MX-5 OC Forum

SAZ posted this originally
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A spreadsheet I created to allow Roadster owners (Mk1 and Mk2) to get an approximate manufacturing date (month):

 http://www.verithingeoff.110mb.com/MX5%20stuff.htm

This is based on publically quoted registration data. Mazda has not released monthly sales/registration figures for 1990, 1992 and 1993, so there may be inaccuracies. If anyone has this information, or finds significant errors, please let me know so I can make adjustments. Note, in some cases, Roadsters were not registered in Japan until quite a long while after manufacture.

I have determined now the holy grail for 1990 owners; the Roadster VIN cutoff for LWSC.

From http://www.do-da.co.jp/sun-mec/na61/na6_f_1100.html

Short nose crank P/N B616-11-300B. This is for Roadsters with VIN upto
NA6CE-127441.

I now see the original error.

From the spreadsheet, that would indicate Aug-Sept 1990 was the change.

But, this must be stressed, this is the build date, not registration date. The only 100% foolproof way to determine if your car is affected is to inspect the crank pulley design.

Interestingly, this listing indicates that this crankshaft is now a deleted part.

P/N B6S7-11-300 would seem to be the long nose crank.

But it gets murkier. 3 woodruff keys are listed:

B630-11-317; for cars with VIN upto NA6CE-110083 (Jan 1990?)
B630-11-317A; for cars with VIN between NA6CE-110083 and 127441.

This might be confirmation of the rumours that Mazda in Japan had an interim "fix". The "A" suffix I think is for revised parts that can be retro-fitted (ie. interchangeable with the earlier part).

B3C7-11-317 is the woodruff key for the long nose crank

And it goes on:

JF01-11-405 is a crankshaft pulley bolt for Roadsters with VIN NA6CE-136055 and above. (Jan 1991). Perhaps this addressed the problem in some long nose crankshafts of the pulley bolt working loose.

The Sept 1990 date chimes in well with what is said here:
http://www.mx5club.org.nz/emaillists/nzmx5list/archives/2005/msg00548.sht

Miata list would indicate that the cutoff for Miatas was a build date of Sept 1990, but that the LWSC was still cropping up on cars registered into 1991.
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* denotes any digit

JMZNB18P***400001 onwards. September 2003 Production.

New Design 16-Inch Aluminium alloy wheel (5 twin spoke).
Speakers added to Aeroboard.
Fuel Pump Operation Changed to improve startability (fuel pressure inceases rapidly)
-Ign. on FP runs for 1 second, then off.
-Cranking/engine running FP on.
-Engine turned off, FP runs for 2 seconds, then off.
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JMZNB18****300001 onwards. August 2002 Production.

Low Fuel Warning Light added
Cone Type Differential introduced
Seat Belt Warning Light added
ISOFIX System added
Wiring for heated mirrors added
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JMZNB18**00204926. February 2001 Production

Car-navigation (Sat Nav) system added (option)
Theft-deterrent system added (alarm)
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JMZNB18**00200001 Onwards

NB Facelift (MK2.5) Introduced.
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JMZNB18**00135999. July 1999 Production

Rear defroster power cut switch deleted
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JMZNB18**00132306. May 1999 Production

Boot lid release lever cancel function added.
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JMZNB18*200117638.

Fuel filler none return valve changed to increase refueling speed.
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JMZNA18*2**300001 September 1995 Production

3 terminal type coil introduced on BP 1800cc engine (low tension side).
Transponder type immobiliser adopted
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JMZNA18B200110630. October 1990 Production

"Long Nose" Crank adopted
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JMZNA18B200105747

Flash-to-Pass facility added from production.

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Mk 1 cars had a couple of minor facelifts.

The first was at:-

VIN 2000001
and the second at VIN 300000