GasGas TXT Pro 2010 Main Bearings very tight

[Nigel_Mercer]

Hi 

I have a question for the guru's out there.  I have a 2010 TXT Pro 250.  Lest year I noticed that there was fuel in the gearbox oil when I changed it.  That precipitated a complete engine rebuild.  Glad I did it because it was pretty worn.  I had only had the bike a few months and bought it to get into trials (a decision I dont regret for one minute  )

I bought literally every seal and bearing, clutch, top end, crank was rebuilt as well.

When it came to fitting the main bearings I took them out of the box (The new style XiU-rdiOnes) they were so tight that it was impossible to rotate them.  IN other words, you could not rotate the inner of the bearing at all.  Even with significant force.  I was told that they are quite tight, but this seemed insane.  Anyway, went ahead with fitting, cases heated, bearings frozen.  Tough to get them in, but they were seated.  Bolted the cases up and the crank was literally solid.  I have rebuilt many many engines over the years and I have never seen a set of bearings this tight.  The crank could only be rotated by popping a high torque cordless drill onto it.  After a few minutes of this, I could now rotate the crank (just) by hand.  This really didnt seem right to me.  Anyway, I was assured by some that this is normal for these motors.  It started up fine and ran well.  However, there was a constant loud whirring noise which was not there before.  It did get slightly less, but has not gone away.

After a few rides I noticed that it is starting to use gearbox oil, but it doesnt smoke.  So I popped off the flywheel cover and its full of oil.  So the left side seal/bearing is failing obviously.  

So it all has to come apart again and get some more fresh mains and seals.  

My main question here is about those bearings.  Are they really meant to be that tight?  I cannot believe that they should be that tight. Surely this will generate massive heat and possibly destroy the seal and the o-rings in the bearing?

I have never come across a main bearing that cannot be rotated by hand (unless it is seized) brand new out of the box.  Makes me think that I was supplied a bad set of mains?

Thoughts anyone?

Nigel

 

[Tr1AL]

@Nigel_Mercer https://youtu.be/MtgZ-vEmIw4?si=Hue5PZ3ZEVzoz   NB As per video "The new LOW FRICTION bearings.".

Edited Tuesday at 06:37 PM by Tr1AL

[aussiechris]

I would recommend trying to source some OEM main bearings with in-built seals.

Back in 2015, I had to rebuild my 2011 300 (due to cracked cases).  I was advised to replace the mains with the new Xiu Engineering "low friction" bearings which were a good bit more expensive than OEM.  Big mistake - within three months the bike was billowing smoke because the crank seals had failed.  I had to rebuild the engine again but this time with new OEM bearings.  I've not had a seal problem since.

But to answer your question, the OEM bearings are fairly tight - hard to rotate with oily fingers while holding just the bearing.  But the crank should rotate fine.  The Xiu bearings felt much the same from memory.

Yours sound way too tight.  You run the risk of them spinning in the cases.  It the left one moves at all, the oil holes won't line up.

Unfortunately, sourcing OEM Gas Gas mains might prove difficult these days.