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This thread is a step-by-step documentation of my 1091cc motor build. The service manual provides excellent guidance on removing and disassembling the engine, but there are certain omissions and tips that I will share so that others can better tackle some difficult steps. I will also share any mistakes and blunders I make along the way so that others can avoid them.
DISCLAIMER: I am NOT a professional mechanic or engine builder. I'm a physics teacher who enjoys working on bikes in my spare time. Given the amount of special tools required, it would be SIGNIFICANTLY cheaper to take your engine to a professional engine builder if you only care about the end result of having a 215+ rwhp engine.
Drain the coolant and oil before this process. It would be best to remove all the radiator hoses as well and plug up the orifices. I left them on and it ended up dripping every time I tilted or moved the engine. There's a lot of residual coolant and motor oil to drip when you least expect it, so keep some shop towels handy. 1-person removal of the engine is best done with the bike supported off the ground with an engine crane via straps through the ram air holes and a floor jack underneath. The front forks should be removed so that the engine can slide straight out the front of the bike in a controlled manner. I will share more pictures during the installation process. With the final upper hanger bolt removed, it's necessary to lift the frame while moving the engine forward. I only used the engine crane to lift the frame up, because my floor jack is difficult to control on the way down, as I slid the floor jack forward out of the bike. I had this part snag on the frame and complicate the process, so I recommend removing this part marked with a star.
I strongly recommend an engine crane if there is no one else to assist because the engine has a tendency to lean to one side and also use masking paper, towels, and tape to cover areas around engine mounts to prevent scratches. With the engine removed and lifted onto my work bench, I disassembled and removed the cylinder head. This is fairly straightforward but you may run into issues with the camshaft holders. It is best to loosen them all 1/2 turn at a time, then take a nylon pry bar and pry up all around the holders. Take another 1/2 turn out, and pry again, etc. This is because if one side is lifted more than the opposite side, the alignment pins will get stuck and you will have to tighten down the side that is lifted more. You do not "have" to disassemble the head to send in for porting, but I chose to do so because I intended to replace valve seals on my 12 year old bike with 30k miles. To protect the bucket walls from getting scratched by the valve spring compressor, cut a strip of plastic (from a plastic jug) and wedge that around the valve spring and retainer. The valve retainers are around 22mm wide and will "pop" when you first break loose the retainers so do not be alarmed if you hear a sharp snap as you tighten down the compressor. Be sure to use a folded sheet of paper to cushion the other side of the valve.
Next, remove the side covers by prying on the tabs with nylon tools. Before prying any two surfaces apart on the engine, leave 3 bolts partly threaded in to prevent the cover from flying off unexpectedly. The stator side is magnetic, and I found it helpful to wedge some wood shims between the stator cover and crankcase as I pried around the cover. I had some difficulty with the clutch side cover, and ultimately removed it by using a pair of snap ring pliers to "spread" in the region marked with a star in the picture below.
Removal of the flywheel and clutch components is very difficult due to the large amount of torque (100+ ft-lbs) to break loose the clutch nut and bolts on each side of the crankshaft. To remove the clutch, the Honda OEM tool is required ($30). Do not try to use the EBC tool, it is too short and will be difficult to use. Honda put a punch mark on the nut to keep it from coming loose so you must unstake it with a hammer and small flat blade screwdriver. I held the tool in place with a 1/2 breaker bar attached to my bench vise and strapped the engine down to my bench so it would not move and allow the tool to slip off. Alternatively, you could remove the clutch nut with the engine in frame and a 2x4 through the wheel/swingarm, but it was too late for me. Note that it is not possible to remove this nut by holding the crankshaft in place as I will show in the next step, because the clutch will slip before the nut breaks loose.
The nut retaining the flywheel and starter clutch can be removed by holding the starter clutch in a vise with aluminum soft jaws. The manual says to use a flywheel holder tool but the tool shown in the manual has sharp teeth that will mar the starter clutch and flywheel, which is unacceptable to me. I tried to use a rubber coated flywheel holder, but it will slip/bend/break long before the bolt breaks loose. The setup that worked for me is shown below. Note that it is not possible to remove this nut with the engine in frame and 2x4 through the swing arm because the clutch will slip before the nut breaks loose. You could try using a pin spanner through the holes in the starter clutch, but you will have to somehow hold it in place while you break the nut loose.
