Forum

[Mark M]

Adrian, you asked about the Bighead tank. It is the same pattern above as the Constellation tank but underneath it is very different. The underside is seriously cut away to accommodate the extra size of the rockerboxes on the Bighead engine. The Connie tank is quoted as 4.5 gallon but I'd guess that the Bighead tank is seriously reduced, maybe as much as a gallon. Remember that the Twin tanks are relatively flat underneath but the Bullets always have a cutaway, just very extreme in the case of the BH!


REgards, Mark

[Phil Ashbrook]

Just a note guys , I'll be running on E84 fuel like my std ported big vave head with the MK2 methonal conversion kit and I want to do this with a T3 GP 2 on a Fury head I'm going all the way this time as I have the race version 612 , the carb conversion is not cheap due to the lack of demand but I am determend to get the 50 bhp from the moter , a pig to start I would think and thats why I roll start , plug couler must be light grey and wet like a Jawa speedway engine or you will hole the piston at a 10:1 comp ratio , race camshafts make it even harder to start, this is my obsesion for more power , so much money has been spent so far .

[Adrian]

Mark, that doesn't surprise me, I did reply to Nico that I'd seen earlier twins' tanks with less underside clearance than the Bullets', so it was business as usual in the Redditch drawing office, then! This must make an original Big Head tank in good condition something of a prized item.



Phil, you are a complete and utter maniac. Good on ya!



A.

[jefrs]

Something mentioned earlier: torque times (angular function of) revs is horsepower. e.g. C5's stock 41.3Nm at 4000 rpm is 23bhp. It has a fairly wide and flat power band. Race bikes get tuned to be used continuously on the red line, they neither need nor want a wide power band.

[Phil Ashbrook]

Mine has the race 612 crank with all the tuned parts that runs on Ethonal which you can buy at the pump in Australia , the engine is as strong as an Ox but the Furt head will top it off with a Fury head on a converted T3 GP2 , there is a waiting list for all conversion parts , it will cope with a 10 : comp ratio but has to use speedway oil to mix with the fuel ...all not cheap .

[Bullet Whisperer]

jefrs - a narrow power band on a race engine is not something to aim for, rather a side effect of some tuning efforts, just like difficult starting, popping and banging from the exhaust and spitting back through the carb. Here is a 350 Royal Enfield race bike on the dyno. Towards the end of the video, I let the revs drop to just below 4000 rpm in top gear and take it just past 8000 rpm. The power graph is also shown, with a peak of 32 bhp at the rear wheel, but also lots of low down 'grunt' as well. Strong mid range gets this machine off the line and out of corners, up hills etc very quickly, while many others are waiting to get 'on the boil'. Cheers, Paul.
https://www.youtube.com/watch?v=hMf5VlHgBEs

[jefrs]

I agree it is a side effect, yet a race engine needs tuning to give best effort at race speeds, which will be up at the red line. With the usual attendant issues of difficult starting, popping, banging and won't idle. Not something you want on the road really, whereas a road machine wants smoother power delivery; it must be able to deal with stop/start and slow traffic. That's not to say you can't tune a road bike, just different animal. Horses for courses.

[Phil Ashbrook]

Well as it stands I can play with the camshafts ...sports or full race but then you can play with the valve timing by our hosts pinion that gives 3 settings , super advance or STD advance , part number 90008 , this is not as Cosworth would have done it , they would have done 5 . I would say run it at full advance and see how it spits at 3,000 rpm but who wants to do that a red traffic light ! , manual ignition control on a digi ignition system is not possible unless you have a real racing magneto , as a note I ran my racing Honda / Cosworth 1 tooth in advance and it went like a bomb but flames came out of the exhaust on the over run . So as it stands I'm not going to do the TT at 8 grand most of the way , I dont want to splutter and stall at the lights and put my hand in the air and push it to the side of the road and start ( if I can ) , I need a flexible engine with a kind of tick over even if it is a bit irratic like a Vello Thruxton , I never had problems starting the Weslake speedway engine and I'm looking for that but man you should have seen the camshafts , the ramps were so near vertical you would half thought they would jam so thats why I went for the big foot cam followers which are more durable , still working on my 50 BHP project parts list , do away with the heavy alernator set up and recharge the battery with solar pannels and go for the crank twin plug ignition less the timming pinions or keep it as factory with our hosts regulator ...so much to think about .

[Adrian]

Which is heavier, the alternator or the battery? If you're deciding on a crank mounted CDI ignition, why not get one with the lighting coils fitted and run direct lighting, no messing with solar-powered battery charging needed? Yes, I know Australia gets more sunshine than we do here! Electrex World over here supplies various kits, with a whopping 50W output for lighting, but how much do you ride at night? (Hint: 35/35W 12V H4 Halogen bulbs). If you're twin plugging then the kit for a twin cylinder bike ought to work, as I'm guessing that on a twin with a crankshaft-triggered ignition you'd be running with a wasted spark, though it would not be wasted at all on a twin-plugged single cylinder engine.



http://www.ebay.co.uk/itm/Royal-Enfield ... 3aabf4cf99



A.

[Phil Ashbrook]

My twin plug kit part number92075 is great , I now have an even burn where as before it was very one sided but the crank magneto would be even better but you cant have an altenator at the same time , I wish our hosts could fix this , when I ordered the race 612 crank I wish I went for the non altenator version as you can have the slim line chain case as per Fury but our hosts told me it can make the engine a pig to start with the Fury head and the T3 GP2 carb on E85 Ethonal with race cams but the engine would be more responsive to rev changes just like the lightened steel flywheel for racing Mini engines , instead of whoom it goes whim , kinetic energy reduction is great for response but like the D type Jaguar you have to spin the wheels or stall on the grid start , this would mean the dry belt drive clutch would be needed for road use as they dont get as hot so fast , tempretures of a speedway bike clutch can get very high due to a number of things and this is why you see them tilt the bike before a race start and let the rear wheel spin to keep the clutch cool , our hosts belt clutch is aimed at road use or tarmac racing , I have no idea how good it is but they boast no drag where as my wet STD clutch drags like hell on a hot day in heavy traffic even with auto transmission oil , it was made for the pre traffic light days so I use my neutral lever a great deal as like a vello you just cant get neutral when stopped at the lights .