Simmy's Naked Turbo Project

today I verified with 100% certainty all the casings fit together without any modifications (yet).
Below is the 891 block on 653Turbo cases


below is my test bench 650turbo head.
I'm using this to set my compression ratio.
It was the scrap head from the swamp motor.
I'm going to measure the combustion chamber volume.
Planning to set up a dial indicator for TDC, with the head cut I can put it right on piston 3.
I'll use #2 chamber for the measurements, #1 is already missing valves.
By greasing the rings of #2 it will hold fluid, you just monitor how much fluid it holds to the spark plug threads.
This gives you the actual combustion chamber volume.

increasing the bore from 63 to 68.5 leaves a sharp edge around the combustion chamber.
I'm concerned this would get overheated and maybe even cause pre-detonation.
I'm going to smooth it out with a rotary file before I take the volume measurement.


I scribed the chamber below showing the sharp edge to round off.
I have 2 other turbo heads,
once this is all figured out I'll make a head with all 4 chambers the same with a rotary file.
At this point I don't know if it will need more compression or less.
I need to get a new head and base gasket from the 891 for the measurement.

 

Simmy, you are doing some amazing work here.........

 

This is the donor motor below for the 772 project
I used the last of my WHIZ Loosen-All trying to free #2 cylinder.
I had this can for 30 years and I think my dad for 30 years before that. LOL.
I had a can of shoe polish which keeps a lid on #2 to keep the penetrant from evaporating.
I'll continue soaking it and pounding on it.
I suspected the motor was seized when I bought it but otherwise it wasn't weathered,
obviously stored inside.
When I pulled the spark plugs #2 was rusty, I knew then #2 was probably the seized cylinder.
The crank moves so once I get this block free I think this motor will work.
Except for a motor mount every fastener so far has come out.
The cams look good, that's one thing I didn't have spares for.




I'm getting ready to weld this nut to the motor mount bolt so I can reef on it.
I've never encountered this before.
That motor bolt is completely frozen in the motor.
I might be better off cutting it flush each side and just drilling it out.
You have to like working on old bikes to overcome this s#it.
I just keep convincing myself that a 772 Turbo is a necessity.

 

That's gotta be some potent stuff! (Has a skull and crossbones on it)

Careful with that, you don't want to break the case section off.
I would heat the crap out of it, and shock it with cold water a few times.

And like you said:

BTW, like the progress your making.
Tony

 

It will be a very important milestone in human progress.

 

I think so to but if only you could convince my wife LOL

 

I think you’re right, I’ve already heated and beat on it several times. What is required to break this free might be enough to break the mount. I’ll cut it close on each side and drill.
Good access and no hurry

 

It’s been 4-weeks soaking in pure penetrating oil with the occasional blow with a hammer and cylinder 2 is still seized.
This piston and cylinder is no value to me so next time I get a chance to work on this I will get it off. Thinking of just drilling into the piston so I can hammer a drift between the piston and cylinder wall.
The block is loose now, I can raise it about 1/2” by rotating the crank. The motor looks good but I suspect it was sitting a long time.

 

Do you have a proper torch? Why not just melt the piston out and clean up the bore with muratic acid afterward?
You'll need to use a pencil tip so you don't overheat the cylinder liner, but it should work faster than using a drill and drift, plus you can use the liner again.

 

all I have is a propane torch so that's not going to melt it.
I will try some heat before drilling though.
I just need to break the rings loose from the wall to get this block off.
The 891 block is going back on, this one goes into the scrap bin anyway.

 

I had a win tonight!
With a drill and a rotary file I was able to cut right through the rings.
Then I was able to get a chisel on the ends of the rings.
Then I pounded on it with a drift, pounded some more, some more then gave up.
Doused it in penetrant and planned to let it sit some more now that I exposed the rings.
Then I realized something. The piston had moved.


below is a photo I took a month ago. 2&3 are near TDC.
At least I'm moving ahead. Just need to continue soaking and pounding.
Maybe this motor really doesn't want to be part of my Frankenstein experiment.
Too bad, it owes me now just for attempting to bring it back.

 

this was my method of holding the block with one hand and hammering the piston with the other.
#2 fought until the end



I noticed I still hadn't drilled through the oil rings.
If I went further I might have broken the piston barrier and dropped shavings to the crank.
But if I had drilled through the last ring it should have come out easier.
I was very fortunate the rubber lining on the studs stayed mostly intact.
Sometimes those things jam up the removal of the block.

