OK, started going through the Bob Briggs racing stuff last night. Of the 4 complete/semi complete engines, this one really catches my eye so desided to start with it. It appears to be a prototype Engine, still has lots of markings and unique things done to it. I will know more when I tear into the other engines.

First off, the monsterous non bridged exhaust spigot jumps out at me. It has just had the 86.20MM sleeve installed, still has the markings for when they cut the port windows. I will need to have it bored to match the first 87.00MM piston. You interested in doing this one Hoser? It has had extensive port work done, ofcourse. The jug still needs to have the water cooling holes drilled to allow flow to the head. Intake window appears the be from a KX500??? The intake itself is very strange too, no reeds and nothing I recognize. Again, when I tear into the other running engines, I will know more because they appear to run the same intake system. I do know they run Mikuni race jet ski carbs, no float bowls n can run upside down. The loose one I measured at 38.50MM small end. The crank also intrests me, it looks possibly to be a stock unit that has been machined or a complete aftermarket??? Pin has welded so if the stock rod lets go...its junk. Each half has 400cc on it. Also, the clutch side gear cover has been replaced by a fully machined piece with a 3rd bearing on the crank, I assume to help with higher rpms and increased load. The other engines also have these. There is no counter balancer setup in this Engine, I will know if they ran them in the other engines...I assume they would. Electrical system has been "modified" for race only, no charging.

Here is a crap load of pictures as I went through it...

Dunno if I can bore a cylinder that big on my machine I will look into it, if not I bet speedchaser can bore.

What is the thickness of the cylinder spacer?

Whats with the welding of the cases under the special balancer gear cover, damage repair or to add strength?

The used piston for that Engine? Take the rings off see if their is any unusual wear on at the exhaust opening.

No reeds, I would ask for details about this the different sleeve and piston makes it a piston port Engine?

Not surprised to see their is no balancer in that Engine if I was building a Pilot Engine to race in the same series that Engine was used for it would have no balancer either.

how do you hold the exhaust on? and if you had to change the rod couldn't you just grind the welds out and push the pin out?

Good call,never thought about the grinding them free and refilling them.

They used a loop washer under the 2 14mm jug nuts and use a long spring on each side. Good catch,sharp eyes n thinking. We have sharp board members here!