1986 VFR 750 Rescue

Discussion in '1st & 2nd Generation 1983-1989' started by vfrMatt86, Nov 29, 2019.

  1. vfrMatt86

    vfrMatt86 New Member

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    Hey guys,

    Well after keeping my ear to the ground for over a decade I've acquired my 2nd 86 VFR 750.

    This one is in it's original Red White and Blue livery and has only enjoyed 50,000km.

    The previous owner seemed to really care for the bike. It's got new tires, brakes, clean fluids, rebuilt forks, new clutch and is in very good spec for an 86.

    Apparently everything was splendid up until a couple months ago when the previous owner heard a loud pop and the bike was running rough. He rode the bike home (which was about 10 minutes) and then began investigating. He did a leak down and a compression test and concluded that the cylinder 4 exhaust valve was sticking and the loud pop he heard was a back fire from from an unseated exhaust valve during a compression stroke.

    Realizing that it was more work than he could handle he sold the bike to me.

    I can turn the bike over my hand and hear the valve slowly moving. Today I decided that I would try to turn the bike over with the starter and when I engaged the starter the relay just clicked. I jumped the relay and I can hear the starter spinning very quietly but the bendix is not engaging, so no metallic sounds at all. Just a quiet whirring.

    My questions are as follows:

    1. How common is it that an exhaust valve on a 50k vfr would get sticky. Would that be an indicator of a worn guide and how rare would that be for a viffer?

    2. Do the VFR starters fail with the bendix not engaging? I'm assuming he turned the bike over quite a bit trying to figure out the issues. Perhaps he fried the starter. I did hook the bike up to a healthy car battery so it's not a battery issue.

    Once I get more time I'll take the exhaust off and try to peak at the valve itself. Maybe get some penetrating lube in there. And I'll bore scope the piston to see if there is anything bent or any other damage.

    Does anyone have any other quick lead for me to chase down? I'm a novice mechanic and my other VFR's haven't given me any issues at all other than carbs and rectifiers so I'm not very knowledgeable about these bikes.

    https://drive.google.com/file/d/0B__Vem8Epky_TWxBWHF4ZmpyZFRBdnZzSDFSdldXem83ZUhv/view?usp=sharing

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    Last edited: Dec 2, 2019
    maduncle likes this.
  2. Captain 80s

    Captain 80s Member

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    So did anybody remove the valve covers and check the valve lash before coming to this conclusion? I would suspect tight valve clearances keeping a valve open before a "sticky" valve, but it's not impossible I suppose. Check the valve clearances (if that hasn't been done) and then recheck the compression and leak down tests.

    The starter clutches can wear out or fail on these bikes. Sometimes the outer housing that holds the rollers cracks. The starter motors themselves are fairly resilient but should be serviced periodically to clean out the brush dust accumulation and clean the armature.
     
  3. vfrMatt86

    vfrMatt86 New Member

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    I only got the bike a couple days ago and haven't personally taken the valve covers off yet. I don't think the PO did either. I'll definitely check that out.

    When turning the bike over with a ratchet you can hear the valve sucking back very slowly though.

    I'll rip the starter apart too. The PO said he turned it over recently but I didn't see it myself. Either way I don't think I can really go too wrong with this thing for the price I paid for it.
     

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