Makita 9903 3" belt sander not tracking correctly

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gasman

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Morning all. I wonder if I can ask your assistance on my Makita 3" belt sander - it's the 9903 model
It suddenly stopped tracking correctly - it has an an adjustable tracking mechanism which when you screw the adjusting screw in, changes the angle of the front roller to the rear one which enables you to get the belt running exactly in the centre.
I have taken it into its component pieces and reassembled -both rollers look OK, the msprings all see OK and nothing seems to be damaged - but whatever you do to the adjustment mechanism the belt just slides off to the side. It is useless as it stands - so I just wondered if anyone has had any similar or could throw some light on what the problem is (I have searched fruitlessly on YouTube etc but can't find any help there)
Thanks in advance
Regards Mark
 
Just wondering if the sander has been dropped recently or have you changed the belt to a different brand as the belt would only have to be slightly longer to fall outside of the tracking adjustment. I have a similar but older model that’s fine until the belt I’m using is abused beyond its limits and the belt will not always track to the centre .
 
Thanks for your reply Bingyman, I havent dropped it and have tried multiple different belts on it - and it is just the same on all of them. When I took it into its component pieces none of them looked particularly worn or bent in any way. Its a bit of a mystery but it is a £200 tool and reluctant to move on hence this post
Cheers MArk
 
This is a long shot, but could it be one or more of the bearings in one of the rollers?

Does the belt come off consistently to the left or right? Can you flip the non-driven roller and see if it comes off the opposite side? That might narrow it down to a front or back problem.
 
Thanks for your reply Bingyman, I havent dropped it and have tried multiple different belts on it - and it is just the same on all of them. When I took it into its component pieces none of them looked particularly worn or bent in any way. Its a bit of a mystery but it is a £200 tool and reluctant to move on hence this post
Cheers MArk
Just remembered I had a problem with the flap under the belt , it’s bolted on and I think it helps the belt run Along the bottom of the sander - mine was breaking up and I didn’t fancy it coming off and slapping me in the face so I replaced it for a few £££ . Not sure if yours has one but it’s worth a shot ..
 
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