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Project A different kind of motorcycle engine rebuild

Discussion in 'Other Projects - Other Bikes (non 250's)' started by Jethalter, Jun 6, 2019.

  1. Jethalter

    Jethalter Active Member Premium Member

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    Hey guys,

    Just thought i'd post this up here, bit more of a completed project / story telling.
    A good mate of mine a few years back brought a 82(maybe83) Honda CX500 Custom for a bargain price (under $1k), all original and most of the bike was in quite good condition. What makes this motor unique is its a horizontally opposed 80 degree v-twin engine with the heads twisted at 22 degrees opposite to each other, its also shaft driven but there are a few bikes with that. The horizontal v-twin certainly sounds different compared to a regular 90 degree v-twin.
    Because it sat in a shed unused for about 10-15 years.
    Anyway, he finally got it on the road at the start of the year and was so stoked to ride it, its certainly a different kettle of fish and with a more unique motor than most other motorcycles out there.
    After he had it all rwc, left the original paint and everything, he rode it for about 2 weeks and on one particular ride to work, he noticed the temp getting up there. So he was able to put some water in the rad and get to work(not too far away) but sadly on his lunch break, he checked over the bike and the bike had prepared him a nice fresh creamy soup in the sump. Whilst he was surprised the bike prepared him a meal in a bowl already, he was rather upset.
    He gave me a call and i was there about an hour or so later on to pick it up and put it in the back of the ute.
    I got the bike back to my place where i started check over a few things, told him a couple of options it could be and he said replace the head gaskets and go from there. I said considering how old the motor is and since its out, freshen up the whole motor with some new seals and everything else to give it a bit better bill of health (rebuild heads, retain old valves if good, new stem seals, piston rings, timing chain etc....) anyway he was pretty set of just doing head gaskets, so took the heads apart, cleaned it all, new gaskets then reassembled it all. He started it and low and behold, still had his creamy soup.
    At this point it was apparent that a seal has gone or he had a more severe issue, i convinced him to let me tear down into it and freshen it right up, make it last another 20 years or more with the right care. He did oblige(it took a lot of convincing to get him to agree to all the work and little bits i wanted him to do) and more or less this is what followed.

    Just to report the bike is running very well now, has more poke and power than before. It runs so much quieter and smoother than previously its unbelievable, to the point you wouldn't think its the same engine. And to date, this would be one of his best bikes. Hope you guys enjoyed the story.

    So the work i did as follows :

    Full engine teardown.
    Heads check level and dye crack checked, new stem seals and springs pressure tested, valves light coarse and finely lapped to seat.
    New genuine piston rings, new rod bearings(couldn't locate new crank bearings), new timing chain, new timing chain guide, new oil pump chain.
    New stator.
    Full engine gasket and seal kit, including new mechanical seal.
    Lots of cleaning of internals and internal channels/passages.
    Full exterior clean, prepared and repainted entire engine, hand painted Honda detailing
    Mechanical fan to electric fan conversion (using donor suzuki across fan).

    Anyway here are the pics, most of it self explains it all.
    Just a few points to note, The tool that locks cam and crankshaft is no longer available and i made up the equivalent, This has a few very precise points or mainly the drill holes and the tooth to mesh with the gears with no slop.
    The gearbox is a cool feature, literally removing the entire assembly.
    There is a good reason why if you must remove the rear case, you would most definitely do the mechanical seal if you dont know when it was ever done or is anywhere near this dirty. The before and after pics of this speak for themselves.
     
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    Last edited: Jun 6, 2019
  2. Jethalter

    Jethalter Active Member Premium Member

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  3. Jethalter

    Jethalter Active Member Premium Member

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    IMG20190214213827.jpg
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  4. Andych

    Andych Well-Known Member Premium Member

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    Nice work... I have always liked the CX500, problem is everyone has twigged they are a nice bike and look good stripped back a bit so prices are always high.
    this one looks like it is good for another 20 plus years.
     
