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.
More Pictures...
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?
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...
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.
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.
Thanks...that is a very cool bike. I can appreciate the hydraulic rear brake.
As I recall, he used a carb from a Ducati Paso.
I think that was tree dragon that used the Paso carb. Wish he was still around.
Tree dragons bike had the most amazing exhaust on it ,,Maybe the Prophet Of Doom could post some photos of it
Iain
NZ
Here they are:-
Very Nice Exhaust and the carb setup is impressive as well.
82mm bore would give 580cc even without the additional stroke. Hmmmm
Some photos in case your thinking what I think your thinking...
The photos above are a comparison between the xz550 piston and the stock 4AGE piston 81mm bore.
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.
Excellent, thanks Dean.
Those stock Toyota pistons look like they were made in the same factory.
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.
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
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?
POD
Stock 4AGE pistons are 81mm
Wiseco pistons come in 81.5mm and 82mm
Fret not
The straight edge is sitting on a stock 4AGE piston and the adjacent XZ piston has the shorter compression height.
Appearances can be deceptive sometimes. At least from where I am sitting. Thanks for this discussion.
thanks for posting the issue / pictures regarding the piston-valve clearance. Years ago i had a set of high-lift cams made/welded, and ran into the same clearance issue on stock pistons... which inevitably lead to giving up on them. You may have just reinvigorated my desire to use them!
Blake
Blake,
Not sure what your plan is to increase PV clearance but thought I would share how I did the work...
Fit cylinders to the crankcase (pistons without rings).
Move piston to TDC
Install head gasket and cylinder head with valve (no valve springs)
Measure valve movement with dial indicator; seat to top of piston
Compare with valve lift
Calculate material depth to be removed from top of piston
Using an old cylinder head and an old valve I removed the required material from the top of piston
The cylinder head was the guide for where to remove material
Velcro was used to stick abrasive material to the valve
The valve was spun using a cordless drill and an extension.
I used varying grit size to complete cutting the piston to the required depth
In my case it was 2mm or 0.080"
The top of piston needed to be finished using a die grinder, file and fine abrasive material (wet sanding)
Not to derail the current line of interaction, but in regard to this changing of stroke entailing the diminishing of the journal size: the original journal/rod did seize, and now the journal is smaller, which means there is less surface area to support he increased load of the increased piston size. In this context, have you made any 'adjustments' to increase the oiling of these parts? Better oil? Higher volume oil pump? or?
The chase for more power exposes the weakest link(s) in the system, and we already know of the potential for the rod to tie up.
Also, how does the new motor feel when under power? When you are coming out of a turn on the gas? Is it buzzy or smooth?
One other thought on the oil pressure thing; there is a seal in the right hand case cover that is held in place with a circlip. This seal has to carry the oil pressure for the system or the pressure drops. The point is that this seal can easily be damaged upon assembly if you are not careful, and it is a critically important part if it fails to hold the pressure. Just another thing to check before reassembly. I think it was Tiger that suggested to replace that seal every time that case was removed, just to be safe.
fret not
The points you made regarding the crankshaft are valid and to add to them, the width of a Busa rod is significantly less than the stock rod. The lesser width is why the rod is piston guided.
Motorcycle 10W40 oil.
The motor felt great and when I get the jetting sorted I'm sure it will be that much better. I was at 145 main fuel and I am still lean. It's been a busy fall and cold came early to October so I have taken time to play lately.
It does have a small rpm range around 7,500 where vibration can be felt. I assume due to the elimination of the balance shaft. When in this range my left hand becomes anxious. So far so good though.
I recognized the seal on the end of the crankshaft is critical and a new one was installed when assembling.
Not sure what you meant regarding derailing the interaction...however just so others know...
This engine build isn't proven and may be a huge waste of time and money...100 plus lb piece of scrap metal with the belly pan holding 2-1/2 litres of oil. Simply sharing for the sake of interest. My fun may end abruptly.
Dean, the fact that something could go wrong is part of racing. The components are all stressed to their limits, and as long as they hold together the Fun happens. It is truly amazing how well things can go when everything is working, and also it can go from flash to trash in a couple seconds.
Hopefully you never find a small part on your work bench AFTER the engine has been closed up.
Wishing you the maximum fun and least troubles.
It would be very enlightening to find out why it is that the rear cyl. rod bearing is always the one to spin. It's almost like the oil passage in the crank doesn't deliver enough oil to the rear cyl. rod bearing, but if I remember right it is the closer bearing to the oil supply.
Possible stock piston replacements....
Thank you for sharing all this great info on your motor!
For stock piston replacement, I wonder if the pistons from the 4afe motor might be a good choice... same bore size, and wrist pin size but this engine is a very narrow valve angle 4 valve per cylinder motor unlike the very wide valve angle of the 4age.
Pretty sure the deck height is similar. Might be a very simple way to get new pistons and rings into a Vision.