6 replies to this topic

[Chris Whitlow]

Hi,

 

My son's 1980 Mini 998 appears to missfire slightly when flat out or when cruising.

 

I've checked the the ignition timing  and replaced the plugs, leads, condensor and have adjusted the points (they look like new). I've also checked the mixture using a colour tune and it appears ok.

 

However, from my internet searching, the engine number, 99H 791 (1974 onwards), doesn't stack up with the distributor, 41882A  58D4 (Mini 1988 onwards). Is it possible that the vaccuum advance curve on the later distributor doesn't match the engine and could be causing the problem?

 

I'm contemplating rebuilding the carb and changing the coil but I'd like to know if the distributor could be the issue first.

 

Thanks for your help,

 

Chris

[Spider]

That dissy is for a Low Compression 998 engine, originally fitted to the 998 Metro 'Commerciale' (no, not a type), I think they were export models.

 

It has a LOT of advance to it (24 degrees at the crank), I think your son's Mini would be happier with less advance, around the 20 degree mark.

 

For a test, set the static or initial) timing to about 5 degrees retarded from where it is now, disconnect and block off the vacuum advance (on the carb side) and try again, it will likely be slugging until it gets up around 3000 RPM mark, so don't worry too much about that, just see if this resolves the high RPM miss. If it does then there is a number of dissys that are suitable, but lets see if this is the problem.

[Chris Whitlow]

Thanks for that Moke Spider.

 

I've done exactly what you suggested and it did made a difference at the top end. It did start to run hotter so I've put it back to where it was for now. Do I need to adjust the mixture a little to help with the retarded ignition in the short term?

 

As the distributor is the wrong one for the engine can you suggest a better alternative please, is a 45D correct or are there better alternatives?

 

Cheers,

 

Chris

[Spider]

Does sound like it's over advancing.

 

I've actually got to duck off to do some paid work right now but I'll suggest something a little later, unless someone comes along in the mean time.

[Spider]

If the engine's standard, then a 41418 is a fairly common and should be easy to find 45D4 Type.

 

Mini Spares have new reproduction types, while I haven't bought one for a 998 from them, I have bought a number of 1275 types, tested every one and found them bang on spec. IMO, good value for money too.

 

https://www.minispar...ic/BAU1962.aspx

[Chris Whitlow]

Is there any benefit in getting this electronic version of the 45D dizzy? It's only a little more expensive.

 

http://www.minispare...px|Back to shop

 

[Spider]

They are quite good and I did mean to suggest that as an option.

 

No points or condenser to fail and they generally hold tune much much longer. You'll also find you get a better spark from them too.

 

You will need to check the Coil though to be sure it's compatible, I'm not 100% sure with those particular modules what the minimum resistance of the Coil should be, most 'want' a 3.0 ohm or more Coil, just check on this as if it's too low a resistance, it will destroy the electronic module. Nothing to be paranoid about, but just something to be mindful of.

 

I've found these types of modules to be quite reliable, though I did have one taken out by a Coil failure (was one of the modern Lucas Coils).