Stihl saw ts400 main bearing help

[Shaun Dolman]

I am rebuilding a ts400 stihl saw as the main bearing had gone. I am on my third set of main bearing now as struggling to fit them.

here is my procedure

 

warm crankcase

cool bearing and fit in crankcase both side ( Go in easy)

warm inner race of bearing cool crank and fit crank in one side.

Warm in race of bearing and fit the other side.

The problem I am having when its all tightened up is that the crank will not move freely.

I have tried knocking the crank either side with a rubber hammer or copper hammer but still no joy and I have to take apart again damaging the new bearings.

I have purchased yet another set and just dont want to do the same again as not sure what i am doing wrong.

Am I heating the middle race of the bearing too much as I am only using a heat gun .

The second part of the crankcase is tight going on and doesnt just slip on, I have to put the screws in to bring it together but goes together fine.

Is there a right or wrong way round for the bearings as I have been told there isnt from the company I purchased them from ?.

Any help much appreciated.

[spudulike]

In general and not TS400 related: -

 

1) Ensure the bearings are fitted the correct way round, some have a sealed end and these need to be correct as they can bind on the crank and may stop the bearing being lubricated correctly.

 

2) Push the bearings home 100%, it is easy to leave a bearing slightly proud of the inner crankcase and it will bind on the crankshaft. Some bearings push hard in to a seat, others are flush with the casting.Lube the bearings with two stroke oil on fitting.

 

3) De-stress the bearing by clouting it hard with a copper mallet. You can use steel but go careful in case you damage the crankshaft ends.

 

If you do the above, the bearings should be loose and easy to turn. They always stiffen a little once new seals are fitted but this is normal!

 

If you have done all this then:confused1:

[Shaun Dolman]

Hi and thanks for the quick reply .

None of the bearings have a sealed end so pretty sure that they are exactly the same either side .

I have done all of the above but with no luck .

I think maybe next time I will try and put the bearings on the crankshaft first if I freeze the crank and warm the bearing .

If that doesn't work I'm at a loss .

Thanks Shaun

[spudulike]

Hi and thanks for the quick reply .

None of the bearings have a sealed end so pretty sure that they are exactly the same either side .

I have done all of the above but with no luck .

I think maybe next time I will try and put the bearings on the crankshaft first if I freeze the crank and warm the bearing .

If that doesn't work I'm at a loss .

Thanks Shaun

 

The bearings are always fitted in to the cases first and then the crank is pushed in to one case and then the other case is pushed on to the assembly. I wouldn't like to fit both bearings to the crank and then fit the cases......not the way it is done!

 

I have never had the need to freeze and heat parts. They are a tight fit but not THAT tight. You are using the outer race to push the bearing in and using a press/vice/G clamp to fit them?

[adw]

Everybody has there own way of fitting bearings, if you do not have the correct tools i would fit the bearings onto the crank first, this will make sure they are right up against the shoulder, heat the crankcase with a small blow torch ( not sure a heat gun is good enought) drop the crank into one side then heat the other half and do the same again, do not pull them in using the crankcase screws, if the beaings is right home there is no need to do this, let it all cool down and if required copper hammer on either end to remove any tention.