[HRAB]

Over the past few weeks we've stolen a few minutes to revive this project. We're not too encouraged by the results at this point.

The first major obsticle is that  when the throttle was rolled open above 20-30mph the engine would balk and accelerate only slowly. We were having fuel starvation with the 30mm flat slide carburetor. We didn't bother to determine if the engine was sucking the float bowl dry, or if the mass airflow was insufficient to feed the beast. Insufficient is not good enough.
(So much for 70 mpg!)

We switched to a Mikuni 32mm carburetor and solved the problem, but now we can't seem to keep head gaskets in it. If we roll on the throttle we get good acceleration. If we snap it open the engine detonates and vents out through the gasket. It's not a pretty sight or sound. The detonation is somewhat improved by using 92 octane premium fuel, but not completely eliminated.

Early on we had some issues with the piston hitting the head gasket. The solution was to use two base gaskets which would create 0.040" extra clearance. I wonder if the extra gasket is allowing some flex in the structure causing head gasket failure.

So, I'll retorque the head one more time and continue to look for a copper head gasket we can cut to an 89 mm cylinder opening, or have a recess cut around the outer edge of the piston to clear the gasket. This would allow us to return the cylinder to a single base gasket and regain the half point of compression.

Perhaps Kevin's apprehension at the size of this engine is in fact founded. We Young'uns should listen to our elders!

PS: I had another reminder to first consider the basics first. The head was in serious need of retorquing. It no longer breathes fire from the head.

jim

[luoma]

I'm glad the big-bore project is still in the works. Makes me wonder about the carb. If the flat slide is too wimpy for the bike, and it is only increased by 60cc, then it may not be the best performance carb for the (non bored out) AVL.

[jonapplegate]

You know, there are larger versions of this carburetor (flatside), bore-wise available. I wonder if they have a larger bowl or if it just airflow increase?

[1 Thump]

What happened to this project ?

[ScooterBob]

It's an AVL - and poorly conceived from the get-go, I'm betting ...... The carcass is still sitting around in the back ..... As I said with an earlier post - I ain't impressed with it. Right NOW, my focus is on the UCE stuff - well - SOME of my focus is ..... If CMW was like Honda, there would be ten people and a dedicated machine shop working with me and we'd CRANK out the goodies - but at OUR volume and amortization of that kind of expense - a set of cams would cost $2K! It may be that I can re-visit this project and we can see what will become of it ....... the RIGHT way!