9 replies to this topic

[MiniFTW]

Does anyone else get this, or have they had it? It's driving me crazy and its costing me lots of pennies in oil.

The car runs lovely round town, no smoke. But say i'm on a national speed limit or over taking, as soon as i shut off from 50/60/70 and let the engine over run, then go to accelerate again, it smokes like a gooden! Its oil as well because I can smell it when it does it. I'm Running 20/50w I'v even used stop smoke, and the problem persists. Engine was rebuilt about 1500 miles back and has always had this problem, its had new valve guides and stem oil seals.

Its a 1275 unit, running an sw5 cam. Dyno tune pointed out that the engine had very high vacuum at the top end when I took it in for fine adjustments. I'v done a compression test tonight and I'm getting between 190/200 PSI on all 4 bores.

Its driving me mental, so has anyone got on ideas on what could be causing this?

Thanks.

[bmcecosse]

It is oil getting up past the rings - so the remedy is obvious. The compression readings are very good - but the oil rings could be damaged - or installed wrong way up?

[MiniFTW]

Chuffin with the compression test I must admit. But the bloke who built my engine has been in the engineering/engine building trade his whole life, I can't justify him fitting rings wrong. There is no real way of telling if there fitted wrong without stripping the engine again is there?

Edited by MiniFTW, 19 September 2012 - 04:49 PM.

[AVV IT]

I have had exactly the same problem since my engine was rebuilt, see my thread on the matter: http://www.theminifo...ge__hl__burning

Incidentally the guy who built my engine has been in the engineering/engine building trade his entire life too, wasn't the same bloke by any chance was it??

Edited by AVV IT, 19 September 2012 - 05:52 PM.

[ANON]

i've seen knackered pistons/rings that give good compression, when the oil seals them, but then smokes like a james bond car!!

[lsto]

Probabily is rings, possibly a faulty oil ring as the lads above stated. I know you said its done 1500 miles since its last rebuild but you may find as time wears on its oil consumption will reduce. Was the engine bored out or is the block standard?
Also this may sound stupid but you said your engine has quite a high vacuum at top end, hows your air filter? As your on the overrun the engine struggles to breathe anyway, you may find something blocking the intake which is causing your motor to draw through the rings. Your motor ain't breathing is it?

[MiniFTW]

I have had exactly the same problem since my engine was rebuilt, see my thread on the matter: http://www.theminifo...ge__hl__burning

Incidentally the guy who built my engine has been in the engineering/engine building trade his entire life too, wasn't the same bloke by any chance was it??

Cheers, I will give that a read through and try some of the things mentioned. Haha probably not unless you brought your engine all the way to Nottingham?

Probabily is rings, possibly a faulty oil ring as the lads above stated. I know you said its done 1500 miles since its last rebuild but you may find as time wears on its oil consumption will reduce. Was the engine bored out or is the block standard?
Also this may sound stupid but you said your engine has quite a high vacuum at top end, hows your air filter? As your on the overrun the engine struggles to breathe anyway, you may find something blocking the intake which is causing your motor to draw through the rings. Your motor ain't breathing is it?

I would hope that the piston rings were not faulty or knackered already as they were replaced when the engine was rebuilt. The engine wasn't re bored just honed, but everything was so tight when it was put back together. The filter that's on it is just a cone filter from mini mine note special, probably a Chinese cheapy. The breathers used to chuff abit on idle but last time a checked they were not, possibly clogged up? there not plumbed up properly to the carb just open breathers.

Just to add i'm running a HIF44, when the carb was being set up the pipe in front of the fuel overflow pipe had to be blocked off because the carb litterally wouldn't set up if it wasn't. I'v read that this is quite normal and thought nothing of it though....?

Edited by MiniFTW, 19 September 2012 - 10:19 PM.

[bmcecosse]

There's at least part of the problem - you MUST connect the carb to a breather pipe to try to minimise pressure in the crankcase - which pushes oil up past the rings, and causes oil leaks at the clutch and the timing cover. The 'breather filters' are a shocking waste of money.......

Edited by bmcecosse, 20 September 2012 - 07:53 AM.

[MiniFTW]

Cheers bmc, I will get the hoses today and hook the breathers up to the carb correctly and take it out for a run. Will post the results later.

[davej]

I've been having exactly the same problem with mine, I've got the head loose and just need to get the exhaust manifold out of the way then off with the head and have a look whats going on, I'm hoping its not the rings but I have a sneaky suspision it is