With the engine in this position, pull the flywheel off with an M18x1.5 tool. You must ensure that the puller tool allows for at least 4-5 threads of engagement or you may strip out the threads. In my case, the Motion Pro puller I purchased barely had 2 threads of engagement because of the large unthreaded portion. I had to turn this down on my lathe. You will put quite a bit of torque on this puller, so it's essential to ensure full thread engagement and grease the threads. The flywheel is seated on a taper, so you will hear a loud crack when the taper breaks loose.
Removal of the clutch basket, various sensors, oil pan, oil pump, water pump, oil cooler, starter, camshaft chain guides, etc. is fairly straightforward and well documented in the manual. If the starter sticks, use a nylon pry bar to gently work it loose. Also, the crankshaft counterweight can obstruct the removal of the clutch basket. I marked this area with a star below. If this is the case, simply rotate the crankshaft until the counterweight is out of the way, then the clutch basket can be lifted slightly and removed. I prefer to cover the main shaft with some paper before removing the clutch basket to prevent marring the shaft surface.
With the crankcase stripped of all parts, flip it upside down and prepare for a little oil to leak out. Before I did this, I wrapped the cylinder studs in paper to avoid scratching the pistons when they will be removed later. Do NOT remove the bolts/parts marked with a star. These hold the balance shaft and gear in place and will only be removed once the crank is separated. Also note there is a hidden bolt in the area marked with two stars.
I spent 2 hours trying to figure out how to separate the crankcase without bending or damaging any parts. The large contact area for the sealant makes it difficult to do with nylon pry tools alone, and what I eventually worked out is to take one bolt and partly thread it in the position shown below and leave about 1/4 inch gap. Then, I used the soft rubber handle of my hammer to push down on the bolt and therefore separate the case. Leave a few other bolts partly threaded and pry around the perimeter with a nylon tool to break it free from all sides, then lift straight up and it will come off without issues. I had planned to use the engine crane to lift it off, but the case was very light and I had no trouble lifting it by hand.
IMMEDIATELY examine the case you removed for missing crankshaft bearings that stuck to the crankshaft. Place all bearings back in the proper location and mark all the bearings 1, 2, 3, 4, 5 and mark the adjacent metal on the case with 1, 2, 3, 4, 5 as well. The bearings are NOT interchangeable and must be returned to their proper locations. In my case, one bearing shows signs of uneven wear, so I will order a full replacement set once my crank comes back. More on how to do this later! At this time, I removed the counterbalance gear. There is a washer on each side of the gear so be careful not to drop those and ding the crankcase.
To remove the connecting rods, first place 2 cylinders at TDC (deep down from your perspective) and use a 10mm 12 point driver to loosen but not remove the connecting rod bolts. Do NOT use an impact wrench on the connecting rod bolts. Then rotate the crankshaft until the other 2 cylinders are at TDC and loosen those connecting rod bolts. Now rotate the crankshaft so that all 4 pistons are about even with each other. Remove all the connecting rod bolts and remove the connecting rod halves. The cover is a snug fit, so use a brass rod partly inserted through the bolt holes to gently rock the halves back and forth until they come off. Be careful not to mix up any bearings! Prior to removing the crank, place some paper under each connecting rod to prevent denting the lower crankcase when the rod falls.
Take a rubber mallet, and gently tap upward on both ends of the crank to "un-stick" the crankshaft from the bearings. Then, with your shoulders directly over the crankcase, lift the crankshaft straight up. It is quite heavy so go very slowly and use your thumbs to push down on the crankcase as you initially lift the crank.
Here is the crankshaft prior to packing and shipping off to APE for +2mm stroking. It will be welded and reground to retain the OEM bearing size. The large gear (*) that drives the crankshaft counterbalancer, normally designed to reduce secondary imbalances intrinsic to a 4-cylinder engine, will be removed and the stock counterbalancer will be replaced with a dummy shaft. You cannot simply install the original shaft without the counterbalancer weight because an oil hole will be exposed, so an alternative would be to weld up the hole on the counterbalancer shaft. However, the OEM shaft is steel and the dummy shaft is aluminum, which is much lighter.
