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[Norm]

Scotty, Vic may be one of the smallest states but the whole of England will fit easily inside its borders and as for population they are saying Melb will have 8 mill people in the not too distant future

[Krish Ramson]

Interesting! Apreciate bringing this topic to the platform. I have a doubt! Excessive oil supplied by AVL oil pump won't be an issue? Because CI's floating bush is not designed for an excessive oil supply as far I know. I assume that in this mod, the crank and connecting rod as well have been replaced with that of a Cast Iron Bullet. If yes, the floating bush will allow only restricted flow of oil unlike needle bearings in AVL Con Rod right? I hope you must have been using the bike with this mod since last 2 yrs atleast now. By any chance have you verified whether this AVL pump has cause oil splash/wetting when you check the spark plug?

[Adrian]

Norm and I took different approaches. If you use the AVL timing covers and high-capacity oil pumps with what is otherwise a mostly standard iron barrel bottom end, then the pressure release valve in the crankshaft ought to protect the floating bush big end and oil pump spindle, etc. The problem with this is that not all model years of iron barrel Bullets actually have the PRV fitted! Make sure you get the right one.

My take on the hybrid engine is to use a set of iron barrel crankcases, modified to use the AVL timing cover, and build the AVL crankshaft, head and barrel into it. Why? Because I like the design of the cylinder head, but I also like fitting magneto ignition, which is a lot easier to do on the iron barrel crankcases than the AVL version. Not that you can't modify Electra-X crankcases, but it's a whole load of machining to re-instate the timing gears and a magneto mount.

If more oil delivery from the AVL pumps causes a spark plug fouling issue, then the piston rings aren't doing their job. Otherwise how would any AVL engine cope? Or a normal iron barrel engine fitted with our hosts high-capacity piston pumps?

A.

[Wheaters]

Hitchcock's do of course sell their after-market Pressure Relief Valve assembly.

I fitted one to my home market 350, which has the standard piston type oil pumps and the floating bush bottom end. I've found that the PRV does seem to pass a lot of oil, more than I'd imagined it might. These days the bike doesn't burn a lot of oil; maybe the PRV helps by limiting the amount oil in the cylinder head casting at higher revs but it will certainly off-load the pump and drive components.

[Adrian]

The Hitchcocks' pressure release valve is for the SCAVENGE side. This won't have any effect on the FEED side as the PRV valve here (if there is one) is actually fitted in the timing side main shaft.

You'd have to check with our hosts or a Chennai Bullet expert about which years' Bullets would have had them fitted from the factory. Redditch Bullets have them.

A.

[Wheaters]

The Hitchcocks' pressure release valve is for the SCAVENGE side. This won't have any effect on the FEED side as the PRV valve here (if there is one) is actually fitted in the timing side main shaft.

I’m very much aware of that - I fitted it myself and it’s very obviously fitted in the external scavenge pipe to the top of the engine. My point is that the rockers obviously don’t need as much oil as even the standard piston pumps can flow. The scavenge pump can only scavenge what the feed pump provides and with a floating bush the standard piston type of pump is obviously more than sufficient. Any more flow won’t achieve much but without a relief valve the scavenge pump will put unnecessary load on the drive quill because it is still actually a pressure pump, albeit to the rockers. I can’t actually think of another engine I’ve worked on that doesn’t have a PRV.

I saw first hand how much pressure an oil system can produce. The PRV on my little Suzuki 1.0 engine jammed shut and the pump produced enough pressure to blow the external oil filter canister up until a couple of spot welds on the base of the case popped and the O ring seal blew out in the car park of Cotswold Aerodrome. I had to pay for the clean up on the new tarmac.