Horizontal Float in the crank
- Thread starter Malcolm
- Start date
gasser
New member
Is the movement in your crank or your connecting rod - I only ask this because you said you replaced the big end bearings which have nothing to do with crank play.
I see no way you could not have movement both horizontally and vertically if it were a bad bearing. That leaves you with just one possibility - the whole bearing must be moving horizontally in the case.
I see no way you could not have movement both horizontally and vertically if it were a bad bearing. That leaves you with just one possibility - the whole bearing must be moving horizontally in the case.
iancp5
New member
Malcolm,
What you're saying could be misinterpretted. Do you mean the crank floats 1.5mm along its axis or do you mean backwards and forwards in the direction of the bike travel? Does vertical mean literally up and down as the bike sits?
I would assume you mean end float - i.e. in the axis of crank rotation. In which case I assume you are measuring at the crank end not as someone alluded to by seeing connecting road float?
I can't help by the way but I reckon being precise is important in getting the correct advice before you strip it down. If my crank moved back and forth 1.5mm I'd think there something very wrong, along the axis I would be uncertain and I would certainly expect the rod to float a bit. Although 1.5mm seems a lot whatever I'm afraid I don't know the tolerance.
What you're saying could be misinterpretted. Do you mean the crank floats 1.5mm along its axis or do you mean backwards and forwards in the direction of the bike travel? Does vertical mean literally up and down as the bike sits?
I would assume you mean end float - i.e. in the axis of crank rotation. In which case I assume you are measuring at the crank end not as someone alluded to by seeing connecting road float?
I can't help by the way but I reckon being precise is important in getting the correct advice before you strip it down. If my crank moved back and forth 1.5mm I'd think there something very wrong, along the axis I would be uncertain and I would certainly expect the rod to float a bit. Although 1.5mm seems a lot whatever I'm afraid I don't know the tolerance.
Hi guys sorry if I was not discriptive enough. If Iam facing the flywheel and I place my hand on the flywheel. If I pull and push the flywheel the whole crank and flywheel move 1.5mm. There is no up and down movement on the flywheel at all.I think the main bearings are moving in the casings. There is nothing wrong with the connecting rod and big end bearing as this was all replaced recently.
iancp5
New member
Hopefully an expert will advise if this is normal. I was playing with timing recently and had the flywheel on and off a few times. I didn't notice any appreciable float. Probably would've felt 1.5mm.
GMP
Active member
This was a problem on a handfull of older bikes, my '00 included. The crank journal/main bearing press fit is loose due to the crank journals being machined slightly undersize. To fix it correctly requires the journal be plasma sprayed and remachined or the crank replaced. What will eventually happen is the crank will spin within the main bearing race, wear, and will become worse. You will notice an increase in vibration if this happens. You can ride it without a problem until then or until you have the ability to fix it properly. My '00 was like this for almost two years before being fixed.
Hello Malcolm, I am sorry this may be a bit late coming. I had the same problem on my 2002 EC 200. So I thougt I should join up and let you know what the problem was with my bike.
The crank should have 0 end float. The end float is controled by a spacing collor that slips over the right hand end of the crank inside the gearbox. The left hand side of the collor sits against the right hand side of the inner race of the right hand main bearing. The right hand side of the collor sits against the left hand side of the gear that drives the clutch basket. On my bike that gear is located by a circlip in a groove in the crankshaft I think later bikes have a bolt which theads in to the end of the cranshaft. Anyway the lenth and fit of that collor is critcal in respect of end float it needs to be just the right length so that when the circlip is fitted or the bolt tightened it pulls the crank hard up against the left hand face of the right hand main bearing.
The problem with my bike was that the boys in the factory had one to maney fiestas or siestas and fitted the wrong spacer it was about 1 to 1.5 mm to short so hence the end float! Some of the spacers are tapered on one face and can be fitted the wrong way round and I have seen a factory buliten on that point. However mine was just the wrong spacer. Took a lot of sorting out I can tell you. I am in New Zealand but in the end GasGas Uk identified the correct spacer for my bike. I was aware of another bike in NZ owned by a mechanic with the same problem he "located" the crank in the main bearings with lcotite! I think the correct spacer would be the better solution and the next rebuild would not pose such a problem!
So I would strip out the gearbox side and have a close look at that spacer. Also ther is a fine "o" ring seal that fits on the crank inside the spacer you will need a new one of these as well.
As a closing coment do not leave the end float because it will cause premature bore wear.
Also I should say Gas Gas NZ were verry supportive once the problem was identified.
RAL
The crank should have 0 end float. The end float is controled by a spacing collor that slips over the right hand end of the crank inside the gearbox. The left hand side of the collor sits against the right hand side of the inner race of the right hand main bearing. The right hand side of the collor sits against the left hand side of the gear that drives the clutch basket. On my bike that gear is located by a circlip in a groove in the crankshaft I think later bikes have a bolt which theads in to the end of the cranshaft. Anyway the lenth and fit of that collor is critcal in respect of end float it needs to be just the right length so that when the circlip is fitted or the bolt tightened it pulls the crank hard up against the left hand face of the right hand main bearing.
The problem with my bike was that the boys in the factory had one to maney fiestas or siestas and fitted the wrong spacer it was about 1 to 1.5 mm to short so hence the end float! Some of the spacers are tapered on one face and can be fitted the wrong way round and I have seen a factory buliten on that point. However mine was just the wrong spacer. Took a lot of sorting out I can tell you. I am in New Zealand but in the end GasGas Uk identified the correct spacer for my bike. I was aware of another bike in NZ owned by a mechanic with the same problem he "located" the crank in the main bearings with lcotite! I think the correct spacer would be the better solution and the next rebuild would not pose such a problem!
So I would strip out the gearbox side and have a close look at that spacer. Also ther is a fine "o" ring seal that fits on the crank inside the spacer you will need a new one of these as well.
As a closing coment do not leave the end float because it will cause premature bore wear.
Also I should say Gas Gas NZ were verry supportive once the problem was identified.
RAL
I was reading some old threads, including this one, so it gave me the idea to check my 2000 EC250. Sure enough, I can push/pull the flywheel a huge amount. I didn't measure it but there is enough play to see it move. Has anyone else encountered this problem? I'm not trying to disregard the other replies but with two different fixes being explained I would like to know which is the most likely cause/fix. Certainly, replacing a spacer is more appealing than repairing or replacing the crankshaft but, I would like to repair it correctly.
GMP
Active member
The '00 has a different main bearing setup than the newer bikes, two ball bearings vs. a 2 piece roller/ball combo. During assembly the crank is tapped with a mallet or "drifted" in the cases (bearing races) to center it. The primary spacer has nothing to do with it. This is how most 2-strokes are designed. If this crank/bearing press fit is too loose, it will move freely axially withen the cases. This was not uncommon on the '00. The fix is a new crank or plasma/remachine your existing crank. Steve @ Motowest did an '01 GG 125 crank for us a couple years ago that had the same problem.
