Having recently had my trimmer head jam up on me, i took it apart to find one of the con rods had started to break up where the bearings rub on the spur gear cam, and as a result loose parts had quickly stopped play!

I took everything out and removed as much of the old grease and bits of scrap bearing as possible, see below.

As mine had damaged parts i just pulled it all out but be aware that if you are reusing bits then the bearings in the larger head end of the con rods are actually loose when removed from the spur gear cam, so care is needed to avoid dislodging any. you will see in a later photo how the spur gear has been worn by said bearings coming loose and shifting position and wearing grooves into it.

Above shows the case cover with gasket attached, the new spur gear and pair of con rods, and a strip of metal ive no idea what its really called, but it goes between the top con rod and case cover, to stop the con rod rubbing on the gasket.

This pic shows the bottom con rod in position in the head and the spur gear on top of that, plenty of grease was squeezed into the case before dropping in the parts.

Top con rod now in position, first though you have to get the blades in place, with the bottom one located into the hole in the con rod smaller end, then drop the top con rod in, again locating the end onto the blade, you may have to move the blades by hand to line everything up, note the white plastic grease seal/clamp screwed in position over the blades. Also in this pic look closely at the larger end of the con rod and you can clearly see the bearings, they can easily be dislodged if care is not taken when removing/installing the con rod onto the spur gear cam.

Metal spacer/rubbing strip in place, not shown in this pic but, squeeze in more grease around the edges and around the smaller drive gear/pinion on the left of the shot. replace cover, and that's it, simples! Run the unit and see if any grease oozes out where the blades enter the head, if it does you've probably got enough in there, if not use the grease point and add some more to be on the safe side. I would certainly recommend adding more grease after the first use with the new components, as the grease will obviously be flung about around the edges of the head, to where there would normally already be grease sitting, thus leaving less on the moving parts.

Remember to put some grease in here as well, the bolt on the left, according to my dealer this grease point is often forgotten about, you have been warned!

This is the old spur gear, you can clearly see where the loose bearings from the con rod have turned side ways and worn grooves into the cams surface!

Hope that's of help to some one

Anthony ;-)

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  • PRO
    Very informative indeed, thank you so much, given me lots of confidence.
  • Brilliant dit !!And great phots. Just done the same to mine, wish I'd seen the story first.

  • Very informative, thank you.

    Having just put mine back together I'm struggling with how tight the bolts for the blade should be to allow movement and be secure. Did you use thred lock?
  • PRO

    Hi, no need for thread lock, they should just nip up tight against the spacer which allows enough of a gap for the blades to slide over one another.

    If you cant do them up tight enough i would suggest some of the threads may be partially stripped, might be better to get a set of new bolts, spacers and nuts from your local dealer. The spacers can start to wear oval with time.

  • Oh right. There was thread lock on the blade bolts when I dismantled. Maybe that could affect it?
    I worked systematically tightening the bolts in order. Feeling when they pinched. The spacers looked good to me but I'm no expert. It runs well but I do get some heat build up part way up the blade so I would think there is to much friction at that point but I have only nipped up the bolt.

    Think I will take it apart again and have another look.
  • PRO

    Make sure the blades are straight/flat, they can kink if you hit some hidden wire and this could be causing more friction in that area.

    I always spray some lubricant on the blades before using them and during work if your at it for a while, and afterwards to stop them rusting in storage.

  • Thanks for you help Anthony and sound advice about lubricant. I tend to spray before and after a job and sometimes during if needed.

    I striped them again this evening. The heat build up is localised to around one bolt so maybe there is a kink. For now I have only nipped the nut up so it doesn't put to much pressure on it and will give it a test run tomorrow. I am hoping it will wear in. Wishful thinking I know....

  • PRO

    I took apart mine just now and the con rods are each missing about 5 bearings (based on the space) no I didn't take them apart to look at that so I'm really not sure if I knocked them off as I did it today (cleaned all the grease out and searched for the bearings in the grease as I did knock two off as I pulled it out but after putting it back together its 5 missing from each). But if I didn't then the last time I took the back off must be about 6 months, in which its done probably 20 full days and lots of smaller jobs of hedge cutting and there's no sign of excessive wear on the main gear. But surely it must be full otherwise the bearings will all move within themselves in the bearing housing and then it wouldn't be doing much good? I'm really not confident at using them I do have another spare set so its not the end of the world but at £300 for a new one I'd rather not break these.

  • Hi Seth,

    I believe that a space is ment to be there. I'm not sure how big that space is ment to be. I had the same concern however I couldn't find any missing and it's been running fine. I am happy to be corrected.
  • PRO

    Okay thank you.

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