Splitting the crankcase

Discussion in 'Motorized Bicycle General Discussion' started by Blm25super, Jul 19, 2014.

  1. Blm25super

    Blm25super New Member

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    Im sure there are many threads about this already but. . . . . . I have all the screws out of my crankcase and im trying to figure out how to get the case apart. I watched fred chelminski video on youtube about taking the case apart. Ive done everything he did except take the actual case apart. In the video he says he has had that specific case apart numerous times. So i guess thats why he made it look so easy. . . Any tips?
     
  2. MotorBicycleRacing

    MotorBicycleRacing Well-Known Member

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    Did you pull the the clutch and bevel gear and the 10 tooth sprocket?
     
  3. Blm25super

    Blm25super New Member

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    Yep , i took all the gears off and the sprocket with the gear puller tool.
     
  4. MotorBicycleRacing

    MotorBicycleRacing Well-Known Member

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    Just did it yesterday.
    Put the nut back on the clutch shaft.
    tap the nut using a plastic or hard wood block on the nut.
    The bearing and shaft will come out the sprocket side.
    Cases should come apart easy.
     
  5. Blm25super

    Blm25super New Member

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    yes that sounds like it is the problem. the front part of the case wants to pull apart but the cltch shaft is holding the back end together
     
  6. Blm25super

    Blm25super New Member

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    got it to move some towards the sprocket side , not sure what i need to do except keep on hammering . . .. ...
     
  7. crassius

    crassius Well-Known Member

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    the mains can stick REAL hard sometimes
     
  8. rogergendron1

    rogergendron1 New Member

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    i actually take a socket and pound out the clutch shafte with the gear still on it so it leaves a hollow with one bearing in the other side then i carfully seperate the case by lightly tapping the crank shaft with a plastic hammer wile holding the top half of the case..... it will seperate and come apart in your hands....

    hey since your case is appart..... you should stuff around the bearing bosses with jb weld and bring your case presure up to a decent amount and port match the case transfers to the jug transfers and smooth out the entire inside of the case and round out and flow the inside castings of the case transfers, it will cost you only your time and will make an unbelievable differance !!!!!!!!!!

    i have a thread with step by step videos of a grubee build... grubee gt5 from the case up.. in the performance section where i show rod and piston and crank combos and some real good case work and case stuffing and csae transfer port to jug match flowing

    you should check it out ... the beginning if the thread is me tryi g to figure out what i want to do with the build but by page 2 its all set to go

    if i were you i would visit juice moto parts and pick up there rebuild kit it has all custom cut copper gaskets and sks case bearings and seals and you can even choose the thickness of the base gasket and the head gasket

    i run a thick base gasket 1.5mm and a .45 mm or .016 head gasket
     
  9. rogergendron1

    rogergendron1 New Member

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    ohh and when reasembleing i must warn you that there is a sweet spot to the case ....

    you will need to keep all the bolts just barley snug and give the case little taps back and forth and spinning the crank at the same time or in intervals to find the best place of alignment.... the case will wiggle a little it doesnt seem like mutch but if the crank shaft is not perfectly lined up with the bearing bosses and then tightend exactly that way it will be slightly out of alignment and cause excesse were on the bearings and drag on the crankshaft

    mine turns near efffortlessly after 45min of tapping backand forth and tightening and testing and loosening and tapping and retightening and testing exe.... but it was worth it because once fully asembled the bottom end turns over the entire assembly clutch and all with only a single finger with verry little efffort.... stock it had a ton of drag and it was slightly mis aligned causeing it to turn over with a LOT more difficulty.
     
  10. Blm25super

    Blm25super New Member

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    That sounds like a lot to decipher rogergendron1 . Can you paste the link to your videos? I wanted to say that i have a fred chelminski cylinder and head going on this case so i dont wanna mess with those two and the piston. I am new to small engines and i have a lot of learning to do. Getting the shaft out is first so i can get to the crank and have someone balance it. I also want to replace the china bearings . Guess ill have to get them out and take em to a auto store so i can compare them.
     
  11. maniac57

    maniac57 Old, Fat, and still faster than you

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    Roger like to tell people everything he knows. You should not worry about stuffing cases or custom porting unless you crave speed and broken parts.
    Splitting the cases is not too hard. Just use taps with a hammer to drive out the clutch shaft (can come out either side) and then split the case by tapping the crank while holding the case.
    The mains often stick on the crank and come out with it, so you may need a small puller to get the bearing off the crank. DON'T try to pry it off with screwdrivers. This is a great way to bend the crank. Remember, cranks are SOFT everywhere but the bearing journal.
    I ALWAYS use a scotchbrite pad on the crank journals until the mains slide on and off easily. This makes re-assembly MUCH easier. Drive the mains in the cases with a socket and hammer, then slide the crank in one side and assemble. If you have to beat it together, you stand a good chance of binding and screwing up the bearing bore or case or bending the crank.
     
