pre '49 G80 valve guides - circlips?

[hatrack]

As my '47 G80 now needs new valves and guides, I have been searching my parts list, AMOC spares and AMC Classic spares and see that only "49 on" valves are available but they are Ok to use and to use the same part numbered valve for both inlet and exhaust, so no problem there.
The head currently has valve guides with circlips fitted. But the parts book seems to show no circlip (not necessarily deffinitive as they didn't seem to think it necessary to show everything!) but I can't find a circlip in the number list either.
The spares sources above, list no valve guides for "pre '49".
So is it the same as with the valves? And the later guides with circlips are Ok to use?

[Rob Harknett]

Your 47 G80 would use the 39 guides used for inlet & exhaust, on 250, 350 & 500. Pt. No. 39-12-E148. up to 1948.
This guide was still in use beyond the 50's for inlet valve guide only. Club spares appear to stock the valve guide, under its NEW pt. no.017019. All old parts still in use circa 1952 were given new pt. no's. 39-12-E148 became new pt. no. 017019. It may only be listed as inlet guide, but for 39 to 48 it was used for in. & ex. Have you considered joining our club. I may be worthwhile joining, if only for all the help its members can offer you. You only have 90 days Free use of our club forum.

[Rob Harknett]

Valves you need for 47 500 would be STD 678 in. STD 679 ex. do not appear to be in club spares stock.
New pt. no's would be 000678 & 000679 as these valves were still used beyond the 50's you are more likely to find new old stock under the new part numbers.

[hatrack]

Thanks Rob. That is very helpful indeed.
I'm sure there are others to whom the phrase "Previous owner" is a dreadful term of abuse.
But then again, we have all passed on bikes to others that carry our own mistakes with them.

[hatrack]

Got the valves and guides from the club spares scheme.
Took them with the head to a local motor engineer who came well recommended.
Picked the head up today, and thought the guides seem to protrude a long way towards the valve seat.
The inlet valve fitted Ok, but the exhaust valve head would not even touch the valve seat. The valve guide comes so low it prevents it.
Circlips are fitted and guides fitted so that circlips are against the head. Oil ways seem to line up Ok.
So it looks like the valve guides supplied by the club are too long for the Iron head, or at least, the '47 head. If this is so the spares scheme listing needs to show this.
Before I take the head back, any clues on how much to get the end of the guide shortened?

As I have seen mentioned in another thread, the valves also seem rather tight in the guides. What clearance is best to go for?

[hatrack]

Anybody?

[g80csp11]

if you fit later guides with circlips to the early head the guide must not go all the way down to the circlip otherwise it will touch the valve head
Opps too late .!
Dont worry , heat the head up and gently pull pull back the guide with a bolt and nut /washer to set the correct depth

what are the measurements on your head ? what year 49 in title or 47 in your text

It should be , see page 40

inlet valve guide protrusion 0.5"
Exhaust valve guide protrusion 9/16 for 1949 and 5/8 for 1947

http://archives.jampot.dk/book/Workshop ... cycles.pdf

[Rob Harknett]

Anybody?

valves & guides appear to be made to fit. If you check a valve stem dia. you may find a size 3/8" dia. check the guide bore, that also will state 3/8". in the makers books, no clearance is given. Check MoD books for clearance of valves/guides. You wont find any given. All that is stated is, if the valve is sticking , replace. With both valve stem and guide bore diameters the same, I would have thought the valve would not fit in the guide. Valve perhaps should be smaller stem dia.??? They must have some clearance when hot. Does heat produce a clearance? Like oval pistons get round with heat so expand to fit. I think your question should be asked of the makers of valves & guides as to tolerance. It seems this is thought no concern to us. As it is never mentioned. Not even in M o D checks. Except if the valve sticks replace it.
Heres her you will find most tolerances that should be of concern. Not for your bike but a good general reference guide.

http://archives.jampot.dk/book/Owners_m ... nnaire.pdf

[Rob Harknett]

if you fit later guides with circlips to the early head the guide must not go all the way down to the circlip otherwise it will touch the valve head
Opps too late .!
Dont worry , heat the head up and gently pull pull back the guide with a bolt and nut /washer to set the correct depth

what are the measurements on your head ? what year 49 in title or 47 in your text

It should be , see page 40

inlet valve guide protrusion 0.5"
Exhaust valve guide protrusion 9/16 for 1949 and 5/8 for 1947

http://archives.jampot.dk/book/Workshop ... cycles.pdf

Perhaps that is why circlips were not listed in the parts list. Which had previously been noted.

[hatrack]

Ok. Thanks.
I hadn't seen, and was not aware of this particular book before and I'm glad to have it pointed out to me, and I note the valve guide projection dimension in there. It solves that bit of the problem that I encountered.
But it still seems odd that cast iron valve guides and valves, from the same source should be supplied with a stiff fit between them, with no mention of necessary clearance or need to ream them.