Ransome Triple Mk4 pertol Mag engine help won't idle

Tagged: ransome triple MK4 Mag petrol idle problems

This topic has 32 replies, 9 voices, and was last updated 7 years, 7 months ago by vhgmcbuddy.

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May 30, 2016 at 9:46 am #21033

trusty220
Keymaster

The head gaskets were prone to leakage on these engines on a regular basis when they are worked hard. The only way to get a useful life out of them was to torque them down as per the diagram in the manual. There was an amendment to the manual that was put out in a Ransomes Service Bulletin quite early on, and that was to increase the head bolt torque to 40 lb/ft and open up the air cowling on the left hand side just above the clutch to increase the airflow.

Good luck with it.

May 31, 2016 at 2:39 pm #21043

vhgmcbuddy
Member

Thanks for the info guys’ I removed the head and all seems ok no signs of head gasket letting by. so I’ve ordered a new one and I’ll send my carb off to be rebuilt at Meetens. Paul was very helpful and should only cost about £100.

I’ll update this again when I get the parts back and put on probably be after the weekend now!

July 18, 2016 at 8:30 am #21516

vhgmcbuddy
Member

A quick update, the rebuilt carb from Meetens is fitted and with the new head gasket I’ve adjusted the timing and it still won’t idle. The idle stop screw on the carb is screwed fully in and as soon as i back it off it will stall with out a good bit of throttle. Interestingly once the rev’s start to drop it is unrecoverable, and just stalls, no matter how much i feather the throttle. I’m really starting to think it’s the throttle linkage/ governor setup as it’s running really well on full load with all the cutters down. I’ve watched the governor lever pull down on the throttle when the rev’s start to die and the engine stalls, could it be something as simple as the linking rod connected the wrong way around closing the throttle instead of opening it as the rev’s drop? If anyone has a photo of how the throttle linkage/ governor should be connected that would be great. I’ll try and video it running tonight and upload so you can see what it going on.

July 18, 2016 at 9:33 pm #21519

wristpin
Participant

Presume that being twin cylinder it has some form of conventional distributor . Does it by any chance have a centrifugal advance and retard mechanism that may be seized up?

July 19, 2016 at 7:50 am #21520

vhgmcbuddy
Member

Yes there is a conventional distributer fitted to the engine but I don’t recall seeing any spring weights on centrifugal plate fitted I’ll take a more detailed look tonight and see if it is fitted it is all moving freely. I suppose this could prevent the engine from running at lower engine RPM as he timing could be permanently set for full engine speed.

July 16, 2017 at 10:55 am #25915

vhgmcbuddy
Member

No news is bad news!
After numerous hours tinkering and 2 more different carburetors and rebuilds later I’ve still got the same problem. It just won’t idle. I’ve been persevering and using it (starting it in gear to prevent damage to the gearbox as with no idle i can’t disengage the centrifugal clutch) Then last weekend it started to run a bit rough and lose power after about 10 mins of cutting. As i drove it back to the barn it finally stalled about 100yds away. I left it to cool down and made a cuppa and went back to it after an hour or so and it seemed fine, so i continued to cut the grass only for the same problem to come back after about 10 mins. I was once told that the little condensers in the distributor can cause this so I swapped that out, then after only 5 mins cutting on Sunday. A very different noise almost metallic and total lose of power, now it will only just run with a lot of throttle. I’m thinking something more sinister might have let go inside the engine. Piston ring perhaps? I think i’ve got the bite the bullet and rebuild the engine, not in the middle of the summer when the grass is growing !!

July 16, 2017 at 1:44 pm #25916

wristpin
Participant

Cam or valve problem – maybe?

July 17, 2017 at 2:57 pm #25927

vhgmcbuddy
Member

I was thinking that a valve seat maybe corroded where it had sat outside so long but as it seemed to run fine on load at higher rpm it was just the idle jet in the carb preventing it from idling. I’m completely stumped by it!!

July 18, 2017 at 8:15 am #25937

trusty220
Keymaster

The one thing that is worth trying is to re-set the governor. Some people used to set it to increase the revs under load to offset the effect of blunt cutting cylinders, so you may have been the victim of this bad practice.

