Moggie engine head scratcher

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Johnd103
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Moggie engine head scratcher

Postby Johnd103 » Wed Mar 08, 2017 2:59 pm

Hi all I've a 67 1000 mog engine starting to get on my t*** when the engine went in first it started no problems at all and ran well after her winter lie up I went to start it again and it's running strange .. it will start and run fine and idles OK but as soon as I touch the accelerator she goes to rev up but I've puffs of white smoke out of the carb .. I've strobe timed the engine on idle and she is bang on 5° btdc . The points and condenser are new .. and there is a good spark at the leads . The carb is adjusted 2 full turns down of the nut .. from experience it's pointing me no the timing or the condenser .. any input as usual would be greatly appreciated . Thanks guys

mobylette
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Re: Moggie engine head scratcher

Postby mobylette » Wed Mar 08, 2017 5:10 pm

Check the dashpot/piston can move easily?

Johnd103
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Re: Moggie engine head scratcher

Postby Johnd103 » Wed Mar 08, 2017 5:23 pm

Yep it moves up easily and goes back down with a clunk . I've tried running it with the top off the dashpot and without and it made no difference as well

kennatt
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Re: Moggie engine head scratcher

Postby kennatt » Wed Mar 08, 2017 6:49 pm

have you put fresh petrol in.

Johnd103
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Re: Moggie engine head scratcher

Postby Johnd103 » Wed Mar 08, 2017 7:17 pm

Yep I also tried running it off the float bowl with no joy either

dp
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Re: Moggie engine head scratcher

Postby dp » Wed Mar 08, 2017 8:13 pm

How old are the plug leads?

Johnd103
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Re: Moggie engine head scratcher

Postby Johnd103 » Wed Mar 08, 2017 8:26 pm

I've tried with 2 sets but one set .. the one I'm using are the original hard leads with the brass tops on them .. I didn't think it would be the leads if it runs perfect on tickover

les
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Re: Moggie engine head scratcher

Postby les » Wed Mar 08, 2017 9:49 pm

I'd say it was having trouble getting enough fuel. Maybe fuel pump issue or dodgy rubber pipe.


Johnd103
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Re: Moggie engine head scratcher

Postby Johnd103 » Wed Mar 08, 2017 10:13 pm

I thought it would run with the top off the float bowl .. I'll go out and have a gander again tomorrow the line from the tank is new and the pump is strong but I might have missed something .. I am after noticing though . I did the valve / tappet clearances and I set em all at what I thought was 15thou .. but on looking today when I came in .. modern feeler gauges are in mm not inch .. so that would work out at .30 .. would this give me the same symptoms

les
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Re: Moggie engine head scratcher

Postby les » Wed Mar 08, 2017 11:02 pm

It won't help but you say it ran ok before the lay up. So unless you made a valve clearance adjustment recently, it's probably not the primary cause. Set to 12 thou though.


oliver90owner
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Re: Moggie engine head scratcher

Postby oliver90owner » Wed Mar 08, 2017 11:57 pm

I think you may have a sticking - or rather relatively slow closing - inlet valve. Likely the one that was left open all winter.

kennatt
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Re: Moggie engine head scratcher

Postby kennatt » Thu Mar 09, 2017 7:18 am

puff of smoke out of the carb, If that's what you mean then looks like its backfiring,could well be the valve settings,if you hadn't said you were sure timing was ok would have suggested the timing. Does if rev up fully or cut out,oil in dash pot ok :-?

philthehill
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Re: Moggie engine head scratcher

Postby philthehill » Thu Mar 09, 2017 8:13 am

Whilst the Manual says 0.012" valve clearance the 'A' Series does run better with 0.015" valve clearance.


Johnd103
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Re: Moggie engine head scratcher

Postby Johnd103 » Thu Mar 09, 2017 8:24 pm

Oil in dashpot and valves set to 15 thou today turned over the engine today with the rocker cover off and all valves seen to be bouncing up and down OK .. it's puffing white smoke out the carb and juddering to a stop of you rev it up .. there was one flame did pop out the carb but the rest is white poofs I did notice I tried choking the engine with a rag while I was revving it up and it did seem to rev better and not conk out .. does that mean anything or am I being daft

Johnd103
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Re: Moggie engine head scratcher

Postby Johnd103 » Thu Mar 09, 2017 8:26 pm

And as I said it idles perfectly .. although a little fast but still running fine on 4 cylinders

IslipMinor
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Re: Moggie engine head scratcher

Postby IslipMinor » Thu Mar 09, 2017 9:06 pm

Once it has thoroughly warmed up, have you adjusted the mixture for the best idle speed? Sounds like it could be running weak?
Richard



les
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Re: Moggie engine head scratcher

Postby les » Thu Mar 09, 2017 9:30 pm

Yes, more air than fuel perhaps, is the choke working?


BrianHawley
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Re: Moggie engine head scratcher

Postby BrianHawley » Fri Mar 10, 2017 6:04 am

Compression?

Possibly an inlet valve not sealing?
Brian

Image "Jodie". '67 Traveller, 1275, discs, suspension mods etc.

edd_barker
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Re: Moggie engine head scratcher

Postby edd_barker » Fri Mar 10, 2017 9:17 am

3rd for running lean! Is it standard carb? Are the symptoms different when engine is cold and warm?

Ask your friendly local garage to stick the gas analyser in the exhaust so you can set the carb properly. Mine now requires a lot more choke than it used to, so if I put the choke in too early it has backfired before, and runs badly until properly warm.

Check choke cable operates correctly and through full range of choke at carb. Could be an inlet leak causing it to run very lean? Squirt of WD should highlight that. I guess gaskets can dry out over winter.

Definitely sounds fuel/combustion related rather than ignition.

Edd

oliver90owner
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Re: Moggie engine head scratcher

Postby oliver90owner » Fri Mar 10, 2017 9:42 am

 valves seen to be bouncing up and down OK .

Not necessarily the same as at higher rpm. A slower closing (and perhaps not a perfect seal at slow speed) valve may not close fully at higher rpm, resulting in the spark igniting the mixture back into the manifold. Had a similar dituation on a 'special' back in the seventies. Engine would idle, but not rev properly as it got warmer As engine got hotter an exhaust valve actually stuck partly open and it went on three pots. The simple fix was that of removing the valve stem seals on that particular engine. So, it can happen.

RAB


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