What should I look for in my HT Engine after Teardown? Previous RPM problems

Discussion in '2-Stroke Engines' started by StrontiumEthics, May 22, 2010.

  1. StrontiumEthics

    StrontiumEthics Motored Bikes Sponsor

    Ok, well I successfully took apart my HT engine, All bearings, Seals, and parts generally seem to be intact. Previously, the problem I had was that my engine did not Idle but kept revving when I started it. I adjusted the carburetor to the best of my ability and even switched it with a spare one I had several time. I also switched the throttle cable, and check the barrel slide in the carb. But no good. Finally I decided to tear this engine down. And not I did. = )

  2. Al.Fisherman

    Al.Fisherman Active Member

    The only thing I can think of is either a cylinder base gasket or the case gasket. Either can leak and suck in air.
  3. AussieSteve

    AussieSteve Active Member

    How old is your engine? If it's not new, I'd recommend replacing the crankshaft seals even if they look OK, while you've got the chance.

    Clean up the mating surfaces of the crankcase halves, so that they'll seal well. (Wet & Dry paper on a sheet of flat glass is a good way to do this.) Don't remove a lot of material.

    Do the same to the head and other mating surfaces, including the inlet tube and exhaust.

    For the crankcase, buy some oil jointing paper and cut a new gasket, unless you can buy one.

    Do the same with the inlet-to-barrel gasket.

    Buy new base, head and exhaust gaskets.

    It sounded like a carb-related problem from the start, but you ruled that out by swapping for another working carb without improving things, so hopefully a careful rebuild will do the trick.

    Ron, you posted while I was typing. Doesn't matter. We're speaking the same language.
  4. StrontiumEthics

    StrontiumEthics Motored Bikes Sponsor

    I am having a problem installing the bottom end of the crank case. For some reason, when I connect to 2 pieces and put gasket in between there is still some extra space. and when I try to tighten the screws on the crankcase the crankshaft gets a little stiff. What can be the problem?
  5. 210061741

    210061741 Guest

    My guess is the seal lip is hanging up on the crankshaft.
    Need to make sure the bearings are seated all the way and check that the inner lip of the seal isn't being pushed out by the crankshaft
  6. StrontiumEthics

    StrontiumEthics Motored Bikes Sponsor

    I think that the bearing aren't all the way in. like a millimeter is poking out. But i cant seem to get it in even when pounding it hard. What can I do?
  7. 210061741

    210061741 Guest

    The mainbearings will sit not quite flush.

    Check the seals and align the cases.
  8. StrontiumEthics

    StrontiumEthics Motored Bikes Sponsor

    Ohh that's why. I thought the bearings were suppose to sit right inside. Just like a millimeter is poking out. But i hammered them on a wooden block and then alligned the cases and even screwed in some of the bolts but there still is extra space It also gives a hard time screwing in and when I start screwing one side the other side lifts up a little.
  9. 210061741

    210061741 Guest

    Here is what i would try.

    Put the crankshaft and the clutch shaft in 1 case half.

    Slide the other case half on and pay attention to the seals.
    The lip is going to want to push out as the crank goes in.

    Carefully use something to push the seal lip back in.
    Im talking about the lip around the shaft.

    If that lip did push out you could have got the spring off the seal jammed between the bearing and the seal which would cause you problems.

    Did you replace the seals.

    I would pop them out and put the bottom end together without the seals.

    Than when you got it together put new seals in.

    also when you got the cases together put all the case screws in loose.

    Then put the cylinder and head on and bolt them down tight.

    that will pull the cases to the cylinder and should line it up pretty good.

    Then tighten all the case screws.

    The crank should turn pretty easy.

    My best guess is the spring on the seal came off and is jammed in there.

    Take the crank out and very carefully pry up the inside lip of the seal and check to see if the spring is on.
  10. StrontiumEthics

    StrontiumEthics Motored Bikes Sponsor

    Oh. I did not mention that all this time I was putting the bottom end together WITHOUT the seals...there was still room.
  11. 210061741

    210061741 Guest

    Something has to be misaligned.

    Id snap it together best as you can.

    Use the bolts to pull the cases together carefully.

    Tighten everything down to seat it.
    Then loosen everything up.

    Put the cylinder on without the piston in and troque the head down.

    Rotate the crank with a ratchet .

    Are you sure you didnt damage the bearings pounding them in.

    Is the ring on one case halve seating inside the counterbore?

    Tap things a bit and see if you can get it to loosen up.

    It sounds like maybe 1 of the bearings is coked a little or the shaft alignment is causing it to bind up. Maybe pop the bearings back out.

    Put them on ice in the freezer and get them as cold as you can.

    Put the cases in the oven and heat them up.

    If your quick the bearings should go in easier.

    Cold shrinks heat expands. It gives you a little more room.

    What bearings are you using. Do they measure the same.
  12. StrontiumEthics

    StrontiumEthics Motored Bikes Sponsor

    The very weird thing is that when I fit the case together without the crankshaft. It fits PERFECTLY! But when I install the crankshaft I get that little room. and the bearings are seated pretty good inside. I pounded them in on a wooden block with a hammer.
  13. 210061741

    210061741 Guest

    So where is the gap?

    Between the cases?

    You should be able to screw them together.

    Then loosen them

    Turn the crank and see if it loosens up.

    Then tighten it back down.
  14. StrontiumEthics

    StrontiumEthics Motored Bikes Sponsor

    Yup the gap is between the cases
  15. 210061741

    210061741 Guest

    And you are putting the same crank back in ?

    Try taking out the clutch shaft and putting it together.

    See if the crank is loose then.

    the bearings to the clutch shaft could be seated in too far and are binding on the clutch shaft.

    I dont know.

    Im guessing here.

    Worth a try anyway.