Dyno testing 'performance mods'

[WillitBoost]

Green was last weeks CDH66 pipe.
Yellow was this mornings with the CDH66
the pinkish line, the hydroformed pipe.

New high score! 5HP! even with the trashed piston and cylinder

Whatever the bottleneck in this engine is, it's still there. It's not the intake, it's not the pipe. Could be the heavily worn/ground down piston and cylinder... Probably the porting. The pipe was designed for a 7000-8000rpm peak and the engine is choking up before it really wakes up. We're loosing more and more low end with each run - even when going back to the BoFeng and stock muffler.

My pallet system is close to its limit too with the 5hp. The bike climbed up the roller onto the dyno chassis on the first pull and took a fair bit off the rear wheel.

A local 2stroke bike engine builder has offered to port a G4 cylinder for me. He says 5-6HP can be expected with the CDH66 vs 4HP stock. I'll take him up on the offer and see what a properly ported jug can do. He mostly makes high powered builds but started out with china dolls. He's got a video of him riding at 80mph on a 44t sprocket. Nuts

 

[WillitBoost]

WillitBoost when you hydra-formed your expansion chamber. How did you release the high pressure water from the chamber after forming it? Thanks.

It'll spring a leak when it's ready. The reason you use water instead of air is because its non-compressible so once there's a leak, system pressure drops to zero. There's no energy in the water itself, except for any air trapped in the pipe or the metal itself resting.

 

[DieselTech]

It'll spring a leak when it's ready. The reason you use water instead of air is because its non-compressible so once there's a leak, system pressure drops to zero. There's no energy in the water itself, except for any air trapped in the pipe or the metal itself resting.

Ok thanks. I appreciate it.

 

[WillitBoost]

No problem. Considering how easy that pipe was to make, and how cheap it was, and how much better it performs than anything you can get off the shelf... I'd say have a crack at making one! It's not too loud either, quieter than the CDH66 and the stock without a cap, it makes the ring-ding-ding two stroke noise too

 

[DieselTech]

No problem. Considering how easy that pipe was to make, and how cheap it was, and how much better it performs than anything you can get off the shelf... I'd say have a crack at making one! It's not too loud either, quieter than the CDH66 and the stock without a cap, it makes the ring-ding-ding two stroke noise too

Yep after seeing how well yours turned out for the 1st exhaust chamber. I'm going to give it go. I'm also curious to check out your local engine builders ported cylinder. I'm thinking with the Tilly carb & the custom built violent hornet exhaust chamber. I'm thinking 6-7hp is realistic fairly easy. Cant wait to see further testing & dyno reports.

 

[GW's Motorized]

That's a sweet setup. I am hoping to do a saw build soon, so maybe I'll go with that carb

 

[WillitBoost]

Thx

I wish you could get smaller main jets for these carbs. Make the adjustments a little less sensitive. I wonder if I can't turn one down on the lathe, I think there's some brass stock here somewhere...

So far there's no real gains to the Tilly vs the BoFeng so I'm considering putting the BoFeng back on. It sure is easy to tune though

 

[GW's Motorized]

Thx

I wish you could get smaller main jets for these carbs. Make the adjustments a little less sensitive. I wonder if I can't turn one down on the lathe, I think there's some brass stock here somewhere...

So far there's no real gains to the Tilly vs the BoFeng so I'm considering putting the BoFeng back on. It sure is easy to tune though

I like it because of the full tunablility and that it will probably bolt to a saw intake manifold. The saw cylinders also already have a pulse pickup separate from the intake. I am wanting to do a ms660 build soon

 

[WillitBoost]

Ahh ok, yeah that'll be ideal. A stock ms660 maxes out at 8krpm?

 

[GW's Motorized]

Ahh ok, yeah that'll be ideal. A stock ms660 maxes out at 8krpm?

I'm not sure. It's probably around there.