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Atco B14 DeLuxe engine problem

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John of Madley Tue, 24/07/2018

Hi, I recently picked up an Atco Fourteen at the local car boot. It looked in reasonable condition except the front rollers had rotted away. I have now replaced the rollers and carried out some maintenance. I have cleaned the fuel tank, replaced the fuel line and air filter and cleaned the carb.

It starts and runs OK but at first wouldn't run the blades let alone drive. I have now thoroughly cleaned the carb and it just about goes but the engine seems to lack power and it won't go for long. It is a JAP sidevalve engine which revs freely using the governor link. I have tweaked the jets just to get the best running. One thing I am not sure of is how the throttle and governor work together. There is a weak and distorted spring on the throttle which appears to go to the governor.

Should the throttle control set the governor to keep the engine at a constant speed under load? Any help would be much appreciated.

Forums

wristpin Tue, 24/07/2018

Welcome.

A point of order - the engine is  not a JAP but an SIF , Suffolk Iron Foundry, someone has unhelpfully removed the ID plate from the cowling just above the dip stick .

An image of the carburettor, throttle linkage and governor will be helpful. However, an appreciation of what you are trying to achieve may throw some light on the matter.

When the engine is running the governor, in your case an air vane within the engine cowling , tries to close the throttle. The handlebar control, via the throttle cable tries to open it . The connection between the cable and the air vane is a spring - the Governor spring. The cable exerts a pull on the spring to increase the speed while the air vane counteracts it. The result is the governed speed.

Other  things that can attribute to the perceived lack of power .  On the output side of the engine is a plate clutch which may be slipping. Further out are the drive chains which may be overtightened or stiff from a lack of lubrication. In the cutting department you may have blunt blades, an incorrectly adjusted cutting cylinder or partially seized cylinder bearings.

Enjoy!

John of Madley Sat, 04/08/2018

Thanks for the update Wristpin. I have finally got around to getting some pics of the carb and linkage. The carb is a Zenith Type 13 TCA-2. The governor spring is the one I am not happy with, it is rusty, bent and stretched and I would prefer to replace it but couldn't find one online. Any links to a possible supplier would be appreciated.

The next step is to remove the covers and look at the governor vanes. It seems to control engine speed OK. My problem is maintaining that speed while cutting.

Atco B14 TCA-2 carb linkageAtco B14 governor spring

wristpin Sat, 04/08/2018

That setup looks OK. As you say, the spring is past it’s best but I’ve seen plenty the same that are working OK. You could try moving it back a hole to put more tension on it to oppose the closing action of the governor vane. Have you checked the blade set and cylinder beatings etc just to see that the engine is not being overloaded?

 Possibly the best place to try for a new spring is Jon Cruse at the Hailsham Mower Centre.

John of Madley Sat, 04/08/2018

Thanks for the update. I removed the cowling and found the governor vane pivot was seized, the free movement I had seen was just the vane flexing. I have now freed it off and seems to have done the business. I also moved the spring up to the last hole. I have now shaved the dead grass on the back lawn to an equal length!

I don't think the blades are tight, I remember the noise they make from my youth. I assume you mean engine bearings. I think they are fine as it ticks over quite happily when hot. I'll try Jon Cuise for a new spring and hopefully a new cork/fibre washer for the fuel tank.

Chris G Sat, 04/08/2018

I am no expert or even close by any stretch but if the engine is running well enough and revving freely, but then struggles under load? Meaning moving and cutting I would drop the cutter and flush the bearings with diesel, clean, air line and thoroughly relube, same goes for servicing rear roller, chains and clutch. If the engine is having to work a bunch of resistant mechanisms it was not deigned to, it will not perform well, not good for the engine nor the other parts.

wristpin Sun, 05/08/2018

All good advice from ChrisG but perhaps having sent you in the direction of a parasitic load I should run through a couple of checks.

If possible get the machine to a comfortable working height - Workmate?

Plug lead off, chain cover removed. Main (engine clutch) disengaged.

Gloves. Rotate the cutting cylinder. Should not need much force. If it does, back off each of the cylinder adjusting screws by one turn. If it is now free to turn, try re-tightening the adjusters by half a turn  - still OK? Tighten another quarter turn and then a bit at a time until it just brushes the bottom blade. Then try mowing. If the machine still bogs down the chances are that the cylinder blades and the bottom blade need to be sharpened.   

However, if with the cylinder backed off it is still stiff, it is more than likely that its  bearings are past their best. In that case the whole cutter unit will have to be dropped out and dismantled - a different job for another day.