Hitchcocks Forum

Hi I have a 1947 model G .Had smoke pouring from the head when engine was warm.
assumed head gasket had gone .o took the head off gave it a de coke valves look new
put on a new old stock head gasket and tube seals put her back together.Fired her up
when warm same story as before.I don,t see any oil leak there is no smoke comong from
the exhaust but a hell of a lot pouring from the head its self.Wondering if the head could
be cracked .I did have a close inspection but noticed nothing.
please advise any help welcome.
mark

Wet sumped, scavenge pump working ok?

Hello Grrrrrrr, Looks like we're both having a bad hair day !!(see Social) Can you be a bit more accurate with your observations ? Try to narrow down the area where you think the smoke is coming from. Is it a black or light blue/white colour ?? How long have you had the bike running-----is this a recent thing or SUDDENLY ?? Is there a "crackling" noise when this happens ? The fact it only does it when warmed up is a strong clue here-----you might well be correct about the head being cracked although I've never seen one with smoke ---"pouring out". Can you load a video showing this happening ??

Hi norm alan r
I recently purchased this bike it had been standing for some time
last tax disc was 1998.Had trouble starting her from day one.Ended up putting
a thorspark electronic ignition on as the mo1 was fried.Drained the tank of fuel and put fresh in
Also drained oil from sump removed both drain plugs for that.So got her running a very loud machine,noticed
some smoke coming off around the head (white smoke) at first I assumed the head had been painted and
didn,t worry about it expecting it to stop.No smoke from exhaust,didn,t stop smoking from around head.
Noticed it was easier to kick over (no valve lifter fitted)when I re started her.Decided the head gasket
had gone and started stripping her down.The piston wasn,t to bad +60 bore looks good,head needed a de coke
the valves look recent the inlet was a gold colour no slot has the original would have had the exhaust valve was
caked up took a while with a flattened piece of copper tubing to get the crud off.The head gasket had oil seepage
so assumed that was it,Only thing I noticed looking into the exhaust port was it looked like a piece of head metal was
missing from around the valve guide.It,s as though maybe when the guide was fitted a chip had been knocked off when
it was pressed in? Anyway put another head gasket and tube seals on and tightened it up,put the rest of the bike back together
re set the tappets inlet 2 thou ex 4 thou noticed play in the rockers actual side movement in the blocks so those will have to
be replaced at some time soon,Fired her up sounded good just let her tick over till warm,then the smoke re appeared.I could only
run the engine for a little while longer as the smoke was quite bad.Coming from the head up not from the barrel But that,s as close
as I can get to tracing where it,s coming from I cannot see a specific place where it,s happening and again when cooled down and I
started her up she was easy to kick over as though the head gasket as gone again?I,m stumped on this one

The little piece of missing head material above the ex valve seat sounds just like the port for the decomp, that threw me when I recently stripped my bullet head to Helicoil it. You say no decomp? As in, it's been removed and blanked or not there at all?

Hi m1ks
The de compressing system has been removed from mine it had no connection to the head
it was connected via the barrel in between the valve adjusters.

The Model G has a valve lifter (not a decompressor) which is a lever inside the tappet chest operated from the handlebars by a cable, so the missing piece near the exhaust valve sounds suspicious!
REgards, Mark

Hi guys --------would that be similar to the Electra set-up then ?? That being the case then ANYTHING missing from the head structure is wrong-----Have a look at this You-tube video.------------------http://www.youtube.com/watch?v=FhgnXjEz ... ---------- Is this your engine ?? If so then it's an IRON HEAD ?-- I've just re-read your first posting and, sorry to have to say this but, based on what you've told us, I would be inclined to remove and strip the head again, only this time pay a LOT MORE ATTENTION to that missing piece area. At this stage my guess ---and it is only that---- is the exhaust valve guide fitment is compromised somehow and you are burning oil from the rocker area. Iron takes a lot longer than Aluminium to heat and expand so that's why there is a fair bit of time until anything happens. Keep those chins up !!

Let's work through this logically. Mark says "There is no smoke coming out of the exhaust"....exhaust gases are generated inside the head....so unless there is some smoke purification plant midway between the inside of the head and the exhaust pipe outlet.....I think we can safely assume there is no smoke being generated INSIDE the head.....SO if we have no smoke on the inside of the head BUT smoke on the OUTSIDE of the head.....it doesn't need the brains of Einstein to work out that the smoke is being generated on the outside of the head!...Mark also says it happens when the engine is hot....so putting the two facts together, I think we can safely assume the smoke is from an oil leak...probably from the inner areas of the rocker covers which is seeping round to the very hot exhaust part of the head.

I think I have to go with les on this one.Will have to take the head
off again. I,m hoping it,s a sealing problem between the head and the barrel.
need to get a new gasket tappet seals.