The Bullet Board

That is looking fine.
The tuned length is more important than the flare. David Vizard(car tuning expert) did tests years ago that showed the difference between a straight cut-off stack and various flare types only was 5% or less, depending on flare shape. So just having a good length for the rpm target intended will do most of the job, and any more from a flare is added "gravy".

Regarding tuned length, the reflection actually happens about 1/2 the pipe diameter outside the top of the flare, so add that to your length calculation.

Ace.cafe wrote:Regarding tuned length, the reflection actually happens about 1/2 the pipe diameter outside the top of the flare, so add that to your length calculation.

In that case it will be more around the 300mm mark. I'm not sure what rpm that would affect but I'll see when I ride it.

I started welding it out last night. Just the trumpet, I was purging it with Argon as I welded it so the TIG weld was shielded both sides. Which makes a nice flat penetration weld on the inside of the tube if your TIG welding from the outside.

But.. it got that hot it melted the end of my purge line shut. Haha. So I ended up having to do a internal pass anyway.

Anyway. I'll have it done this afternoon and I can test it.

Ben

300mm should be a good length.

All finished! Turned out better than I thought!

Next week I'll send it to the powder coaters. It will look like it bought one.







It's perfect Queensland winter at the moment. This was shortly after I had been taking it for a test ride at sunset.

Ace.cafe wrote: ↑Fri Jun 10, 2022 1:01 am 300mm should be a good length.

I got to ride it this afternoon. It actually tidied up the bottom end. There isn't a profound hit into the top end now. It transitions a lot smoother. Throttle response is a HEAP better with this airbox setup. Idles a lot cleaner. So it was a good step ahead.

And mate. The induction noise! She's slurpin!

I did notice it is wet with fuel inside the airbox after my ride though. It must be the cams inlet timing sending a pulse back into the airbox, sending a mist of fuel with it.

I can feel now that advancing them with the 3-way might hopefully get it in a good place. Yes they definitely peaky, just a smidge earlier in the rpm range and they'll be perfect for what I'm trying to achieve. Which is more of a linear power delivery up to a strong top end.

Looks great.
Too early inlet valve opening is causing reversion up the intake. Big overlaps are like that. It's better at the higher rpms.
You should have see Henshaw's racing Bullet 500 that we did the head for. His cams were very very long duration with huge overlap, and then we put in the high ratio roller rockers for .609" lift on his 38mm inlet port Big Head. It got him over 50hp at the crank, but you could see a cloud of fuel standoff outside the velocity stack on his 1.5" GP carb during warm up. Methanol and 13.5:1 compression. Harmon & Collins vintage flat track cams, our porting and rocker system and squish band combustion chamber. He won the British Historic MC 500 championship that year.

Wow. I wouldn't of thought a engine of this era could make such horsepower. Those heads look like they mean business!

35-38 hp at the rear wheel is about the limit for a street 500/535 Bullet. Ton-Up is definitely on tap at that level of hp.
The drive line losses are 4-6 hp depending on the gearbox, so it is possible to have a crankshaft hp over 40 on a street Bullet. That's equivalent to a Gold Star 500 DBD34 which had 40 hp at the crank from the factory. Not bad for a bike(Bullet) that was originally intended to be a mundane commuter.

I don't know what final drive sprocket you are using, but either 18 or 19 tooth works very well with the modded engines, vs the stock 17. Fireballs used 19 tooth most often. Nice comfortable cruising at 70mph, and just slightly over 100 mph at 6000 rpm top speed.

Thats very impressive for something bone stock barely makes over 20hp.

Mine is a 5 speed with a 19 final drive. I've installed the upgraded 5 plate clutch also.

I'm not too worried about hitting the ton on this bike, the roads around here.. Its a bit wild!The GT535 will get that treatment.
I just want to make this a fun bike to ride and a
different in behaviour compared to my GT.

I rode my GT for a 500km run today. After tinkering with the Bullet all week. The GT runs out of puff when the Bullet is on full blast. Although now the the GT has more torque than the Bullet, but the Bullet would walk away from it in higher rpm.
GT is mild. Air Kit + velocity stack , I made a header, straight through silencer and Power Commander V

Once this 3-way pinion arrives. I'll see how that goes. Then remove the base gasket if it needs further improvement.

Going through my notes, The spigot seal uses 0.75mm gasket. So lapping the spigot down to suit a 0.5mm gasket probably won't make a huge improvement.

If no joy with any of that I'll order new phosphor bronze bushes from H and press them in the R cams and give them a run again. Which will be different again with the new TM and Air Can. I can say that my old airbox was definitely a restriction up the top end compared to the new one. But was fine with stock cams since it was modified to the best it could be.

I am curious about why your compression dropped down so far with just a cam change, considering that it has the 8.5:1 piston in it. What do you reckon caused that? I would have expected maybe 20 or 30 psi drop, but 70 psi drop seems unusual.