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By windmill john
#96171
Okay, still on monobloc and have just raised the needle one notch. I’d say an improvement and I’ll stop there.
Gets to 60 pretty well, can’t seem to get above 65; or so I’ve been told.... ahem....

But I’m happy with the pull now. May try the concentric at some point, but a cup of tea now beckons.
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By windmill john
#96175
I did that Paul, when I fitted the piston.

The bike runs well. It’s interesting that wheaters says he gets 70mph. I’ve read he has a 5 speed box... could be a reason.

I’ll try the concentric for the hell of it, but pretty pleased so far.

It’s interesting, I’ve had too many bikes. Possibly a curse rather than a blessing, but I’ve learned the foibles of many bikes and it has increased my mechanicing knowledge.

Having a Bullet is the first time I’ve deviated from standard-ish.

I’ve rebuilt many carbs, but I’ve always worked to the standard baseline, that is, standard jets etc.
I’ve never had a bike as..... sedate... as Gupta, so never needed to alter my performance; let’s ignore my first Yamaha DT100.
I’ve adjusted the TPS if an aftermarket silencer needed it.

But now... different piston, inlet cam timing changed, non standard needle position etc. I’ve always maintained my own bikes, changed clutches, wet and dry, rebuilt forks, change wheel bearings, changed tyres etc blah blah..... but now...... I’m a real mechanic :mrgreen:
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By Wheaters
#96177
John,

My 350 Electra will definitely do 75 mph. I've just done about 95 miles on it today (great fun before I got too cold).

The 5 speed box does help, but the top ratio is still 1:1, as per the original 4 speed. The gearbox came with an 18 tooth drive sprocket fitted. I already had a modified rear hub and a longer than standard rear chain on the bike and I decided to fit a 42 tooth sprocket to that, which makes the overall gearing almost the same as the standard 350, 16/38. There might be slightly less transmission drag than standard doing things this way; I don't know.

I've DIY gas flowed the inlet and exhaust ports (but left the valve guide "humps" and guides completely intact). The exhaust port was easy to improve with a round cutter in my Dremel.

It now has a 26mm "Wassell" Concentric carb. It was easy to get that to match the inlet port; if anything the VM24 is undersized for the head as it came from the factory. The "Wassell" came with a short, screw on "stub stack", for better gas flow. It wasn't possible to fit my existing cone type air filter over it, because it uses the same part of the carb body to seal against. Instead I fitted a foam "pit bike" filter that I just happened to have in my cupboard. This does go over the stub stack and clamps inboard of it. It's probably as free flowing as anything else and they only cost about a fiver. There's plenty of "headroom" from the end of the stub stack in these filters, which again helps gas flow. The jet supplied was a 160. The bike ran OK with that but I felt it might just be holding back a little so for safety (of the piston) I fitted a 170 to richen it up a little. Everything else is as it came out of the box.

I fitted a high level Woodsman type exhaust from Mr H. It's a "straight through" type muffler with no baffle so it is LOUD. I do have a bolt in type baffle but it definitely drops the top end performance down a bit.

I recently fitted an NGK Iridium plug, as per Mr H's recommendation. I don't know if it gives any top end advantage but it certainly seems to idle more reliably with it, which is why I tried it.

The cams are standard, standard timing, too. So is the piston, very slightly domed with small cutaways for the valves.

When I had a new exhaust valve seat fitted (original one was soft) the engine shop said they couldn't get an exact match for the original. Instead they machined into the existing seat and fitted a different type inside it. This may have reduced the combustion chamber volume slightly because the valve seems to sit "proud" and compression pressure is slightly above that quoted in my workshop manual; it's just above 125 psi, measured cold.

However! I suspect the main secret to getting a bit more power from this engine is removing the standard exhaust silencer, which seems very restrictive indeed and just making sure that the inlet and exhaust paths are cleaned up and smoothed.

One final thing: Although this seems totally obvious, do make sure that both brakes don't drag - even slightly! With a relatively low powered engine like these, every little helps!
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By windmill john
#96181
You didn’t mention you only weigh one stone! ;)

As far as I am aware, Gupta has standard gearing. I’ll be interested how the concentric performs. If it revs too high when started, I’ll give up. I bought and fitted the smallest cut out slide. It is a 900/930, so might be too big for Gupta.

It’s all mostly out of interest-ish. I didn’t buy a Gupta for performance. But the better I can make him for modern traffic, the better.

Of course, mine’s not an Electra, but a cast iron.
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By Wheaters
#96182
Mine’s also an iron barrel!

It’s known as an Electra because it has electronic ignition (crank driven TCI, so it doesn’t have a distributor). It is kickstart only, unlike the 500 version which had electric start.

(One stone x12 is about right, btw).
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By windmill john
#96183
Sorry, still don’t know all the models properly.

I’m 11st so should be faster....

I did have a more through silencer, but my wife wouldn’t go on him due to noise. Someone at work commented too, so I got this silencer from our hosts.
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By Wheaters
#96184
windmill john wrote:
Thu Apr 08, 2021 5:53 pm
Sorry, still don’t know all the models properly.

I’m 11st so should be faster....

I did have a more through silencer, but my wife wouldn’t go on him due to noise. Someone at work commented too, so I got this silencer from our hosts.
I've just about got the models sorted out - but I still get confused by the term "Bullet Classic" which to me should mean the oldest versions but apparently it doesn't - I think!

You should have the advantage on acceleration but how aerodynamic a shape are you for top speed? :lol:

My wife had had enough of my bike's dual seat after ten minutes and only ever went on it the once. So I took that as permission to remove the rear footrests, fit the passenger unfriendly high exhaust and fit a solo saddle! She's quite happy with that. :mrgreen:
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