Chain saw carburettor.

[ukracer]

Foolishly I got involved in buying a second hand chainsaw for the next door neighbour.
1. because I will end up using it and 2. because I know that second hand is not the best.

It was either that or he was buying an underpowered cheap chinese one.
Anyway I saw a spear and jackson and in my stupidity I trusted the bloke selling it as he seemed genuine.
Said it had been serviced and he did not really want to go below £60. And it looked clean and tidy with a decent sharp blade and oregon chain guide.
However it was gummed up with chain oil as it does when left (its obviously very sticky) so I stupidly took a punt.

Its got decent compression and after we degreased and cleaned it it runs fine but its a buggar to start. SO I thought ok take the carb of and check the bowl and needles etc. Well it has no bowl and I cant find much info on the carb But it has a diaphram and thats looks good.
SO I cleaned it all up and realised the pipe coming from the bottom of the carb had come up with the carb. However it looks like it was previously connected to something inside as it has a bulge on the end as if it had been pushed onto a spall pipe.

My problem is I dont know what that pipe is for and cant see how to get inside the saw to where the pipe goes to see if it pushed onto something.
Any suggestions other than dont be a ""£$%^ in future.

 

[Seadog]

In my limited experience of motorized tools there are two pipes, flow and return. The feed comes from the priming pump and the return goes straight back to the tank.

 

[Memmeddu]

Pictures ?
It can be a return line ,an impulse line ,a pressure line

 

[ukracer]

In my limited experience of motorized tools there are two pipes, flow and return. The feed comes from the priming pump and the return goes straight back to the tank.

I was thinking the same. But how to get into the place where it goes back to the tank is more than difficult.

 

[ukracer]

Pictures ?
It can be a return line ,an impulse line ,a pressure line

It's the brass coloured pipe in the first photo.
The black plastic one is fuel in from the priming bulb.

 

[Migmac]

Two pipes, one will be a return, one will be the pickup. Both go to the fuel tank. The return is just a pipe, the pickup goes onto a weighted filter. You may have to split the saw body to get them back in. Top handle off and undo the anti vibration elements, disconnect the throttle and it should split. It might differ slightly from what I’ve said but it’ll be very similar

 

[Seadog]

I'm pretty certain that the brass pipe is the return to the tank. I've had to replace the pipes on two of my tools this year, a Partner chainsaw and a McCulloch hedge trimmer. They can be a bit tricky to do. I ended up modifying both tools to make pipe routeing simpler.

 

[ukracer]

I'm pretty certain that the brass pipe is the return to the tank. I've had to replace the pipes on two of my tools this year, a Partner chainsaw and a McCulloch hedge trimmer. They can be a bit tricky to do. I ended up modifying both tools to make pipe routeing simpler.

Yeah that is where the pipe goes. I have just pushed it down there for the photo.
This is the end that went down the hole.

 

[Seadog]

It goes very hard and brittle after a few years. If you find that you need to replace it there are quite a few different sizes, some varying only by fractions of a millimetre.

I had a leak from around the return pipe on the trimmer, where it was just pushed through an opening in the tank.. Bought new pipe and then sealed around it with Loctite 577. It seems have done the job.

 

[MCKDAVID]

have miles of that pipe here in stock, measure the OD and I'll chuck a decent bit in the post, long enough to change it all....

 

[James1979]

Looks like a copy of a ZAMA as fitted to Stihl? There are only a couple of carb makers and most saws seem to be fairly common as far as the carbs go. My 2p as per above is that its the return. To be honest if you paid £60 and its got a decent bar and chain on it then its a fair price. I appreciate you didn't want a project but as long as all the bits are there and intact it'll run with minimum effort.

You can get a repair kit for the carb if you can ID it. If its not been run dry for long term storage, then there is a gauze inside the carb which can get a 'limescale' type residue on it. May be worth a look and a clean....

RE OP's first post, it won't have a bowl. If you take it apart there are one way 2 flaps in a diaphragm which are reed valves. They can split or stick so cause running problems. There is a needle valve which regulates the fuel flow when you operate the throttle - you dont get much issues with these apart from poor seating due to crud.

Hope this helps

 

[zzr1200]

Ones the fuel pipe the other ones the impulse line basically it powers the fuel pump diafram.

There's no fuel return pipe on a chainsaw, apart from maybe one and that's the very latest Stihl 500i...

 

[ukracer]

Ones the fuel pipe the other ones the impulse line basically it powers the fuel pump diafram.

There's no fuel return pipe on a chainsaw, apart from maybe one and that's the very latest Stihl 500i...

Yep. I stripped it down more and found that brown pipe was the other side of the priming bulb.
I put it all back together and again it runs but keeps stopping.
So checked what any normal person would have checked first. Fuel filter and found the pipe inside fuel tank disintegrated......biggest problem is. I need it for the weekend so need to get a filter and pipe locally.

 

[ukracer]

have miles of that pipe here in stock, measure the OD and I'll chuck a decent bit in the post, long enough to change it all....

Cheers mate. I really need it for the weekend and need a filter so I am going to have to pop to lawnmower shop if it's open............I might have to take you up on your kind offer though. Watch this space.

 

[awemawson]

Stihl chainsaw carb have an ‘impulse pipe’ from the crank case to move the fuel. They are rubbery but go hard and are worthwhile replacing on servicing the saw.

 

[MCKDAVID]

no problem, just shout, this is only one of the boxes of it, cheaper to buy it in bulk, equates to pennies per metre... always handy..

 

[Seadog]

cheaper to buy it in bulk, equates to pennies per metre... always handy..

It's dearer than spun gold at my local servicing place

 

[MCKDAVID]

exactly, same here. just let me know, deals can be struck, much cheapness, many many bargains etc etc.... hahahahah

 

[Memmeddu]

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It's the brass coloured pipe in the first photo.
The black plastic one is fuel in from the priming bulb.

I'm pretty sure that priming bulb goes on the return line .
I say that because this is how everything I've worked on was that way .
So fuel line from the tank should be just a line that goes from the tank (with the filter on the bottom right corner of the tank) to the carburettor black fitting in your case .
Then the return (brass tube ) goes from the carb to the priming bulb vacuum side an then from the output side of the bulb to the tank .
It should be fitted this way from my knowledge and experience .
Because the bulb is there to fill the carb it will cause vacuum inside the carb an positive pressure in the tank.
Fuel goes up on the line filling the diaphragm cavity and pushing out the excessive fuel again back to the tank .
Once the engine is running the suction from the engine will cause the diaphragms to pump the fuel to the carb .
Always hated the priming bulbs , I think that are pretty useless , they are there just to cause problems .
They should make the life easier but are just an additional step and another thing which could fail

 

[Memmeddu]

exactly, same here. just let me know, deals can be struck, much cheapness, many many bargains etc etc.... hahahahah

My local parts shop have them in stock .
0.30 euro meter .