It is a simple setting to make but you need three hands. With the engine stopped, key out of ignition and handbrake applied, follow the governor rod down from the throttle butterfly to the governor arm. On this arm you will find a small clamping bolt which you must undo. Hold the throttle into the fully open position on the carb and note which way the governor arm turns to reach the fully open position. Insert a small, slotted screwdriver into the slot on the end of the governor shaft and turn the shaft in the same direction until you feel a stop, then tighten the clamping screw to fix the arm to the shaft in this full throttle position.

After this the governor should pull the engine down to tick over if the governor is working correctly.

Best of luck.

July 18, 2017 at 8:52 am #25938

vhgmcbuddy
Member

trusty220 your a true gentlemen, I’m pretty sure there is something wrong with the governor setup and this is the setting I was looking for. I will give it a try tonight when I get home, I still think there is an issue deeper in the engine but hopefully this will hold on until the autumn when I can strip the engine down for a rebuild. Thanks again

July 18, 2017 at 9:30 am #25939

vhgmcbuddy
Member

HI, I had this problem with one of these and it was caused by either gasket gone on manifold or a cracked manifold.

August 10, 2017 at 2:58 pm #26220

vhgmcbuddy
Member

I removed the valve access cover on the side of the engine and found a cracked exhaust valve spring. Removed the inlet and exhaust manifold and the head and replaced the cracked valve, rebuilt and the engine is running fine again, but still won’t idle if I adjust the tick over down it just stalls. I’ve reset the governor as per trusy220’s advise and still the same problem. Also I’ve still got the problem that the mixture screw on the carb has no effect on the running of the engine I can screw it all the was in and even remove it completely and the engine note doesn’t change a bit. I’m almost 100% convinced I’ve got a blockage somewhere in the carb but how else can I clean it apart from cutting it open?

August 10, 2017 at 4:23 pm #26221

wristpin
Participant

Some good news, at least you can mow !
Ultrasonic cleaning is the way to go but even that is not always successful. Borrowing another carb could be a way to go but I guess that they are few and far between . I’m sure that you have, but double check for air leaks between the carb and the inlet manifold and the manifold and the engine. If you have had to reuse existing gaskets a good smear of heavy grease or Vaseline on all mating faces is a good get out of trouble fix . Should also have said to check all mating flanges for flatness , especially any alloy ones that may have bowed due to over tightening in the past.
A way of checking for induction air leaks is, with the engine running, to spray or squirt WD , thin oil or Redex around the flanges and joints between the carb and engine. If there is a leak it will suck the stuff in and change note and make a bit of smoke.

August 12, 2017 at 11:01 pm #26242

vhgmcbuddy
Member

Thanks for the reply Wristpin I tested around the inlet manifold gaskets with WD40 but no change in engine note so looks like the new ones i fitted when i did the exhaust valve spring are all good.

Still convinced it’s a fault with the carb somewhere, Saturday morning again i stripped it down and this time put the housing in a pan of boiling vinegar for 15 mins, plus following the advise from the man in Amersham who sells numerous bits for the Ransomes Triple and seems to know a lot about them, i drilled out the 2 seals fitted to the carburetor after it was machined at manufacture. This should once an for all rule out any blocked air or fuel passages in the carburetor as i can now push a small piece of copper wire down every one to guarantee they are clear. I then drilled and tapped them with an M4 tap and super glued stainless bolts back to reseal them. It took me almost 3 hours including air lining and repeated spraying with carb cleaner and rechecking with a torch and air line that all passages were clear. I refitted it to the engine and it’s still got the same problem. !?!??

I then spent another 2 hours adjusting the governor and throttle cable positions as well as the throttle stop and idle mixture screw.

Whatever i seemed to do the engine runs at a good fast speed with the throttle butterfly in the carb fully shut. It runs on a bit and then after 20-30 seconds begins to die and is normally unrecoverable no matter how much you reopen the throttle. There must be fuel leak somewhere in the carb as with the throttle butterfly fully shut, only the idle or pilot jet should be allowing a tiny amount of fuel into the venturi in the carb. Only when you open the throttle butterfly does the main jet come in to play?

I’m going to draw a sketch of how the carb’s designed to try and better understand it.

August 12, 2017 at 11:54 pm #26243
vhgmcbuddy
Member
I’ve drawn a lite diagram of inside the carb. It’s a fairly simply one compared to car / bikes. The red bits are the plugs I’ve drilled out to check passages are clear and then resealed.
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