 

I degreased the lower cases - they were nasty.
Polished it with some detail spray and it looks great.
No need to paint under here.
I had the clean oil pan in a box of items I started before when I planned to use 900 cases.
I'm feeling good about this motor.
I ordered a head gasket for the 891 from UK and a base gasket from Italy
The Turbo has a really nice aluminum wafer base gasket but it doesn't fit the 891 sleeves.


Below are cylinder block heights I just measured in my garage.
The standard XJ650RJC block is the 1st measurement but the motor is still together so I couldn't get an accurate reading.
the Turbo, 853 and 891 measurements were taken directly from the blocks.

 

there is exactly half a mm difference between the blocks of a 650T and the 891

 

This is awesome information!!!
Now center of wrist pin to top of crown????

 

Here's a pic instead.
I measured the top edge of the wrist pin to the glass table and the measurement is virtually same for either piston.
The 68.5 has a longer skirt but that presents no issue.

 

This is what TDC looks like with the 891 block and piston installed on the 650 Turbo crank.
Sure looks like this 772 is going to work!
I need to find the old 853 head gasket and enlarge it to fit, can't wait for the correct one on order.
Then file the head to match the bore and I can take my fluid measurement, probably tomorrow.

 

I would measure it first, at least that gets you a good start datum. Then mod the head and measure again.
Good stuff.

 

I think you’re right. If I need to raise compression that extra material might be needed

 

I put the motor together with the 31A 67 mm head gasket just because I had one on hand.
The lip at the top from the smaller gasket is very subtle, I figured this would get me in the ball park for a measurement.
As @Minimutly suggested good to have baseline.
I measured the combustion chamber to be 33 cc's
The bore x stroke is 193 cc's
So CR = (193 +33)/ 33
this give a CR of only 6.84:1

Running the numbers for 32 cc's (some inaccuracy in my eyed-up fluid measure)
CR = (193 + 32)/ 32 = 7
CR 7:1

So pretty affirmative that I need to raise the compression.
Once I get the proper head gasket it will lower this number even more.

Currently the math shows I need to shave 1.6 to 1.7 mm from the head or the block to be in the 8.0:1 to 8.2:1

Obviously I need to redo this once I get the real head gasket.
This block was already .5 mm taller so once I have some machining done, overall the motor will be physically smaller by about 1 mm.
That's good, more room between the large Turbo petcock and #1 carb hat.

 

The T marking on the ignition rotor lined up perfectly with the pointer Yamaha install in there for aligning TDC.
The screws still had the paint from the factory so no one changed anything.
I verified this anyway with a dial indicator and my TDC tool which threads into the spark plug hole.





filled to the bottom of the spark plug threads, I used cooking oil from the kitchen

 

During the fluid measurement I took yesterday I couldn't be certain I was starting with 50 cc's of fluid.
I think I did but having a senior moment doubting myself, so I redid the test with more QC monitoring of the fluid used, LOL.
Still coming up with about 7:1 CR.
This is pretty astonishing that it's this close already.
The Kawasaki GPZ750 Turbo was only 7.8:1 -and a puny 738 cc's

 

new head gasket arrived.
I expect to get some time tonight I can measure the combustion chamber one more time.

how ever much needs to be machined I think it needs to come from the bottom of the cylinder block.
The problem with this is the barrels will need to be removed from the block.
Look below you can see that there is little room to skim the head without disturbing the intake valve seat.

and it can't come from the top side of the block because the YICS ports will be machined away.
They are only 1.49 mm deep. There is a brass orifice that shouldn't be machined.

 

Weather was perfect today for a Turbo blast through the countryside.

 

Are you totally wedded to keeping the yics? Skimming the top of the block is by far the best option, as you say too much off the head takes you close to the valve seats - maybe some off both? I don't know about xj blocks but the liners I removed from a vmax needed an adaptor to tie a hydraulic puller and some boiling water to free them - and they were not just push fit, they were finish machined flush afterwards.
Alternatively, if you must machine the bottom of the block a cnc mill should manage it with just surface marks on the liners?

 

Can you get in to the port with a small end mill?
How would you remove the cylinder sleeve?
Also if we can get good measurements I am a pattern maker and could absolutely model a mockup cylinder in autodesk and get you some cut files on powermill. If you have capable machines can mill bottom off block while the sleeves are in. I would be more then happy to send you a USB with it all free of charge

 

I didn't even think of that. Awesome

 

Removing liners is not something I will attempt at home, that's some ordeal you just described @Minimutly
I've watched a Millyard video where he threw a Kawi block on the propane barbecue and they fell out.
I have a performance bike shop real close. He does this sort of stuff all day long.
If he thinks the liners should come out then that's what we'll do.
My preference is to take it out of the bottom of the block, just seems the cleanest approach.
The base gasket surface finish is much less critical also.