Prior to removing the pistons, wrap each connecting rod in paper so it does not mar up any part of the crankcase or cylinder block. Then, push each piston from the crankcase side so it comes out the side with the studs. Alternatively, since the cylinder block will be removed, the pistons can be taken out after the block is separated from the crank. I noticed a thick layer of carbon on the pistons. The valves also had a thick layer of carbon. I suspect that it is the crankcase breather allowing oil mist to enter the intake.
Here is the cylinder block prior to shipping to Millenium Tech. for overbore and replating. Remove the 2 pins if any are stuck to the cylinder block. Even if you send your cylinder block to APE it will go to Millenium Tech. in the end so I opted to send it directly. However, I later realized that APE offers a $100 discount with a piston purchase so I will go that route next time. It's a bit dirty, but it will be blasted as part of the +2mm overbore process so should look much better when it returns.
Removal of the transmission is poorly described in the manual. To remove the "larger" set of gears, gently pry both sides up at the same time until the rubber seal on the sprocket side breaks free. Lift each side slightly and pad the bearing edges with some paper to prevent it from sticking back down and slowly lift it straight up. The "smaller" set of gears is far more difficult, because it needs to be moved and tilted in a particular way. I have described this in the picture below on the left. The blue line shows the original position of the shaft. Prior to starting, place a plastic freezer bag over the shaft and gears to avoid marring. Move the shaft back until it clears the bearing on the other side, then tilt it as shown in the red line. Note how the red line is tilted, backed out, and offset in the picture. It's a very precise fit and has to be moved to exactly this position before it will clear the lower crankcase.
It is not necessary to remove the remaining parts, so I will leave that. In the meantime, I am removing the remnants of gasket material. I tested various solvents in an inconspicuous area and found that ODORLESS MINERAL SPIRITS in addition to a small nylon scraper will melt the OEM gasket material right off with no damage to the painted surfaces of the engine. Put some mineral spirits on the mating surfaces and scrape all the gasket material off. Use a rag soaked in mineral spirits to remove any residue and the mating surfaces will be in pristine condition for reassembly!
That's all for now (3/14/2021). The turnaround for crankshaft stroking is 8-10 weeks and I have the Carrillo connecting rods, pistons, retainers, etc. on back-order as well. So I will follow up with updates as various parts arrive.
While waiting on parts, perhaps it's appropriate to explain a bit of theory behind a stroking a crankshaft. Increasing the stroke of a crankshaft decreases piston clearance (at TDC) and increases compression ratio. These factors must be compensated for by one of 2 options:
Option A requires custom length Carrillo connecting rods ($$$). Option B requires a $38 aluminum spacer plate. I chose the second option so I could use standard length Carrillo rods (also compatible with stock pistons and overbore only builds).
To maintain the same compression ratio for a KNOWN piston/rod/crankshaft setup (i.e. JE piston kit designed to have 13.5 comp. with, stock thickness head gasket, stock cylinder base gasket, stock length connecting rods, stock stroke), the relationship between the amount a crankshaft is "stroked", compression ratio, and additional "cylinder height" must be known.
Using two critical concepts, we can write the following equations:
Using the definition of compression ratio, we can write the following equations:
All these equations simplify nicely to give us this very important relation that allows us to calculate the required spacer thickness (or reduction in connecting rod length) needed to maintain the same compression ratio for a KNOWN setup when using a stroker crankshaft.
In my build, I will be using 78mm (overbore but accounted for by the piston manufacturer) JE pistons with a compression ratio of 13.5 and a +2mm stroker crankshaft (NOT accounted for by the piston manufacturer). Therefore, to maintain the manufacturer's intended compression ratio of 13.5 (and simply to know the compression ratio without tedious volume measurements), I will need a 1.16mm spacer.
It may not seem like much, but 0.15mm is the difference between a compression ratio of 13.5:1 vs 14:1.
APE's website states that "the height of the cylinder base spacer plate needed is EXACTLY half the stroke of the crankshaft." According to this equation, wouldn't a thicker spacer plate would be required? No, because this extra height comes from the additional cylinder base gasket required (stock base gasket + 1.0 mm spacer + 0.15mm HRC base gasket).
