Author Topic: BSA B33 sticky exhaust valve advise please  (Read 311 times)

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RichardAB

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BSA B33 sticky exhaust valve advise please
« on: 11 August, 2017, 18:05:14 »
Hi I've previously had problem with exhaust valve sticking & pushrod jumping off on my 1960 B33 This hadn't occurred for a number of miles - probably 2,000 - until today. I had done 30 miles closed down throttle a little to take a corner,the engine note changed & off came pushrod. The problem is the exhaust valve sticks/seizes temporarily Luckily no damage & an easy roadside fix with some tools I've adapted.I continued but only did another 5 miles & same happened again. I nursed bike home by stopping every 4 miles to allow bike to cool a little.

The engine seems to be running very hot. I've made no recent adjustments to settings so why has this re occurred?

I'm aware this is a problem with other 33's & mine has been ok for a good while as I say at least 2,000 miles.

Any thoughts please?

Thank you
Richard

JulianS

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Re: BSA B33 sticky exhaust valve advise please
« Reply #1 on: 11 August, 2017, 19:00:50 »
Could be build up of carbon on valve stem causing slow closing?

Greybeard

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Re: BSA B33 sticky exhaust valve advise please
« Reply #2 on: 11 August, 2017, 19:30:48 »
Hello, Richard.
How's the flow of oil to the rockers?. I know that the B31/33 doesn't have a feed directly into the valve guides, at least my B31 doesnt, but relies on what splashes around after its been through the rockers. Try slackening the feed pipe banjo bolts when the engine is ticking over to see if some seeps out. Putting your finger over the oil return in the tank will force more oil up to the rocker feed so you can check it isn't blocked.
You could also check that the banjo bolts have been put in the right order as they do have different sized holes. Smallest for the inlet, next size for the exhaust and the biggest for the drain pipe at the back.
My Matchless single inlet valve has a separate feed that can be metered by a pilot type screw on the head. Helpfully, the book says if you hear the valve squeaking then increase the flow of oil  :-\ Did you hear any sort of chirruping noise before the valve stuck?
As Julian says, it could just be a build up of carbon, so a head off job might be the only sure way to find out. It's not a difficult job and can be done in an afternoon.

Steve
Steve from East Yorkshire - Not the Greybeard of the A7/A10 forum who was not actually registered on this one when I signed up ;-)

RichardAB

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Re: BSA B33 sticky exhaust valve advise please
« Reply #3 on: 12 August, 2017, 05:55:25 »
Thank you to both of you for tips/advice. I wonder if anyone else has had this problem or can offer an opinion.

Mike Farmer

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Re: BSA B33 sticky exhaust valve advise please
« Reply #4 on: 12 August, 2017, 10:38:03 »
 :)

Firstly I must admit that this marque is outside of my knowledge but may I make a general point.

Your engine wasn't designed to run on the types of fuel now available, so that MAY be at the route of the problem. Try an additive in your fuel to enhance upper lubrication. Good 'ol Redex is as good as any, but there are many other brand available. Or simply add a small dose of two stroke oil  each time you fill up.(Personnally I don't like this particular idea).Blimey!!!! do you remember when a "shot of redex" only cost a penny.

Trust this may help.

Mike 8)

Greybeard

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Re: BSA B33 sticky exhaust valve advise please
« Reply #5 on: 12 August, 2017, 11:17:04 »
When I rebored the B31 I wanted to add some redex as an upper cylinder lubricant, but everything I read suggested it was now a totally different beast more for cleaning injectors etc. I suppose with modern cats etc they steered away from oils towards using other nasties.
I couldnt find anything that was sold specifically as a lubricant. I resorted to a splash of 2 stroke oil instead, but im not convinced it did any good - the motor did nip up slightly as i recklessly took my eye off the speedo and it strayed up to 35mph  :o There was no harm done as i always ride with my hand over the clutch lever and by the time Id coasted to a stop itd freed off again. I took the barrel off to check it over and I got away with it. Its not done it since and im now able to creep towards 40 at times  ::)

Steve
Steve from East Yorkshire - Not the Greybeard of the A7/A10 forum who was not actually registered on this one when I signed up ;-)

Mike Farmer

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Re: BSA B33 sticky exhaust valve advise please
« Reply #6 on: 12 August, 2017, 19:48:08 »
 :)
I understand what you are saying but now there are all different types for differing types of engine.

MIke 8)

paulm

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Re: BSA B33 sticky exhaust valve advise please
« Reply #7 on: 14 August, 2017, 20:43:30 »
this is a common fault caused by pattern parts, the new guides being made are not corretly Machined, if you look at the aizes BSA quoted the new guides are to small, get a guide made and fitted to the exact bsa size and check it after fitting, i seized a lot of these untill i got the correct reamer

RichardAB

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Re: BSA B33 sticky exhaust valve advise please
« Reply #8 on: 14 August, 2017, 22:02:49 »
Thank you. Where do I get correct dimensions from?

STAR TWIN

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Re: BSA B33 sticky exhaust valve advise please
« Reply #9 on: 14 August, 2017, 22:42:03 »
I had a similar problem with a guide fitted to an iron head A7. What I did was to buy a set of engineers drill bits from Screwfix. I selected one that was a neat sliding fit in the valve guide. I then selected the next one up and carefully ran it through the guide. Problem solved.