Got needle bearing to replace bush but....

Discussion in '2-Stroke Engines' started by go you good thing, Aug 7, 2007.

Tags: Add Tags
  1. After several attempts I now have a bearing to replace the brass bush in the conrod.

    My first attempt (pictured in the middle below) fit the conrod but I could not get the pin in the hole. This came as a spare part from the new shipment of 70cc china motors that have them included.

    I went to a specialist bearing supplier and after measuring my bush/pin got one that is 12mm wide, has a 10mm center hole and 14mm outer diameter.

    The first one (in the middle) has exposed needles so the hole in the top of the conrod would feed oil to it when it us running but wont fit:(

    The bearing on the right from my supplier should fit but has a solid outer casing so oil will not get down from the top to lubricate it.

    As you can see by the original bush (on the left) the hole continues through it to lube the pin.

    My question is will this bearing get oil? I will fully grease it up before installation and their is a little play when the pin is installed as with the bush but is this going to be ok or is it going to seize after a while??? The bearing guy said that it should be ok.

    Any suggestions would be appreciated as I want to install it asap.

    Attached Files:

  2. HI,
    I may be wrong but I believe the entire crankcase and area under the piston fills
    with fuel/oil vapors before being routed into the combustion chamber through the transfer ports...This should provide the necessary lube for the internals and bearings. As far as the bearing installation I am not sure how but I would be interested in doing a performance upgrade like that too so I'll see if anybody else chimes in.
  3. Thanks andyinchville1,

    I think you are right with the vapours but I wonder how much pressure it is under to force it in the bearing??

    As for some instruction on how to do it, I found this link while I was looking:

    I found heating up the conrod with a small blow torch helped getting it out.

    I have also read here that puting the bearing in the freezer and heating up the conrod is the way to get it in. Guess I'll find out soon:D
  4. OldPete

    OldPete Guest

    I would fit the middle one and if you have a 1/4"drill motor, hack saw and some basic skills I will tell you how.
  5. uncle_punk13

    uncle_punk13 Guest

    I am very interested to see how this works out.
    Just a thought here (NOT advice, as I don't know) but on that third from the left bearing, couldn't you drill a small hole, or series of 3 holes, around the casing (similar to the brass bushing), at say, 120 degrees spacing from each other to provide openings for lubrication? Heck maybe even add two more small bores at similar locations on con. rod as well...?
    Please keep us updated on this as it would be great to upgrade/improve my 80cc in this way...:cool:
    Last edited by a moderator: Aug 7, 2007
  6. uncle_punk13

    uncle_punk13 Guest

    oh wait...

    That might not work as the drilling would create a small burr on the bearing side of the casing, thereby creating premature wear on the bearing surfaces...]
    Hmmm... I'll have to think some more. Anyone else have thoughts on this?
  7. uncle_punk13

    uncle_punk13 Guest

    Then again, you might be able to get a needle file down into the bore, at an angle, from the top side, to cut down the burr. You'd have to make absolutely sure there were NO residual filings in the bearing assy. but that might be a way of making it work...
  8. Thanks for your thoughts guys.

    Dang I don't have a drill and a hack saw.:D

    I had thought about this but was concerned about a burr and their is a bearing race inside holding the bearings equally apart so I may bend this if the drill went in too far. This bearing is very small so a file may not be possible to use with my eyesight:eek:

    Another method might be to get a dremel or grinder and make a slot type hole in the outer casing. That way the burr may not happen or I could try to bend any thin metal up and out. What do you think?
    Last edited by a moderator: Aug 7, 2007
  9. I just had another thought.....

    I could grind 2 or three little slots on both ends of the bearing cylinder across the top and bottom rim edges. That way when installed it would get vapors entering from both sides and the hole in the top would not be required....mmmm.:confused:
  10. OldPete

    OldPete Guest

    I asked augi to check the wrist pin clearance on that new Dax motor he has the top-end off of. This would be a good thing to know. I think it will be .001"~.0015".
    The pin clearance will be effected by the amount of interference fit that the Torrington bearing has when installed into the rod's small end. Too tight a fit and the pin will not go home. Your supplier should be able to tell you what the interference is...prolly < .002". If this bearing is pressed in w/o preheating the rod's small end the hardened outer shell will crush enough to lock-up the tiny rollers. Not a good thing.
    Pre-heat the rod end with a low flame from a propane torch. The heat must get into the internal mass so the bush hole will open. The Torrington should just drop in when it comes out of the freezer(do not let it fall through the hole). Cool it off with several squirts from a pump oil can.

    To open up the bush hole if needed? Use the non-existant 1/4" drill with some carborundum cloth wrapped tightly around a 1/4"split shaft, it should fit the hole snugly. Take your time and check dimention often with atleast a good dial caliper. The other bearing could be fitted this way also.
    Did you notice that the rod has a strike of copper plating? This should be removed from the bore it the roller bearing that came with the motor is used because it will start smearing as it gets on the rollers. Not a biggie but even if this bearing proper fit, a light cleaning off of the copper should be done.
    I have several air and electric die grinders here as well as a decent selection of flap wheels. A small new flap wheel and the air die grinder running at 7000~10,000rpm would make quick accurate work of this.

