Gasket for G9

ChrisD200 · Post by **ChrisD200** » Tue Mar 01, 2011 7:33 pm

Hi Guys. My 1951 G9 is almost rebuilt after I too forgot the anti-wetsump tap (I got 11 miles I did!). All working OK, had to sew up a new filter for the crankcase as I can't find another - but I used the felt from a spare new oil tank filter so I guess the material is OK.
But....the 2 brand new gaskets we put in blew out together soon after startup. So, here's the question "can I have copper gaskets made up or must I use composite ones"?
Look forward to your thoughts
Cheers, ChrisD fom Cape Town

Flash · Post by **Flash** » Tue Mar 01, 2011 8:07 pm

Hi Chris. You can get copper gaskets for the G9 from Jampot spares, they are very good quality.

TTJ

Groily · Post by **Groily** » Tue Mar 01, 2011 8:28 pm

Assume you're talking here about head gaskets Chris. Also assume you had composite ones in there and they 'blew out'.
If they blew out, then they blew out for a reason. The reason may be that the heads weren't seated properly on the barrels owing to the gaskets not being thick enough to be compressed before the spigots on the barrels hit the annular recesses in the head; lack of tightness; uneven surfaces; etc. Composite gaskets should be, if memory serves, around 65 thou thick new - I've had some, not from Jampot Spares (JSL), that were way under that and couldn't seal. It's a relatively well-known problem.
I've also had copper of unknown provenance, but reckon composites are fine and use them all the time on 500s, no trouble, loads of miles. 650 owners might have more to say, but a '51 G9 isn't going to tax things too much.
Felt oil filters are also available from JSL and from others too. Long way from you, but the post works and it's worth having the right bit in there given the various sensitivities. Won't get you round a closed oil feed tap situation though.

1608 · Post by **1608** » Tue Mar 01, 2011 9:40 pm

Hi Chris, as Groily says, I don't think its the gaskets
as I haven't had any problems with composite gaskets ( so far 1200 miles ) on my G12. The fact that BOTH gaskets blew seems to qualify Groily's point.

wilko · Post by **wilko** » Tue Mar 01, 2011 10:06 pm

As with my 650, i'll bet the head nuts aren't pulling down far enough because your spacer spools are too short.That will be $100 for my advice, thank you!!

ChrisD200 · Post by **ChrisD200** » Wed Mar 02, 2011 7:36 pm

Hi Guys.
Thanks for the input - I bought these gaskets new from reputable dealer in UK. I didn't know there were thickness gaskets. Wilko, would you please explain what the "spacer spools" are? If I can get new gaskets, I'll need to know what to add to the spacer spools so the problem will not recur.
Cheers
Chris

wilko · Post by **wilko** » Wed Mar 02, 2011 10:30 pm

Do a trial fit with the headgaskets and peer down the throughstud holes with the spacers on and see if there is enough thread below each spacer to allow for crush on the gaskets. You might be running out of thread before this happens. I ended up maching my own spools a little longer.

paul knapp · Post by **paul knapp** » Wed Mar 02, 2011 11:51 pm

G'day Chris, thse 'spacer spools' are the cotton reel looking things that you drop in the head over the studs first.
You can check to see that you can achieve enough gasket crush by fitting the heads with out the gaskets but place several pea size pieces of plasticine on the cylinder top. Wind down the head nuts with spacers till they tighten up, then remove them with head to see how much the plasticine has flattened out.

Also, I like to grit blast the cylinder face and the corresponding barrel top to rough it up so as to make them not so slippery. Gives the gasket something to 'key into'

ChrisD200 · Post by **ChrisD200** » Thu Mar 03, 2011 4:26 pm

OK, I see, the spools need to be abit longer if the gasket is a bit thin - because there may not be enough thread to apply the correct pressure to the gasket. I'll pass that word.
Thanks
ChrisD

ChrisD200 · Post by **ChrisD200** » Thu Mar 03, 2011 4:39 pm

BTW where can I get a manual for the 1950 or 1951 model G9. No, you can't get from the Danish site because the only twins manual before the 1955 one (the 1950 one) fails to open. And neither of the 1955 or McNeills 1957 manuals show the head or its bolts.
Thanks
ChrisD