MTD YardMan Yard Bug doesn't stay engaged in gear

Stones

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Jul 21, 2014
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Hello, I just purchased a used MTD yard bug, Model 13B-325-401. Engine runs great but after I brought it home I was unable to get it into either forward or reverse. Today I tried adjusting the brake cable since engaging the brake allows the shifter to be engaged for forward or reverse. I also noticed the the reverse cable was broken. With the adjustment to the brake cable I was able to get the mower to engage in the forward gear but it would disengage after a short distance. Stopping and using the brake pedal I could re-engage the forward gear but it would continue to disengage after a short amount of time. I was going to try to adjust the brake pedal even more and see if I can determine if there is an adjustment that can be made to the shifter cable. Does anyone have any other ideas on what may be causing it to pop or disengage from gear?

Stones

Update: After adjusting the brake cable and the shifter cable I was able to get it to go a little longer before it would stop moving. Engine stayed running fine. I also noticed that if I just tapped the brakes, I could start moving forward again. Didn't have to touch the shifter. I also noticed that it truly was staying in gear not only because tapping the brakes would allow me to continue moving forward but if I killed the engine I couldn't push it forward because it was still in gear. There must be some tie-in between the brakes and the gear/transmission.

Anybody have any ideas?!?!?!

Stones

Ok, one last thread of thought before I call it a night. Can the root cause be the clutch safety switch located behind the brake? It seems that if I have to tap the brake it must be causing the clutch safety switch to be reset allowing for the mower to move in gear.
 
Last edited:

Carscw

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The way MTD drive works. Is the gear selector and brake is one unit.
If the mower stops moving and will go if you tap the brake. Then you need new belts.

Sent from my iPhone using LMF
 

dad7432

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Mar 15, 2013
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Whatever happened to your Yardbug?

I doubt it's the belts, but you should check both their condition and that they are properly mounted anyway. The belts on mine were replaced at the beginning of last season. I know the belts were replaced because the mechanic improperly installed a belt guide. I damaged the belt in 5 minutes of (very smokey) operation. I had to replace the blade belt a second time. Then, later last year my Yardbug started to have trouble with reverse. Forward worked OK, but reverse was irregular, at best. So at the end of last season I took my mower to a different shop. But instead of preparing my mower for winter and checking the operation of reverse, he went bankrupt and it took me 6 months to get my mower back (last week).

So I decided to become a backyard Yardbug mower mechanic and obtained service manuals for the mower and engine and got hold of a nice diagnostic Q&A chart, which had me first checking the operation of NOT the belts, brake/clutch pedal, or the "go pedal", but the operation of the two cables that operate the forward and reverse gears. The reverse gear is engaged by pulling on the cable mounted towards the front of the mower. It just needed to be tightened! The procedure was easy enough, once I removed the steering wheel, yellow plastic gear and throttle handles (held on by tiny hidden screws), and the plastic decorative/protective cover. If your mower is dropping out of both gears without shutting off, it is likely that both the forward and reverse cables need to be tightened. Try this first (it's easy). If this doesn't work, move to the brake/clutch and the "go pedal" cables, which are more difficult to adjust. If either of these is not properly operating, both forward and reverse will be affected. Only if the mower is shutting down is a safety switch an issue, since they cut the engine.

Bottom line for a Yardbug: I would always suspect the issue is a cable before anything else. It's the nature of the beast. Its mechanics are sound, but highly dependent on control cables that are properly adjusted.
 

turtle

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Oct 25, 2016
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HI just read your story on Yard Bug and problem with gears I'm rebuilding one and having an issue with it only rocking back and forth now I haven't gotten to the point of the engine running yet my question for you is must the engine be running to put theses lawn mowers in gear how can I put it in neutral will it roll freeing with out the engine running need some help
 
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