mx5cartalk.com

Has some wobble on the accessory pulley.. Not much at all when the engine is cold started, not enough too worry me but when it gets hot it's wobbling a bit more. Has some belt squeal when cold started the first time on the day.

Engine is a BP-D 1.8L turbo, & I've had a check on the 4 outer bolts & the centre bolt. All still tight & couldn't tighten them anymore. Hopefully not something like the shortnose crank problem that happens with the old B6, although rare & almost unheard of to happen to the BPs but still a possibility.

When I had the NB6 98 model B6 1.6L engine put into my 89 MX-5, the crank accessory pulley looks the same as the BP one I've got above, except it had a full rubber ring in the groove that my current one doesn't..

Cars drives & feels great otherwise though.

look deeper in that groove, I'm sure you'll see rubber in there.

The rubber coming loose is most likely what's causing the wobble, but make sure the hub of the pulley is running true.

if you look directly from the side, you will see the rubber inside the crank pulley.

over time, the unbalance may cause oil pump issues.

Unorthodox Racing makes underdrive pullies however it is not recommended to
use any underdrive crank pullies from any company at all because it can cause
oil pump failures. All Protege engines are directly crank dríven and if an under-
drive crank pulley is used, it can cause accelerated wear in it which will event-
ually lead to failure! Typical underdrive crank pullies do not have a harmonic
balancer and therefore all the oscillating forces from the crankshaft are
transmitted elsewhere. Even on the typically well balanced stock crankshafts,
there is always a very slight imbalance in them and as such the forces caused by
them results in the oscillations. Many turbo Miata engines have blown up from
oil pump failures due to the installation of underdrive crank pullies. Be warned!

hrmm, the NB6 pulley had the rubber right at the front of the groove, couldn't see into the gap at all

it is there, i have the same crank pulley. NA8 MX5s, BA Astinas and GTR Familias all had the same pulley.

remember this? http://www.astinagt.com/forums/showthre ... ank+pulley

that particular photo is an early NA6 B6 with the 4 slots in the pulley. mines the 1 slot the whole way round. i can't actually find a proper flippin BP pulley photo. this ones really similar though, it's from a frankenstein MX-6 engine but shows the rubber all the way round at the front of the groove.