Chain saw carburettor.

[armalites]

If you don't have one to compare to don't assume the diaphragm is ok. They should be as soft as tissue paper almost. If there is any stiffness it will affect it. I've done a few of mine recently, some of them were a dog to start but were fine once running. Carb kits transformed them.

A top tip if you aren't going to be using it much then buy premix like Stihl Motomix/Aspen or if mixing your own use Esso Supreme 99, it has no ethanol in it. The Esso website confirms this unless you live in a certain areas. The amusing thing is the pumps are still marked E5 because they are required to do that by law. It's the ethanol that gooses these things if not used regularly

If you look on one of these sites and look at the carb kit pictures you will most likely find a kit even if it doesn't specify the exact name. Diaphragms can be a bit funny as there will be subtle differences in hole locations. Sometimes it doesn't matter as the hole is covered.

https://www.gardenhirespares.co.uk/
https://www.lsengineers.co.uk/

As @Seadog says the tubing can be a nightmare, many sizes and often you find different outers with the same inners, this can be an issue they need to fit tightly in a tank grommet.

I wouldn't get too carried away with it, you can buy a bottom end Stihl or Husqvarna for £130-145

 

[Robotstar5]

When you have time look for Mustie1 on youtube, he has rebuilt lots of different (mostly small engine) carbs, it was his channel where I first saw the carbs without fuel bowls.

 

[armalites]

When you have time look for Mustie1 on youtube, he has rebuilt lots of different (mostly small engine) carbs, it was his channel where I first saw the carbs without fuel bowls.

It was him who started my urge for an ultrasonic cleaner. I look forward to his new videos on a Sunday. They come out at 11:00, I sit and watch them while having a sandwich at lunch time.

 

[ukracer]

There's an animated video explaining how the chainsaw carb works, I found it useful getting my head round it. I've refurbished and repaired quite a few saws and they are all still running but I never did any of the "supermarket" saws with any great success, they are made to a price and there are a lot of variations so you are stuck for spares apart from the main consumables like bar, chain and spark plugs. Buy a Stihl, Husqvarna, Echo or Dolmar and the parts are all readily available from somewhere



Some saws have the impulse built into the manifold and a hole in the carb flange to pick up the impulse. Zama and Walbro are the main carbs used on better saws.

The biggest problem was I found a guy who showed how to tune it. BUT he was telling us wrong.
The correct way is identical to an RC nitro engine.
Turn tick over up a little. Tune the bottom end...low speed needle.
Once that's running well you drop the Rickover so it does not hold the bottom end artificially high.
Then tune the top end..remembering not to go too lean.

 

[ukracer]

If you don't have one to compare to don't assume the diaphragm is ok. They should be as soft as tissue paper almost. If there is any stiffness it will affect it. I've done a few of mine recently, some of them were a dog to start but were fine once running. Carb kits transformed them.

A top tip if you aren't going to be using it much then buy premix like Stihl Motomix/Aspen or if mixing your own use Esso Supreme 99, it has no ethanol in it. The Esso website confirms this unless you live in a certain areas. The amusing thing is the pumps are still marked E5 because they are required to do that by law. It's the ethanol that gooses these things if not used regularly

If you look on one of these sites and look at the carb kit pictures you will most likely find a kit even if it doesn't specify the exact name. Diaphragms can be a bit funny as there will be subtle differences in hole locations. Sometimes it doesn't matter as the hole is covered.

https://www.gardenhirespares.co.uk/
https://www.lsengineers.co.uk/

As @Seadog says the tubing can be a nightmare, many sizes and often you find different outers with the same inners, this can be an issue they need to fit tightly in a tank grommet.

I wouldn't get too carried away with it, you can buy a bottom end Stihl or Husqvarna for £130-145

It's not mine...I purchased it for my next door neighbour.....

 

[DAPPH]

I think this the most confusing as I dont think the cheaper saws have an impluse pipe. To me its logical that the plastic pipe on the carb would be fuel IN from the filter.....BUT I am not convinced as its not running correctly yet.
This could be because the carb is blocked or dirty I guess but having never seen one without a bowl I am not keen on trying to clean it until I am 100% certain its plumbed correctly!

Cleaning a carb can often be done by cleaning the air filter area ..take the air filter off start the machine , run it as high a speed as you can without it stalling then slap a stout blank ,( book etc that will fully seal the carb inlet ) over the hole & let the engine speed developed vacuum drag a bit of fuel through the jets & ways . You might actually flood the cylinder and wet the spark plug doing this so be prepared to take the plug out and pull the engine over several time , dry the plug and put it all back including a new or cleaned & dried air filter .

 

[pedrobedro]

The biggest problem was I found a guy who showed how to tune it. BUT he was telling us wrong.
The correct way is identical to an RC nitro engine.
Turn tick over up a little. Tune the bottom end...low speed needle.
Once that's running well you drop the Rickover so it does not hold the bottom end artificially high.
Then tune the top end..remembering not to go too lean.