  12. Blm25super

    Blm25super New Member

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    Thanks for replies. I also last nite got curious about my fred head and cylinder. Took the piston out and while trying to get it back in one of the rings snapped. Im trying to get it back in cylinder with a ring off of my extra piston i got with one of my kits. Ain't going in there the ring looks like it is the same size .......... Damn if it aint one thing its the other. When it comes to engines i seem to need help with everything. I tried to use a socket and hammer for the crank. The largest socket i have sortof rests on the black plastic/rubber that is a visible part of the crank it may be messing it up. And i got it so far and it doesnt seem to want to move anymore. ... .. .. I move weeks at a time with this. I have to put it up and then come back to it when i calm down . . LOL Dammit i wish i had better tools and knowledge of this stuff. I think freds piston is the same size as a 66 cc china kit. . . . . . . . .. . .I have no idea which part of the crank is the journal .. .
     
    #12 Blm25super, Jul 20, 2014
    Last edited: Jul 20, 2014
  13. Greg58

    Greg58 Well-Known Member

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    The crankshaft doesn't have plastic or rubber on it the seal does. Like has been said already put the nuts back on the crank and clutch shaft and use a plastic or rubber hammer to tap it apart.
     
  14. Davezilla

    Davezilla New Member

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    I'm not saying anything bad about Roger, he does know his stuff, but that's some more advanced stuff that you can do once you learn the basics of these engines a little more... or be ready to have a lot of nice long conversations every step of the way so you don't mess anything up.

    For your current issues, the pistons have small locating pins in the ring grooves so the ring can't be put on upside down and so the ring gaps don't migrate toward the intake and exhaust ports where it would surely destroy a ring or worse. The rings should go into the cylinder with very little force, if it stops going in it's most likely that the ring slipped over that little pin in the ring groove.

    Greg is right about the seals and you should replace them if they look to be damaged, you can pry them out with a screwdriver and the new ones should push in fairly easily with your thumbs, or just the right sized socket and a gentle tap... again, use as little force as possible.

    Another method of getting your bearings and seals in and out is by using a socket and a long bolt and nut where you can draw the seals or bearings in or out by tightening the nut, no hammering necessary with this method, you'll need one socket that's bigger than the part to be drawn into place or pulled out, and one that's slightly smaller, as well as a bolt long enough to go thru everything and a nut... and a few washers to keep the bolt/nuts from going into the sockets. This is a far more gentle method for getting the new bearings or seals into place since there's no need to hammer. Plastic mallets are better than hammers for assembly too if you can't press them in or out with the sockets and a long bolt method.

    Hopefully some of this will be of help to you.
     
  15. Blm25super

    Blm25super New Member

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    Davezilla thx is there anything inside the case that the clutch shaft could be getting caught on? Does it need turned any way so that it is lined up and can be pounded out? I seem to have hit a wall there and cant move the shaft any further.
    Another question is about bearings. I want to upgrade my bearings once i get this apart. Jake from jakes motored bikes tells me he found some german ones called 'fag' 6202 bearings. No pun they are really called fag anyways he says get the shielded ones . . . and to remove the sides with a pick. . ... anyways when i search the internet for what i just told you about it comes up numerous different things. I don't know how many bearings are even in there. anyone know and want to do an internet search to tell me which ones will work please copy and paste the link. I'm slow to learn but once i get it i get it.
     
    #15 Blm25super, Jul 22, 2014
    Last edited: Jul 22, 2014
  16. Blm25super

    Blm25super New Member

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  17. Davezilla

    Davezilla New Member

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    Yes... and if you can find the SKF bearings at a better price, these are some of the best out there... but bookmark that page for future use, Juice has some good parts nobody else sells
     
  18. Blm25super

    Blm25super New Member

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    Ok well my clutch shaft willl not go through the bearings because of the piece that sticks out . there is a piece that sticks out on each side of the clutch shaft(sprocket side and clutch side) . It seems to move and i was thinking that it would fold into the crank shaft if i can push it far enough but im not sure i can push it that far because the piece on the other side will butt up to the seal and bearings not allowing me to get it any further so i can fold it in ? if it even folds in?
     
  19. turnofftheradio

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    is it the key for the crank holding you up? You can take the key out with a pick or small screwdriver. Don't lose it :) Don't beat too hard on the threaded ends, as stated it's amazing how soft they are.
     

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