    I would not notch the ends of the Torrington. If I used this bearing a notch would be made to meet the top hole of the rod. A thin sharp scribe could be used to pick out burrs. Blow air on it as you use prolly a cut-off wheel on the Dremal to cut a lubricating notch. Might even hold the Torrington in a shallow dish of water. The point is that heat will generate a large burr that will be next to impossible to remove. So it must be done slow 'n cool to avoid a burr. The top hole on the rod could be chamfered with a 1/4" drill bit to help collect oil. Just a light chamfer mind you.

    Torrington bearings are normally used on the lightly loaded ends of gear shafts and run in an oil bath. The other end of the gear shaft will had a large ball bearing. This bearing might work out for ya.

    NOTE: I raced Mercury outboard hydroplane boats while in high school. Played 'n raced two stroke dirt bikes in the '70s and helped a friend of mine maintain his son's TZ250cc Yamaha road race motorcycle for two seasons. Lots of tear downs with the Yamadog. So yes, I have done my share of stroker work.
  11. Thanks for your suggestions O'l Pete.

    Ok so I used the dremel to cut the slot hole and it all went well. I just removed the burr with a small copper wire and gave it a good blowout to remove anything else.

    I used the dremel on the slowest speed and had my air compressor going flat out to keep it cool. The air kept it very cool in fact.

    I heated up the conrod and squeezed the frozen bearing in with a clamp.

    Again all went well until I tried to insert the pin. The bearing had shrunk enough to make it impossible to install:rolleyes:

    I do need to open up the conrod more to take it but have for now just re-installed the bush. I haven't ridden my bike now for way tooo long so will attempt this later. If I do I will continue here.
  12. Hmm I thought augi just posted that Dax has a needle bearing for his engines.
  13. uncle_punk13

    uncle_punk13 Guest

    Hey thanks for this thread guys; I learned some things, and reconsidered others. That's what it's all about here in our little community...
  14. The bearing in the center of my picture is the one from the new generation of motors with these bearings as standard. I got the bearing in quite easily but when I went to install the ping it would not fit so the new bearings are not suitable for the old motors:mad: I would have to make the hole in the conrod bigger to take any of the needle bearings that I have.:(

    Mate so have I, so have I.:eek:

    It may be an easier task to just buy an new motor from my supplier as they sell just the motor itself with out the kit for $170.00au plus $20 delivery. I could then use my current motor as spares. My current motor has only done 200kms so I might wait a while to get the value out of it first.
  15. rcjunkie

    rcjunkie Guest

    When you install/press the roller bearing it gets deformed slightly which makes it difficult to install the wrist pin. I insert the wrist pin onto the bearing before tapping it into the con rod. This ensures that the roller bearing is not deformed and the wrist pin can be easily installed/removed. I use a socket wrench to install the new bearing.
  16. Ok rcjunkie installing the wrist pin sounds like a great idea I would like to try.

    My problem was it was very very tight even though I had a frozen bearing and a hot conrod. I think I would need to make the conrod hole bigger as in Ol' Pete's post otherwise I am thinking I would get the bearing and rod in there and not be able to move it.

    It was so tight that I thought I may crush the bearing while installing with the G clamp. When I extracted it I could see slight crush like deformities on the outer casing. That can't be good:eek:
  17. iron_monkey

    iron_monkey Guest

    bearing upgrade for the 2 stroke, straightforward?

    I searched, the most informative thread being this one:

    However the thread dies at the critical point; whether the method of putting the pin into the bearing first (before putting the frozen bearing/pin assembly into hot connecting rod) solves the fitting issue.

    Second question is whether the bearing/bushing sizes for all 2 stroke motor is standardised, or are they different? Can I order a thatsdax bearing for my generic motor (appears to be same as kings 80cc)?

    If it is easy/strightforward without requiring special fabrication/enlarging of the rod hole etc then I would order a bearing from thatsdax.
    Last edited by a moderator: Jan 27, 2008
  18. davidsis

    davidsis Guest

    Ya, I need to do my bearing too, I will be watching this thread. So replaceing the bushing with roller bearings may not be a good idea hu?
  19. Ive had 2 strokes for a grip and you just tap a hole at the angle the conrod is tapped then clean it and realign it when repressing it under and oversized nut bolt press (homemade of course)

    when it condenses it gathers across the top of the conrod as it pulls closer to a vacuumit is at the end so the oil goes in it.aaI have yet to see this right side bearing.
    Last edited by a moderator: Nov 2, 2008
  20. wildemere

    wildemere Member

    The bushing engines have a 11mm piston pin the bearing engines are 10mm

    The rod hole is ~14mm on both.

    When changing the bearing type the correct sized piston and pin will be needed as well.