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General => Douglas Motorcycles - General Discussion => Topic started by: Dougiethenoo on 29 May 2016 at 20:18

Title: Valve guide replacement
Post by: Dougiethenoo on 29 May 2016 at 20:18
Any advice on technique to remove and replace post-war valve guides? Should the head be heated to press them out? Thanks.
Title: Re: Valve guide replacement
Post by: eddie on 30 May 2016 at 07:38
Just turn up a suitable sized drift to drive them out. There is no point in applying heat as both the head and guide are cast iron and will expand equally.
   Regards,
                  Eddie.
Title: Re: Valve guide replacement
Post by: shuswapkev on 30 May 2016 at 11:58

  the head guy that I use simply reams out the original and inserts a brass bush...some sort of proprietary system??
  does the little Asian cars by the dozen...and...
my Harley,(shovelhead) 26  EW, 2 BSA,s...(B33 and A10)  triumph (650 and 500)and matchless (G/80))...and soon to be doing an AJS...and another triumph..
and also my F-150...300-6  and all are giving or gave good service
 I reckon its better...  because sometimes...your new (my) new valve guide is just a hair too small....then what??....never know how many times they have already been banged out...or how much damage you do banging them out
Title: Re: Valve guide replacement
Post by: Daren W Australia on 30 May 2016 at 12:03
https://www.youtube.com/watch?v=xOaOTnpacV0
Title: Re: Valve guide replacement
Post by: Doug on 30 May 2016 at 17:39
The bronze guide inserts are used in the automotive world as a time saver, and it is cheaper to sleeve than replace the entire guide. Bronze works fine in these applications as there is plenty of lubrication; indeed often valve stems seals are fitted to keep excess oil out of the valve guide. Older engines that do not have positive lubrication to the valve chest or that run pretty much dry (other than a drop or two of oil at the beginning of a run) like the 2-3/4hp are better off with the natural lubricity of cast iron.

-Doug
Title: Re: Valve guide replacement
Post by: Dougiethenoo on 31 May 2016 at 09:34
Many thanks for the info.
There's a mix of old and new valve guides in the heads, one is recent custom made bronze item and I believe the others were replacements fitted years ago, or maybe original. They appear to be cast iron.

On the LHS, there has been an obvious lack of lubrication, the older of the two valve guides is very worn, as is the valve stem. The small end bushing was also badly worn.
I have new guides and valves from LDMCC now. The guides are cast iron.
I'll try to use a press to push them out, if that fails, a drift and a hammer will be the escalation path.