DISCLAIMER: I am NOT a professional mechanic or engine builder. I'm a physics teacher who enjoys working on bikes in my spare time. Given the amount of special tools required, it would be SIGNIFICANTLY cheaper to take your engine to a professional engine builder if you only care about the end result of having a 215+ rwhp engine.
Millenium Tech. M-spec CNC head port w/ valve job
Millenium Tech. +2mm overbore w/ Nikasil replating
APE +2mm stroker w/ race balance, lightening, and removal of balance gear
APE Ti valve retainer/springs
APE adjustable camshaft gears
APE dummy shaft (remove counter-balancer)
78mm JE 13.5 comp. forged pistons
HRC transmission
HRC camshafts
HRC thermostat
Carrillo H-beam rods (104.5mm)
+1mm cylinder base shim plate
Suter slipper clutch w/ APE Trac King plates
Drain the coolant and oil before this process. It would be best to remove all the radiator hoses as well and plug up the orifices. I left them on and it ended up dripping every time I tilted or moved the engine. There's a lot of residual coolant and motor oil to drip when you least expect it, so keep some shop towels handy. 1-person removal of the engine is best done with the bike supported off the ground with an engine crane via straps through the ram air holes and a floor jack underneath. The front forks should be removed so that the engine can slide straight out the front of the bike in a controlled manner. I will share more pictures during the installation process. With the final upper hanger bolt removed, it's necessary to lift the frame while moving the engine forward. I only used the engine crane to lift the frame up, because my floor jack is difficult to control on the way down, as I slid the floor jack forward out of the bike. I had this part snag on the frame and complicate the process, so I recommend removing this part marked with a star.
I strongly recommend an engine crane if there is no one else to assist because the engine has a tendency to lean to one side and also use masking paper, towels, and tape to cover areas around engine mounts to prevent scratches. With the engine removed and lifted onto my work bench, I disassembled and removed the cylinder head. This is fairly straightforward but you may run into issues with the camshaft holders. It is best to loosen them all 1/2 turn at a time, then take a nylon pry bar and pry up all around the holders. Take another 1/2 turn out, and pry again, etc. This is because if one side is lifted more than the opposite side, the alignment pins will get stuck and you will have to tighten down the side that is lifted more. You do not "have" to disassemble the head to send in for porting, but I chose to do so because I intended to replace valve seals on my 12 year old bike with 30k miles. To protect the bucket walls from getting scratched by the valve spring compressor, cut a strip of plastic (from a plastic jug) and wedge that around the valve spring and retainer. The valve retainers are around 22mm wide and will "pop" when you first break loose the retainers so do not be alarmed if you hear a sharp snap as you tighten down the compressor. Be sure to use a folded sheet of paper to cushion the other side of the valve.
Next, remove the side covers by prying on the tabs with nylon tools. Before prying any two surfaces apart on the engine, leave 3 bolts partly threaded in to prevent the cover from flying off unexpectedly. The stator side is magnetic, and I found it helpful to wedge some wood shims between the stator cover and crankcase as I pried around the cover. I had some difficulty with the clutch side cover, and ultimately removed it by using a pair of snap ring pliers to "spread" in the region marked with a star in the picture below.
Removal of the flywheel and clutch components is very difficult due to the large amount of torque (100+ ft-lbs) to break loose the clutch nut and bolts on each side of the crankshaft. To remove the clutch, the Honda OEM tool is required ($30). Do not try to use the EBC tool, it is too short and will be difficult to use. Honda put a punch mark on the nut to keep it from coming loose so you must unstake it with a hammer and small flat blade screwdriver. I held the tool in place with a 1/2 breaker bar attached to my bench vise and strapped the engine down to my bench so it would not move and allow the tool to slip off. Alternatively, you could remove the clutch nut with the engine in frame and a 2x4 through the wheel/swingarm, but it was too late for me. Note that it is not possible to remove this nut by holding the crankshaft in place as I will show in the next step, because the clutch will slip before the nut breaks loose.
