I started my clubman up today and noticed it is running a little rough, it idles nice, and revs flat out nicely, but holding stable rpm with 1/4 throttle or whatever it is really lumpy.. Like it's miss firing but the fact that it revs freely makes me wonder if it is.. Anyone know what it could be?

Oh, it's a 998 with a 1.5 inch s.u on a water heated manifold. Extractors blah blah..

Cheers

Sean

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Potato

Hi Sean,

Sounds like you have pretty much the same mini as mine - 998, 1.5" SU, water heated manifold, extractors.

You say it idles nice, revs high nice, but lumpy in between?

I'd be placing my bets on the piston - it may be jamming when you only use part throttle, but full throttle 'un-jams' it. Try taking the piston out, giving it a bit of a clean and check the needle and jet. It could also be the choke sticking - just give the jet a little push up and see it it moves.

How does it go when accelerating or decelerating? If it loses power on acceleration, I'd check your dashpot oil - it may be too low of too thin. If it's only having problems when the throttle is steady, this won't be the problem.

It could be timing or perhaps your rockers need adjusting, but the carby is the first place to start.

have a look & see what distributor you have, the 29D type has a common problem where the base plate (vac-Advance) mech wears & lets the points open & close as vac-advance system tries to work on light throttle

an easy check is to take the vac hose off the distributor (or carby) & block up the hole to the carby, & then drive it again to see if the surging has stopped

if that stops the surging then the distributor is the problem

if you don`t have a 29D type dissy then disregard all what i`ve typed & replace your points maybe

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No offence intended here but--> anyone writing a book about minis 30 years ago may not have experienced such worn or stuffed-with components as we are finding these days.

You should put your heart & soul into everything you do.

how old is the fuel in it?