Forum

[devon john]

i am about to build a 612 bullet a good frend of mine is a gas flow specialist on Harley heads.
he is willing to work on my bullet head, he wanted to know what the valve angle was in the heads ie 45 deg or what ever???

also i would like some advice as to building the engine , i want a good torque and not to worried about top end.
it needs to be able to cruse at around 70ish on thew motorways and have a bit in reserve if needed
crank bigger bore ported head 32mm concentric now when it comes to cams as i have sead i want torque so what should i go for and whats available
economy is important as well
am i wanting to much???

john

[trevorch]

I think it would be unwise to touch the 612 kit developed by our hosts. Everything you could wish for is already in, tried and tested.
Most people seem to report satisfaction with the 612 engine development, instead I would look at better tyres, brakes, suspension and a 5 speed gearbox.
Good luck, TrevorCH

[devon john]

Tervor the pot is only so big ,i have to do this with in my budget, as i sead i am not looking for out and out performance,
john

[Marcel]

I use the standard cams on my 612. It pulls a 20 teeth sprocket with ease. 110 (real) km/hour is no problem on the long run. I changed cam timing a bit and use mr H's special gear for that. I also put the inletcam one tooth anti-clockwise. You can google for this old trick (enfield cam timing Ace, something like that) Check space between valves and piston! Almost for 17K kms now
Oh, and I put the strongest springs I could handle in the clutch!
My aim was to have a bike that could easily handle a daily 20 kms highway to my work and being very enduring. I am satisfied with the results however sometimes I fit the more sportier cams and they go much faster. I always wonder which of the set-ups is the best one as it comes to durability. I do not know! Maybe my set up is very uneconomical in more ways?
have fun!
Marcell

[trevorch]

Hi Devon,

I sympathise about cost. I was considering with my 2007 Bullet 535 to fit disc brake, 5 speed gearbox and some further performance upgrade. It was cheaper to sell it and buy the standard EFI then upgrade that to a 535 with a new Power Commander. In the end I did not believe I would be satisfied with the increased power offered so I sold the EFI and bought a Bonneville. Happiness.

Cheers TrevorCH

[Phil Ashbrook]

I ported my head and removed most of the mass around the valve guides in the ports with the guides out then fitted bronze ones and larger valves ..the exhaust being the most important as the original sits too deep .
I fitted race springs , alloy rockers and spring caps and twin plugged it so it burns more of the fuel/air charge , I also fitted the Amal mk 2 concentric as it's way better than the mk1 .
With sports cams and 535cc piston I geared up by 2 teeth on the final drive sprocket and the whole effect was I had far more grunt and higher bhp but...
I made 1 error and that was not fitting a roller RE13 or RE15 big end as my std Madras floating big end has just gone ..in fact it went terminal yesterday .
I dont know what kind of big end the 612 crank has nore do I know if it has a forged steel rod but what ever it has I think you should fit the double flow oil pump and bonded seal worm to protect the big end .

[simon]

The floating bush big end is clearly an Achilles There is huge potential to get substantial power increases for relatively simple and cheap mods but every time mine approaches 70 mph I get a decidedly nervous feeling. I split the crankcase on my 350 and checked all the bearings and they were all absolutely fine but if I ever do it again I will split the crank and it will be roller big end time.

[simon]

That was supposed to read "Achilles Heel"

[Phil Ashbrook]

I think the floating big end bush is only good for 22 bhp or 30 tops but I got 15 years out if it but as my bhp went higher I was set for doom . the RE15 sounds like the right stuff but what the heck does the 612 have fitted ..aint no nut on the ends of the crank pin so some spec details in the new 2014 parts book would be handy .

[Phil Ashbrook]

Just as an after thought on what the right stuff is , Velocette did 24 hours at average of 100mph at Montlhery on the speed dome pre WW2 on methonal ( 10:1 comp ratio . Now thats very cool for a 500cc single ..could a 612 Bullet make it...LETS TRY !