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Engine gearbox removal model 50

Submitted by richard_whitfield1 on Monday, 9 June, 2025 - 20:26
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Hi all
I have a 1959 model 50 wideline.  I am in the process of replacing the gearbox.  I have worked out that I will need to remove the engine and gearbox as one.  I do not want to strip the engine as it is running well.  

Will I be able to remove the engine and gearbox from the frame without removing the cylinder head? 

which is the best side to remove them from, on searching the site it looks like it is best to slide them out on the right side, is this correct for a wideline?  

do I have to remove the main stand?

any advice will be greatly appreciated as it looks like a complicated process.  

I have stripped the inner and out primary chain cases already and the engine sprocket is off!  

I have searched the site and not found much info on this process so far. 

thanks in advance for any help. 

Submitted by richard_whitfield1 on Tuesday, 10 June, 2025 - 18:41

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Further to my earlier post, I think. Have worked out that I will need to remove the main stand as it is attached to the engine plates.  

I am continuing to remove  the battery box and oil tank and hopefully I will be able to see a bit better how I should continue.  

The gearbox looks like there may be room to take it out without physical removing the engine but not sure.  

Looks like the left hand side might be the best side to remove engine gearbox if gearbox will not come out on its own.  

suppose I should just "do it" and see what happens. 

Submitted by richard_whitfield1 on Thursday, 12 June, 2025 - 08:15

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Of course while I am about to just do it, please feel free to offer any advice that might help.  I am still wondering weather head needs to come off and which is best side to remove the lump from?

Submitted by dan_field on Friday, 13 June, 2025 - 09:05

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On a pre featherbed I just took out the RHS engine plate after dismantling the primary side and wiggled it out that way - I may have had to loosen/remove the oil tank to help - I can't recall! 
Dan

Thanks for reply Dan. I was beginning to wonder if my posts were get through.  I have made some progress which is good.  I now have the gearbox out of the frame and didn't have to take the whole engine gearbox lump out.  It was not easy but I am working on my own and need to keep the lifting and shifting down to a minimum.  All I need to do is remember how it all goes back together. 

Richard, well done. Your post has just come to my notice, as l don't regularly visit. l would have thought that th manual explained how to turn &wiggle th g/box (only)out of th R.h. side .th manual may be available through NOC, th Dominator one seems to be, and has similarities except th engine. l have recently acquired a M50 slimline collection of most big pieces,and have another project (N15) before starting 

Submitted by richard_whitfield1 on Wednesday, 18 June, 2025 - 09:11

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Thanks Barry.  I have a 1959 Maintenance Manual and Instruction Book for 88, 99, ES2 &Model 50, which is very helpful. Unfortunately it does assume a level of knowledge skill when removing the engine gearbox.  It states the the engine gearbox should come out as a unit, no info on removing gearbox on its own.  As far as instructions for lifting out of frame it tells you to undo everything and lift the unit clear and suggest that you might need someone to help hold the frame steady.  

In "just doing it" on my own I have managed to get the gear box out without lifting the whole unit out.  I intend to put a post up with what I learnt a bit later.  I was a bit surprised that I did not get many post from fellow model 50 members but assumed that it couldn't be that difficult and didn't warrant mush thought.  

busy putting it all back together now. 

Submitted by john_oldridge on Wednesday, 18 June, 2025 - 21:27

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Hi Richard 
Sorry about our lack of response re your engine removal, just got back from the international rally in France and didn't look at any posts! 
Dan is right about the engine plate removal, and from memory it is fairly easy to remove the engine especially if you take the weight via a small rope/ engine lift through the top of the frame, (much easier because it's a featherbed) 
Hope all goes well, it's not rocket science, take photos it may help with the replacement.
I assume it is an alternator model, mine is a slimline 1960 M50 with coil ignition, and like Dan, its years since I did a full engine/gearbox removal.
Regards John O

Submitted by richard_whitfield1 on Thursday, 19 June, 2025 - 07:38

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Thanks for reply John.  

I am in the process of putting it all back together now. Gearbox successfully replaced without having to remove the engine.  It was a bit of a fiddle trying to lift the engine gearbox plates high enough to get the gearbox lower bolt out.  I guessed that the lack of response was probably down to most owners were probably riding they bikes rather than working on them in the middle of the summer!   Thanks again Richard 

Submitted by richard_whitfield1 on Thursday, 19 June, 2025 - 20:25

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Just a quick roundup of the questions from my original post. Firstly a removed the battery box, oil tank and tool tray as suggested in the workshop manual. I also unscrewed the gearbox sprocket nut while still in the frame using top gear and rear brake. 

From my original reading I thought I would have to take the engine and gearbox out as one unit. This was not the case, it turned out that I could get the gearbox out on its own while leaving the engine in place. Once I was able to remove the lower gearbox bolt it was easy to twist the gearbox around and remove it from the right side.  Thanks goes to earlier post from Bruce Mitchell, Neil Wyatt, Tim Stockdale plus numerous other from the big twin forum regarding engine gearbox removal from wideline frame Dommis.  

I thought I would have to remove the main stand as on inspection it looked like the main was attached to the engine plates.  Again from following earlier threads on the forum I realised that my wideline frame had the hollow mainstand nut and bolt with a smaller nut and bolt going through to the engine gearbox plates. Once I had removed the through bolt I was able to leave the main side in place. This was very helpful as I needed to support the frame in a few different ways. 

My questions about removing cylinder head and which side to take the engine out became superfluous as I was able to remove gearbox on its own. 

following advice from the heavy twin guys I thought I would be able to remove the rear four plate to frame  bolts, slacken the front mounting plate to frame bolt and then jack up the rear plates enough to remove the lower gearbox bolt. Unfortunately this did not quite work. The lower rear plate has a slight hook shape that stopped the gearbox from lifting high enough to get lower gearbox bolt out.  I then used a platform under the engine and removed the front plates that gave me the room to move the whole engine gearbox unit far enough froward to lift the gearbox high enough to get the bottom bolt out. Job done.

Sorry about the length of this post and the lack of any technical jargon.  

 



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