Lotus Elan

Starter Motor compatible with Ford MT75 gearbox

PostPost by: RichardHawkins » Fri Sep 30, 2022 8:37 pm

I am fitting one of these gearboxes to my Elan S4, and had selected a Lucas starter LRS 736. Having tried this starter on my engine it seems to struggle to turn the engine over fast enough. The engine is not in the vehicle, and the starter is connected directly to the battery.

Does anyone have a recommendation for which starter to use?

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PostPost by: stugilmour » Mon Oct 03, 2022 3:54 am

Richard, I originally got my replacement starter from Spyder Engineering. It was a Wosp unit with a clockable face plate to fit my MT-75 with Lotus Twin Cam within the Spyder chassis. I actually had to modify the chassis slightly to fit it. If you are fitting to a Lotus chassis you may have difficulty.

I understand this exact Wosp unit I first got is no longer available. The part number was LMS1045 for Ford BDA / X-Flow / Twincam.

I recently purchased a replacement starter LMS558 from this supplier that is working well. It is the middle Hitachi based unit on the page, recommended for tight fit.

https://www.autoelectricsupplies.co.uk/ ... #flash-msg

The starter itself is the same as my original one except it has beveled teeth on the pinion, which was required in my application. However, I had to use my original face plate to mount it. The plate that came with this particular starter could possibly be modified to fit by reducing the thickness. IIRC the bolt pattern was similar or the same, but the spacing to the ring gear is the issue. I ended up having to get my mount machined locally to get everything to fit.

Sorry I cannot recall the details better for you. I was actually considering purchasing a second unit to have available in case mine fails again.
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PostPost by: RichardHawkins » Mon Oct 03, 2022 6:27 pm

Stu,

Thanks for the information. The AES website tells me that their starters are 1.4 Kw. The LRS736 (Lucas starter) I am told is 1.2 Kw and the original bendix type Lucas starter is 0.81 Kw. If this information is correct then the starter I have should do the job. Perhaps I need to look elsewhere for the engine turning over slowly. My engine has not run yet and certainly could be a bit stiff. If the engine won’t turn over fast enough to start, then maybe a bump start will loosen everything up before I buy another starter that I maybe don’t need.

Thanks for the help,

Richard Hawkins
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PostPost by: promotor » Mon Oct 03, 2022 7:18 pm

RichardHawkins wrote:Stu,

Thanks for the information. The AES website tells me that their starters are 1.4 Kw. The LRS736 (Lucas starter) I am told is 1.2 Kw and the original bendix type Lucas starter is 0.81 Kw. If this information is correct then the starter I have should do the job. Perhaps I need to look elsewhere for the engine turning over slowly. My engine has not run yet and certainly could be a bit stiff. If the engine won’t turn over fast enough to start, then maybe a bump start will loosen everything up before I buy another starter that I maybe don’t need.

Thanks for the help,

Richard Hawkins


Richard, I'm guessing your starter is high torque - if it is, the higher torque is made available by lowering the speed. A relevant phrase that springs to mind (which I hope I've applied correctly to the starter motor issue) is "half the speed, double the torque".
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PostPost by: RichardHawkins » Tue Oct 04, 2022 5:06 pm

Promotor,

Yes I think you are quite correct if the power is the same half speed will be double the torque. An LRS 736 is a simple pre engaged starter, with no reduction gear. I will look to see if there is any other reason for the engine turning over slowly.

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PostPost by: promotor » Tue Oct 04, 2022 8:02 pm

RichardHawkins wrote:Promotor,

Yes I think you are quite correct if the power is the same half speed will be double the torque. An LRS 736 is a simple pre engaged starter, with no reduction gear. I will look to see if there is any other reason for the engine turning over slowly.

Richard Hawkins


Cheers for the info. Check earth connections (is starter getting very hot, or not?).
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PostPost by: RichardHawkins » Wed Oct 05, 2022 5:43 pm

Promotor,

I hadn’t thought of checking if the starter motor is getting hot, I will do, but was more thinking along the lines of the pinion and ring gear not meshing correctly.

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