OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Walk Behind Lawn Mower Frames Reel Lawn Mowers, Atco & Villiers etc. Morrison Olympic 600 Reel Drive Sprocket

Hi. I'm new to this forum and live in UK. I'm restoring an old (1990) Morrison and have to replace the double sprocket that drives the reel (or cylinder as we call it over here).

I sourced a spare from Spares in Australia (cheaper than buying it here even with shipping). Unfortunately, when it arrived, although it looked identical to the one I was replacing, it did not screw onto the shaft properly. After a couple of turns it got very stiff. Initially, I wondered if the thread pitch had changed between 1990 and now but the part number I ordered is the same as shown on the "old Morrison" parts list I downloaded from this Forum.

I therefore believe the replacement part has a defective thread. Before contacting spares supplier I would welcome any comments - particularly on the possibility of the thread specification being changed. I have emailed Masport with the same question but previous experience is they have limited information on these older machines.

Thanks.

Finnkai,

Please supply the part numbed that you were after and also if you have it the serial number. The thread pitch could be different depending on the age of the unit. If it was made before 1974 then it would have been imperial thread and the one that you received would have been metric.

Hello Finnkai and Bruce
Finnkai, this must be so frustrating.

I cannot find any reference to any change in the reel sprocket used on Morrison Olympics, and
then on early Masport Olympics, and I can only identify one change - the move to a keyed sprocket
in the 1990s (?).

Surely, an engineering house should be able to, free-of-charge, put a thread gauge over the reel
and sprocket threads to identify the issue.

We have not come across this issue before.

-------------------------------
Jack

Thanks for the quick response.

The serial number of the mower is 471179. The parts list gives the number as 004298 - it's the same number in the list you have on this forum for both old and new Morrisons.

The part I obtained from supplier was described as Genuine Masport Sprocket Assembly-10/23 Lh Thread Rm 004298, 032006.

The machine has a 1989 Briggs and Stratton 3hp engine so I assume it was built sometime after then.

Am away from home but when I get back will post photos and try to measure the pitch of the thread on the reel/cylinder shaft.

Thanks again.

I have attached the dealer notification regarding the sprocket and spoken to the technical guys regarding your problem. They have stated that the thread has never changed since the start (thread could have been damaged on shaft when removing old sprocket as new one would have no damage) and the only change is when they moved to a keyed sprocket.

Note that the threaded sprocket was discontinued back in 2012 and is no longer available for purchase through them and the suggestion is to replace the cylinder to the later model.

I would also be assuming that they sent you the correct sprocket as it would have been sitting on the shelve for over 5 years.

That's very interesting. The sprocket I was sent is definitely not the revised, keyed version. It appears identical to the one I am replacing. Ie it is a single piece welded item with 2 toothed wheels on a left hand threaded boss. The one shown in the bulletin you usefully attached, is clearly completely different and made up of several parts.

The thread on the reel is not damaged. The old sprocket screws on perfectly.

So, if you are correct and the thread pitch was never altered, the only explanation is that the thread is damaged on the part I received.

I received a reply from Masport today that simply said "I have checked with our engineer. 004298 is obsoleted and new SPROCKET ASSY-10/23,KEY PKG (item 032006) doesn�t fit the old model unfortunately" which seems to suggest they think I've been sent the keyed version when of course I haven't.

When I get home I'll post photos to illustrate.

Please let me know if you think my analysis is incorrect.

Thanks.

Here's the page on the Suppliers website showing the part I ordered.

Image of part is below.

It has a picture of the item showing it's clearly not the keyed version.

We will not allow advertisements on the forum as this could cause legal issues to our end.

Hi Finnkai
I hope you sort this issue.
Please let us know how things turn out.

--------------------------------
Jack

First, I would like to apologize for inadvertently breaking one of the Forum rules. Thanks to Bruce for editing my post so the dealer's photo of the spare sprocket I purchased is still visible. Now an update on what I have found out about this problem over the last week.

A very helpful engineer at Masport unearthed some technical drawings for this component and sent them to me. I have uploaded them in this post for others to see. I have also uploaded pictures of the "old" sprocket I am replacing and the new replacement part I was sent from Australia which shows that visually they appear virtually identical.

The first 2 drawings are for the "re-introduced" sprocket which Masport tell me was brought back as a spare part in 2008. They show that this sprocket has a M16 (metric) left hand thread at 1.5 mm pitch. The third drawing is older and shows the reel/cylinder spindle or shaft for the older Morrison Olympic mowers. This drawing shows the thread on the end of the spindle is 5/8 inch 18 TPI Left Hand UNF. So it seems (despite the earlier post in this thread) that Masport did in fact change the spec for the reel and drive sprocket from Imperial to Metric around 2008 but (unfortunately) retained the same part number for the new spec sprocket. I have asked Masport if there is anyway to differentiate between the 2 sprocket versions when ordering but have not had any response.

I am therefore left with a "genuine Masport" replacement sprocket of the correct part number (004298) shipped to me in the UK all the way from Australia (at a considerable cost) but which unfortunately does not fit my reel/cylinder. I cannot blame the supplier (although I will let them know about the problem) and I suspect it is unlikely they will have a old spec sprocket even if they were prepared to swap it for the one supplied. So I am investigating other possible solutions.

My best option is to find an "old-spec" spare by asking the supplier to confirm the thread spec before purchasing... but that may be a long shot. Second option is to re-tap the metric thread to imperial - the M16 1.5 metric thread size is pretty close to the old 5/8" 18 TPI UNF (which explains why it does screw on for a few turns before jamming). Another solution would be to re-use the old sprocket "boss" and get someone to weld on a new blank sprocket to replace the one that is damaged - it's only the smaller of the 2 sprockets that is damaged (you may be able to see this in my new and old sprocket pictures).

Thanks to everyone who responded to my initial inquiry and I hope the results of my investigations will prove valuable to others. Any brilliant solutions to my problem or further advice will be gratefully accepted!

Hi Finnkai

Many thanks for that Brilliant research!
I think you have finally solved the mystery there.

To me, it makes no sense why the part number was not changed.
It has clearly cost you a penny!

That's a question beyond my capacity.
If do-able, it would be the best solution.

It may be this topic will help others.
It is a credit to your perseverance that this issue is now better understood!

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Jack