Hitchcocks Forum

Hello to all.
I am rebuilding a crank for my 1951 J2. it has a relief valve on the end of timing side shaft. thinking that it may stick open and starve the big end of oil I looked at the indian bullet 2000 model and found that its been deleted off. The English versions all had this relief. my question is is smart to have it or just plug it off and ensure better oil supply to the big end.

I'm not an expert but I believe the relief valve is a desirable thing to have and is something of an unwelcome omission from the Indian models. There can be problems with the Indian bullets damaging oil pump splines if the scavenge pump goes over pressure, which they are prone to, especially when the throttle is blipped.



It's enough of a problem for Hitchcocks to have designed and marketed an aftermarket scavenge side pressure relief valve that bolts on in place of the tappet cover.

Definitely leave it in place, without it any excess pressure will lift the pump rocker of its seat causing wear to both, as Stinkwheel says it also causes strain to the pump drive, with clean oil it will never stick open unless the spring breaks and I have never known that to happen?

Hi Jassie. Definitely keep the relief valve, it was put there for a purpose a long time ago, when the engine was designed and remained a feature of all Redditch big singles and earlier Indian ones. I am currently rebuilding and tuning a CO / G type engine, I have had the crank apart to lighten it and fit a new big end and I checked the relief valve works and kept it there. Only this morning, I pumped oil into the reassembled bottom end from a squirty oil can via the worm nut and, as the top end is still off, I could see some oil coming from the plain big end and the rest coming out from the relief valve. The big end is getting what oil it needs and the rest, thanks to the relief valve being present and working is available to lubricate the piston, barrel and mains. If there was no relief valve, this surplus oil would not find its way into the crankcase in the first place so the piston, barrel and mains would get less oil and the oil pumps and their drive train would have a harder life as well. Regards, Paul.

Thank you for your responses guys. I now see the importance’s of this relief. I will just take it apart , clean it out and make sure it works.

If I had to design a crank and the only oil available to me was straight 50 I'd probably shove a relief valve in there as well

Ric, regardless of the oil type the relief valve is a good thing, the pump on these bikes supplies more oil than an unworn big end can pass also the extra oil still goes into the crankcase and lubricates the bore/piston main bearings et al, without it less oil gets in there and the pump also gets a hard time.

Hopefully you’ll spot one of these as I believe you may have missed my earlier one

Yes Ric, I did see it but the meaning is open to interpretation. 😁😁