipping. Not even worth my time to get calipers out to measure.
     
  9. Dennis Micky Jensen

    Dennis Micky Jensen New Member

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    Hi again guys.
    I really appreciate you guys taking your time to help me out.

    I went for another ride this weekend, and I tried to observe a bit more what was happening.

    So the things I have observed now:

    It actually doesn't seem like it's the clutch slipping, as the RPM's doesn't go noticeably up (as it does in some YT movies about clutch slipping) so I might have gone the wrong way around explaining this.
    It seems like in all gears, accelerating hard from low RPM up to around 5k is no problem at all. After that, throttling hard, it goes into a sequence of 1/2 second of accelerating and then 1/2 not accelerating. Around 120km/h I start to feel a lot of power loss.
    So what I've initially thought was the clutch slipping (could still be tho?), in the sequence of accelerating and not when throttling up, when the RPM goes up it actually DOES accelerate.

    So from my rookie perspective, it sounds like it doesn't get enough fuel or air around those 5k+ RPM when throttling up hard, or maybe even the spark plugs are worn down?

    I still feel this is a bit coincidental to happen after oil change, where I did overfill it unfortunately. I did drive around 120km with overfilled oil where everything was smooth, but then this started to happen. I did immediately drain the excess oil when I came home.

    After some more research, I had some pointers on perhaps checking the air filter (excess oil could have clogged it?). I've bought a new one and I'm replacing it right now.

    Thanks again for helping me out guys!
     
  10. COS_VFR

    COS_VFR New Member

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    Old hydraulic fluid in the clutch reservoir can clog up the small return hole and cause the clutch cylinder to retract slowly. This can cause the clutch to slip for a time after the lever is released. I would change out the hydraulic fluid before I did anything else and have a good look at the small return hole in the master cylinder.

    If the hydraulic fluid in the clutch is old, I would also replace the fluid in the brakes as it is probably old too. If the small return hole on the brake master cylinder clogs up, the brakes will drag and possibly lock up.
     
  11. Dennis Micky Jensen

    Dennis Micky Jensen New Member

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    Hi again guys, thanks for everyone contributing fail searching this issue!

    I managed to solve the problem!

    After last post, I replaced the air filter. It was dirty and old, so it needed a replacement, but it didn't solve the issue.
    I had a call with a MC shop, where I was gonna buy new spark plugs and clutch replacement equipment, and I explained my problem to him. He have had a similar issue with an old bike of his, and he said water has condensed in the carburetor, causing incorrect fuel supply, and that I should add some carburetor fluid in the gas tank and ride it for a bit. So I did. 20km and there was no noticeable effect, but then it suddenly started accelerating properly in right RPMs, and now the issue is non-existing!

    I'm so happy I managed to fix the issue. I will for sure need to replace the clutch fluid and get it bled, so I at least know when it was done the last time, but luckily the issue was not clutch related.

    Thanks for helping me out. I'm gonna have my bike repainted in a few weeks, and I'll make sure to upload some photos! Cheers!
     
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  12. Captain 80s

    Captain 80s Member

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    Good news.
     
  13. squirrelman

    squirrelman Member

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  14. Terry Smith

    Terry Smith Member

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    It is good when a supposedly serious problem has an easy solution. I had the opposite on my Suzuki RF900R which developed a lurch under acceleration which I was sure was electrical but turned out to be a failing 2nd gear issue (and many $$$)...
     
  15. ridervfr

    ridervfr Member

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    Draining carburetor bowls and siphoning old gas out of tank replenishing with new could work too. Have had my share of water in gas scenarios. Glad it was a happy ending, I luv those. Peace
     
  16. Dennis Micky Jensen

    Dennis Micky Jensen New Member

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    I will definitely have that in mind for next time. It looks like it's pretty difficult to get to the carburetor bowls however..

    Aww man that sucks. I hope you got it fixed eventually.
     
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