It's best if you have a recommended starting point with the L & H screws. Most Zama and Walbro are something like 1.25 turns out from completely in on each and then work from that. If your L screw is running weak you will get a flat spot between low and high circuits. On the H side the saw should 4 stroke (revs go fluffy like a misfire almost) at the top end then it cleans up and pulls when it's in the wood under load. Don't use the saw under part throttle they are supposed to run flat out.

 

[mtt.tr]

Some saw will appear to not have an impulse line, in fact they do but it's on the inlet manifold.
Echo often use this approach and some stihls

 

[ukracer]

It's best if you have a recommended starting point with the L & H screws. Most Zama and Walbro are something like 1.25 turns out from completely in on each and then work from that. If your L screw is running weak you will get a flat spot between low and high circuits. On the H side the saw should 4 stroke (revs go fluffy like a misfire almost) at the top end then it cleans up and pulls when it's in the wood under load. Don't use the saw under part throttle they are supposed to run flat out.

Well the saga continues. Like rocking horse pooh to find that exact cab. I know that saw was manufactured by einhell but they are not interested in providing info.

I have not stripped it yet as I got it running perfectly earlier `today and just as I had done 5 test cuts and stopped I could not start it since. SO....perhaps its not card and its piston and rings (even though their seems to be lots of compression).

So I have fond a similar carb as the diaphrams seem even harder to identifiy. But I am not convinced yet.https://www.gardenhirespares.co.uk/4175-tarus-silverline-4500-5200-carburettor.html

 

[pedrobedro]

Take the exhaust off and wind the piston past the exhaust port and you should see if there is any damage. Heavy scoring will be obvious if it has seized at any time or look to see if the rings are seized. It's not a good saw to be spending any time or money on, you could get a Husqvarna 120 new for £135.

 

[ukracer]

Take the exhaust off and wind the piston past the exhaust port and you should see if there is any damage. Heavy scoring will be obvious if it has seized at any time or look to see if the rings are seized. It's not a good saw to be spending any time or money on, you could get a Husqvarna 120 new for £135.

Mines better than this one....I am waiting to watch his follow up to see how he fixed it. Lol

 

[pedrobedro]

Mines better than this one....I am waiting to watch his follow up to see how he fixed it. Lol

That old Echo is alright for a curiosity or collector but it's an old saw with no chain brake or anti-vibe so I wouldn't want to use it regularly in a modern setting.

 

[ukracer]

That old Echo is alright for a curiosity or collector but it's an old saw with no chain brake or anti-vibe so I wouldn't want to use it regularly in a modern setting.

What I meant is that is exactly what the one I have was doing. I then cleaned the carb and it ran better for a few mins before failing to start after cutting a few logs.

 

[pedrobedro]

Did you strip the carb? If you did I would do it again and make sure everything went back in the right place, diaphragms in the right way and gasket right side of the diaphragm and is the metering arm set high enough but not too high. Also squirt some carb cleaner through all the passages and check the jet and the strainer in the carb is clear. It's all basic stuff but easy to get wrong if you are not familiar with the model. Stick with it you'll get there in the end.

 

[ukracer]

yeah I have done that twice. BUT I think I have identified the same Carb in a walbro . WT-596-1 and a lot oif others it would seem. JUst gota find a carb now. I have found a few but all say not available..

 

[armalites]

yeah I have done that twice. BUT I think I have identified the same Carb in a walbro . WT-596-1 and a lot oif others it would seem. JUst gota find a carb now. I have found a few but all say not available..

Walbro WT carb kits are cheap as chips. You can get genuine Walbro ones for £8 and non genuine for £3-4

If the carb is clean inside I just swap the gaskets and diaphragms and it nearly always cures running issue unless someone has been exploring in there before and adjusting settings

 

[ukracer]

Walbro WT carb kits are cheap as chips. You can get genuine Walbro ones for £8 and non genuine for £3-4

If the carb is clean inside I just swap the gaskets and diaphragms and it nearly always cures running issue unless someone has been exploring in there before and adjusting settings

Got both coming now mate. It's annoying me. Oh plus a brand new Chinese one I can give the next door neighbour. Lol

 

[ukracer]

Walbro WT carb kits are cheap as chips. You can get genuine Walbro ones for £8 and non genuine for £3-4

If the carb is clean inside I just swap the gaskets and diaphragms and it nearly always cures running issue unless someone has been exploring in there before and adjusting settings

Well......it all looked ok. Gaskets turned up today and I set the low and high screws one turn out.
Few pulls and it ran sweet. Did a bit of adjustment on the low and let it warm up.
Readjusted the low the Rickover and the high and it sounded good.

But the damn thing does not like ticking over and respond quickly without bogging when hot.

It's not easy to tune when it's hot either.

Seems similar to what it was like before changing gaskets even though the new diaphram is way softer than the old one.