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Potential Purchase advice

Submitted by greg_salthouse on Wed, 30/10/2024
Forums
Heavy Twins

Hello good people of the NOC,

I have just joined the club in anticipation of collecting my Dominator 99, for which I have paid a deposit. It is a private sale. Having viewed the bike for a second time I am concerned about a slight oil weeping from the left, near side, of the cylinder head. It does not drip all the way down the engine but is there in a couple of fins. Owner assures me it has got no worse in 8 years and best left alone. There is also a minor weep from the sump casting on the opposite side which is not cracked but has a porous pin hole. This worries me less. It is tiny.

I don't expect a fully dry engine on a Brit bike circa 1957 but how serious might this be? Would it affect compression? It is not a project bike. I want to use and maintain, not rebuild. 

Any advice welcome. I can still regroup, learn more through the club and find another bike but if "they all do that Sir" then I'll dive right in. 

Thank-you 

Greg

 

Submitted by jonathan_newton on Thu, 31/10/2024

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And you have riden it to confirm its performance then two weeps on an old motor would not unduly worry. Take it out, get it hot, bring it back then watch the weeps. If it confirms the owners statement then you can decide. 

Are you buying a "rider" or a "showpiece ". Riders will always weep and not always in the same place. What you have described is common on Dominator engines and can falsely show as head joint issue, but can be found to be emanating further up the motor. 

Hi Jonathan,

Thank-you so much for the sage advice. The bike is used seldomly but starts and runs great hot or cold. It is in good presentable condition but patinated commensurate with age. That is exactly what I like and I will use the bike more frequently and aim to keep up with the mechanicals. I have an old classic car and find the more I use it the more reliable it is. 

I'll likely come back to the forum for advice on changing the oil. When I get the thing I'll probably work it out but the manual (Haynes and owners) confuses me with regard to oil tank and sump filters. 

Thanks again. Really appreciate you sharing your knowledge. 

Cheers

Greg

 

Submitted by david_cooper on Thu, 31/10/2024

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The standard 'sump filter' is a strainer device fitted within the drain plug at the bottom.  Owners quite often add a Commando full flow filter which won't appear in Haynes.  Filter elements from RGB, Andover and Norvill.  Citroën 2CV I believe.

Thank-you David

Great sounds straight forward enough. The other anomaly was the oil tank filter. The manual advises to leave it in situ but remove the whole oil tank and flush it, thereby cleaning the filter as well as the tank.  It advises "not to disturb the filter joint" So where would I disconnect the feed and return pipes from the oil tank in order to effect removal?

Cheers

Greg

Submitted by robert_tuck on Fri, 01/11/2024

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Leaks which "appear" to come from the head gasket  are often from other places but can be from stud holes where they pass through the gasket. It does not affect running and is very common and usually minimal  (helps prevent rust ! ) Fitting a reed or flap breather will help a lot . The orriginal unreinforced soft oil pipes would just easily fold and  pull off.They were not fitted with pipe clamps as there is no significant pressure and were not needed. Owners fit heavy reinforced  pipes with clamps which cannot be manipulated any more. Not needed!.. If the Union is disturbed a new copper washer is needed ,plus a bit of sealer.

Thanks Tony,

I have had a quick search through both.  Hopefully it will become clear when I have the bike in front of me to look at.  I am thinking it must be a reasonably common procedure to remove and flush the oil tank on the Dominator, as it is recommended with oil changes.  My post heading is not really specific to this question so I may repost once I have the machine, if I cannot fathom it.

Thanks again for those useful resources.

Cheers

Greg

Submitted by robert_tuck on Sat, 02/11/2024

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If you dont want to remove the tank . after draining,  tip  the bike over with a wedge under the center stand and with a long narrow paint brush agitate the bottom of the tank with some petrol until it comes out clean . You can also get a finger in the tank through the supply hole once the union removed.. After filling the tank with fresh 20/50  you can pull off the return pipe  and run the engine untill clean oil is returned . Pour a quarter of a pint into the exhaust rocker box for the cam before starting .  I have been known to run the motor with the sump plug removed ,and watch what comes out till i am happy its clean !.

Thanks Robert. I will supply a picture once I get the machine home. I am not against removing the oil tank but if it is not necessary then I will leave in situ and clean as best as I can following all the helpful advice posted.  I have no reason to suppose it is especially dirty or sludged but I would like to start with clean oil.
What specifically concerns me is this quote from the manual  "not to disturb the filter joint" so I am not sure where to disconnect the oil tank feed and return pipes.

Note your point about protecting the cam with some oil. No further need to prime the system?
In my simple mind I see the procedure as:-
1.Drain oil tank from drain plug
2. Drain sump and clean sump filter
3. Replace sump/drain plugs and refill with fresh low detergent 20/50

or additionally between steps 2 and 3, remove or disconnect the oil tank and flush/clean  without disturbing the filter joint.

Thanks

Greg

 

Submitted by jan_nelder on Sat, 02/11/2024

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if unlucky, there can be a layer of SOLID sludge in bottom of tank. A suitable wooden stick could be carefully used to assess this.

Submitted by greg_salthouse on Wed, 06/11/2024

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OK, well I have completed my oil change. Did not seem very sludgy. I elected to leave the oil tank in situ but I cleaned the sump filter which was not too bad at all. Thanks all. I am enthusiastic to tackle other jobs but I will post to the relevant forums with an appropriate subject heading, if I cannot find the information elsewhere within the NOC etc. 

Submitted by david_cooper on Thu, 07/11/2024

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Modern oils have 'dispersants' to prevent sludge build up.  Not to be confused with 'detergents' which keep the internals clean.  So some of the advice in old documents is no longer as relevant as it once was.
Dispersants ensure that microscopic particles of carbon etc stay microscopic (when they are relatively harmless) and do not clump together together into harmful lumps.  So modern oils can go black quite quickly simply because the particles stay suspended.  But they aren't necessarily in need of replacement just because they are dark.

 



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