Atco - clutch too stiff for manual pull start

I suspect that the engine has been intermittently seizing and has now got to the stage where it is more permanently seized. 

Take the engine off the mower and try turning it by hand .**  If it is still stiff, take the cylinder head off and look for signs of seizure on the cylinder bore. No signs there but still stiff; It's then either the big end or main bearings. 

** never try to start the engine with the centrifugal clutch shoes out of the drum and exposed . They may fly out and cause serious injury.

Thanks wristpin, I really appreciate your advice.

I haven't taken the engine off the mower as I couldn't see that it would be any different to manually turning the flywheel by hand with the engine still on the mower, which may indicate my complete lack of knowledge!

I've taken the cylinder head off and can't see any signs of seizure on the cylinder. Although, one of the valves was "sticking" but I've got that moving freely now.

I'm already at the limit of my ability. You mentioned big end or main bearings, could you possibly provide more info on what I should look for and how to go about it?

Many thanks,

Cube

What you have there is actually a Suffolk super colt, it was a form of badge engineering. They were painted Atco green, fitted with a different fuel tank and had Atco decals slapped on them and you were only charged about an extra £30-ish for the privilege.

You are going to have to remove the engine, which is fairly easy to do, unhook the throttle cable from the lever on the handles and remove the four bolts holding the engine down (you will need an 1/2inch AF ring spanner for this, 13mm at a pinch). At this point, you should be able to turn the engine over by hand easily, if not, drain the oil and remove the sump by removing two bolts (one at the front and one at the rear of the engine). you will then be able to see inside the engine and hopefully see what is binding, probably the big end.

Thanks hortimech, very helpful.

I removed the engine and it was still hard to turn by hand. As instructed I removed the sump. However, turning by hand I couldn't see anything untoward, albeit it still very hard to turn over. One thing I have noticed, if the engine is left even for a short while then the first "turn over" is even more difficult.

I've attached a couple of photos in case they are of some help?  Any further suggestions would be very welcome.

Thanks again,

Cube

OK, at least it doesn't look wrecked ;-)

If you turn the crank, does it turn very easily or not ?

If it doesn't, you are going to have to remove the con-rod cap. knock back the two tabs stopping the bolts from turning and the undo the bolts (7/16AF). You can then remove the cap, but make sure you know which way it fits (it may already be marked, if not, mark the cap and rod with a centre punch).

You can then try to turn the crank again, but watch out that you do not push the piston out at this point, you will need a ring compressor to put it back.

You should be able to rock the crank backwards and forwards very easily, if it does, peer very closely at the con-rod and crank bearing. If it doesn't, then it sounds like it is one of the crank bearings and you are going to have to make a flywheel extractor (do a search on here, it was discussed recently), the clutch will have to come off and the front crankshaft plate (the piston will also have to come out). Before you remove the crank from the block, check that you can identify the cam timing, there is a dot on the cam that lines up with a mark on the crank, remember these.

If you have got this far, you should be able to identify just which crank bearing needs sorting.

Thanks again hortimech,

I think I have discovered the problem now. Looking at the first photo of the engine the two gears/cogs are out of line. The smaller one is jammed up against the engine casing hence the extreme difficulty in turning the crank. I hope this isn't terminal?

thanks,

Cube

The larger gear is the camshaft, the smaller is the crankshaft gear. You say the smaller gear is 'jammed' against the engine casing, how ? is there any crankshaft endfloat (you should be able to pull the crank in and out slightly). If there is no endfloat, you will need to remove the flywheel and aluminium backplate and fit gaskets between the backplate and cast iron block to give you endfloat

Raises the question of why / how  has the end float disappeared ? The magneto back plate has probably got to come off discover the reason. I’m still suspecting a partial seizure .