Howard Bantam – Villiers Mark 15 Engine – Not running properly

[vhgmcbuddy]

Help required.
Howard Bantam did not run so I stripped the carb which I believe is an S12 type. The throttle cylinder was stuck so i freed this and cleaned the inside and blew out all the jets.
The villiers Mark 15 engine starts ok now but the throttle does not seem to increase the speed of the engine? The governor seems to be coming in and out (hunting) a bit too much as it just ticks over.
Is the air intake not correct or fuel intake is not right? Adjusting the mixture screw or the cable adjuster for position didn’t seem to change the engine speed either? Any ideas.
I thought I would check the contact breakers for enough spark and maybe replace the condensor which I know from past engines can cause problems.
I have undone the 13/16 nut holding the flywheel rotor on but it clamps tight again, do I use this nut to pull off the flywheel rotor? I didn’t want to strip the thread so have been reluctant to lean on it and give it too much force. Should it be that tight and will go eventually?
Any advice is greatly appreciated.
Thank You
Steve

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[wristpin]

Hunting, as opposed to misfiring, is usually a sign of a weak mixture. See if a little bit of choke smooths it out. If so it confirms a weak mixture. Probably requires further cleaning of the carb.

[charlie]

The nut in centre of flywheel should go loose then start to tighten again as it pulls the flywheel off the taper. Beware removing the flywheel will require resetting the timing on assembly as there is no key on crankshaft. Timing is easiest to do with cylinder head removed to accurately measure position of piston.

[andyfrost]

Before you even think about removing the flywheel , THOROUGHLY go over your carb again , check the jet and its passageway in the bottom of the float bowl , these have a nasty habit of corroding badly. The mixture jet is for tickover only , main running mixture is achieved by raising/lowering the fuel needle

Andy.

[vhgmcbuddy]

Thanks for the comments Wristpin, Charlie and Andy.
I have not removed the flywheel yet, I decided to check the carb again as Andy suggested.
The jet at the bottom of the float bowl seemed ok, I removed it blew out and checked the passageway with a piece of wire and was clear.
The fuel needle seemed free and the carrier it is attached too sliding up and down the keyway no problem.
I ran the engine again. It seemed to run a bit better.
The mixture screw I set at 1 and half turns undone.
With no throttle on I screwed the adjusting screw on the main jet until it was nearly at its lowest point this natural slowed the engine running speed to an acceptable tick over without racing away and not to slow that it was trying to cut out.
Now if I open the throttle lever the engine speed did pick up but to me didn’t seem smooth. If I left the throttle open it did hold a higher running speed. but if I released the lever it stayed at the higher speed?..but the cable had returned the needle.
If I manually pulled the cable on the carb it increased the speed and if released it slowed down?..
It seemed to be giving a bit of black smoke as if too rich mixture?
I removed the plug which was sooty also indicating too rich?
Strange I could not seem to get it to settle or accelerate correctly?
Can the magneto timing be upsetting the smooth acceleration and return to idle speed as if it’s not firing at tdc?
Thanks again for any advice or sequence of checks or adjustments to try
Steve

[andyfrost]

Steve , there is no main running jet , adjustment is done by altering the height of the fuel needle , slip the holding circlip out and lower the needle by one notch.
Incorrect timing will cause poor running , but we must try to help you eliminate one problem at a time.

Andy.

[vhgmcbuddy]

Thanks Andy,
I am sure the fuel needle is all the way down.
There is a bigger end diameter that is up against the circlip already.
So I cannot lower anymore?
Steve

[andyfrost]

From memory there are 5 positions , it should (as a starting guide) be in the 3rd or 4th grove try it and go from there.
One point I have overlooked , is the manifold butterfly free and working.

Andy.

[vhgmcbuddy]

Andy,
apologies for the late reply on your last comment.
I checked the fuel needle position and it was in the 2nd groove from the top.
I put it in the 4th groove from the top which would lift the needle and in my understanding let more fuel through on acceleration?
I started the engine and did not see a lot of difference on adjusting the throttle lever.
It picks up speed a bit but the governor seems to be cutting in too quickly?
It looks to be running to rich and the plug is getting coked up too implying too rich.
I have put two videos on You Tube showing the engine running, it may help you to see if there is a problem or not and maybe advise me to try something else
Links:


Thanks again for your help
Regards Steve

[wristpin]

Being an overhead valve engine it is easy to check the valve gaps, so do that. Then check the plug gap and without removing the flywheel, the points . You then know that three of the possible variables are correct. Should you find that the points are way out they will have affected the timing – slightly – but correcting the setting may just improve things.
With all that lot known to be correct, re- check the carb ; return it to book settings and work from there.
If you are still in trouble you can check the timing without removing the flywheel but it may be easier if you remove the cylinder head – just depend upon the position of the plug hole in relation to the bore for measuring piston position. If with the correct points setting, the timing is way out, it will be necessary to loosen the flywheel – and while you are there remove it and with the improved access give the points a thorough clean.

[vhgmcbuddy]

Thanks Wristpin, regarding the valve gaps and spark plug I have checked and adjusted these already. The points didn’t seem to be visible through the flywheel in that there seemed to be a cover over them… I don’t recall seeing the actual points through the 3 gaps when rotating the flywheel.
If there is a cap or plate over the points…which is removable through the flywheels 3 gaps (see pic above from my first post) to get access and check and adjust the points without removing the flywheel.

[andyfrost]

It’s always hard to say without actually being there , but from your video it does seem to me like a timing issue.
In your ownership has it ever ran OK , or are you the new owner.

Andy.

[charlie]

There is usually a cover over the points which can be removed by sliding the retaining clip across and to side of cover, it is a bit of a fiddle.

[vhgmcbuddy]

Hi Andy,
I am the new owner and it didn’t run at all when bought at an auction.
The carb was the issue initially with the sticking needle piston and dirty.
Now I am where I am trying to get it running better.
It would rotavate as is but the engine is not picking up or seem stable enough to me and definitely the mixture or firing is not right looking at how rich the mixture is from the coked up spark plug.
Did you notice the governor coming in on the video even with very little throttle …is this normal?
One other thing I take the air filter gauze out to see if it runs any better and it didn’t really help but noticed the oil is full of small bubbles as it’s been trying to pull in the air…is this normal?

[andyfrost]

It may be “process of elimination” check the timing is correct. It’s far better to remove the cylinder head to do this , the points should just begin to crack open at 1/8″ BTDC.

Andy

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