What's up with the Kawi A7 Avenger?

BenEberle

I have a beat on a '70 A7 that's in good shape, unknown running condition, for 900.00.
What can you guys tell me about the rotary induction and the ignition systems? I'm a meat and potatoes piston port, eazy-peezy guy. I've read a bit about the rotary valve deal and it sounds amazing...kind of like a reed block system in terms of performance, but totally different physics, right?

Also, from what I've read, these had CDI instead of points, right? Any info would be awesome. This is a potential purchase for my brother who is looking for something different, fast, and awesome.

Hippykid · Posted: Wed Jan 05, 2011 9:38 am Post subject:

I've had quite a few of these old Kawas and they are nearly bullet proof if you keep oil in them and keep dirt
out of the engine...The carb is located inside the engine cover and only the air breather is visible...This is a
good idea for street bikes as the carb is protected from the elements...The problem with enduro type setups
is if you do any water crossings then you might be asking for trouble..Overall a great bike..

KirkN · Posted: Wed Jan 05, 2011 9:43 am Post subject:

No worries with either one.

The rotary induction system has been around for so long and has so proven itself that I wouldn't even give it a negative thought. The physics are just the same - the rising piston creates a vacuum in the crankcase which is then exposed by the opening rotary port, drawing fuel/air into the crankcase. the port closes and the falling piston creates a postive pressure which forces the mixture up and into the combustion chamber as per normal two-stroke practice.

A reed block is just a refinement on the basic piston-port design. By themselves, reeds do nothing to improve performance, but they DO allow more aggressive porting. Porting which would otherwise lead to blowback thru the carbuetor and poor running.

The advantage of the rotary induction system is that the opening and closing of the port from carburetor to crankcase can be made independant of each other, in terms of degrees before and after center. In a piston port (with or without reeds), the opening and the closing is the same number of degrees before and after center. With a rotary, the opening degrees and closing degrees as a function of crankshaft rotation can be independant, although the actual opening and closing from crankcase to combustion chamber is still piston-dependant.

As for the CDI, I don't have any first-hand knowledge of the A7's system, but I've never heard any real problems with 'em over the years.

Good luck with it,

Kirk

H2Lou · Posted: Wed Jan 05, 2011 10:55 am Post subject:

Steve Searles · Posted: Wed Jan 05, 2011 2:17 pm Post subject:

Had one. Man is that bike ever wide! It was difficult for me to sit comfortably due to the width of the saddle. That is due to the wide engine because the carbs are sticking out of the sides of the engine. They are definetly old school Kawasaki pre 70's styling and handling and manufacturing. Seemed top heavy to me. A7 was the 350cc Avenger and the A1 was the 250 Samari I believe.

BenEberle · Posted: Thu Jan 06, 2011 9:18 am Post subject:

Awesome, you guys, thanks for the info.
I called the guy last night and the bike runs fine (apparently, this shouldn't be a surprise). It doesn't have the original paint, but I guess he says it looks alright. The chrome is good, and there's minimal, if any rust.

Fair to say I'm DEFINITELY going to check it out, hopefully tomorrow. Oh, and it has the twin straight pipes, not the scrambler pipes. Not that it really matters, but I like the straights better.

If I buy it, I get a picture or two up.

rdaystrom · Posted: Thu Jan 06, 2011 4:55 pm Post subject:

I had a rotary valve Bridgestone 350GTR. It was almost identical in basic engine design to the Kawasaki A7. Best 350 I ever owned. Fastest 350 I ever had too. Rotary valve engines can idle really slow. My Bridgestone would idle stable at 300 rpm. Rotary valve engines are my favorite 2 cycle design.

sr71cbx · Posted: Sun Jan 09, 2011 2:08 pm Post subject:

Good price on that "A" bike........they are a blast to ride and will give an old air-cooled RD a good run for their money with some port work and good expansion chambers.

I helped build an A1(250cc version)done up with A7 28mm carbs, a set of one-off Spec II pipes, and some other sundry engine improvements such as boring out fuel passages in the carbs to improve top end fuel flow, and the A7 CDI ignition. That little bike did an honest 109 mph with my big 6'5" 250# ass on it, and won in 250cc '60's modified class at the 2-stroke bike show in '04. It is still running to my knowledge.