Forum

[Norm]

Phil, we built a pair of 612,s both costing about $6000 each to build just in parts and they put out 28 hp on the dyno so don't get your hopes up too high. The $6000 included Newby clutches and that was close $1000

[Phil Ashbrook]

Only 28bhp ! Our hosts claim of 40bhp with the compleate 612 kit is taken as given fact as they publish their dyno charts .
Only 6 bhp more than a std 500 classic engine sounds strange .
I started tuning engines when I was 16 with the Yamaha RD50 ( 1980 )and had to do lots of work with performance parts to suck more bhp out of the engine but it was great fun because every little bit raised the top speed and in the end I got 60 mph but decades later some dude has got 80mph out of one .
If your 612 had every part of the kit including cams and high compresion piston and the ported head I would have thought of gains higher than 6bhp .
I ported my head myself with valve guides removed and took the casting guide support lumps out so it was smooth bore , in some places breakthrough was a real risk . It took a long time to get the port shape I wanted but the truth is I have never dyno tested my machine . When I have the 612 crank I might just do that or do the risky 115mph blast ( without fairing )on public roads . I just cant belive our hosts would over exagerate the gains to make money as I find their honesty 10/10 so far .

[Norm]

Phil, the true figure on a Bullet on the dyno is about 18hp so the 612 kit is about a 75% increase which is pretty good considering what you start with. Forget about all the claims.

[Norm]

Besides Phil if you were a Club member you would be able to talk to members who are doing this stuff so you can compare notes which can end up saving you money by avoiding some of the pitfalls others have fallen into

[another Allan]

Power losses between the crankshaft and the rear wheel on a dynamometer test can be as much as 25%. If our hosts' figures are 'corrected' figures relating to bhp at the crankshaft, and Norm's are taken at the rear wheel, then it seems to tally.

[Phil Ashbrook]

Very true , our hosts claim is 16 bhp at the wheel of a stock 500 classic , so on the rolling road dyno test there is a stated 6bhp loss in the drive train , now not all rolling road dynos are the same so Norms 612 power loss stands at 7bhp less than our hosts claim of 34bhp at the wheel or 39.6 bhp at the crank , I'm not sure why he falls short at 27 bhp .
I find it all very intresting .

[another Allan]

From what I've read about dyno testing, I think there are many uncalibrated dyno's out there! It seems like the only way to see how much power you may have gained by tuning an engine, is to put the bike on a rolling road before tuning, do the work then put it back on the same rolling road.
At least you will then see what should be a true comparison, but whether the before or after results are 'absolutes' is a moot point.

[Phil Ashbrook]

I would imagine that our hosts have a calibrated rolling road dyno and it would be hard for us guys to know if our local dyno is correct , Anouther Allen ..your right about sticking to the same dyno after testing ones stock engine for a checked starting point , There was a popular dyno not far from me in Sydney , it had a pub next to it with a outside garden , I remember trying to talk over the hot V8's screaming their nuts off and most of that might have been the blowers , we would make bets for a round if one could predict a banger . I dont think Royal Enfield could ever break Velocettes 500cc 24hr/100mph average in the late 30's but then again nor could a Goldie .

[Norm]

From memory the Speed Dog Racing 612 was above 42hp before it went bang, but this time it is being built as a 500 so it can run in the up to 500 class and not trying to compete in the unlimited class as it was when a 612

[Phil Ashbrook]

I kind of agree with you Norm , if one is going to develope a kick arse engine it's best to stick to the 500cc class so if you can pick off Goldies and Velos on the back straight without going bang and the feeling of victory would be even better . Royal Enfield never really developed a works Fury so it's up to us with our hosts help . I can understand why to make a 612 as one gets the power without the stress but it is still a form of cheating .
I'm already at 535cc so I wont be going backwards on capacity now until it wears out , I'm on my last oversize after something jumped down my carb trumpet on my first piston . I now use a S&B filter !