Stihl TS400

[HorseShoeInFork]

I have a Stihl TS400 that I can get to pop occasionally, but won't start. Gas runs out the air filter after pulling it a dozen or so times. It does have a good spark and fresh gas. The decompression button stays down like there may be a piece missing; you can manually pull it up but it falls back down easily. I can't pull the muffler to look at the cylinder because the bottom torx head screw is almost non existent.

 

[lone wolf]

I have a Stihl TS400 that I can get to pop occasionally, but won't start. Gas runs out the air filter after pulling it a dozen or so times. It does have a good spark and fresh gas. The decompression button stays down like there may be a piece missing; you can manually pull it up but it falls back down easily. I can't pull the muffler to look at the cylinder because the bottom torx head screw is almost non existent.

Sounds like the button is fubared.Do a compression test.

 

[jus2fat]

Just out of curiosity..what is a Stihl TS400??

What size is the engine that it needs a decompression button??

J2F

 

[HorseShoeInFork]

Its a 14" chopsaw for steel or concrete. I'll try to post up a pic later. I think it's a 64cc.

 

[HorseShoeInFork]

Ok so after pulling it a dozen times I take the cap off the fuel tank and it blows air and gas out. What does that indicate?

 

[jus2fat]

Check your fuel vent..!!

J2F

 

[HorseShoeInFork]

I will check the tank vent but it's buried down in the saw so it will take some doing to get to it. I did pull the spark plug and the decompression valve and could see 1/2 of the cylinder wall. There was one scored line on the side I could see but it wasn't really that deep. My compression gauge is MIA today or I would check it.

 

[ckelp]

i'd get an easy out and pull the muffler
IMHO pulling the muffler will tell you alot about he saw
like i had a huskey55 that was poping about 145psi but the piston was trashed...

 

[HorseShoeInFork]

I haven't had time to get the muffler off yet, but if I do and find that the cylinder and piston are junk, what are the chances that the crank and bearings will be shot as well. Just trying to figure out if it will be worth it to rebuild or not.

 

[fearofpavement]

It'll be worth about $400 running so use that as a guide to what you want to invest in it.

 

[HorseShoeInFork]

Well, I got the muffler off and here's what I could see. The first pic is of the piston. It looks really good and the rings look great. The second and third pics are what I could see of the cylinder wall. Their not the greatest pictures but its about as good as I know how to do. The cylinder wall doesn't look as bad as the pictures make it out to be I don't think. I'm not against a new cylinder, but if I can reuse this one I will. Also, the piston doesn't have a scratch on it that I can see from here. Should I pull the cylinder completely and see what the other side looks like? When pulling it over, it isn't the easiest at the top and bottom but it's free in the middle.


Piston

Cylinder

Cylinder

 

[HorseShoeInFork]

I have a better feeling about the crank after seeing this.

 

[bcorradi]

Bearing failures and intake side piston wear are really common on concrete saws. I've seen a lot of concrete saws including TS400's that had bad case bearings or an extreme amount of intake skirt wear due to lack of air filter maintenance. I'm not implying this particular saw has it, but its just another thing to look for.

 

[fearofpavement]

It should pull over pretty smoothly if you pull it with the spark plug removed. Try that. If there is significant roughness, it could indicate bad bearings. (assuming the piston is good all the way around)

 

[HorseShoeInFork]

I pulled the plug and it's the same resistance at the same spots. Almost feels like the piston is sticking at the bottom and there's a squeek. I've used newer 400's and even without the decomp pushed in, they still roll over a lot easier and freely than this one. Only way to find out for sure is to get the cylinder off. Regardless of what I find I'm going to make it a runner again. I'll try to post up as I get into it.

 

[HorseShoeInFork]

There was a small square piece that came out of the muffler. I assume this was just something that wasn't completely stamped out from the beginning and it finally fell out. Or is it supposed to be attached?

 

[simonUK]

Got 16 of these in my shop all but one needed crank bearings you need 6202 and 6203 c3 bearings if your replacing them. Take the cylinder off most likely there will be plating lost on one or both sides, this will cause a lack of compression.

The exhaust is totally normal happens to all of them.

Watch out for 3 hole coils very likely to go wrong and hard to find if you want to replace it.

Either plug the decomp or replace it the saw will not start if it is open
Simon

 

[HorseShoeInFork]

Do the crankshafts themselves ever show much wear or is it usually just the bearings?

 

[simonUK]

The crankshafts seem to be alright and are pretty tough ive found compared to some you wont know until you open the saw up

 

[HorseShoeInFork]

I got the saw tore down yesterday and the piston is definitely shot, the cylinder is not that bad but I am going to go ahead and replace it. The crank is in excellent condition. On the cylinder replacement do I go with the Nikasil?