Worn Rings? Ransomes Fourteen Mk1
Tried to solve this problem last year and gave up and moved on.
Starts and runs fine for about ten mins then gets week stops and wont restart despite having a spark,fuel getting through ( cap breather clear )valves moving free and adding fuel direct, petrol or easystart and wont fire till cooled down.
I am starting to think the rings are worn and when hotter looses compression, does that sound feesable?.
I have a compression tester but it doesnt register on my mower, What reading should I expect to see?.
I’m not a fan of compression testers on small single pot engines . An issue with many engines is that they incorporate some form of compression release to aid starting . This may be mechanical in the form of a centrifugal valve lifter or a design of cam that lifts a valve a minute amount just before top dead centre. If an engine has such a feature a rope starter won’t spin it long enough or fast enough to get a useful reading for a conventional compression gauge to give a useful reading. A more useful indication of an engine’s condition is obtained with a leak down tester, but while the cost of a suitable tester has now fallen into DIY territory, it does require a source of compressed air.
That said, I don’t think that your engine has any form of compression release but I still wouldn’t bother with an automotive type compression gauge. What I would do is to check the cold valve clearances. If they are tight or non existent cold, it could well be that the valves are not seating fully as the engine warms up. Doing a proper “ valve job” , refacing the valves, skimming the seats and setting the clearances , will often brig about a worthwhile improvement for not much more than the cost of a couple of gaskets.
Thank you, Great advice.
I have looked up leak down tester and looks alot more suitable for the test I need to do, Inexpensive and a handy peice of kit to have around.
My engine does not have a compression reduction valve, I know the type of thing you mean my old Raleigh wisp had one.
The valves have good clearance and have been reseated.
Another thing that's happening is oil spirting out the crank vent, Would that indicate worn rings?...Pressure leaking past the rings on compression pressurizing the crank case.
Can you recomend a firm for new rings?.
Oil from the breather can indicate crankcase compression and possible piston blow by. I’m not sure what type of breather valve is used on your engine but what ever it is, make sure that it is working and not gummed up. The purpose of that valve is to allow an exit for crankcase air displaced by the downward stroke of the piston and to seal the crankcase, creating a degree of negative pressure , on the upward stroke. Negative crankcase pressure assists in keeping the engine oil tight. If worn rings, and bore wear, are allowing excessive crankcase pressure that valve may not be able to cope. Most breathers incorporate some sort of filter to retain oil vapour and this may be just a little disc of sponge that has now gone crusty..
For new rings, try Paul Child at Meetens , Jon Cruse at the Hailsham Mower Centre, or L&S Engineers.
Should have suggested this a way back. Have a trigger oil can filled with SAE 30 or heavier handy . When the engine stops and won’t restart take the HOT plug out and give a good squirt of oil aimed at the top of the piston. Plug back in and try again . If it is rings the oil may raise the compression enough for it to fire up
Thankyou I will give that a try.
Rings orderd from meetens.
Will let you know how it is next week.
New rings arrived fitted, Started ran well for a few minutes then died as before.
Checked for spark... present.
Checked fuel supply...present ( I have another carb running on another mower ).
Kept checking for spark and became intermittent at times, Checking again when spark present moving cable around no change.Kept checking,Then suddenly no spark.
Started to dismantle to get to electrics and just before removing fly wheel I checked and had a good spark, so abandoned and reasembled and around and round it went until I ran out of time.
So I'm at a loss now,If it stops producing a spark altogether I can find and fix the fault.
I think I'll have to avoid the temptation to run it again until I've stripped back the electrics ( It just sends me round in circles and wastes so much time).
From cold it always starts and runs, so unless I find something untoward I fully expect the coil to read ok when metered.
Any suggestions would be gratefully recieved.
Find someone with a proper ignition tester, not just a multimeter taking coil resistance readings and doing a sort of condenser test.
Failing that , fit a new condenser.
With the absence of an ignition tester,Stripped back to coil... points were abit pitted so cleaned and reset.
Condenser charging and discharging, All leads intact, apart from the lead to coil doesn't seem a tight fit... Is it a screw fit same as cap?, Didn't want to risk destroying the coil by breaking the lead off.
Anyway put it all back together... Started ran well for 10mins then died, wouldn't restart, got the odd fire but wouldn't run.
Will order new points and condenser next week.
Almost certain that the ht lead is screwed onto a tapered spike at the bottom of its socket.
A proper condenser tester will give multiple charges to show whether the condenser is “filling up” followed by a waiting period to show any spontaneous discharging . A while back I had two “new” condensers both of which failed the charge, hold and discharge test and turned out to be rather old stock.
Thankyou for your kind advice Wristpin, I will order a HT lead also and hope iv got it all covered.
Interesting about the nos condensers, Fingers crossed I dont end up with one of those.
Now running sweet after replacing points condenser lead and plug, Prime suspect I think may have been the ht lead that wasn't all that tight in the coil ( Not enough meat to shorten and refit )and hardened plastic.
The old air filter ( doughnut shape )is beyond cleaning so intend to cut a foam filter.
Final job is to Sharpen the blades, A whole different ball game.
Thankyou for all the tips.
intend to cut a foam filter.
The foam should be “ open cell “ to let it breath properly.
Purchased as air filter foam, So hope it's the right stuff.
Relocated to the Technical Forum - only just spotted the original post is in the wrong place.