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Old man and a VF750 Sabre

This is a discussion on Old man and a VF750 Sabre within the NEW MEMBERS READ HERE! forums, part of the Caferacer.net Forums category; Originally Posted by Cyorg Have a read here. IMHO, there are a couple of other factors that he doesn't discuss., but ... if you need ...

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Thread: Old man and a VF750 Sabre

  1. #21
    Senior Member XB33BSA's Avatar
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    Quote Originally Posted by Cyorg View Post
    Have a read here. IMHO, there are a couple of other factors that he doesn't discuss., but ... if you need to, having the cams and followers redone where he suggests will likely get you more miles than you'll want.

    https://www.motorcycleproject.com/te...cams_what.html
    thanks for posting that
    i learned a few tidbits and the writer is i feel 100% spot on in every detail of issue

  2. #22
    Senior Member Cyorg's Avatar
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    Quote Originally Posted by XB33BSA View Post
    thanks for posting that
    i learned a few tidbits and the writer is i feel 100% spot on in every detail of issue
    He (again IMHO) misses at least two factors that can contribute depending on engine condition ... plus oil sometimes is a factor. Mineral oil breaks down fairly quickly right from the get go and it generally starts to show on the cam and followers first, so I don't think he is entirely correct there .... plus all brands of oils are not created equally. I would use a high quality oil and change it reasonably frequently. So while maybe not a cause, its something that should be factored in.

    Have a look at an oil flow chart for those engines V45 and V65, both Magna and Sabre. You'll spot a contributing factor that he missed. Albeit minor, but it can be a contributing factor.
    If both the lobes and the followers are sufficiently hardened then it's not much of a concern. The other thing he missed is that any extra clearance (and best they be at the minimum end of the spec) in the cam bearings allows the cams to oscillate slightly. The ends of the cams are supported by the cam bearing cap on the top, but there is not much of a bearing surface in the head on the outboard end. There are only two lobes on each cam and they are not at full lift at the same time.... this will cause the cam to rock within whatever clearance there is. The cam holding tool that they came out with that was supposed to be used when setting valve clearance speaks to the fact that there was perhaps a little more clearance between the cams and bearing surfaces than there should be in some cases. Ideally you want the cam lobe and follower surfaces to remain perfectly parallel so the oil has a better chance of doing its job. If the cam is rocking or oscillating the follower (or lobe) acts like a wedge and tends to force the oil off to the side instead of providing that protective layer..... again sufficiently hardened cams will tolerate this to a higher degree.

    Although from time to time I'm full of shit, I'm reasonable confident of this one.

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    Last edited by Cyorg; 01-17-2019 at 02:59 PM.
    "Non urinat in ventum"

  3. #23
    Senior Member XB33BSA's Avatar
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    yeah but i aqlways wondered e4xcactly why the lobes on the honda cast iron cams chunked-out
    his explanation covers that
    i have talked to whats her name the chic that owns web cam
    her main thought is the overly thin hard layer on the honda followers combined with a soft underlayer
    inow i am speaking of like a cb350/450/xl350 cam sounds like the v4 exaberates things with its higher spring pressure
    at web cam theym use good old farm implement hardfacing applied with an oxy ace torch process
    of course grinding theb correct tradius in the correct orientation is critical
    even the follower profile is quite diff between cb350 fat cams and all the later 312's
    i think for thjese old bikes a plastic cam or plastic follower would be tits
    my 350 that i flog has nos cam and followers that i have coated with kg gearkote
    i also have the cb450 primary drive gear set upgrade which gives more oil all the time via 10% increased primary shaft rpm
    i am going to say that i believe lots of wear comes on cold startup and an impatient rider
    but yeah the hondas have shitty followers too thin and they cannot handle abuse

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  5. #24
    Senior Member XB33BSA's Avatar
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    na its not the tilting or unerven pad contact
    it will maintain flatness and remember the 2 valves and spring sets are soft flexible loads that do not control the followers flatness to a cam lobe ate all
    if some movement of the follower is needed to stay lobe flat it will simply lift one valve slightly,very slightly behind the other

  6. #25
    Senior Member Cyorg's Avatar
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    Quote Originally Posted by XB33BSA View Post
    na its not the tilting or unerven pad contact
    it will maintain flatness and remember the 2 valves and spring sets are soft flexible loads that do not control the followers flatness to a cam lobe ate all
    if some movement of the follower is needed to stay lobe flat it will simply lift one valve slightly,very slightly behind the other
    I'm not saying "its the reason", it is simply one of the factors that can contribute to the wear. If the cam bearings have any "extra clearance" and lots of those V4 engines do, whichever end of the cam that happens to be opening a valve will be forced upwards to the extent that the clearance will allow. This means that the cam will not be running perfectly true. When it lifts the valve at the other end.... the opposite occurs. The follower rotates on a shaft, it is not a floating rocker that can align itself. The 2 valves on one rocker has nothing to do with rocker/lobe alignment unless the rocker pivot shaft clearance enters the knackered category.

