Forum

[Gwilly]

The next time you’ve got your chin on the tank and the throttle wide open remember this picture…

Even the new EFI’s can throw a rod just like the old stuff.

If you want fast, then buy fast…

[another Allan]

Hi Pony. Have you tried a full-bore plug test? Go as fast as you can in top gear, throttle wide-open for half a mile or so. Then cut the motor and pull in the clutch and coast to a halt. When things have cooled-down, take out the plug and have a look at the colour. If it's too weak or rich it will be obvious, and this could be the reason for lack of top-end 'go.' (Obviously, take care with road conditions, traffic etc. when carrying out this test.)

[simon]

I agree Pony, you should get better speed that 65 although 80 is actually pretty fast and a tad optimistic. What you should have though is good even pull up to at least 70-75. Hell's bells my 350 will do that. I'm suspecting that you may have a combination of issues principal amongst which is the mixture. If you are setting the mixture hot (best) then the idle screw should be set so that you get a good even idle but no black smoke when you blip the throttle. I might also be tempted to check that you are getting a proper advance on the timing with a timing light on a wheel. You might have to beg, borrow or manufacture a timing wheel but it will show you that you are getting an advanced spark as the engine speed increases. A retarded motor will idle nicely but will feel sluggish at speed although I'd be surprised if it would get to 65 mph. A 500 single should pull like a schoolboy but if it's an old fashioned iron barrelled motor will never sustain high speeds with overheating and seizing. A 60mph cruising speed is pretty much it and anything above that will require a more modern machine or some serious mods.

[Paulk]

Pony,

Echo what folks have said about the mixture, get your carb tuned correctly. Also losing weight (your or the bike) will only help acceleration it will not increase top speed - just get you there sooner.

[Alan R]

Sorry matey but I think by now you'll have got the general idea that an old ( design as well as build ) Iron barrelled Bullet is really not the bike to suit your needs......and no one's even mentioned about the really important items ie}--- the big end and oil pump mods. let alone the chassis and brake upgrades to match this sustained 80mph performance that you seek............Here's a 500cc bike that was designed and built with just what you want in mind }>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

[Anders F. R.]

Pony wrote: "I had hoped that in terms of power to weight coefficient, there would be some improvement." .-.-.-.-.-.-.-.- Making the bike lighter will not make it faster on level road. It is not the mass but the air resistance and rolling friction that limits top speed on level ground. .-.-.-.-.-.-.-.-

Making it lighter will increase acceleration, and also the top speed uphill, but not very much, as at 70 mph the air drag is still the main problem on a bike, which as very poor aerodynamics. .-.-.-.-.-.-.-.-

Regards, Anders F. R. .-.-.-.-.-.-.-.-

PS. Not even 70 mph? My 1953 "G" 350 cc in standard trim does 69, according to period road tests, and I have seen 120 km/h on my reliable but somewhat optimistic Smiths Chronometric, which equals about 110 km/h (=68 mph) in reality. Sorry, just rubbing it in, I guess......

[MadMike]

Last one from me on this topic. Firstly the magical "power to weight" ratio. This will only tell you the BHP per kilo, and so if you have a bike producing 30BHP then losing a few kilos will have little or no measurable effect. Secondly weight reduction: what did it weigh before you started removing parts and what did it weigh after the event? Sadly the reduction will not be as much as you expected. Thirdly maximum speed: As I have said repeatedly road speed is a function of engine speed, and gearing. If your bike cannot do more revs then it simply will not go any faster. Raising the gearing is often possible but most bikes have a top gear designed to give optimum top speed with out over revving and thus grenading the engine. Not good for warranty claims you understand. Few bikes have the ability to go faster simply by raising the gearing. Indeed the vast majority will actually go slower due to being over geared. Have you raised the gearing, or are you currently on standard gearing? If the former then you may be over geared and require more power and torque from the engine, if the latter applies then you have to be able to make the engine rev faster, and again engine work is necessary. You may want to consider the effects of drag and friction but frankly apart from binding brakes slowing you down, you would have to be travelling significantly faster than your Enfield will ever be capable of in order to make any difference. As I keep saying the laws of physics apply here. If you can find a copy of Phil Irvings classic book, Tuning For Speed then you will see that the principles of improving engine performance have not changed. That is why racing teams from the big manufacturers spend millions every year on trying to squeeze out another handful of horses.

[Scalyback]

I did 'try out' my old iron bullet once. it never made 70 either.I guess yours will never make a 'pony express'



But do you sell or keep? They are brilliant fun on local roads, and do have their own character.

[simon]

They should do 70 mph with ease though. My mates old G80 pulls 70 in a flash and it's a bog standard 1950 model with an iron head. My 51 350 Bullet would do 65 albeit with a flat road and no wind. I still say he should check the bob weights are working.

[Pony]

If I could afford to keep it I would, but I need a bike I can use every day and it has to be able to keep pace with modern traffic. Hate getting onto the dual carriageway and having people driving right up my arse just cos I can't keep up