mx5cartalk.com

I have just bought another mx5,it is a 92 model,just noticed a wobbly crank, so i took the pulley off to have a look, it has a broken woodruff key,it has moved a bit and enlarge the edges of the pulley, so I will need a new one, will a Na8 pulley fit a Na6? I have a B6t motor with a 8 hole pulley, but it is different to this one,still uses the smaller bolt, any info would be great on the difference in crank pulleys.

It's a well known weakness with both the B6 and BP motors. It may or not be recoverable. Try googling "short nosed crank" or just SNC here and on miata.net and settle down for a few nights' reading.

I probably can fix it, just wondering what model crank pulley would fit.

I don't think B6 and BP pulleys are interchangeable.

The main fix that people use is this one ... http://www.miata.net/garage/hsue/LoctiteCrank1.html This means a new NA6 timing belt pulley,woodruff key and main pulley bolt. Not really all that expensive from Mazda (or at least not from Max Kirwan where I paid under $100 for the NA8 set)

I've never heard of putting a different pulley on. I'm pretty doubtful that a BP pulley would fit, the whole design and sizing is different. Mazda part numbers are different too.

spikey wrote:I have just bought another mx5,it is a 92 model,just noticed a wobbly crank, so i took the pulley off to have a look, it has a broken woodruff key,it has moved a bit and enlarge the edges of the pulley, so I will need a new one, will a Na8 pulley fit a Na6? I have a B6t motor with a 8 hole pulley, but it is different to this one,still uses the smaller bolt, any info would be great on the difference in crank pulleys.

spikey wrote:I probably can fix it, just wondering what model crank pulley would fit.

the later NA6 has a different looking pulley amongst other things to combat the SNC problem. by the sound of it you should have the later pulley, i.e. with 8 instead of 4 slots on the front, which could mean you need another 8 slot pulley from a late model na6.