Strange engine stuff

Discussion in '4 Stroke Bicycle Engines & Kits' started by xXNightRiderXx, Oct 11, 2019.

  1. xXNightRiderXx

    xXNightRiderXx Active Member

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    So, I just squeezed in some Lucas Oil treatment for my engine oil, and in the process, noticed some lags in my engine that sounded like some internals were grabbing in some way. I'm thinking it's the conrod, crankshaft, or the needle bearings...

    The issue is that I've never opened up any engine, so idk what's going on with it. I know it has something to do with wear though. I need to get some replacement gaskets before I open it up. Any ideas as to what it could be?
     
  2. waynesdata

    waynesdata Active Member

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    I would not spend much to fix that engine. The predator is only $99 here. I did a quick search for rebuild kits, but found nothing only 212cc stuff. I guess people do not rebuild 79cc engines? If that is the case I may start looking at 2 stroke engines.
     
  3. xXNightRiderXx

    xXNightRiderXx Active Member

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    I refuse to pay $200 just to get a two stroke that will be reliable for this bike. Those china engines I won't even look at anymore. I need cheap reliable. I don't mind payin $99 every two years. All I'd have to do really is just swap the head over to the new engine.

    I may attempt another two stroke build sometime in the future, but not now. My budget is far too tight at the moment to deal with constant engine failures, or to build my own engine (parts, I've noticed, are really easy to get). And yeah, I really don't understand why there aren't as many upgrades available for the 79cc when you can get the same 6 horses of a stock 212 with the same reliability but less displacement.
     
  4. waynesdata

    waynesdata Active Member

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    You are MUCH farther along than I am. If I had a 79cc and jackshaft kit I would not look at a two stroke. Still building a bike from a pile of parts to motorize.
     
  5. xXNightRiderXx

    xXNightRiderXx Active Member

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    What can I say? Two strokes are just high torque, high rpm beasts when done right! There aren't many four stroke engines that can claim 12,000 rpm like several of the really nice two stroke engines. Mazda's Wankel is the only one that can come close, or even exceed that, and that's just because it's a rotary. Not even a stroker.
     
  6. waynesdata

    waynesdata Active Member

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    Starting from scratch what engine would you pick and why?
     
  7. xXNightRiderXx

    xXNightRiderXx Active Member

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    Oh boy, I could run away with this question, but I'll keep it tame.

    I would still go with the 79cc. If I have a bigger bike that can fit it, then I'd go 212 simply because of the available upgrades, and way more power than the 79cc. However, the 79cc is a decent, reliable crate that can do pretty good for power if you have your own cnc machine. You can make your own parts. 3d scanner + cnc means one can scan a part, beef it up or make it lighter in a CAD, and then form that part out of raw aluminum. Also, a cnc machine means high precision, high reliability head milling. A solid, flat surface every time, precisely milled to exactly the dimensions set in the CAD program.

    Then again, I could go two stroke again, but build it from scratch. I would start with a high quality case, and then build the motor with handpicked parts, starting with the crankshaft, jug, conrod, piston, and clutch. Also, while building this engine, all internal parts that are not the clutch will be soaked in two stroke oil prior to assembly. This way, I can ensure proper lubrication during assembly and any excess won't cause much harm at all. The clutch will be separately lubricated. I'll do as I suggested a few times already: take a syringe with a small tube, grab some heavy grease, and very carefully apply a dollop of grease to each bearing in the clutch before spinning it to distribute that grease. They never lubricate these clutches and it pisses me off. Bearings anywhere need to be properly lubricated so they don't damage themselves under load.
     
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  8. curtisfox

    curtisfox Well-Known Member

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    212 is to big for a bike unless you are ready to build special wheels and reinforce the frames, or build special ones. Motorcycle brakes, hubs, and heavy spokes. If not sooner or later you will have a big problems.
    Sure would be nice if they mad a predictor motor in between 212 cc and 79 cc, like a 140 cc..........Curt
     
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  9. xXNightRiderXx

    xXNightRiderXx Active Member

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    Sure would. It would also be nice if they made more performance parts for the 79cc. But, since that won't happen anytime soon, I'm not too optimistic about a whole new engine comin out.
     
  10. curtisfox

    curtisfox Well-Known Member

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  11. xXNightRiderXx

    xXNightRiderXx Active Member

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  12. waynesdata

    waynesdata Active Member

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    IMG_20191028_153839.jpg
    I have a bike that would fit 212. Just think the 212 is too wide. I am split between 69cc SuperRat two stroke and 79cc predictor 4 stroke.
     
  13. xXNightRiderXx

    xXNightRiderXx Active Member

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    The two stroke is definitely a lower profile motor, but the 79cc predator can certainly hold its own, and it sounds nice. If you can ship it to AGK, they'll install a bunch of their parts for $700, but these parts are only available for stage purchases. However, you will be able to swap these parts out if you have to buy a new motor, so in my opinion, it's worth it. You get an adjustable flywheel, custom ground cam, porting and polishing, head milling, 19mm carb and manifold, governor removal, etc. All in all, its really more about what you want out of it. Imo, four strokes are good for commutes, while two strokes are good for pure race power. They don't last as long anyway, so why not just suck as much power out of the machine as you can, right?
     

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