Hayter 56 poor drive

[Kevin18]

First of all please excuse my ignorance as I know very little about mowers. I have been using this machine for years and until now it has never let me down. The symptoms are that it has lost 90% of its drive and it happened suddenly. The drive belt is intact and if I lift the rear roller it can be seen to be going round. I have removed the plastic casing and exposed the shaft that comes from the side of the base of the engine. This shaft has a pully on the end which in turn has the drive belt. I assume that the shaft/pully should turn all the time. However when I put the mower into drive I only have to hold the mower back slightly for the shaft and pully to stop turning. I assume that is not right? Any ideas what is the cause of this and do I need to go shopping for a new mower!! Thanks

[pleasant]

That is quite an old model harrier 56 with the side pto drive...got to be at least 20 years old now, as the side pto briggs engines were discountinued at least that time ago, to the more popular briggs engines without a pto and the drive taken from a pulley on the crankshaft like 99% of mowers we see today. The side pto engine drive mechanism was very reliable as it was a very simple set up. Yes, the pulley on the left side of the engine is a direct drive...so all the while the engine is running, the pulley is rotating. If your pulley stops rotating when there is roller resistance such as simply placing the weight of the mower on the ground, then this suggests to me one or both of the roll pins that secure the pulley and spacer tube to the pto shaft have either fallen out or sheared off allowing the pully to rotate independent from the pto shaft. The pulley is a tight fit on the pto shaft so it may well rotate when not under any load...which is what you have mentioned. Part number for the roll pins is 03997.

 

I suspect this is definitely your issue..it was not an unusual problem especially on older machines due to fatigue of the pins. Look at that first, then come back to me if you are convinced they are fine.

Edited May 12, 2023 by pleasant

[Kevin18]

Thank you for your reply. I have looked and there appears to be a hole near the pully where I suspect one pin should be and I can feel maybe 3mm of what must be the other pin protruding from the shaft. I assume then that it has sheared and the protruding 3mm is what is left of the pin The inner pin sits very close to the engine and looks difficult to get at. Would you suggest I remove the engine to replace it or is there an alternative. Thanks 

[pleasant]

There are two seperate pins...one in one end of the connecting tube and one the other. The end of the connecting tube nearest the engine is a pig of a job to get at. Most likely you will need to loosen the three engine mounting bolts to get better access if that one need replacing. If it is still there and part of it has simply worked its way out, then if you can, knock it back in flush with a drift and then thread strong locking wire down the centre of it and wrap around the connecting tube...this will prevent it falling all the way out in future and will save you having to replace it now. If it is missing or you feel you need to replace it, then ideally yes remove the engine for access BUT I guarantee you won't get off the large metal friction disc on the underside between the blade and the engine...they weld themselves to the crankshaft over time, which means you won't be able to remove the engine fully. Like I say, you can just access the three bolt heads behind it enough to loosen them to give some clearance. If it is the outer roll pin you need to replace, then that can pretty much be done in situ- however if there is any of the old pin remaining in the hole, don't do what most people do and punch it out from the top down, as it will have nowhere for  the broken part to come out the otherside and will lock the pulley against the chassis so you wont be able to move it......unless you loosen the engine bolts for clearance. Best punch it through at an offset angle so it can just drop out the other side. Also be careful punching these pin in or out too hard....it is very easy to shear off the pto shaft flush with the engine...these parts are obsolete, so if you do it will be scrap.

 

I used to charge just over an hours labour (assuming it all went to plan) for this job, and people couldn't understand why it cost so much just to replace two pins. When I said I had to take the engine off to do it, they didn't beleive me!

 

Edited May 12, 2023 by pleasant

[Kevin18]

Thank you so much for your advice. The pin at the pully end is missing completely . I have managed remove the rear pin. The small piece that was protruding broke off like a biscuit from which I conclude it wasn't attached to the rest of the pin. I took off the exhaust and turned the shaft to a quarter to three and managed to knock the remains of the pin out sideways. I am now about to buy the new pins. The only thing is I noted that the front pin is much smaller than the back. I guess I just buy a box of assorted sizes? Thanks again. PS I am rather enjoying this!

[pleasant]

No, don't use generic ones- use the right ones. They are readily available and are not expensive... doesn't make sense to me to cut corners when this is a pain in the backside job to have to do again if they fail. Part number you need is 03997. They are all the same pin used in the PTO components, so maybe someone has had a go at yours already. I am assuming yours is the 340 series? Note your serial number on the sticker on the body and it will tell you....if it is, then they are definitely that part number and are all the same.

[Kevin18]

While I agree with you and have found the back pin using that part number the front one is tiny compared with the back one. I have measured the remains of the back pin using calipers and it is 3/16 as per the part number but the hole for the front pin is no more than half that size!

[Kevin18]

No ID sticker unfortunately 

[pleasant]

Well, it would be unusual if it wasn't the 340 series TBH, but like I say all the pins are identical.

[openspaceman]

21 minutes ago, pleasant said:

Well, it would be unusual if it wasn't the 340 series TBH, but like I say all the pins are identical.

If it is a roll pin it may have snapped flush both sides so the OP is looking at the hole in the middle