X80A motor?
- Thread starter biknut
- Start date
This motor vibrated a lot, and at certain speeds sounded like a rock crusher. It was worrisome, but I have so little experience with these motors I wasn't sure if it was unusual. Finally at about 550 miles it started making the noise at all engine speeds and it was way loud. It sounded like metal scraping on dry ball bearings. That's when I decided to to take it apart.Wow that's off by a lot
I also notice where the crank bearings press into the cases, it looks like the races were walking around in the cases. If I could check this crank I think it's probably way out of true.
This is the only motor I've bought from Luckyearlybird, and I'd have to say it was a lemmon. Aside from everything else, when I removed the pinion gear it almost fell off it was so loose.
It did have some things going for it though. It has a wide front motor mount. It has a long, bent clutch arm, which makes for an east pull. It has pretty nice castings, a lot better than a Skyhawk, and the cylinder casting is better than the one I bought from BGF recently.
It seems like it was put together poorly. I think from now on I'll have to build all my MB motors.
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Biknut
The one engine that I have that was a lemon and fowled me three times had the same crankshaft as the one you have in that engine, it had the same kinda play on the bottom bearing that you spoke of with yours, mine started making a bunch of noise before it gave it up also, I noticed that the needle/pin bearings between rod and crank journal were just loose free floating instead of being caged like the upper bearing, I think this is a major problem with those particular engines because it was one of those pin bearing that broke and came up through the transfer port and shelled out my engine, it was obvious to me that there wasn't enough of the needle rollers installed in my engne which allowed so much space between them that they could actually turn at an angle between the rod and crank journal, if the correct amount of the pins had been put in there it would have probably been just fine but not having enough is what caused the loose tolerance and allowed one of them to get turned into a bind where it broke and trashed my engine when a piece of it hung between the piston & port.
Mine may have had the bearing problem you spoke of also, not sure yet because I haven't took the time to tear that engine back down after the last failure, is will still run but has a serious air leak because the crankshaft shifted over toward the clutch side and allowed the mag rotor to eat into the case to the point that it ruined the crank seal behind the mag rotor, it may be that the crank bearing seized up and the outer race of the bearing spun in the case until it ate it out enough for the crank to shift over that direction enough to allow the rotor to make contact with the case/seal on that side, this is what I suspect has happened but I wont know for sure until I get into it later.
Peace, map
The one engine that I have that was a lemon and fowled me three times had the same crankshaft as the one you have in that engine, it had the same kinda play on the bottom bearing that you spoke of with yours, mine started making a bunch of noise before it gave it up also, I noticed that the needle/pin bearings between rod and crank journal were just loose free floating instead of being caged like the upper bearing, I think this is a major problem with those particular engines because it was one of those pin bearing that broke and came up through the transfer port and shelled out my engine, it was obvious to me that there wasn't enough of the needle rollers installed in my engne which allowed so much space between them that they could actually turn at an angle between the rod and crank journal, if the correct amount of the pins had been put in there it would have probably been just fine but not having enough is what caused the loose tolerance and allowed one of them to get turned into a bind where it broke and trashed my engine when a piece of it hung between the piston & port.
Mine may have had the bearing problem you spoke of also, not sure yet because I haven't took the time to tear that engine back down after the last failure, is will still run but has a serious air leak because the crankshaft shifted over toward the clutch side and allowed the mag rotor to eat into the case to the point that it ruined the crank seal behind the mag rotor, it may be that the crank bearing seized up and the outer race of the bearing spun in the case until it ate it out enough for the crank to shift over that direction enough to allow the rotor to make contact with the case/seal on that side, this is what I suspect has happened but I wont know for sure until I get into it later.
Peace, map
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mapbike,
I think you are right. I already noticed the big end needle bearing just has loose rollers, with no cage, just like you describe. From what little I can see, I was thinking it looked like there aren't enough rollers. I don't think I lost any yet, but the way it sounded when I turned it off, it was ready to start spiting rollers any minute. There seems to be a lot of play in the big end now. That's probably the only thing wrong. The crank being out of balance is probably normal.
I think you are right. I already noticed the big end needle bearing just has loose rollers, with no cage, just like you describe. From what little I can see, I was thinking it looked like there aren't enough rollers. I don't think I lost any yet, but the way it sounded when I turned it off, it was ready to start spiting rollers any minute. There seems to be a lot of play in the big end now. That's probably the only thing wrong. The crank being out of balance is probably normal.