The nut retaining the flywheel and starter clutch can be removed by holding the starter clutch in a vise with aluminum soft jaws. The manual says to use a flywheel holder tool but the tool shown in the manual has sharp teeth that will mar the starter clutch and flywheel, which is unacceptable to me. I tried to use a rubber coated flywheel holder, but it will slip/bend/break long before the bolt breaks loose. The setup that worked for me is shown below. Note that it is not possible to remove this nut with the engine in frame and 2x4 through the swing arm because the clutch will slip before the nut breaks loose. You could try using a pin spanner through the holes in the starter clutch, but you will have to somehow hold it in place while you break the nut loose.
With the engine in this position, pull the flywheel off with an M18x1.5 tool. You must ensure that the puller tool allows for at least 4-5 threads of engagement or you may strip out the threads. In my case, the Motion Pro puller I purchased barely had 2 threads of engagement because of the large unthreaded portion. I had to turn this down on my lathe. You will put quite a bit of torque on this puller, so it's essential to ensure full thread engagement and grease the threads. The flywheel is seated on a taper, so you will hear a loud crack when the taper breaks loose.
Removal of the clutch basket, various sensors, oil pan, oil pump, water pump, oil cooler, starter, camshaft chain guides, etc. is fairly straightforward and well documented in the manual. If the starter sticks, use a nylon pry bar to gently work it loose. Also, the crankshaft counterweight can obstruct the removal of the clutch basket. I marked this area with a star below. If this is the case, simply rotate the crankshaft until the counterweight is out of the way, then the clutch basket can be lifted slightly and removed. I prefer to cover the main shaft with some paper before removing the clutch basket to prevent marring the shaft surface.
With the crankcase stripped of all parts, flip it upside down and prepare for a little oil to leak out. Before I did this, I wrapped the cylinder studs in paper to avoid scratching the pistons when they will be removed later. Do NOT remove the bolts/parts marked with a star. These hold the balance shaft and gear in place and will only be removed once the crank is separated. Also note there is a hidden bolt in the area marked with two stars.
I spent 2 hours trying to figure out how to separate the crankcase without bending or damaging any parts. The large contact area for the sealant makes it difficult to do with nylon pry tools alone, and what I eventually worked out is to take one bolt and partly thread it in the position shown below and leave about 1/4 inch gap. Then, I used the soft rubber handle of my hammer to push down on the bolt and therefore separate the case. Leave a few other bolts partly threaded and pry around the perimeter with a nylon tool to break it free from all sides, then lift straight up and it will come off without issues. I had planned to use the engine crane to lift it off, but the case was very light and I had no trouble lifting it by hand.
IMMEDIATELY examine the case you removed for missing crankshaft bearings that stuck to the crankshaft. Place all bearings back in the proper location and mark all the bearings 1, 2, 3, 4, 5 and mark the adjacent metal on the case with 1, 2, 3, 4, 5 as well. The bearings are NOT interchangeable and must be returned to their proper locations. In my case, one bearing shows signs of uneven wear, so I will order a full replacement set once my crank comes back. More on how to do this later! At this time, I removed the counterbalance gear. There is a washer on each side of the gear so be careful not to drop those and ding the crankcase.
To remove the connecting rods, first place 2 cylinders at TDC (deep down from your perspective) and use a 10mm 12 point driver to loosen but not remove the connecting rod bolts. Do NOT use an impact wrench on the connecting rod bolts. Then rotate the crankshaft until the other 2 cylinders are at TDC and loosen those connecting rod bolts. Now rotate the crankshaft so that all 4 pistons are about even with each other. Remove all the connecting rod bolts and remove the connecting rod halves. The cover is a snug fit, so use a brass rod partly inserted through the bolt holes to gently rock the halves back and forth until they come off. Be careful not to mix up any bearings! Prior to removing the crank, place some paper under each connecting rod to prevent denting the lower crankcase when the rod falls.
Take a rubber mallet, and gently tap upward on both ends of the crank to "un-stick" the crankshaft from the bearings. Then, with your shoulders directly over the crankcase, lift the crankshaft straight up. It is quite heavy so go very slowly and use your thumbs to push down on the crankcase as you initially lift the crank.
Here is the crankshaft prior to packing and shipping off to APE for +2mm stroking. It will be welded and reground to retain the OEM bearing size. The large gear (*) that drives the crankshaft counterbalancer, normally designed to reduce secondary imbalances intrinsic to a 4-cylinder engine, will be removed and the stock counterbalancer will be replaced with a dummy shaft. You cannot simply install the original shaft without the counterbalancer weight because an oil hole will be exposed, so an alternative would be to weld up the hole on the counterbalancer shaft. However, the OEM shaft is steel and the dummy shaft is aluminum, which is much lighter.
