makita cutoff saw dcp7311

rlp in Co. · Jan 13, 2018

Well the carb quit pumping gas so I put in a new kit. I wasted a whole day trying to get it to pump gas. Gas line is not plugged. I have watched the video on rebuilding the carb several times and done everything they say. The only thing I can think is wrong is the new gasket is rough whereas the old gasket is smooth. It is a walbro wj type carb, no primer bulb. Anyone have experience rebuilding these carbs?

Jiles · Jan 13, 2018

(quoted from post at 18:59:47 01/13/18) Well the carb quit pumping gas so I put in a new kit. I wasted a whole day trying to get it to pump gas. Gas line is not plugged. I have watched the video on rebuilding the carb several times and done everything they say. The only thing I can think is wrong is the new gasket is rough whereas the old gasket is smooth. It is a walbro wj type carb, no primer bulb. Anyone have experience rebuilding these carbs?

For the diaphragm to pump, there must be impulse to the carburetor.
With this particular saw, impulse is provided by a separate line to the carburetor top plate through a hose barb.
Vacuum can be checked with a good gauge but pulses will be very slight.
Insure the hose is in good shape and connected to crankcase.

rlp in Co. · Jan 13, 2018

Thanks Jiles. I checked the impulse and it is good. I hooked a clear hose to some gas and spun the engine over with a drill. I could see the gas being sucked up and down about an inch. It seems like a check valve is not working but I did do the check by taking a rubber hose and putting it on the check valve hole a sucking on the hose. I could hear the valve working up and down. Needle valve is new and looks good and adjusted according to the video.

Jiles · Jan 13, 2018

(quoted from post at 00:06:35 01/14/18) Thanks Jiles. I checked the impulse and it is good. I hooked a clear hose to some gas and spun the engine over with a drill. I could see the gas being sucked up and down about an inch. It seems like a check valve is not working but I did do the check by taking a rubber hose and putting it on the check valve hole a sucking on the hose. I could hear the valve working up and down. Needle valve is new and looks good and adjusted according to the video.

Be advised that it has been a while since I rebuilt this particular carburetor but it is basically the same as for a chainsaw.

Gaskets on diaphragm side and needle valve side have a different installation procedure.
Check to be sure they are installed in the correct order. Thin rubber gasket goes on first then the thicker gasket next to cover. The small horse shoe shaped "flappers", serve as check valves and must be next to carb body.
Hope this helps.

rlp in Co. · Jan 13, 2018

Thanks for the pictures. That looks exactly like my carb.
I do have the flapper valves next to the body but they don't look like they fit tight to the body and they are made of a stiff plastic, not like the original black gasket type. That is the only thing that I can see that is wrong. On the diafram side it seems to me that the diafram would fit next to the body and then the gasket but the picture shows it the other way. I have tried it both ways but no difference. You can see it in the link.
I'm going to order a new carb kit that looks like it has the original type fuel pump gasket and try again. I hate to give up and buy a new carb.
Untitled URL Link

Jiles · Jan 13, 2018

I think I have used the type diaphragm gasket before with no problems.
To my memory, they were a whitish colored plastic and appeared and felt rough but worked ok.
How did the original gaskets look?
Usually if these little flappers are flexible and cover the holes in the carb, they are usable.

Have you squirted gas in the carb to be sure it is carb related?
I haven't had a lot of problems with carbs on these saws but have run into a few with bad ignition coils.
If impulse was weak or virtually non existent, I would have suggested checking crank seals or (unlikely) cylinder base gasket.

JD Seller · Jan 13, 2018

Have you checked the crankcase for leaks???? I have found that often the carburetor issue can be cause by a crankcase leaking. Hard starting in 2 cycle small motors is often leaking crankshaft seals.

rlp in Co. · Jan 13, 2018

The one of the little flappers was in bad shape on the original gasket. The engine will start on ether so I am sure that it is the carb.

rlp in Co. · Jan 13, 2018

Thanks for the reply JD seller. I haven't checked the crankcase for leaks. What's a good way to do that? The engine does start on ether but I checked the compression and it only has 60 pounds. I don't know what it it is supposed to have. It did have cement dust on the wrong side of the air cleaner but as long as it still starts, it still should work for awhile. Maybe cement dust is so fine it can go thru a paper filter?

makita cutoff saw dcp7311

rlp in Co.

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Jiles

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rlp in Co.

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Jiles

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rlp in Co.

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Jiles

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JD Seller

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rlp in Co.

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rlp in Co.

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