What else can i do?.

mikeydpippin · Post by **mikeydpippin** » Wed Dec 29, 2010 8:13 pm

My 1957 G3 had a seized exhaust valve this was reseated and lapped by an engineering company.Reset timing,fitted new points and condensor and had a weak spark,changed Lucas SR1 Magneto with another i had, and now have a big fat spark,put petrol in spark plug hole and it fired.Fitted petrol tank and it ran like a good un last night sounded lovely ticking over as it should.
Tonight tried again,big fat spark not firing,checked points gap,all okay,petrol down plug hole but nothing,valves opening and closing okay,
Tried 5 different plugs on cylinder head 3 sparked tother 2 didnt.
Can the spark disappear under compression?,if so why?.Good compression, Surely if good spark, petrol in plug hole should see it fire,or am i missing something.
I have disconnected decompressor lever.
What else can i do.
Compared to my other G3 the only difference seems to be the exhaust valve lever arm slightly higher on the non starter,but that should be okay if the valve is operating okay.

itma · Post by **itma** » Wed Dec 29, 2010 8:25 pm

petrol down the plug hole is a daft idea mickey it will guarantee to foul the plug, are these new plugs you are trying or old ones out the tat box?

So, reconnect valve lift, fit NEW plug, go through the start drill as per normal, no go? remove plug is it WET?
if not must be fuel problem

mikeydpippin · Post by **mikeydpippin** » Wed Dec 29, 2010 9:08 pm

Thanks Ken,
2 New plugs 3 old ones,refitted valve lifter, cleaned carb,tickled till petrol flowed out of tickler kicked over several times not starting.Plug dry.so fuel problem.

mikeydpippin · Post by **mikeydpippin** » Thu Dec 30, 2010 12:00 am

Unblocked pilot jet,now have wet plug.and phutting out of carb.will try other plugs tomorrow,if not i will start over again,timing etc.

Rob Harknett · Post by **Rob Harknett** » Thu Dec 30, 2010 12:46 pm

Mikey, With everything correct your old bike should go with a gentle kick first time, every time. SR1 mag.Things that can go wrong.You forgot to jam the advance /retard unit in the fully advanced possition. I use an old wooden peg to jam it open,you set the piston on the wrong stroke. Having got that all correct the bike goes first kick. But then plays up again. The old poarts are getting worn. Check the advance retard unit is not jamming in the fully advanced possition, flust it well with WD40 working the unit by hand untill its cleaned and working well. You will be amazed at all the rust coloured fluid that has dipped on the floor. Springs should be good and no snags through wear on flats where the parts open up onto. If theres a noisy clatter. Slip a bit of wiring sleeving over the 2 flats where contact is made. First remove any sharp edges caused by wear. My old 55 bike had a cork gasket between the bakelite cover when new, I have seen paper replacements for these. I prefer the cork, paper may result in over tightening and a cracked bakelite cover, make sure the spring is pulled out to make good contact on the coil nipple. Rob Harknett

mikeydpippin · Post by **mikeydpippin** » Thu Dec 30, 2010 3:43 pm

Thanks Rob,To recap,
I first set the points with the valves closed at tdc.
I removed the Mag cover, loosened the mag sprocket nut and levered forward until loose on the shaft taper,turned engine over until both valves closed and checked for tdc.
inserted rod in spark plug hole and marked,removed rod and marked 1/2" above this mark.
Turned auto advance anti-clockwise and held with cardboard wedge,inserted rod in spark plug hole and turned rear wheel backwards until top mark on rod level with spark plug hole. turned the contact breaker cam clockwise (easier than turning the magneto armature shaft anti clockwise)until points starting to seperate,tightened mag sprocket and removed wedge.
Engine will fire and run now but lots of kicking (and swearing).4 new plugs,2 old plugs,2 sets points.and 2 condensors tried.tappets set and rocker arms rocking,valves opening okay,will remove cover and check auto advance next.

itma · Post by **itma** » Thu Dec 30, 2010 3:50 pm

make sure its the RIGHT TDC with pushrods free to turn, its sounds as if you may be on the wrong stroke.
1/2 BTDC inch is too much, try 7/16 or even a tad less.

mikeydpippin · Post by **mikeydpippin** » Thu Dec 30, 2010 5:50 pm

What a day,removed rocker and cylinder head to check valves working okay.No problems there so replaced now engine fires first or second time and ticks over nicely.Dont ask, dont know why.
Can i be sure timing is set on right stroke now?remember been here before,may not start later.
If i get a re occurrence i will change to 7/16.
Fingers crossed.
Thanks Ken AGAIN!!!

itma · Post by **itma** » Thu Dec 30, 2010 6:03 pm

Old bikes.......oh, what fun ............

Merlin · Post by **Merlin** » Thu Dec 30, 2010 9:24 pm

quote:
Old bikes.......oh, what fun ............

Like our old ladies sometimes they run often they don't

Enjoy 2011 and have as much fun as you can, lost too may old friends in 2010