multiple kick backs then pop smoke loss of compression

[Wayne Cole]

put the bike together after rebuild (matchless g3l 350 single) I have been irritating the hell out of Clive and SPRIDDLER with PM'S so let me put it to the board. such care was taken in reassembling the bike, every step of the way I would ask a question, at first I thought timing was off but then I have found that is wasn't. when I got the bike there was no copper gasket and extra washers on head bolts to compensate for this, so the lack of gasket was intentional for some reason? so when the bike was together (properly by the way absolutely sure about this) I kicked it so lightly because I was actually nervous, every kick I got huge kick back about three four kicks then a pop and a little smoke from around a few areas, then I checked timing and thought maybe it was off reset then kicked again, now air is coming from somewhere which feels like spark hole but, did soapy water test and no bubbles to be seen from anywhere? stripped the bike again! no damage or cracks bent valves anywhere in sight! not a clue where air is coming from??? could this be the reason there was no copper gasket in the first place? is air escaping up through head bolts into rockerbox which is where air might be coming from? did I just blow the head gasket? spark and valves were tested and no thin fluid leaks at all apart from a tiny insignificant amount from inlet valve, will try with wellseal and no gasket for head and fingers crossed the bike is ok, I'm literally losing sleep over this...

[clive]

is it possible the engine is a comp one, some were not fitted with gaskets. what is the engine number? To answer your last PM, looking at the mag from the points side if the advance retard take of is on the right advance is tight wire, if it is on the left then its slack wire for advance. Is it possible you have timed the bike on full retard rather than full advance? We will get there at some stage!

[1608]

I know somebody who recently rebuilt a twin and had very similar problems. The escaping air in this case was actually coming from the carb. He swore blind that the valve timing was set correctly, but on checking had misaligned the timing marks on the pinions. I'd suggest re-checking valve timing .

[Wayne Cole]

is it possible the engine is a comp one, some were not fitted with gaskets. what is the engine number? To answer your last PM, looking at the mag from the points side if the advance retard take of is on the right advance is tight wire, if it is on the left then its slack wire for advance. Is it possible you have timed the bike on full retard rather than full advance? We will get there at some stage!

comp one? first I have heard of that! seeing as the previous owner told me that the bike had been taken to only the best mechanic's in it's life time I will assume it is indeed a comp one. as for the mag, here it is Clive on left side of bike. what damage if any could be caused here? all I know is with the lever tight it's got more of a spark and with it loose less so, so when I do timing where should lever be?

mag.jpg

[Wayne Cole]

is it possible the engine is a comp one, some were not fitted with gaskets. what is the engine number? To answer your last PM, looking at the mag from the points side if the advance retard take of is on the right advance is tight wire, if it is on the left then its slack wire for advance. Is it possible you have timed the bike on full retard rather than full advance? We will get there at some stage!

and just for fun here is the bike before and after I restored it, still a couple of little details to do but nearly there. top pic before

IMG-20220902-WA0002.jpg

20221024_121110.jpg

[clive]

That mag is tight wire for full advance. Wayne take us through what work you have done on it? Was it running when you first got it? What have you removed and replaced? That barrel is an ordinary road one and the cylinder head should have a plain copper gasket between it and the barrel. With all due deference to the previous owner I think you should not assume that all the previous work done to the bike is correct. I think its helpful to continue use of photos as I am not sure my explanations are that clear.

[Wayne Cole]

That mag is tight wire for full advance. Wayne take us through what work you have done on it? Was it running when you first got it? What have you removed and replaced? That barrel is an ordinary road one and the cylinder head should have a plain copper gasket between it and the barrel. With all due deference to the previous owner I think you should not assume that all the previous work done to the bike is correct. I think its helpful to continue use of photos as I am not sure my explanations are that clear.

in that case the timing has been set at full advanced. I changed piston rings, new carb, new primary chain, new electrics i.e battery wiring. yes it was running but burning oil and exhaust vale and guide needed to be changed. that's about it nothing major done to engine just a clean and rebuild, crankcase not touched gear box not touched. clive if I took chain off primary and things got moved around surely that would effect the timing? again forgive my lack of technical terms but I move both clutch and the cog with spring in it in primary, the cog that is connected to mag? timing must have been effected maybe I am wrong it doesn't effect mag does it? something has happened and I fear it isn't good, clueless as to what though.

[laxy]

Hi Wayne, it sounds like you might be attempting to start the engine with the advace /retard lever in the fully advanced position which is cable tight . Although this position is correct for setting the ignition timing , you need to slacken the cable a little when starting the engine. Attempting to start the bike on full advance will result in it kicking you back as you have described. This does not apply to automatic advance and retard but yours is a manual advance retard.

[Wayne Cole]

Hi Wayne, it sounds like you might be attempting to start the engine with the advance /retard lever in the fully advanced position which is cable tight . Although this position is correct for setting the ignition timing , you need to slacken the cable a little when starting the engine. Attempting to start the bike on full advance will result in it kicking you back as you have described. This does not apply to automatic advance and retard but yours is a manual advance retard.

ah but no I made sure the lever was in the middle where it's always been happy in the past when starting. the thing is if timing has been effected somehow then if damage has occurred I can't find it. timing, I just can't see how it was effected though, replacing rings and valve and guide and primary chain, moving things around in primary when changing chain doesn't effect timing I hear?

[Wayne Cole]

I know somebody who recently rebuilt a twin and had very similar problems. The escaping air in this case was actually coming from the carb. He swore blind that the valve timing was set correctly, but on checking had misaligned the timing marks on the pinions. I'd suggest re-checking valve timing .

cheers mate, pretty sure it wasn't carb, didn't mess with pinions either. hmmm