Yep I agree on all points, I would replace the crank roller bearings with quality 202 units and then I would get a new crankshaft assembly and use a quality upper bearing, then you'll have something that should last you a good while.
Here's best deal I've found on a new crank.
bicycle Motorized BIKE ENGINE parts 66 70cc cc crank | eBay
Peace, map
I noticed a set of caged big end bearings on the piston bike site.
I already ordered a new crankshaft. A whole crank with big end, bearing and rod cost $18, so I'm sure it's of the highest quality lol.
The crank on this motor has two different size flywheels. No extra charge.
Yesterday I was in Harbor freight eyeing the presses. They have a nice little 12 ton press for $100. I'm thinking about doing it myself. I don't think it's hard to press the crank pin out, but putting it back together and getting it true sounds a little difficult maybe.
I also contacted Powroll, and ask if they could balance, and true a china girl crank. Of course they have no idea what that is, but I think they can do it. They ask me to send it to them and they'll take a look.
Why does this not surprise me?
If this is what the outside looks like, who knows what the inside looks like.
If this is what the outside looks like, who knows what the inside looks like.
I like the fact it has a quiet muffler, I'm trying to figure out a way to make mine quieter. I was thinking of putting steel muffler stuffing on one of the chambers inside my muffler. Of course I don't want too much restriction causing my engine to over heat. What do you guys think?
That looks like crap too. If that's one of these same X80a motors from LEB then they must have all been bad.Why does this not surprise me?
If this is what the outside looks like, who knows what the inside looks like.
Probably smaller. A quite muffler = less air flow, so probably less gas too.
Even with no mods most of the motors with a NT carb are jetted rich from the factory.
This sounds like a down grade mod, I don't think I want my bike to perform less than current. Thanks for your input.
I have an x80chrome.runs very well,smooth,easy start.so far no probs.ps, the PK in pk80 stands for power king.Good luck rebuilding that thing!
Was your motor in the same factory as this one? Pizhou Yongxing Gasoline Engine Factory.
That's for telling me what pk stands for, I was wondering about that.
I would buy another one of these same motors, but I would take it apart and build it back together before using it next time. I'll probably do the same to all the motors I buy from now on.
I got it from lucky early bird probably about a year ago.I dont remember the factory name.
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Last month I bought a Z80 from BGF. BGF and LEB are owned my the same company I think.
The Z80 motor has the same bent arm, which I like, and the same wide front motor mount as the X80 from LEB, but the castings look different. The X80 has OK castings, but the Z80 from BGF look pretty rough, exactly like SkyHawk castings.
I think I've finally found out what went wrong with this motor. It all revolves around the crankshaft being out of true.
This is what I've discovered.
The crankshaft is way out of true. That means the shafts aren't true when the crank turns. As the crank turns the shafts wobble. Since the crank bearings are tight to the shafts, that means the bearing races wobble in the block halves when the crank turns. In short time this wears out the holes in the block halves where the bearings are pressed into.
In addition the this problem, the flywheels were not true either. One was bigger than the other. The bigger of the two, had very close clearance to the crankcase. The outer race of the crank bearing, wobbling back and forth in the block, wore the hole out in the block half enough, that it allowed the flywheel to lightly contact the crankcase. This is what made the loud metal scraping noise I heard.
I now have tested 3 crankshafts, and only one of the three seems true enough to not cause this problem. I think the crankshaft is the weakest link in these motors.
This is what I've discovered.
The crankshaft is way out of true. That means the shafts aren't true when the crank turns. As the crank turns the shafts wobble. Since the crank bearings are tight to the shafts, that means the bearing races wobble in the block halves when the crank turns. In short time this wears out the holes in the block halves where the bearings are pressed into.
In addition the this problem, the flywheels were not true either. One was bigger than the other. The bigger of the two, had very close clearance to the crankcase. The outer race of the crank bearing, wobbling back and forth in the block, wore the hole out in the block half enough, that it allowed the flywheel to lightly contact the crankcase. This is what made the loud metal scraping noise I heard.
I now have tested 3 crankshafts, and only one of the three seems true enough to not cause this problem. I think the crankshaft is the weakest link in these motors.
Biknut, I'm glad you figured out the issues, so the solution is to replace it with a true crankshaft? Do you still have the exhaust that came with this engine? Wanna trade? I have a chrome one that is in great condition.
The stock exhaust broke apart, and I'm using the header pipe with my expansion chamber.