There is a visible difference in the 650T and 891 blocks in the section below the last cooling fin.
The 650T block actually has more space here, strange because it's the shorter block.
Both blocks have 7 fins, that just dawned on me to verify that LOL.
I'll ask him to tap the hole for the anti-ping microphone to.
That's metric taper threads and Yamaha decided to slope the surface of this boss on the 891 casting.
The block needs to be clamped in a big drill press at an angle.
He does vapour blasting so we'll see what all that costs.
That will keep everything to just 1 modified part.

I want the YICS just so I'm not adding another variable to this.
It runs really nice now.
I'm doubtful YICS does anything while under boost but I think it helps cruising around.
The purpose of more displacement is to improve the off boost response.
The response under boost is crazy stuff already with 650cc.

It looks like the YICS port could be machined in deeper so the o-ring would still fit but I'm not sure how deep those brass orifices are.
As mentioned above I would not attempt cylinder liner removal at home.
The bike shop I have close builds race bikes, he used to list on his website pricing for re-sleeving.
He's set up with a hydraulic press and all the tricks. Full machine shop.
Thanks for the offer Phoenix, but I'm expecting I can drop the block off with Jim and have something ready to paint and install.

After this will be restoration of a 650 Turbo head.
I bought a head off eBay, all in perfect condition just missing the camshafts.
All the cam caps came complete with it. All studs good.
I will likely start with it, lap the valves and new stem seals.

I think now my biggest question mark is jetting.
The 650T has 127.5 and 132.5 main jets.
This will be a WAG as to what works best and safely
To start I need big main jets to make sure it's getting lots of fuel.
A lean mixture under all that pressure will melt those pistons pretty quick I would think,
and all that debris could end up down in the turbo.
There's always possibility this could richen things, who knows??

 

You might be right about the yics not doing much on boost, and as you say off boost is where you're trying to improve - which by the way you will, massively, since not only are you going up in torque courtesy of more cubes, but the turbo will be spinning up something like one third sooner due the the increased gasses coming through it. Win win I think.

Re the turbo head, if I was suspicous of anything holding you back it would be the exhaust ports - any chance you could put a hacksaw down one of them to see how much metal there is around the cross-section of the valve guide?
If it were mine I would have the die grinder in there, but I wouldn't like to do it without knowing...

Oh, good call re pulling the sleeves yourself, it's not a home shop job unless you have some decent machinery, I will be suprised if the block top surface doesn't need a lic with the flycutter.

 

Let me see about cutting my scrap head to give you a good look.

 

I finished another fluid measurement with the new head gasket.
This time I measured out 32 cc's as accurately as I could.
This filled the chamber exactly to the bottom of the spark plug threads.
After settling and tapping the head I fit 1 more cc in.
33 cc's it is.
As it stands now the CR is 6.8:1

By shaving the block;
1.7 mm makes 8.2:1 - same as stock Seca Turbo
1.6 mm makes 8.1:1
1.5 mm makes 8.0:1
1.4 mm makes 7.9:1
1.3 mm makes 7.8:1 - same as Kaw Turbo

Not sure which one to pick?
Much bigger non-forged pistons,
I'm leaning towards the lower number.

Not sure if I'm going to worry about that sharp edge in the head.

 

Kawasaki Turbo 7.8:1 CR 10.5 psi boost
Honda CX500T 7.2:1 CR 19.3 psi boost
Honda CX650T 7.8:1 CR 16.4 psi boost
Suzuki XN85 7.4:1 CR 9.6 psi boost

My Seca currently measures 9 psi and stock CR is 8.2:1

 

The cr is only part of what could prove fatal - detonation/knock is what will send your combustion temps skyrocketing, and melt a piston in about 5 seconds (I have that tshirt). Weak mix is one factor, too much ign timing advance is another.
Too low a cr will make it sluggish at the bottom end though...
8.2 should be fine, provided the tci retards the timing according to boost - does it, and by how much?
I wouldn't worry about the step at the head either, might give you some extra turbulence which will help.

 

You mentioned the tdi(tci right?) curving the ignition timing as it builds boost? Are non turbo ignition adjustable?
@Simmy the sharp edge your talking about is the diameter of the 650 combustion chamber in thr 900 bore right? That was a concern I had too. 900 heads have fewer options in terms of cams and intake. They also take up more space right?

