Made a Motobecane engine mount tool (pics)

As was mentioned in previous posts, the engine mount bushings in my 1977 Motobecane 50V needed to be replaced. Or, at least removed and properly reinstalled. The manual is emphatic that the factory special tool, #100024 must be used. And looking at the design, I didn't doubt this.

The factory tool was not available, but Mototbecane was nice enough to publish a scale drawing of the tool in the service manual. The manual can be found in the Articles section of From this diagram, making a few careful measurements, and a guess or two, I designed a tool to do the job. I worked with a friend to machine the needed parts from heat-treated 6061 aluminum billtet.

Here is a copy of the drawing I worked from, taken from the Motobecane shop manual:

Here is what I ended up with. First, a photo of the tool, with all parts loosely assembled, for better viewing:

This is a photo of the component parts, laid out for identification. Starting in the back row, left to right - main tool body, installation stop, push piece. In the front row is the grade 5 drawbolt (additional thread added) and the drawbolt hardware.

Last photo is of the main tool body, with the installation stop installed. This stop sets the correct installed depth for the bushing, at 3/32" (based on measurement only:

So far, I've used the tool to remove & replace the bushings in a spare frame that I have, and it seems to work well. The real test will come later this week, when I attempt an actual repair on my Moby. If it goes well, this is the last step, and the bike is oficially done. This feels good.

Anyway, questions and comments welcome.

MA IRC Chat is online!


Re: Made a Motobecane engine mount tool (pics)

Great looking solution for this problem. Let me know if it works on the actual repair. If you would be willing to build another one...I would like to buy one from you. Let me know.

You the Man

You may have to start renting that out.

Re: You the Man

I am considering building up a batch of these.. half a dozen or so.

Problem is, they would not be cheap.. probably around $65/ea. The machinework on the first one was done for me on a friendly basis, but additional machine shop time would have to be scheduled at $45/hr.

If interest is strong, I'll shop the drawing around to a couple of other machinists I know, with CNC lathes, etc. The original was all manual work.

And of course, this tool is aluminum.. I assume the orginal is steel.

Re: You the Man

Looks good. For cheapness sake, do you think it would be possible to use stacks of fender washers for the pusher and stop, so only the housing would need to be machined? I was thinking about using a socket with the right OD for the housing, but I guess the hexagonal hole is problematic.

Did you buy your flexi-blocks for +$15 each at themopedjunkyard, or is there a better source?

Re: You the Man


MoPedLar mentioned that this can be faked with a socket, washers, etc.

You wouldn't need a stack of washers for the stop, just a single washer would do. Once you feel it hit the stop, you stop applying force. You make a good point - I'll see if I can find a standard washer that will serve in place of the machined stop.

Faking the pusher is a little more difficult, as it needs to be relieved to not put force on the center portion of the flexiblock. The OD of the pusher is also fairly critical; it has to be large enough to engage the OD of the flexiblock, but small enough to chase it through the mounting boss. I just measured a flexiblock and called for 0.010" less on the OD of the push piece.

Haven't purchased any new mounts. I'm re-using the original parts, and possibly the ones from the used frame.

Re: You the Man

Ah, I thought I could see a dimple in the middle of the pusher. Maybe a couple of washers with larger IDs, then a proper-sized washer to push those? Assuming they came in the right OD, which sounds unlikely.

So have your mounts just worked their way out over time? Mine seem to have stayed exactly where they belong, despite the fact that they've nearly dry-rotted through.

Re: You the Man


When I acquired the bike, not only were the flexiblocks improperly installed (one was in way too deep), but both of the mounting bosses on the frame were bent. The lower engine mount was also badly bent, and partially broken.

In fact, the bike is mostly still in this state. It's been too hot here for me to do any work outdoors. I did some rigging with the top spacers, bent back the lower mount, and got the motor into a workable position.. however, the airbox still lightly interferes with the chain.

When I get a good workday, I plan to correct these issues once and for all.

As for the bushings / mounts getting into this state, I have no idea. Could be crash damage.. or bad work by someone without the proper tool, and no understanding of the design.

Re: You the Man

What is the status of the response to your suggestion that you might make a batch of these tools? I forgot to respond but I am still interested. $65 sounds cheap enough compared to a jerry rigged bunch of washers.

Re: You the Man


I used the tool a couple weeks ago, and it worked perfectly.

Haven't looked into making up any more.. many other irons in the fire right now.



Re: Bump

This is an outstanding tool. Well done! You wouldn't want to see the make-shift apparatus i put together...a close fitting socket, a piece of copper drain pipe and a sturdy bolt and washer a-la shade tree style. Necessity is definately the mother of invention...

Re: Made a Motobecane engine mount tool

I'm still interested in buying one of those tools. Maybe the cold north winters will provide the time to build some.

Re: Made a Motobecane engine mount tool

hi, I know this is an old post but is it possible to get the dimensions of this thing? Something that users could present to a machinest.

I have about 20 mounts that need to get moved around between bikes and not to keen on setting the depth with the socket aproach.

Re: Made a Motobecane engine mount tool

i just used a heated up steak knife and just replaced the rubber insides of the mount..and put a single washer on the outside of the mount itself....ghetto.

Re: Made a Motobecane engine mount tool

i'm hoping ghetto will not be a word used to describe the 6 I'm building. Going for stock.

Re: Made a Motobecane engine mount tool

i gotta admit that's impressive.

Re: Made a Motobecane engine mount tool

seriously now people, I have 14 motobecanes. thats 28 engine mounts. I REALLY need one of these.

oh, what I'd do for a set of dealer tools...

Re: Made a Motobecane engine mount tool (pics)

hey man

I WANNA BUY THIS TOOL.......................i know there is a market for this tool. why don*t you sell them to all the poor

suffering moby masses .

Re: Made a Motobecane engine mount tool (pics)

I wish someone cleverer than I could create some "specialty" tools for the ZA50 engine. Keep hearing complaints about the correct spacing between clutches, etc.

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