my motor kit arrived but possible problems?

Discussion in 'General Questions' started by Yeshua, Sep 13, 2016.

  1. Yeshua

    Yeshua New Member

    So my 66/80cc flying horse kit arrived all parts were there in good condition for the most part. They sent me a slant head instead of flat head I ordered. My tank had a slight ding and a slightly skewed mounting bolt no rust inside.
    Gonna put jb weld at the mounting studs weld to prevent possible leaking. Gonna replace all kit studs with BBR engine studs and replace wheel mount studs. One possible issue is there's a visible gap between head and cylinder body head is not flat and smooth head and cylinder sides have a noticeable combined gap like 1/2mm to 1mm. They're not straight on either side and the original studs are really tight but the gasket isn't flat and definitely not air tight. The gasket is aluminum. The 2 sides don't contact each other either but the studs are tight.My Questions #1 Could it be possible they weren't tightend all the way at factory. #2 how do I remove the unevenness on both sides? Could I sand them flat and smooth? Then use a torque wrench? Please let me know soon. I want to deal with this now rather then later. I'm willing to purchase torque wrench and sanding supply's. Thanks,
    Joshua P.S it seems head is backward? Plug hole is facing to back of engine not forward. Which way should it face? Thanks.
     

  2. Frankenstein

    Frankenstein Active Member

    Plug hole best put whatever way it best fits, mine had to face forward.

    For the head issue, glass and fine sandpaper, both the head and the cylinder top, this will help compression a tiny bit but will make for a very nice flush seal, usually the head and cylinder gasket only meet up right around the cylinder hole, it doesn't extend all the way to the headbolts. If you understand what I mean.

    Also use a couple extra washers on each headbolt, this prevents the acorn nuts from bottoming out and preventing good torque.

    Word of advice for gas tank leaks, don't try to prevent them, it's like trying to fight city hall, takes a lot of work to make it happen so don't try just do it all in one shot. The paint isn't all that gas resistant, putting jb weld on top of it will just let the fuel eat the paint and then it leaks anyways, the jb weld usually cracks too.

    Use a tube of something called seal-all, it's a gas and oil resistant sealant, just remove paint from the tank and studs where the sealant will be applied, I used a steady hand and a cut off wheel in a dremel to get the paint of the surrounding area, then a steel wire wheel in the same tool on the stud. Apply liberally and in multiple coats. After all set and done, put a strip of old ture tube between the frame and tank, you can use seal all to glue the tube to the tank if wanted. Tighten the strap on the studs down to the frame LIGHTLY! I emphasize lightly, it only needs to be barely snug on the frame so it can be rather easily rotated by hand on the tube. Get a self tapping sheet metal screw, like used on a license plate, drill a small pilot hole through one strap and right into the bike frame, use the self tapper in that hole, this will prevent the tank from twisting on the frame, while also lessens the stress on the studs, which ultimately causes leaks.
     
  3. Frankenstein

    Frankenstein Active Member

    Also the self tapping screw idea works well on chain tensioners, after you have it aligned right, drill a hole, put screw in, then it won't fall out of alignment and drop into your rear spokes and kill you and/or your bike.
     
  4. MotorBicycleRacing

    MotorBicycleRacing Well-Known Member

    There is a raised sealing lip on the head so there will be a gap.
     
    gary55 likes this.
  5. Yeshua

    Yeshua New Member

    Oh ok. I saw a gap and thought it was a shitty head job from factory. That gap is normal? It's just that the gasket is so thin and flimsy doesn't seem to fill the space at all it curlse up at the edges. So that gap will always be there? Seems the stock gasket does nothing at all. But I wouldn't know I've never taken the head off a engine. This is my second motorized bike. First one I had someone build and never looked at the finer details past changing spark plug. This time I have a hobbiest motorized bike builder teach me the build from the ground up and I've read through hundreds of threads on this forum. I'm starting to understand how small engines work now. But any way, to get rid of gap and have better compression I should smooth out head and add thicker gasket? Cuz the stock suds are tight and there's still that gap. Also the BBR tuning studs I'm putting in are hex heads. Should I just put hex adapter on torque wrench or put nuts between stud heads and crush washer to use wrench normally?
     
  6. Yeshua

    Yeshua New Member

    Couldn't I just use a rotery hand sander to spooth out head?
     
  7. crassius

    crassius Well-Known Member

    DO NOT sand it so much that you remove the sealing ring, you need that
     
    gary55 likes this.
  8. Frankenstein

    Frankenstein Active Member

    Yea, don't sand the ring out, that's a bad idea, you might get away with the hand sander, but it needs to have a hard non flexing back behind the paper, otherwise expect less than perfect results.
     
  9. crassius

    crassius Well-Known Member

    I have never, ever sanded one in the 1000 or so I've worked on at my repair shop this last 10 years or so - never had a problem once torqued properly.
     
