Questions on compression, squish clearance and pipes

[Bear45-70]

First this;


Then this,


on this

[ottoman]

Nice boat... is that from the 1980's?
But this is more of a scooter forum I thought... so what you have for a fast scooter?

[Bear45-70]

Nice boat... is that from the 1980's?
But this is more of a scooter forum I thought... so what you have for a fast scooter?

The blue boat is from the 80s at the last race on Green Lake in Seattle. The white boat was in 1994 on the Willamette River at Newberg, Ore. Oh, radar gunned at 125+ mph. The fall before I did 132 mph and change in the kilo.

I've been fast, record setting fast. Now at 63 years old, retired on disability, I have a good time and go at a rate that is comfortable to me, since in 1994 I almost died tangling with a deer on my Honda.

Oh and those are two strokes, multi-cylinder 2 strokes with multiple carburation and with the exhaust tied together so changing this changes it for 3 cylinders. Tuning made really hard.

But 2 stroke tuning is 2 stroke tuning which I guess you don't agree with. Oh and the carburetor experts say that 1 big carb hurts acceleration while minimally helping top end. A 24 mm carb on a 74 cc motor is not big. We have guys running 28 and even 30 mm carbs on that size motor, that's too big.


As to Ron Anderson and what he knows and doesn't know; he designed Mercury Marine's first V6 outboard and on a racing version used 3X2 barrels normally and 6X 1 barrels mounted on the transfer port covers with no reeds. He was also involved in Johnson and Evinrude setting their speed records with their V8 outboard and he is paid to advise the majority of professional boat race teams. He also put 11 mph on my first race boat with a prop change along with minor set up changes, after he built the motor for me. That 11 mph was only a 10 % increase but he don't do crap. I'd listen to him over you without having to think about it.

[patthesoundguy]

I havent been around here on the board all that long... But Bear I have no doubt you know what you are talking about!!!

[Trafficjamz]

I have been reading the performance and build threads and I keep seeing most people recommending to keep your compression readings in the 135 or so range.

When I build a fast ped I always shoot for between 150 and 175 PSI compression and I found that between .5 and .6 mm squish clearance works best to produce the most power.

My 86cc dragstrip only moped has a comp ratio of 160 and it runs on race gas, and has a 30mm carb.
The carb is probably a tad large. I will be trying a 28mm next.

[Trafficjamz]

Also I never seen the types of pipes such as the V8, PG short and long type I see here. Everything I ran was always more traditional style expansion chambers.

What is the advantage of this type of pipe... if any... over the type of pipe I am use to using?

I always like to learn from guys who have "been there and done that" so I am looking forward to hearing from you guys!

They are quieter that is all.
The traditional style expansion chambers work the best for dragracing.