 

Nothing yamaha made is adjustable. I don't even know for sure the turbo tci retards on boost, but I would expect it to. My vmax adjust according to manifold vacuum, or it would if the little sensor inside wasn't rattling around..

 

This shows everything feeding into the Turbo's ignitor unit.



this is a real complicated flow chart LOL.

 

I literally spent 2 minutes with a rotary file then took another fluid measurement.
The change in volume was hardly discernable.
I'm still undecided if I'll do this to the head, maybe just round it with sand paper.

 

Don’t is my advice, just take the sharp edge off - most if not all car cylinder heads have a square edge, if I skim a head I will carefully run a needle file around it, job done, and these would be race engines.
Re the ignition tci, it must have a vacuum-pressure variable adjustment built in as well as antiknock, quite advanced for its day.

 

Hey @Simmy I just now ordered a cylinder. It's the 68.5 go big or go home. I'd like to run a murray carb set up but he doesn't make one for the 900 I gather the spacing Is different. I'm going to use the yics port on the 900 so I need a head because I've got a 1980 pre yics. Does a 750 head have bigger valves or anything that would make it the better option opposed to the 650

 

That's what I will do.

You could use your 650 non-YICS head. The YICS passageways in the block will just lead no where.
The 650 and 750 use the same valves.
You might want to compare the head volumes as you will need to raise compression more for a normally aspirated motor.
I suspect your 650 head might be tighter in this regard and the better choice.

Why would you go to the trouble of the big bore then take a step back performance-wise with the Murray carbs?
I would think a 772 should work well with the stock 750 jetting.

 

Is it really a step backwards? If you can send some good links on the subject I'd read em I I figured the constant pull of air would be beneficial

 

Was also thinking doing something along the lines of putting two filter in the air box one for 1 and 2 and the other running 3 and 4.
I'm aware that it's not a small block and more air in isn't always better

 

I don't have factual information, just assumed 4 individual carbs would be better.
What does Murray claim?

 

Of course it is, at anything approaching full throttle and beyond. For pooling about town, no issue, but out on the open road it sure will be. Maybe a bigger engine will compensate

 

Look up xj650 murray carb it'll take you straight to his site.
Gentlemen I don't mean to be niave. My thought behind it is that during the 3 strokes that do not create vacuum. air traveling threw a single carb per cylinder setup would lose momentum or cease completely. If the second cylinder firing opposite to it is drawing air threw the same carb then less lose takes place. That's just what I've come to know. But I'm completely new to these bikes and I'm up for hearing your thoughts and experiences. And if you hit me with sources I like to read that kinda suff.
Similar to the scavenging affect of good header compared to factory cast manifolds. I've read a few thing on cv vs cr carbs still have quite grasped it yet tho

 

Explain why it might not be good on open road?
2x36mm carbs means over all less volume then 4x28 or whatever the hitachis are so it makes sense that it responds better at lower rpm. But would you really lose top?

 

With single carb per cylinder you can use pulse length tuning, since there are no conflicting waves. You have no bends, tees etc, so less losses. Yamaha were experts in sound and pulse tuning.
On the negative sides of twin carbs your intake pulses are not even, unless you have acrossover manifold? I must confess never to have looked the manifold up. But if it worked anything like as well don't you think Yamaha would have offered it - two carbs less etc?

 

Small change in plans.
I talked to my engine guy.
He said if he removes the sleeves and puts them back he can't guarantee they will remain round.
I had worried about this but he said he would match mark them so they go back in exactly the same position.
He wondered if the piston clearance would allow a good honing to true them up afterwards.
Once I got home I got thinking, hmmm...
I also have an 853 cylinder block, why not use it and bore it from 67 to 68.5.
I showed him the 853 block, he measured the sleeves and determined it would be no problem.
The sleeves will still be about .250" thick after boring.
He has seen cylinder sleeves bored to .090" thick without problem.
However they weren't likely turbocharged.

Not going to be cheap but this is certainly the way to go.
A nice fresh bore will be great, perhaps new rings to.
No rush, still lots of work to finish the bottom end, mostly just new gaskets, inspect the clutch.
I'm not planning to split the cases at this time.
Fingers crossed that the starter clutch and primary chain guide are good.
New cam chain with master link.
And restoring a head.
The plan will be to have the 772 running next spring.

 

Wow! Living on the edge........

 

For as far I as you are and engine is out of bike, I think I’d just split and make sure. Like you said not in a rush and I’d kick myself for sure if I skipped this and had a problem once in bike.