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I have a fairly new DR Trimmer with a Briggs ex675 motor. I didn't empty the gas over winter. The nit wouldn't start. I bought a new carburetor and installed it. The mower started right up but it doesn't run smooth, it lopes. What is wrong?

Loping or throttle surging is normally caused by a dirty carb that has idle passage in the carb clogged. If you engage the trimmer head does the loping go away or no different

No different.

No different.

ILENGINE said:

Loping or throttle surging is normally caused by a dirty carb that has idle passage in the carb clogged. If you engage the trimmer head does the loping go away or no different

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If not a Briggs carb the aftermarket carb could be suspect. Also an intake air leak between the carb and were the intake pipe connects to the engine block could cause lean issue. And third an issue with the governor. If you hold the governor steady to stop the surging how does the engine sound. Smooth running or running rough.

I will look at these things tomorrow, thanks. Is there something besides spraying the carburetor with cleaner can I do to the original carburetor?

jyl23 said:

I will look at these things tomorrow, thanks. Is there something besides spraying the carburetor with cleaner can I do to the original carburetor?

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With a new aftermarket carburetor, and the engine is hunting and surging, it is running lean (not enough fuel). The air/fuel mixture ratio is not right. Best thing you can do in this case is completely clean the original OEM carburetor and reinstall.

Tiger Small Engine said:

With a new aftermarket carburetor, and the engine is hunting and surging, it is running lean (not enough fuel). The air/fuel mixture ratio is not right. Best thing you can do in this case is completely clean the original OEM carburetor and reinstall.

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And just to add to Tiger if it is the carb with the metal fuel bowl, don't figure the bowl nut because that is were the main carb jet is located.

I tried to clean the original carb., the unit still wouldn't fire. I went ahead and sent the aftermarket one back and ordered a good one. Thanks, you guys for all of your help.

Do you have good fuel flow AT the carb inlet?

How much trash is in the fuel tank?

Fuel tank cap vent venting?

Would it fire on starter fluid? Just to rule out a spark issue. If it was running with it before(I know it was poorly) and will not now suggests you did not put something back correctly. Check the O rings and make sure everything is tight. I would double check everything from the spark plug wire to the Governor links and springs. Gas issues? Put in Fresh gas to rule that out.

As IL Engine has said the aftermarket carbs today are a crap shoot. You may get lucky and it runs great. Often enough they are jetted wrong and you will get surging or just not running correctly. I know OEM parts are expensive. That is why 90% of the time I rebuild carbs. The Aluminum is better and they will work as they should after being cleaned out and replacing any bad gaskets and seals.

I think the EX675 has a plastic carb. Right? The benefit is that the plastic will not rust. Did you snap the main jet assembly all the way in? Is the spacers in place correctly ? When cleaning these carbs you have to be gentle with the any compressed air. You can blow out the ball plugs and lose them. I actually like cleaning these carbs. They are easier to clean. I can have one out, cleaned and reinstalled in 30 minutes.