Scooterotica

I've just had a new build engine on the scooterotica dyno with a gt186 kit on.

I was slightly disappointed with just under 10bhp.

I'm running 25phbl through a drilled airbox and an ancillotti clubman. 58 107 crank. Exhaust raised by 1mm. Varitronic with 24degrees at tickover.

Am i getting what you'd expect? Dan reckons it's about right, but i just wanted to double check as I was expecting closer to 15. Maybe I'm just expecting too much.

I'm prepared to fit an open 30phbh and even a different exhaust (although I'd prefer to keep the standard looks of the ancillotti).

Thoughts?

What kind of air intake are you running?

I'd expect more but I highly recommend you do not use a Varitronic. If you PM me the carb and engine set up we can check that then just try a straight ignition swap to Indian static at circa 18-19 degrees.

The gt186 that was dynod in scootering issue 336, june 2014 was as follows. 58x110 crank, Indian electronic , MB Devtour pipe, 25mm phbl Dellorto, large foam filter on standard air hose and a slight bit of exhaust port work. This gave 20.7hp at 6600rpm and 17lb ft torque. It revved beyond 8000rpm where it still made over 16bhp.cheers.

Gt186 with 30mm PHBH open mouthed, Varitronic (early version), PM 25EV pipe.
Recently dynoed at PM Tuning giving 19.3 @ 7500, torque was 13.3.
I know Rich doesn't like Varitronic but I've had no issues.

Just to add my two-penn'th.......this isn't an engine we built at Scooterotica, I was just asked to Dyno it to setup Air/fuel levels on the carb, which we did.

The most common question we get asked by nearly every customer is of course.....'so how much power did it make?'. This of course is completely secondary for us when dynoing an engine not built by us, our primary concern is achieving safe A/F settings.

In this case, the question was no exception, and I always respond with......'what power are you expecting?'. Hendy indicated he was expecting 15bhp on this setup, which I had to say I thought was optimistic for this kit with small carb, air filter and box pipe.

By way of reference, to help the customer make a comparison......I highlighted the Avanti225 review we did for Classic Scooterist Magazine:

Avanti 225 kit out of the box, 30mm Delly (open mouth) and Franspeed expansion - 22bhp. Then fit an AF Clubman, re-Dyno and the power dropped to 13bhp. A 9bhp drop !!!!

Had we removed the 30mm open mouth and fitted a 25mm and bellows/filter then I'm sure we would have seen a further drop.

So, by way of comparison an 'unknown' build using a 186 kit with filter, small carb and box pipe.....circa 10bhp seems reasonable.

And, as I pointed out to Hendy on the day, I felt an expansion chamber and 30mm carb would easily result in a 50%+ power increase, pushing this kit into mid/late teens. Plus of course fettling port timings and ignition timing for optimum performance. Examples from jonzo and speedy in above posts backup my thoughts on expansion chambers vs box pipes/clubman exhausts. The pipe is the heart of ANY 2-stroke.

Another difficulty here is the variability of dynos.

Maybe Dan's is a low reading one? and Diablo has a high reading one? Of course I have no idea if that is the case or not. I did once have a dynojet kit and open silencer fitted to a zxr400 which then gave 87bhp (started with 54!); of course that's nonsense, and turned out to be due to a low battery in his barometer and it actually went from 54 to 59bhp. I'm just demonstrating that a dyno is a difficult thing to consider to be properly calibrated.

I'm going to try a fixed ignition (anyone near Newcastle want to lend me one?) and original jetting although without a gas analyser I may simply be leaning out my mixture, so I'm not too keen on that.

I hope it doesn't appear that I'm knocking either Dan's work or Rich's kit, merely investigating what appears to need addressing.

And of course as Dan points out, he didn't build the engine, I did so it may just be a s**t engine

Well you have two examples here (mine and scootering) that give you a variance of 1.4hp over two different dynos.
It's worth noting also that the "scootering" featured 186 had an exhaust port mod.

I had the GT186 kit slightly tweaked by dan . I ran it with an open 30phbh and franspeed race pipe , indian static ign set to 17 or 18. Cant tell you the bhp but know it was more than what your getting by the way it went and comparing this to my other engines/kits.

I initially ran my GT186 on 25 PHBL through drilled airbox with an AF clubman and it was disappointing. I replaced the airbox with a remote filter on an elbow + bit of waste pipe and fitted an ADS3 pipe and it completely transformed it. Will do 75mph GPS loaded up on standard SX200 gearing and cruise at 65 no bother. I'm happy with the 25PHBL, can't see the 30 making much difference without porting the barrel and would rather have the better mpg