    As for the rest of his comments I'm not saying he's wrong.... just missed a couple of factors.
    "Non urinat in ventum"

  7. #26
    Senior Member TrialsRider's Avatar
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    My trials bikes have roller rockers and roller bearings on the cam shaft, SOHC 4 valve, very slick. They should all be built so well lol valves are super easy to adjust once you pull the engine.

  8. #27
    Senior Member Teazer's Avatar
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    OK, so back to the plot....

    Notice the second bike has modern USD forks and needed a specially machined top triple clamp because those USD forks are too short for that chassis. Check the fork diameter and if you want an upgrade, see if you can find a pair of legs say 2mm larger and the same length and have the triples machined to match them. The builder appears to have filled in the rear of the tank where the seat fits into indents. That could be a lot of work or a lot of filler.

    The first bike seems to be a photoshop mash up and has those stupid Firestone/Coker tires which have no place on an actual motorcycle IMHO. Steer well clear of them. I like the re-shaped side cover and seat fairing but that could also be a lot of work. Maybe cut the stocker down and use it to take a mold for the real thing. It's on youtube and you can see the image morph. I like that half morphed look, even though they didn't do that - maybe because they didn't do that.

    I'd avoid clipons below the triple clamp on such a large/heavy bike, but wither of those samples works as an idea generator.
    Last edited by Teazer; 01-17-2019 at 09:16 PM.

  9. #28
    Junior Member bachelorb's Avatar
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    Quote Originally Posted by Cyorg View Post
    Have a read here. IMHO, there are a couple of other factors that he doesn't discuss., but ... if you need to, having the cams and followers redone where he suggests will likely get you more miles than you'll want.

    https://www.motorcycleproject.com/te...cams_what.html
    Thanks..... I’m hoping I won’t, but if I do, I’ll sure look into this a bit deeper.
    Brad Bachelor
    "Marrying an old bachelor is like buying second-hand furniture." - Helen Rowland

    Current: 2018 CBR300


    Former Rides: 1971 Honda CT90, 1973 Honda CB175, 1978 Yamaha XS650, 1981 Honda CM200T, 1983 Yamaha XJ650 Turbo,1983 Honda VF750S, 1985 Kawasaki GPZ550, 1989 CBR600F1, 2006 Yamaha TW200, 2006 Suzuki GZ250, 2014 Honda CTX700N

  10. #29
    Junior Member bachelorb's Avatar
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    OK... 7 months later, a new kidney in the family, and a lot of thinking and not much doing.... but I think I've got a plan.

    There were four bikes that meant a lot to me over the last 40 plus years. Two Honda's (a CB175, and a CBR600) and two Yamaha's (the XJ Turbo and the XS650). I'm thinking about incorporating parts of these four bikes into the Sabre while trying not to make it look like a train wreck. For example, I hate the look of the Sabre's instrument cluster. I think I can replace it with an XS650 cluster. It would take some doing (including the swapping of a electric speed sensor for a mechanical one), but things like that.

    I think this would be more of a GT build than a racer build. One of the things I have loved since the CB900 days was the Hondaline sport fairing. Well. this bike came with one of those, but the moment I add it, that bike will be heavier than a dead preacher. Than again, I would like the bike to handle as well as possible.

    Anyway.... Still thinking... It's dusted off and in the garage again, waiting on a new starter. Should be here any day......
    Brad Bachelor
    "Marrying an old bachelor is like buying second-hand furniture." - Helen Rowland

    Current: 2018 CBR300


    Former Rides: 1971 Honda CT90, 1973 Honda CB175, 1978 Yamaha XS650, 1981 Honda CM200T, 1983 Yamaha XJ650 Turbo,1983 Honda VF750S, 1985 Kawasaki GPZ550, 1989 CBR600F1, 2006 Yamaha TW200, 2006 Suzuki GZ250, 2014 Honda CTX700N

  11. #30
    Senior Member TrialsRider's Avatar
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    After giving your situation serious consideration,

    I think you should strip it right down and turn it into a competition flat track racer
    start it with a roller starter.

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