Suffolk Super Colt - Idle and Blue Smoke Problems

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cclaw9519
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Suffolk Super Colt - Idle and Blue Smoke Problems

Hello,

I own three different cylinder mowers which include a Suffolk Super Colt, Qualcast Commodore and 35DL. All beautiful mowers but a pain when they do not work correctly.

The two questions I would like to ask is that I have recently cleaned a Suffolk Super Colt lawnmower, but there is blue smoke coming out of the exhaust with an unburnt fuel smell when accelerating/on high revs . So obviously it is burning too rich but I am unsure what screws to adjust on the Zenith Carburettor. I have attached photographs, I do not want to adjust anything else without some professional advice as there are many different types. 

The second question is how to get the lawnmower to idle without 'jumping/revving up slightly', I can only get the lawnmower to idle when I hold the lever (marked with a white circle) back; It is well worn and lose. So it can idle with assistance.

Please note that the lawnmower has had a correct oil change, fresh fuel, new air filter and spark plug. There is no burning oil smell. I know the lawnmower is old so it won't work like its new but want it tuned to where it should be (VERY well used over the years). 

Thank you,

Chris and John

hortimech
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Joined: 08/04/2013 - 17:02
You say the arm is loose, is

You say the arm is loose, is this loose on the spindle or is the spindle loose in the carb body ?

If the former, you may be able to fix it by soldering it.

I take it that the air filter has been oiled with SAE30 oil and the excess squeezed out.

If you look under the fuel inlet, there is a large 'screw', this is the main jet, if the engine is running slightly rich, try turning it in slightly whilst the engine is running, the engine should pickup slightly and run cleaner. Keep 'tweaking' the screw slightly backwards and forwards until you get the best result.

The tickover screw is the one shown the last picture (the screw 'pointing' at the ground) and you adjust this in a similar way.

If you cannot get the engine to run cleanly, it may be that the carb is flooding slightly, stripping and cleaning the carb should fix this and you will be able to check the float and its needle.

cclaw9519
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Great! Thank you for replying

Great! Thank you for replying to me. I am going to give the whole governor side of the lawnmower a good clean and oil at the same time checking the butter fly (spindle) as it does seem rather loose. I must say now I see the flap (governor flap does seem rather sticky also, so I do not think this will help) I will adjust the mixture screws once I have checked those parts. I will be in touch again once I have had a go at your suggestions on the mower (whether working or not). 

wristpin
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Normally blue smoke is

Normally blue smoke is associated with oil burning , not a rich mixture. However if you think that it’s running rich, turn the angled adjusting screw , just below the fuel inlet , a fraction clockwise at a time and see if it makes a difference. The vertical screw on the top of the carb is for the idle mixture adjustment.

The loose throttle spindle needs to be treated with respect. Resist the temptation to try to fix it in situ or to attempt to peen the brass spindle at all  - it will chip off and make the job worse. Note the position of the throttle butterfly and carefully undo its holding screw and then withdraw the spindle. The options are then, clean the end of the spindle and the lever and make a soldered joint; or, carefully apply Loctite penetrating adhesive into the joint and allow to set. Then reinstall the shaft and refit the butterfly  with just a tiny drop of adhesive on the screw.

If tightening up the spindle doesn’t cure the idle issue, make sure that there’s a bit of slack in the throttle cable and that  the governor spring is in the furthest forward hole of the cable relay arm. If that doesn’t cure it , carefully just bend the relay arm very slightly downward.

 

 

cclaw9519
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Thank you for the suggestions

Thank you for the suggestions also. Will take note and let you all know on what the outcome is once I take another look to clean, repair and adjust.

cclaw9519
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Joined: 06/06/2019 - 18:27
Hello all,

Hello all,

Great news, after taking all of your advise I have managed to correct the carburettor settings to get it to tick over and speed up without smoke - also it sounds 100% healthier. I am now ALLOT HAPPIER so thank you all. However, now there is a minor issue with the engine stalling every so often on tick over. Sometimes it does correct itself, but after a while it does die but with one small pull it ticks over again. 

Could now this be due to a sticky governor, or what else would you suggest the issue could be? I have cleaned the carburettor, daylight is visible in the slow running pin/hole tube.

In regards to another lawnmower a Qualcast Commodore DRC, there is a oil leak in the valve breather cover. I have cleaned the crankcase breather hole and renewed the gasket to the cover. But still there is a small trickle of oil from the bottom of the cover, running down the engine. What is your suggestion on stopping the oil leaking? Apart from that it is a good runner.

Thanks,

Chris

wristpin
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Stalling. may just be set a

Stalling. may just be set a bit weak or the tick over rpm is just a bit low.

Oil leak. When you take the outer cover off there should be a "tin" splash shield and in the bottom of the valve chest a three piece (four if you count the washer) breather valve held in place with a spring hooked over the cover fixing stud.

The purpose of the breather is to allow air displaced by the downward stroke of the piston to vent from the crankcase. Then, on the upward stroke it shuts and contributes to a small amount of negative pressure , assisting in keeping the engine oil tight. A worn valve may allow the valve chest to flood with oil. Alternatively the chest cover may be a bit warped and not sealing properly. Rubbing the cover some abrasive cloth on a flat surface may true it up.

Breather valve