Sloper valve seizure

Started by LES, 11 Jul, 2020, 23:53

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LES

11 Jul, 2020, 23:53
I recently finished the restoration of a 1935 BSA 600cc Sloper, including total engine rebuild with new valves and valve guides. I found the correct valves in Australia, but the guides were a problem, and I finished up using C11/C12 cast iron guides from Draganfly, with the correct OD, and had the machinist ream the ID out to the correct 3/8" size. Bike started up OK, several times over the next week, but while trying to fine tune the idle, one day, it suddenly lost compression.  Removing the head showed that the exhaust valve had seized in the guide. The machinist looked at it, but no obvious reason was evident, there was plenty of clearance between valve stem & guide. Bearing in mind there is no lubrication at all to the exposed exhaust valve gear, I'm wondering if the cast iron guides meant for an enclosed and lubricated C11/C12 are suitable for my bike, with no lubrication. Anyone able to give any technical advice?

Mike Farmer

#1
12 Jul, 2020, 10:41
 :) :) :)

Only thing that I can suggest is run it with REDEX petrol additive. It is specifically for upper cylinder lubrication.

Mike 8) 8) 8) 8)

LES

#2
12 Jul, 2020, 12:20
Good advice,I wasn't using an upper cyl. lubricant, and certainly will  in the future, but I'm hoping someone can give an opinion on the type of cast iron to use for the valve guides, even if it means having a pair made. Having the valve seize before I even rode it is a bit worrying, and I'd like to be sure I have done everything I can to prevent a re-occurrence.

JulianS

#3
12 Jul, 2020, 12:25
Not sure whether the exhaust guide depends on lubrication introduced into the cylinder via the drilled inlet valve guide lubrication system?

Dean Southall

#4
12 Jul, 2020, 12:58
Quote from: Mike Farmer on 12 Jul, 2020, 10:41
:) :) :)

Only thing that I can suggest is run it with REDEX petrol additive. It is specifically for upper cylinder lubrication.

Mike 8) 8) 8) 8)

I have struggled to find Redex upper cylinder lubricant as I was keem on using it for my Sloper and Trike. There's plenty of other Redex products but I haven't UCL one for years.
(For the nostaligic who remembers....."Shot of Redex Sir?")
BSA: turning ordinary men into mechanics since 1910

Dean Southall

#5
12 Jul, 2020, 13:02
Les,
the handbook for my 1930 Sloper states that the valve stems should be given a few drops of oil from a can directly onto them regularly. Not sure if this applies to 1935 model.
BSA: turning ordinary men into mechanics since 1910

LES

#6
12 Jul, 2020, 14:17
Dean, I didn't know that, and I will be doing it, along with an upper cyl. lubricant, but I oiled the valves during assembly, and it took only around 10 minutes at tickover for the exhaust to seize, so I'm convinced lubrication isn't the problem. I was lucky in that it stuck in the almost closed position, so no piston or bent valve damage. I desperately want to avoid a repetition, since next time could be terminal. I'm wondering if there is a more suitable cast iron to use when making valve guides for unlubricated guides.

Julian, the inlet guide only is lubricated by BSA"s mysterious "oil vapour"- nothing for the exhaust, but these bikes ran forever this way,
so why has mine seized?

JulianS

#7
12 Jul, 2020, 16:57
Overheating caused by 10 minutes at tickover?

LES

#8
12 Jul, 2020, 17:46
Yes, a total of around 10 minutes spread over 3 days, although the valve was the only thing that seized, and no evidence of engine overheating. Oil pressure at 16-17lbs

Mike Farmer

#9
13 Jul, 2020, 08:36
 :) :) :)

If you cant get REDEX a thimbleful of 2stroke oil will probably do the trick. If I was now having guides made I would take advice but seriously consider a bronze???alloy of some sort.

Mike 8) 8) 8)

Mike Farmer

#10
13 Jul, 2020, 09:10
 :) :) :) :)

Ebay item No283111101732 Redex lead replacement, appears to be the same as the old stuff. Probably available in Halfords or any of the motor factors.

Mike 8) 8) 8)

LES

#11
13 Jul, 2020, 19:29
Mike, I'm going to use 2 stroke oil. I remember Redex, but not available this side of the pond, if it ever was. Tech guys advise not to use bronze guides due to different expansion rates in cast Iron head. I'm going to stick with cast iron guides, a generous dollop of oil in the gas, and crossed fingers.

Mike Farmer

#12
13 Jul, 2020, 19:58
 :) :) :)

You want to try some REDEX???send me an address and I'll send you some.

But first there is another brand selling same-ish stuff. I think its lucas but I'll let you know later.

Mike 8) 8) 8)

Mike Farmer

#13
13 Jul, 2020, 20:01
 :) :) :)

Its LUCAS upper cylinder lubricant. Made in the USofA.

Mike 8) 8) 8) 8)

LES

#14
13 Jul, 2020, 21:19
Yes, I've seen Lucas products around. I'll get some.
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