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Curtis B.
Curtis B., Technician
Category: Small Engine
Satisfied Customers: 13581
Experience:  have worked on and around most engine models for 35 yrs./Polaris ATV expert
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I have a Gravely ZT HD60. When I try to mow, it bogs down

Customer Question

I have a Gravely ZT HD60. When I try to mow, it bogs down like it's under a load and won't cut any faster than a slow walking speed.
JA: I'll do all I can to help. How long have you been dealing with this?
Customer: It started the last time I mowed a couple of weeks ago, in the middle of the mowing session.
JA: Do you have fuel in the tank? If so, is the shut-off valve open and the fuel clean?
Customer: fuel is wide open and a month so old.
JA: Do you plan on doing the work yourself?
Customer: depends on how complex the job is.
JA: Anything else we should know to help you best?
Customer: Nothing more at this time.
Submitted: 1 year ago.
Category: Small Engine
Expert:  JohnF2015 replied 1 year ago.

Hi, my name is***** will be assisting you.

Does this machine have a twin cylinder engine? My first thought is that you are only running on one cylinder which would explain the power loss.

Customer: replied 1 year ago.
it is a two cylinder.
Expert:  JohnF2015 replied 1 year ago.

Being a two or twin cylinder my suspicion would be that you are only running on one cylinder.

The first step that I would take is to remove one of the spark plug wires from the plug and try to start the engine. If it starts then we know that the opposite cylinder is running. Then replace that plug wire and remove the other one. If it still starts then we know that both cylinders are functioning and should not be a problem. However if it fails to start with either of the plug wires removed then we would move on to focusing on the cylinder that did not start. Or the cylinder that would not start with plug wire attached.

Expert:  JohnF2015 replied 1 year ago.

Is this a Briggs, Kohler, Kawasaki branded engine?

Customer: replied 1 year ago.
Kawasaki. I'll run out and pull plug wires now.
Expert:  JohnF2015 replied 1 year ago.

Let me know what you find.

Customer: replied 1 year ago.
sitting in the seat, the left bank is not working.
Expert:  JohnF2015 replied 1 year ago.

So the next thing that I would look at is spark to the left cylinder. Are you getting spark to the plug?

Expert:  JohnF2015 replied 1 year ago.

Everything that you want to do from here would involve the left cylinder since you now know that it is not working.

Customer: replied 1 year ago.
give me 15 min. to pull the plug and check for spark.
Expert:  JohnF2015 replied 1 year ago.

Maybe as simple as a fouled spark plug. If you have a spare plug you might try changing it. If not maybe swap the two plugs.

Customer: replied 1 year ago.
pulled plug, found carbon across the gap. cleaned that up. gap looked good. checked for spark, not quite as blue as I would like. Pulled plug and traded with "good" plug. no start. checked spark on good plug on bad side, better blue spark. put bad plug on good side, engine started, pulled plugs alternating between good/bad side. Bad side still not starting/running. Bad side has some oil, not overly oily. engine oil is good.
Expert:  JohnF2015 replied 1 year ago.

I would move to a compression check on the left cylinder to make certain that it at least has compression.

Customer: replied 1 year ago.
I checked and it is "blowing" out. I don't have a compression gauge handy.
Expert:  JohnF2015 replied 1 year ago.

It "blowing out" is at least a good thing. It would be nice to know exactly what kind of compression the cylinder has. If you want you can move on to removing the valve cover from the left cylinder and check push rods and rocker arms.

Customer: replied 1 year ago.
ok... it's going to an hour + to get a compression gauge. I can pull the valve cover. I'm familiar with rocker arms and push rods. Are we checking for bent, non-functional parts?
Customer: replied 1 year ago.
guidance on pulling valve cover?
Expert:  JohnF2015 replied 1 year ago.

Two bolts in valve cover can be removed then you should be able to pop the valve cover off and check the push rods and rocker arms. I would be looking for bent push rods or broken/loose rocker arms.

Customer: replied 1 year ago.
You've been a lot of help tonight. Unfortunately it getting too late for me to continue tonight. Can we pick this up again tomorrow?
Expert:  JohnF2015 replied 1 year ago.

Yes, you can come back here and continue our conversation at any time. I will not be available until around 7:30 tomorrow evening however.

You can post comments at any time and as soon as I see them I will respond.

Customer: replied 1 year ago.
sounds good. what time zone?
Expert:  JohnF2015 replied 1 year ago.

Eastern time zone

Customer: replied 1 year ago.
ok I'm central talk to you tomorrow
Expert:  JohnF2015 replied 1 year ago.

That will be fine. Have a good night.