18 replies to this topic

[dennismini93]

Morning!
I'v got a little problem with my 1.5 riley rma. Now I know it's not a mini but an engine is an engine and the basics are all the same which is why I posted here.
When I accelerate I find it spits back though the carburetor. Am I right in saying that this could mean it's running too lean or too retarded?
Thank you in advance.

[dklawson]

Define "spits back".  Do you mean that without the air cleaner on you can actually see fuel vapor coming out of the carb intake or do you mean that the engine is backfiring through the carb when you rev it?

[dennismini93]

Backfiring through the carb, and the exhaust now I think of it.

[dklawson]

Next questions.  How long has the engine been doing this and when did it last run correctly?  What has been done to the car/engine since the engine last ran correctly?

 

With it backfiring out of both the carb AND the exhaust I would carry out a complete tune up.  Set the valve clearance with the engine cold.  If still fitted with points, change both the points and condenser then set the ignition timing.  If the problem persists after that, look for a lean fuel condition.  

[KernowCooper]

With it backfiring out of both the carb AND the exhaust I would carry out a complete tune up.  Set the valve clearance with the engine cold.  If still fitted with points, change both the points and condenser then set the ignition timing.  If the problem persists after that, look for a lean fuel condition.  

 

Took the words right outa my mouth Doug before I had time to think about it.

[dennismini93]

The car has been stood since my grandfather fell ill and I'm getting it running again. It was his daily car and he kept a record of every mile it drove.
However seeing as it has sat for a few years everything could have changed through lack of use.
I'll upload photos later of the mess in the fuel system but I'm sure you can imagine.
I'v done a general service, plugs, leads, oil, Coolant and all new fuel (shell v power). I haven't changed the cap or arm on the electronic dizzy but they looked in very good condition and I know they have only covered about 500 miles.
Value clearance have been done but timing is carried out by measuring the hight of the piston in cylinder one and I haven't located his tool yet.
I richened the carb by one flat on the carburetor just out of interest and it did improve the running but I haven't got a gas analyzer and I don't want to guess the mixture.

[Wim Fournier]

Take it easy. Don't start at the 'far' end. First thing that comes to mind is irregular firing. The ignition system works bij interrupting the primary current.

Now think about loose contacts in the primary circuit. For instance the connection at the coil.

Every time the blade and spade connection moves as a result of the mouvement of the engine as it runs, and the contact is broken for a moment; there will be a spark. A spark at the cilinder which contactpoint in the distributor cap was nearest to the rotor point. When this cilinder is in its stroke with the inletvalve open, you hear it bark in the carburettor. When the cilinder was in its working stroke and the ignition did not come because of lack of contact at the coil, and it comes a little later and the exhaustvalve has openend already, you hear it bark in the exhaust.

So, look at all the connections in the low tension circuit of the ignition system. And your problem will be over!

Edited by Wim Fournier, 10 October 2015 - 12:58 PM.

[dennismini93]

My mini had exactly that issue a few weeks ago. I'v gone through the lt side but I can't see a fault, doesn't mean there isn't one. Will have another look

[sledgehammer]

agree with what everyone above says

 

also check condenser & LT wiring esp base plate earth in dizzi, & points condition

 

if all above is good , then I would check compression , in case valves are leaking / sticking as engine has been stood

[dklawson]

However seeing as it has sat for a few years everything could have changed through lack of use.  I'll upload photos later of the mess in the fuel system but I'm sure you can imagine.

 

Value clearance have been done but timing is carried out by measuring the hight of the piston in cylinder one and I haven't located his tool yet.

 

I richened the carb by one flat on the carburetor just out of interest and it did improve the running but I haven't got a gas analyzer and I don't want to guess the mixture.

 

Having sat for years, you should count on cleaning the carb thoroughly as its float bowl and jet are likely full of gum and varnish.  That will prevent fuel flow and will cause a lean condition.  Is this an HS or HIF series carb on your car's engine?

 

You are confusing valve timing with ignition timing.  I am suggesting checking the ignition timing which involves using a timing light to illuminate the timing marks on the front pulley.  However, if the engine "ran when parked" and you have changed all the ignition parts you listed... don't touch the timing at this point.

 

If richening the mixture made the engine run better, this further points towards a gummed up carb that needs cleaning.  However, don't do anything to the carb until you have read up on what is involved and posted back identifying which type carb is on the engine.

[carbon]

If the RMA still has original carb fitted it should be SU H4 type.

 

As Doug suggests, a good clean-up of the petrol pipes and carb could be first move.

 

If the petrol in the tank has been there more than a couple of years drain it all out and don't use it in any engine, not even a lawnmower unless it's a really cheap 2-stroke engine.

[dklawson]

If the RMA still has original carb fitted it should be SU H4 type.

 

H4 or HS4?  

[dennismini93]

However seeing as it has sat for a few years everything could have changed through lack of use.  I'll upload photos later of the mess in the fuel system but I'm sure you can imagine.
 
Value clearance have been done but timing is carried out by measuring the hight of the piston in cylinder one and I haven't located his tool yet.
 
I richened the carb by one flat on the carburetor just out of interest and it did improve the running but I haven't got a gas analyzer and I don't want to guess the mixture.

 
Having sat for years, you should count on cleaning the carb thoroughly as its float bowl and jet are likely full of gum and varnish.  That will prevent fuel flow and will cause a lean condition.  Is this an HS or HIF series carb on your car's engine?
 
You are confusing valve timing with ignition timing.  I am suggesting checking the ignition timing which involves using a timing light to illuminate the timing marks on the front pulley.  However, if the engine "ran when parked" and you have changed all the ignition parts you listed... don't touch the timing at this point.
 
If richening the mixture made the engine run better, this further points towards a gummed up carb that needs cleaning.  However, don't do anything to the carb until you have read up on what is involved and posted back identifying which type carb is on the engine.

It has a h type carb and like I said I'v cleaned all the fuel system so I'v cleaned the carb, fuel pump, fuel regulator, lines and the tank as well as changing the fuel filters. It was amazing the rubbish you find.

The Rileys didn't have timing marks fitted to them. You instead line the rotor arm up to the cap when the piston is so many thousands of an inch before tdc. In the workshop manual I have it gives a conversion of tho to degrees.

It's running alot better now so I think I'll get the correct tools to adjust the timing then fit my own marks and also ask a local garage if I can use their gas analyzer once the timing is correct.

Like you say the timing shouldn't have changed by just sitting so maybe I'v moved the mixture nut when I rebuilt the carb.

[dennismini93]

agree with what everyone above says
 
also check condenser & LT wiring esp base plate earth in dizzi, & points condition
 
if all above is good , then I would check compression , in case valves are leaking / sticking as engine has been stood

I'll do a compression and a leak test that's a very good idea.
Luckily it's got electronic ignition so no condenser or points.

I have checked the lt leads but I think I'll have another look as it won't harm and sometimes it takes another look.

[dennismini93]

If the RMA still has original carb fitted it should be SU H4 type.
 
As Doug suggests, a good clean-up of the petrol pipes and carb could be first move.
 
If the petrol in the tank has been there more than a couple of years drain it all out and don't use it in any engine, not even a lawnmower unless it's a really cheap 2-stroke engine.

It's 5 year old fuel and Oh my it was orange! The muck that separated out as well was just alarming.

I filtered it and ran my clubby on it every second fill for a few tank loads :/
It's having a new engine soon tho so will be fiiiiiiine