improving VB performance

[brenton.roy]

Thanks Barry,
I'm aiming to just get more from it as a road bike. I know it will have limitations - mostly due to heat buildup, but the big sidevalves are great engines.
Should the engine bits ever arrive, I'll get going with it...
PS, I'm looking for page one of this article. Does anyone have it?

[david.anderson]

Brenton
to raise the oil level to the inner timing chest is quite easy and probably the most worthwhile mod you can do to a single. Put simply drill a 1/4" hole in the crankcase at the level you desire the oil to be at, preferably with the cam lobe dipping into the oil. It is then a matter of cutting a bit of 1/4 copper pipe to length and bending it to fit between the outer timing cover oil drain hole and the original oil level drain hole in the crankcase. I push the pipe all the way through the timing cover an put a bend at the inner face to stop the pipe moving out. likewise I put a bend at the crankcase to stop the pipe moving inward. It can be a bit fiddly biending the pipe until you get a fit. Alternately I have seen the original crankcase hole welded up and a new hole drilled to line up perfectly with the hole from the outer timing cover. see the attached pics.

new hole directly above original drain hole

note the bends in the pipe

pipe extended to front of timing cover stops pipe from rotating and maintains alignment with crankcase hole

the pipe will stay in position in the inner timing case when you remove the timing cover

[brenton.roy]

fantastic, thanks David.

[brenton.roy]

Hi David / other experts,
I''ve done this modification, but am now wondering why I shouldn't just block the lower hole and throw the copper pipe away?
It's not like it will be apart every 5 minutes, but...
Will it affect the cam to be hitting the oil? - or will it cause leaks?
Either way, the oil level has to raise in the outer timing cover area, which is going to mean more oil flying around and potentially ending up in the magneto / going out the breather.
I've made the copper pipe up, and it fits OK, but it's a pain to line everything up.
I've drilled so that the cam would be in 2mm or so of oil.
Thanks in advance,
Brenton

[robin.parker]

Hi Brenton,
Tuning side-valve motors is a fascinating part of your Aussie heritage, go for it.
You might find it interesting to Google "BSA M20 & M21 Side-Valve motor mods for performance" the pic showing an extra Carb sticking out sideways is a delight, and makes sense! How about a VB Special, to beat the 108mph M20?
Enjoy yourself,
Robin.

[brenton.roy]

Thank you Robin.
It's interesting stuff. Yes, there is a bit of history with SV's here.
I started this about the same time as John did his "flying toolbox". So far, mine is still a pile of parts...
I'd be really happy with 80mph!
Brenton

[david.anderson]

Brenton
If you block the lower hole in the crankcase then you raise the oil level in the outer timing cover also. Oil will flow into the outer timing cover through that drain hole. That may result in oil coming out the breather and around the magneto seal. The idea of the copper pipe is to drain the outer timing cover direct into the crankcase, and prevent the oil level from rising to the new level of the inner timing cover. The outer timing cover will only receive mist through the 15mm hole that is located higher in the timing cover and will drain through the pipe to its original level.
The raised oil level to the inner timing cover will not result in any more oil leaks but will prolong the life of the cam as it is now running in lubricant rather than a mist.
The copper pipe is fiddly but to maintain the alignment once set up I ensure that the copper pipe extends all the way to the outer face of the timing cover. That way it is held by friction. If it is lose a little Loctite or sealant will hold the position. The pipe only extends about 6mm into the crankcase, ie the thickness of crankcase at that point. just file a taper around the crankcase end of the pipe to help it find alignment when fitting
I have raised the oil level in all my singles and have had no problems
David

[brenton.roy]

Thanks David. That all makes sense. Done.

[pete.collings]

I have done this mod, and found it good for prolonging cam and follower life.
One slight disadvantage is that on standing, the raised level of oil drains through the timing side main bearing and into the sump area. On starting, the flywheels can pick this up (especially if cold straight 50 grade oil) and throw it out of the drive side breather, leaving a neat puddle under the bike unless you ride far enough to pump it all back to the oil tank and allow any breather loss to be evenly spread over the road surface.
I modded my drive side breather to exit into the primary chaincase, so any excess oil thrown out is keeping the primary chain well oiled

[Danny.Lee]

Brenton

In searching for standard parts for my VB I came across two versions of the ally head, one with a much higher CR than the other and this was not down to skimming either but a real diff in the shape of the head. I posted piccies on this some weeks back, so it may be worth you searching out one of the high comp heads. Danny Lee