Forum

[Adrian]

I mentioned tax and MOT exemption above, and why not benefit from that if your vehicle is eligible? If you live or ride in London you could also factor in ULEZ exemption for historic vehicles, I believe.

A.

[Nitrowing]

I'd agree with Adrian - get the 350 big bored and fettled. I've read so many bad things about the Electra X (now that I already own one ) that I would never consider it as a viable donor

[Adrian]

Upping the size of a 350 to a 450 (actually a 441 using a BSA Victor piston) or a 500 isn't just a re-bore, there's a bit more machining to it than that.

There's usually nothing wrong with the Electra-X that can't be put right, but I like my Electra-oid bitsa engines to have an Alpha big-end, old style Bullet tappets and Redditch cams, a decompressor valve fitted into the cylinder head, some very non-standard ignition and no electric start.

A.

[Nitrowing]

Upping the size of a 350 to a 450 (actually a 441 using a BSA Victor piston) or a 500 isn't just a re-bore, there's a bit more machining to it than that.

There's usually nothing wrong with the Electra-X that can't be put right, but I like my Electra-oid bitsa engines to have an Alpha big-end, old style Bullet tappets and Redditch cams, a decompressor valve fitted into the cylinder head, some very non-standard ignition and no electric start.

A.

When the cost of 'putting things right' costs as much as a reliable bike...

[Wheaters]

Just found the right side gear change shaft in the parts list. Cost would be about £55 posted...ouch. More than it cost me to do the whole conversion.

[windmill john]

After reading the article below, it's nice to know that the bottom end is strong enough for 100mph. Looks like all his fiddling is top end.

Just out of interest and at the minute just a question and I appreciate this is not de rigueur for the 350... What is the best way of slightly increasing the power of a 350 that does not involve machining?


https://www.outlookindia.com/website/st ... let/347802


John

[Wheaters]

Windmill John,

I’ve managed to release quite a bit more “go” from my 350 without having machining done.

I had to have a new exhaust valve seat fitted (original was soft) and I rebuilt the top end with a Hitchcock’s stainless valve which I modified slightly (used my lathe but could have done it using an electric drill in a bench vice). I also gas flowed the inlet side of the head and opened it out for a 26mm concentric carb. I kept the small bell mouth that came with it and fitted a foam filter over it. The restrictive standard silencer was replaced by a “Gold Star” pattern one.

I have since fitted a high level “Woodsman” system with a straight through bottle silencer.

The best mod however was to replace the Albion type gearbox with a later five speed one. The ratios suit the bike really well. The final drive gearing is now 18/42, using a Hitchcock’s modified rear drum and sprocket. This means the gearing is very slightly “taller” than the standard 350‘s 16/38. I think it might pull a very slightly taller gear still. I have been tempted to just refit the original 38T rear sprocket but haven’t so far because I think that might just be a bit much. 17/38 would be good I think.

As I’ve written elsewhere, I’m now confident enough in its speed to “mix it” with motorway traffic, albeit for relatively short journeys. I’d never have done that before. I reckon the bike is 15 mph faster than when I bought it three years and 12,000 miles ago.

[Adrian]

Besides tweaking the gearing, the classic tuning path would be higher compression piston, ported cylinder head (doesn't need a fancy machine shop), sporty cams, bigger carb and a tuned/less restrictive exhaust, bigger inlet valve (use hand powered valve seat cutters), as well as the time and effort to get it all set up properly. Lightened flywheels would also feature quite often, but that's definitely a machining job.

A.

[windmill john]

Higher compression piston, bigger valves, port polishing. All the things that crossed my mind.
Five speed gear box would be down the line financially.

Thanks guys.

It also crosses my mind to leave well alone and enjoy Gupta as he is. I’m happy generally, but would just like to push up cruising speed ever so. My cruising speed is 45 to 60-ish.... no hang on, that’s the swinging speedo needle
I’d say I have an indicated cruising speed of 50-55. I’m sure I could up it slightly, but it sounds about right to my ear.

[Wheaters]

The five speed box has the same 1:1 top gear ratio as the four speed so top speed depends on the other mods.

There is a hill on a main road near me which has a 50 mph limit, where my bike used to get “tail gated”. After doing the other mods I mentioned the bike now flies up there in top and the boot is on the other foot, as it were. Having said all that, I think the main restriction to performance on my 350 was the exhaust silencer.