Hitchcocks Forum

Redditch 1960 350 Bullet:
According to my manual the ignition timing should be set to 1/64" BTDC. That must have been set with leaded 4 star petrol? Or maybe they used 3 star?
Now we have unleaded with reduced octane, so is any adjustment needed to the timing with this fuel? As I understand it:
• Standard unleaded octane = 95
• Premium unleaded octane = 97/98
• Old 4 star octane 98
• 3 star was about octane 93
Or could it be that these engines are not that sensitive to octane vs timing?
Grateful for any insights!
Many thanks.

If it starts pinking, you either need to up the octane, reduce the compression or retard the timing. If it doesn't pink, carry-on.

There is a certain random factor with ignition timing on bullets anyway after it's gone through two idler gears and a distributor gear. What you measure isn't what you're getting unless you are strobing it.

Quite right SW, you can't rely on the figures. They get you on the ball park then it's tweaking time.

My year 2007 Bullet 500, with a sidecar, was pinking when going up hills.
So, I now use the more expensive petrol (can't remember; is that 97 octane?) and it's been perfect on that for ages now.
(I didn't adjust anything.)

My year 2000 solo Bullet 500 is happy with the cheaper stuff.

Hope that's something of use to put into your calculations....

Chris,

as far as I know the standard compression on the old 500 Indian Bullet is only 6.5:1. Upping the petrol to 97 Octane (my local Tesco sells 99 Octane) is an easy fix, but is your outfit on sidecar gearing or solo gearing?

A.

This was bought direct from Watsonian Squire, as an outfit.
I think they automatically put it to sidecar gearing, though I must say, I've never checked it out... as it seems pretty good anyway.
Certainly not had any concerns since using the higher octane. But always willing to listen and learn if there's anything else. Thanks, Chris

The old 350 Iron barrel will not pink or pre detonate. As said the compression ratios is very very low probably to run on India fuel in the 60's.

I had a 2008 350 Iron Barrel in Malaysia and she would love a mix of diesel in the fuel. I did add as much as 20% and then backed off. It gave a lovely long burn for the low ratio and gave it more torque . So much so I would carry some diesel in a bottle with me as most gas station would not sell me 20 pence worth of diesel.

My 500 iron barrel runs happily on standard unleaded, but if I have SWMBO on the back, it does pink a bit on hills etc. (no, she is not a hippo), so, if I know beforehand that an excursion is afoot, I refill with super or vpower or whatever, and there is no pinking at all.

I reckon that the build quality of the cylinder heads of these older iron barrelled bikes is so variable that it’s probably difficult to give a “one size fits all” answer regarding the fuel quality needed.

My 350 Bullet Electra seems to have relatively high compression, although it’s on standard parts. It’s certainly higher than 6.5:1. It’s cold compression pressure on the kickstart is 130-135 psi.

It has a fixed timing point, with an advance curve controlled by the TCI box. It runs well enough on standard unleaded but it runs noticeably better on the higher octane stuff, even from a supermarket. It also prefers cold, dampish weather. I’ve no other Bullet to compare it to but it seems quite sprightly, fast enough for me to feel fairly confident on the M1 motorway. It’s certainly well able to overtake all the HGVs and cars doing slightly higher speeds than them.

Remember this is a 1960 REDDITCH 350 Bullet in the original post, so the compression might be about 8:1. 1/64" BTDC will refer to the retarded ignition timing, it is usually in the region of 5/16" fully adavanced and should work fine if adjusted to these figures.