New Engine

[Dean]

Rather than be long winded I'll try to keep this brief...

I like the Vision engine and I think it's a cool engine to race. When an engine is raced something will break. In 2017 I seized the rear rod to the crank. My goal for the winter 2017-18 was to build the engine using off the shelf parts from other engines readily available.

I built an engine for 2018 using the following parts:
- Pistons are Toyota 4AGE Wiseco 82mm bore...Yamaha and Toyota worked together developing Toyota's 4 valve head.
- Crankshaft offset ground for 61mm stroke...Reduce the journal diameter to fit Hayabusa Rods offset to increase stroke.
- Suzuki Gen 1 Hayabusa connecting rods...Very strong connecting rod and availability is no problem.
- Copper head gaskets by Cometic...No problem providing the gasket for a 82mm bore.
- Aluminum shim between crankcase and cylinder by Cometic...Again, no problem providing a shims based on the gasket.
- Camshafts re-ground by Colt Cams...Geoff is great to work with.

The pistons are lighter and the connecting rods are considerably narrower and lighter. The inside of piston pin boss(s) were ground to provide for a flat surface for shims. Shims are used to provide piston guided connecting rods.

The piston/connecting rod/crank assembly was balanced to a factor of 60% (ROV newsletter).

The balancer shaft and bearings removed (ROV newsletter).

Valve seats were re-ground.

Intake/Exhaust ports cleaned up.

Challenges with new engine include:
- Piston crown angle didn't match valve angle of the cyl. head.
- Piston to valve clearance with re-ground cams.
- Oil leakage between the crankcase/shim/cylinder head.
- Stock carb jetting.

[Dean]

More Pictures...

[fret not]

OK, so what is the new stroke?  82 X ??
How much did you have to do to the pistons for valve clearance?

are you using the stock carburetor?

[Dean]

82mm x 61mm

Still using the stock carb. Some may see it as a waste of time but my intent is to jet the stock carb as best possible then move on to a weber downdraft style. My intent is to use a carb style that was available 1982 or earlier.

I play with this engine as a hobby/challenge...racing it is just icing on the cake...

[fret not]

I can identify with that.  Good luck with your carburetor.  I recall some carbs that used remote float bowls, so the carb bodies could be mounted at any angle.  But that was back in the 60s and 70s.  I know DelLorto and AMAL both made these. 

[cvincer]

You might find this post courtesy of pinholzen, interesting:-

http://ridersofvision.net/rovforum/index.php?topic=15554.msg143021#msg143021

with regard to carburettors, look up a post by  'treedragon'  who fitted a twin down draught from (I think) a Ducatti  plus experimented with velocity stacks on the standard Vision carbs.

[Dean]

Thanks...that is a very cool bike. I can appreciate the hydraulic rear brake.

[fret not]

As I recall, he used a carb from a Ducati Paso.

[jefferson]

I think that was tree dragon that used the Paso carb. Wish he was still around.

[iain]

Tree dragons bike had the most amazing exhaust on it ,,Maybe the Prophet Of Doom could post some photos of it


Iain
NZ

[cvincer]

Here they are:-

[Dean]

Very Nice Exhaust and the carb setup is impressive as well.

[Prophet Of Doom]

82mm bore would give 580cc even without the additional stroke.  Hmmmm

[Dean]

Some photos in case your thinking what I think your thinking...

[Dean]

The photos above are a comparison between the xz550 piston and the stock 4AGE piston 81mm bore.

[Dean]

The spec sheet above is for the Wiseco 82mm bore.

The photo below are Wiseco pistons modified (fore ground) for PV clearance versus pistons not modified.

[Prophet Of Doom]

Excellent, thanks Dean.
Those stock Toyota pistons look like they were made in the same factory.

[Dean]

Very similar aren't they...

I came across 8 used pistons for sale as a package. I bought them with the intent of lessening the compression height using my lathe.  They are a bit heavier but I think they could work well as a replacement piston for a road bike. New rings are easy to come by. The stock head gasket will also work so no need for a custom gasket.

I'm looking for new valve options...I'm investigating Mazda Miata valves.

[Prophet Of Doom]

But 81mm is that right? you need to go the wiseco (or similar) route if you want 82mm?


Very tempting, skimming off the top looks as easy as it could possibly be

[fret not]

That pic with the straight edge across the two pistons looks like the XZ piston is higher compression than the Wiseco.  Have you measured the compression with the "new" pistons?