stihl FS 460 gear box issue

[Aspen51]

I have a stihl fs 460 brush cutter and I have replaced the gear bearings as they failed. I have replaced them and the gear box works but when i put the blade back on and tighten the nyloc bolt the gears jam up and i cant move the gear box. I can take the gear box apart but it does the same thing when i put it back together. Any ideas on how to fix this? Cheers

[spudulike]

Take a look at the IPL below and make sure the components are in the correct order. It sounds like on securing the blade, the gears are forced further together than they should be. Check part "4" as it may be in the incorrect position. Possibly screws "16" are too long and not original?

 

Edited March 30 by spudulike

[GarethM]

Was it just the bearings you replaced or did you change 2&3/6&7.

 

Plus make sure it's well greased, as per above ensure the 4 washer is in the correct place as when you tighten the blade it pulls everything downwards seizing it against the housing cover.

 

Playing devil's advocate I'd also ask if the original bearings just seized or grenaded as that may have damaged the teeth on the gear wheel and head as they may operate but under load they have to mesh perfectly.

[Aspen51]

All of the other parts are original the only things I changed are bearings 8,9&10 photo below of it today when i took it apart bearing 8 is still in the gear box head.

[GarethM]

As per spud, is 4 fitted ?

[Aspen51]

yes its hard to see in the grease but it is definably there

[GarethM]

Kinda running out of ideas, but I did think.

 

Assemble it without the input gear and see if it binds up again, just wondering if something is worn on maybe the input shaft side.

 

So when it's assembled it's like a UJ joint that's not straight if you get my idea.

[spudulike]

The problem would most likely be that the longer shaft gear is being pulled against the smaller gear when you are fitting the cutting head. You just need to work out why this is happening. I don't have the part in front of me but you need to work out why.

Just looking at the parts list...bearing 9 could be too thin - are they OEM and fitted in the correct price. if washer "4" is missing, it would have the same effect. If bearing "8" isn't seated correctly then the same.....

Is part "15" fitted as without it...the same condition as it would appear to secure the last bearing.