  10. MotorBicycleRacing

    MotorBicycleRacing Well-Known Member

    No!!!
    You can never get a flat surface with a sander.

    You are seeing problems that aren't there.
    The sealing ring on the head is about the same height as
    the thickness of the 25 thousands head gasket.
    Of course you are going to see a gap.

    The top of the cylinders are nice and flat.
    The heads can occasionally warp but it is not that common.

    You are getting bad advice from a noob.
    I have the same experience as crassius, my heads have a machined flat surface.

    Leave the cylinder and head unmolested and don't change the studs to allen bolts.
     
  11. Yeshua

    Yeshua New Member

    Also the BBR tuning studs I'm putting in are hex heads. Should I just put hex adapter on torque wrench or put nuts between stud heads and crush washer to use wrench normally?
     
  12. MotorBicycleRacing

    MotorBicycleRacing Well-Known Member

    Run it the way you got it.
    you have no understanding of what you are doing.
    Adding nuts under the allen heads will make the studs too short and how
    the hell could you get a wrench on the nut with the fins in the way???

    Of course you would have to use an allen bit.
    I recommend you don't change the studs.
     
    Steve Best likes this.
  13. Yeshua

    Yeshua New Member

    Makes sense sorry I'm a noob. But the slant head is on backwards.
     
  14. MotorBicycleRacing

    MotorBicycleRacing Well-Known Member

    There is no problem with the head facing in either direction.
    The slant heads were made so the plug can go forwards to fit in small
    bicycle frames.
    Technically the head facing backwards would be better, but all the high
    performance heads have a centrally located plug.
     
  15. Frankenstein

    Frankenstein Active Member

    I'm sorry did you just call me a noob lol?

    I do recall one of the first things I said was that the seal doesn't extend to the headbolts, I may not have made it obvious that there would still be a gap, but the intentions were there. Pardon my lack of descriptiveness.

    I said might get away with a hand sander, never doubted steady hands before, won't start now, I also first said use a pane of glass and sand paper. Didn't know I was lacking professionalism, thanks for the update.

    He said numerous times that things are not flat, even said not air tight, how am I supposed to interpret how he came to that conclusion. I would figure that the problem was genuine as stated, and gave solution.

    I don't think I have ever left a head and cylinder as stock other than my first motor. Haven't used a stock head gasket in ages either. He probably needs a new head gasket anyway, those cheap stock ones get pressed once and they take on all the imperfections (that you say should be left there for unusual reasons) of the 2 mating surfaces, if you go for a second try they tend to leak early. They tend to leak in general actually. 2 sanded surfaces for super fine mating and an annealed copper head gasket would do fine and last longer, and without all the super crappy bumps waves in the cylinder and head you can usually reuse the gasket, just anneal once again and go for it.

    We all know these things lack proper compression anyways, a few thousandths off the top will probably be helpful to him in the long run. Not as if he wouldn't eventually venture into performance mods either.

    Tell me if I'm politically incorrect by recommending self tapping screws to keep the tank from getting retarded or stopping his chain tensioner from rolling into his back wheel as well please. I'd hate to know I was f***ing peoples lives up by handing out what I thought was good advice that was practiced and perfected enough times to show otherwise..

    Sheesh
     
  16. crassius

    crassius Well-Known Member

    when a guy with over 1700 posts says a guy with only 400 posts is a noob, it often just means the advice given was unnecessary rather than completely wrong
     
  17. Yeshua

    Yeshua New Member

    Thanks guys I just miss understood everything this is my first build after all. I'm just gonna replace all stock bolts with better ones and use lock tight and leave everything as is for this first build. I don't plan on performance just getting around town. Next build will be a quality kit with quality bike and performance parts. I'm glad I found this forum tho and thanx for all yer advice guys I'll keep y'all updated on my build and let y'all know if there's any problems,
    Joshua
     
  18. crassius

    crassius Well-Known Member

    You might want to leave all as it came, then replace bolts as you spot problems - this can be a good way to develop an understanding of how these act, and what it takes to fix them.
     
    Steve Best likes this.
  19. skyash

    skyash Active Member

    Never screw in to your bike frame it's just a weak spot for it to brake .and to stop tank leaks just glue the tank to the bike frame with silicone from the start do up the bolts lightly till glue is dry then you can take off the bolts put them in the bin if you like .or keep for looks
     
  20. Yeshua

    Yeshua New Member

    What about at least changing the mounting bolts? I keep hearing horror stories about them breaking off. I'd rather not have that happen. A few American made bolts from Lowe's is. Just a few bucks. Nothing rong with preventative maintenance. Just taking the advice often put here on this forum. Also plan atlest to change the plug to a NGK B6HS. Do you know if that would fit in a slant head without hitting piston? Also what's a good gap for that plug? I've read anywhere from .23-.35. Thanks please have patience with me
     
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