BSA Owners' Club Forum

The BSA Workshop => Singles => Topic started by: Starphil on 29 January, 2018, 16:32:34

Title: Scavenge Valve Replacement
Post by: Starphil on 29 January, 2018, 16:32:34
Hi,
My Starfire has a lot of il in the sump. looking at the scavenge valve it's difficult to see if it's working ok. The end of it looks a bit chewed up so i would like to get it out and inspect it and if necessary replace it but how do you get it out? Iv'e seen reference to a grub screw but can't see one.

Has anyone done this?

Cheers
Phil

Title: Re: Scavenge Valve Replacement
Post by: AWJDThumper on 29 January, 2018, 17:42:06
I believe it is just an interference fit but you would probably need to heat up the casing around it to be able to pull it out. I think I've tested one before now by putting a tight fitting rubber pipe over the end and then sucking and blowing to check whether the valve is working ok.
Title: Re: Scavenge Valve Replacement
Post by: Starphil on 29 January, 2018, 18:05:37
Thanks for responding.

The engine is still in the bike so I'll have to have a think about how I might heat that bit up.

Cheers
Phil
Title: Re: Scavenge Valve Replacement
Post by: AWJDThumper on 29 January, 2018, 19:43:51
Just re-reading your original post again, I think you are looking at the wrong non-return valve (NRV). There are two inside the engine, one on the feed side and one on the return side. You have been looking at the return (scavenge) NRV which doesn't really do a great deal. It is the feed NRV which is there to help stop oil in the oil tank draining into the sump and a problem with it can result in wet sumping. On your engine, it is located in the inner timing cover and there is a grub screw that has to be removed to get at it. Therefore, it is a bit of a job to overhaul the feed NRV but it depends on how bad your wet sumping is.
Title: Re: Scavenge Valve Replacement
Post by: AWJDThumper on 29 January, 2018, 19:51:30
Feed NRV is shown with part nos 20, 21 & 23.

Title: Re: Scavenge Valve Replacement
Post by: Starphil on 29 January, 2018, 19:59:30
It's been 2 - 3 weeks since I ran it and today when i took the sump cover off (because there's a leak) about half a pint came out.

Also, when I did have it running it was OK at idle but smokey when revved. Hoping this is just because of oil in the sump.
Title: Re: Scavenge Valve Replacement
Post by: AWJDThumper on 30 January, 2018, 06:43:06
About 1/2 pint isn't too bad and shouldn't cause any problems when you start the bike - the excess oil will quickly get pumped back to the tank. Unfortunately, the smoking is more likely to be due to worn piston rings or valves.
Title: Re: Scavenge Valve Replacement
Post by: Starphil on 30 January, 2018, 10:29:29
That would be a shame if it is.

The bike hadn't been run for a 2 -3 years prior to me buying it at the end of October. Since then I've been sorting out a few minor things so it has only been started a few times. I'll have to see how it goes when I give it a longer run.
Title: Re: Scavenge Valve Replacement
Post by: AWJDThumper on 30 January, 2018, 11:36:32
If it hasn't been run that much it might simply need to bed in again and to burn off anything that accumulated inside the exhaust system!