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Ignition timing problem

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Ignition timing problem

Post  Science is Au on Thu Mar 15, 2012 7:57 am

Hi all

My Kestrel fitted with an 8E was not idling (picked it up about two weeks ago now).

It ran okay at low revs by just cracking the throttle open a bit, so I knew not too much was wrong.

Things I noticed in no particular order.
Air cleaner just has a gauze in it, no foam or wool - could be too lean
Air mixture screw did not seem to have any effect, it has been sanded down a bit and does have a slight bend in it.
No spring between the tapered needle and the screw that holds it down.
Jets are correct as per specs.
Cleaned carbie and blew it out.


The clincher is however, the timing mark does not line up as expected with the points just opening, the timing mark is a good 1 inch before the timing mark in the case.

As I understand the process, set your points gap, loosen the flywheel and turn it so the points just start to open, turn the engine to 5/32 BTDC, tighten flywheel.

I have checked the flywheel with one from a 6E and they seem very similar, the length of the actuator arm on the points is similar to one from a 6E.

Any hints on this?

Thanks

Grant
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timing

Post  piston 197 on Thu Mar 15, 2012 8:24 am

Grant ignore the points just opening figure,set points at fully open to be 15 thou/inch,put piston at top dead centre position,align arrow on flywheel with notch in timing case backplate,tighten flywheel.
If the air screw is having no effect then the length of needle protruding from the throttle slide is probably wrong? adjust the screw in the centre of slide until there is approx 1.95" of needle measured from the bottom of the slide (this is the original factory setting for an 8E ,but may need increasing to compensate for wear,set airscrew approx 1 1/2 turns out from fully home and fine tune from there.
If you start from these basic positions you will have a good start point for minor adjustments.JH
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Timing Issue

Post  ChrisTurner on Thu Mar 15, 2012 8:31 am

JH beat me to it.....


Last edited by ChrisTurner on Thu Mar 15, 2012 8:32 am; edited 1 time in total (Reason for editing : Already answered above.)
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Re: Ignition timing problem

Post  Science is Au on Thu Mar 15, 2012 9:00 am

piston 197 wrote:Grant ignore the points just opening figure,set points at fully open to be 15 thou/inch,put piston at top dead centre position,align arrow on flywheel with notch in timing case backplate,tighten flywheel.
If the air screw is having no effect then the length of needle protruding from the throttle slide is probably wrong? adjust the screw in the centre of slide until there is approx 1.95" of needle measured from the bottom of the slide (this is the original factory setting for an 8E ,but may need increasing to compensate for wear,set airscrew approx 1 1/2 turns out from fully home and fine tune from there.
If you start from these basic positions you will have a good start point for minor adjustments.JH

Cool, I'll give that a go tomorrow or the weekend.

Thanks a heap

Grant
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Re: Ignition timing problem

Post  Science is Au on Mon Mar 19, 2012 2:24 am

piston 197 wrote:Grant ignore the points just opening figure,set points at fully open to be 15 thou/inch,put piston at top dead centre position,align arrow on flywheel with notch in timing case backplate,tighten flywheel.

It seems the flywheel was slipping on the shaft causing a few problems, a little dab of locktight seems to have fixed the problem

piston 197 wrote:If the air screw is having no effect then the length of needle protruding from the throttle slide is probably wrong? adjust the screw in the centre of slide until there is approx 1.95" of needle measured from the bottom of the slide (this is the original factory setting for an 8E ,but may need increasing to compensate for wear,set airscrew approx 1 1/2 turns out from fully home and fine tune from there.
If you start from these basic positions you will have a good start point for minor adjustments.JH

Still no dice with the carbie adjustments, I modified a ballpoint pen spring to put under the needle to give the correct adjustment, have removed the carbie and given it a good clean and blast with compressed air.

It has improved, but still needs the throttle open just a bit (slide open 1/8") to idle. I have checked the jets, needle and slide and all are standard items.

There is a lot of rust coming through from the tank, getting as far as the banjo fitting on the carbie, so may sort that out (my neighbour suggested small stones in the tank and swirl them around to knock the rust off) first.

The air cleaner is just a metal gauze that you can see through, two layers, should it have some finer material in there?

Thanks

Grant
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air cleaner

Post  piston 197 on Mon Mar 19, 2012 5:32 am

Grant,the gauze is all you get! nothing else ,seems like you are on the way ,just some minor tweakling left to do.JH
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Re: Ignition timing problem

Post  Kim on Mon Mar 19, 2012 8:12 am

Further too the air cleaner. The manual says wash with petrol and allow to dry then immerse in light oil and allow to drain before refitting to bike. I assume the oil traps particles before entering the engine.
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Idle problem

Post  fulmar88 on Mon Mar 19, 2012 12:02 pm

I may be missing the point but are you sure the bike should idle without holding the throttle open? My 10E Falcon 81 doesn't have an idle stop screw and I don't think my 8E Falcon 74 did either.

Steve.
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idle screw

Post  piston 197 on Mon Mar 19, 2012 12:11 pm

On the later carbs there is a untapped hole that can be tapped out and a screw with a pointed end fitted to lift the air slide for tickover,the slides all have a tapered slot for this screw to bear against,but the carbs were only fitted with a tackover adjustment on car installations.Many trials riders have adapted this system so tickover is not reliant on cable adjustment.On the standard 8E with s24 or s25 carb the tickover has to be adjusted on the cable,which may result in revs increase when turning the bars,JH
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Re: Ignition timing problem

Post  Science is Au on Mon Mar 19, 2012 9:43 pm

fulmar88 wrote:I may be missing the point but are you sure the bike should idle without holding the throttle open? My 10E Falcon 81 doesn't have an idle stop screw and I don't think my 8E Falcon 74 did either.

It was just an assumption that the bike would idle, had not thought about otherwise. Although just looked through the 8E manual and it states "The pilot jet must be set when the machine is stationary with the
engine running at the required idling speed."
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Re: Ignition timing problem

Post  Science is Au on Mon Mar 19, 2012 9:46 pm

piston 197 wrote:On the standard 8E with s24 or s25 carb the tickover has to be adjusted on the cable,which may result in revs increase when turning the bars,JH

John

I have been pondering the cable, it is way too long and at (past) maximum adjustment.

Does anyone know how long the standard cable should be?
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cable length

Post  piston 197 on Tue Mar 20, 2012 7:35 am

The Romac cable book gives the figure of 3 feet and 4 inches overall for the merlin ,but this does not give the length of inner and outer,just the overall length,presumably as you have the 197cc engine fitted the carb will require slightly longer inner cable?? JH
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Re: Ignition timing problem

Post  Kim on Tue Mar 20, 2012 7:54 am

Villiers services will sell you an overlong cable with the fittings included that you can trim and solder to suit. About 10 Pound if memory serves me well.
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Cable length

Post  Science is Au on Sun Mar 25, 2012 4:15 am

Hit the nail on the head (almost).

Got me thinking about the cable length an in particular the length of exposed cable, mine was 78mm, I chopped 10mm off as this was the amount of adjustment I had an hey presto!

An Idling motorcycle (after a twidle with the adjustment just a bit.

As it stands, the cable, inner and outer, are still way too long, there is way too much slack hanging out the front of the bike, but the important measurement is the exposed length of inner.

Thanks all for you suggestions and help.

Next, the brakes and lighting.

Cheers

Grant

piston 197 wrote:The Romac cable book gives the figure of 3 feet and 4 inches overall for the merlin ,but this does not give the length of inner and outer,just the overall length,presumably as you have the 197cc engine fitted the carb will require slightly longer inner cable?? JH

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Re: Ignition timing problem

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