  5. Murdo

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

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    Nice work. :thumb_ups:
    I hope you put a piece of rubber under that mount at top of radiator to stop it rubbing through the tank.
    (You do know that a 'horizontally opposed V twin' is an impossibility. Horizontal means flat like a BMW, V twin can be any angle of 'V' like the 15 deg of 1920's Lancia car engine to 45 deg of Hardley/Indian to 105 deg of 1930 Moto Guzzi.)
     
  6. Jethalter

    Jethalter Active Member Premium Member

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    Well it kinda is, same orientation as a boxer/flat motor, its just got V cylinders uptop. The difference is its alignment in the frame is different to most V twins, anyway why you getting all nit picky, just enjoy the story :p

    The CX with the way the engine is mounted and designed is one of the only bikes to include knee heaters. And you notice it.
    The downside of the design is that the bike when your riding it, does feel very top heavy. Its a different feel.
    My Cruiser is like a go-kart/lowrider, that low your sitting on the asphalt, The suzuki across (and other sport bikes ive ridden) feel not quite as low but low weight and nothing heavy uptop. The CX feels kinda like a 4x4/dirt bike with its height but more importantly there is a top heavy nature.

    Other things that were done, was freshen up with new thermostat, housing o-ring and all the pipes got new o-rings. When i get the chance i'll put a pic of the entire bike up. Gotta go through all the pics and find one.

    Also one detail i forgot to mention, the mechanical fan to electric fan swap. With this there is sweet fek all room for a fan and most of the cx people cut the end of the camshaft(thats right) to fit one. I refused to do such and was able to mount and offset the suzuki across fan in such a way that it just clears.
     
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  7. Murdo

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

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    Wasn't being picky, just getting the right terminology for the young ones. :) You've done a great job of rebuilding it, and I did indeed enjoy reading your story. Keep it going.
    Perhaps a longitudinal V twin would be the correct term (as in the crankshaft runs longitudinally in the frame and a Hardley Rideable runs across the frame).
     
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  8. Jethalter

    Jethalter Active Member Premium Member

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    Would be more fitting i guess.
     
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  9. risky

    risky risky

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    top job.
     
  10. Linkin

    Linkin The Apprentice Premium Member Dirty Wheel Club Contributing Member

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    Looks really good, professional job. Would have to pay top dollar for something like that at a bike shop.

    Colleague at work has a cx500 custom thing. It needs headgaskets because they're leaking coolant out. Also has an oldish xj900 he is cafe-ing... but done in good taste and professionally.
     
  11. GreyImport

    GreyImport Administrator Staff Member The Chief Contributing Member

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    I bet he drinks Latte

    :cool:
     
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  12. Linkin

    Linkin The Apprentice Premium Member Dirty Wheel Club Contributing Member

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    He's from the Philippines mate, I don't think he knows what a latte is either :prankster:
     
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  13. Jethalter

    Jethalter Active Member Premium Member

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    Its quite an improvement over what he had in there originally. A few things could have been done a little better but its quite good still.

    The great thing about CX500's is for your mate to do head gaskets , its super simple and easy as. So long as he doesn't be silly its almost a cant muck up scenario. If i was to do head gaskets on one again and rebuild them, i would say i could take the heads off, full strip, rebuild them and refit and have the bike running in 2 hours. They are so great to work on in that regards.

    The only downside is i found the valve clearances very very touchy, since they are a push rod motor(think of it as a V8 but a V2), when you adjust and set one side of the inlet, the other side of the inlet gets set and then the first inlet reading is out. This is due to using a single pushrod on a twin rocker assembly, there is however minor flex in it. So they need to be progressively set both at the same time to minimize this. Its a minor thing but just makes it a touch difficult if you've never set it before and cant quite work out why its changing slightly.

    The valve clearances call for 0.08mm inlet / 0.10mm exhaust. This is the most touchy esp on the inlet side. I set them to 0.10mm inlet and 0.12mm exhaust which was balanced quite easy. This summer will be due for a recheck. So far however, no tappet noises or such that you can get from excessive clearance and its all nice quiet and smooth.
     
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