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Jswd32

Makita DCS3501 Bogging down under load

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Hi,

Picked up this saw about 6 months and it has run brilliantly. However, when I tried to use it at the weekend it started to bog down under load. It idles fine, however, even under minimal load it starts to lose power and stall. Afterwards it smelt hot and you could hear pinging sounds where the metal of the engine sounded like it was hot.

 

At first I thought maybe its a clogged air filter, so took that off and although a little bit of dust nothing to write home about, cleaned up and no better. I then thought maybe its the sprocket/ clutch slipping, but I would think if it was slipping revs would surely increase and not cause the saw to stall under load.

I pulled the chain and it doesn't look like its got a lot of chain oil on the bar grooves, so thought maybe the oiler is not working. I don't know how to check this, but have recently seen you can clean out the hole on the bar in case it is clogged. But again, couldn't see how this would cause engine to stall under load. Also have since read about making sure the bar grooves are not in poor state, causing the chain to begin to eat into the bar, causing friction. So will check these next time and file down flush if looking rough.

 

 Lastly I thought, as the engine idles a little high, perhaps its too lean on jets, but I'm no expert in tuning jets.

 

Any advice would be helpful. With the Coronavirus isolating, I would like to put my time to use in clearing up some of the winter fallen trees, also would be good to just be doing something proactive.

 

All the best

 

Joanthon

 

 

 

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How old is the machine, is "picked up" a new unit or second-hand?

With the idle running high and the saw smelling hot/pinging, I would say you either have a fuel shortage or an air leak.

If you carry on using it, if you haven't already, you are likely to seize it.

A new machine should be unlikely to have an air leak unless an impulse line has come off..... a fuel issue is more likely.

You could retune the carb....1/4 - 1/2 turn anticlockwise on both screws, readjust the idle and check the colour of the spark plug. Manufacturers do tune their carbs a bit lean now and can cause over-revving.

Check the colour of the spark plug, tan is OK, white is OMG, grey is feck it as white is overheating and grey is where the piston has started to melt and the grey is combustion mixed with aluminium spatter.

If the above is no help.......

Check the carb internal gauze strainer - take it out and make sure the open areas are unblocked. Replace the fuel filter,

Worth checking the compression or just take the muffler off and make sure the piston looks OK when viewed through the exhaust port. Check the fuel line isn't split - less likely on a newer machine.

If the above checks out and it still isn't right, you probably have an air leak so split manifold, impulse line or crank seals are the usual suspects.

 

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Thanks, Thats really comprehensive. Its second hand and I would guess about 8yrs old. I have removed the muffler to check the piston and its looking beautiful, so thankfully its not that.

Will later tonight investigate the air leak and potential fuel shortage.

 

Thanks again.

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Fuel starvation! The main fuel tank line was completely perished. Makes sense why it idled ok, but under load it was sucking air in!

 

You could only see this after completely removing the carb. Only issue is, I created a bigger job for myself, by trying to pull the fuel line through the tank as had some spare fuel line to try. Anyone looking to do this, what you can't see is that the the fuel pipe that goes into the carb, is only a short pipe that connects to a nipple. I had thought it was all one pipe like on my old Jonsered. 

 

The problem I then caused was pulling the fuel pickup pipe of the connector inside the fuel tank. So this essentially means I had to remove more of the chassis to get to the fuel pickup nipple, that then was a pig to remove as a previous owner, had siliconed it in.

 

So after snapping the fuel nipple lol, I am now ordering one of these as well as new pipe. But overall at £3 for new pipe and plastic nipple. Thats still pretty cheap.

 

 

   

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1 hour ago, Jswd32 said:

Fuel starvation! The main fuel tank line was completely perished. Makes sense why it idled ok, but under load it was sucking air in!

 

You could only see this after completely removing the carb. Only issue is, I created a bigger job for myself, by trying to pull the fuel line through the tank as had some spare fuel line to try. Anyone looking to do this, what you can't see is that the the fuel pipe that goes into the carb, is only a short pipe that connects to a nipple. I had thought it was all one pipe like on my old Jonsered. 

 

The problem I then caused was pulling the fuel pickup pipe of the connector inside the fuel tank. So this essentially means I had to remove more of the chassis to get to the fuel pickup nipple, that then was a pig to remove as a previous owner, had siliconed it in.

 

So after snapping the fuel nipple lol, I am now ordering one of these as well as new pipe. But overall at £3 for new pipe and plastic nipple. Thats still pretty cheap.

 

 

   

Glad you sorted it .

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Sounds like you are well on your way, glad you know what the issue is now.

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