Prior to removing the pistons, wrap each connecting rod in paper so it does not mar up any part of the crankcase or cylinder block. Then, push each piston from the crankcase side so it comes out the side with the studs. Alternatively, since the cylinder block will be removed, the pistons can be taken out after the block is separated from the crank. I noticed a thick layer of carbon on the pistons. The valves also had a thick layer of carbon. I suspect that it is the crankcase breather allowing oil mist to enter the intake.
Here is the cylinder block prior to shipping to Millenium Tech. for overbore and replating. Remove the 2 pins if any are stuck to the cylinder block. Even if you send your cylinder block to APE it will go to Millenium Tech. in the end so I opted to send it directly. However, I later realized that APE offers a $100 discount with a piston purchase so I will go that route next time. It's a bit dirty, but it will be blasted as part of the +2mm overbore process so should look much better when it returns.
Removal of the transmission is poorly described in the manual. To remove the "larger" set of gears, gently pry both sides up at the same time until the rubber seal on the sprocket side breaks free. Lift each side slightly and pad the bearing edges with some paper to prevent it from sticking back down and slowly lift it straight up. The "smaller" set of gears is far more difficult, because it needs to be moved and tilted in a particular way. I have described this in the picture below on the left. The blue line shows the original position of the shaft. Prior to starting, place a plastic freezer bag over the shaft and gears to avoid marring. Move the shaft back until it clears the bearing on the other side, then tilt it as shown in the red line. Note how the red line is tilted, backed out, and offset in the picture. It's a very precise fit and has to be moved to exactly this position before it will clear the lower crankcase.
It is not necessary to remove the remaining parts, so I will leave that. In the meantime, I am removing the remnants of gasket material. I tested various solvents in an inconspicuous area and found that ODORLESS MINERAL SPIRITS in addition to a small nylon scraper will melt the OEM gasket material right off with no damage to the painted surfaces of the engine. Put some mineral spirits on the mating surfaces and scrape all the gasket material off. Use a rag soaked in mineral spirits to remove any residue and the mating surfaces will be in pristine condition for reassembly!
That's all for now (3/14/2021). The turnaround for crankshaft stroking is 8-10 weeks and I have the Carrillo connecting rods, pistons, retainers, etc. on back-order as well. So I will follow up with updates as various parts arrive.
While waiting on parts, perhaps it's appropriate to explain a bit of theory behind a stroking a crankshaft. Increasing the stroke of a crankshaft decreases piston clearance (at TDC) and increases compression ratio. These factors must be compensated for by one of 2 options:
(a) shorter connecting rod (piston does not go up as much)
(b) move entire cylinder block up with a shim (piston has more room to go up)
Option A requires custom length Carrillo connecting rods ($$$). Option B requires a $38 aluminum spacer plate. I chose the second option so I could use standard length Carrillo rods (also compatible with stock pistons and overbore only builds).
To maintain the same compression ratio for a KNOWN piston/rod/crankshaft setup (i.e. JE piston kit designed to have 13.5 comp. with, stock thickness head gasket, stock cylinder base gasket, stock length connecting rods, stock stroke), the relationship between the amount a crankshaft is "stroked", compression ratio, and additional "cylinder height" must be known.
Using two critical concepts, we can write the following equations:
at TDC: 1/2 the additional crankshaft stroke subtracts from the volume of the combustion chamber and the spacer (or shorter rod) adds to the volume of the combustion chamber
at BDC: 1/2 the additional crankshaft stroke adds to the volume of the combustion chamber and the spacer (or shorter rod) adds to the volume of the combustion chamber
Using the definition of compression ratio, we can write the following equations:
All these equations simplify nicely to give us this very important relation that allows us to calculate the required spacer thickness (or reduction in connecting rod length) needed to maintain the same compression ratio for a KNOWN setup when using a stroker crankshaft.
It may be intuitive to think that reducing the connecting rod length or shimming the cylinder block by 1/2 the stroke length would balance out perfectly, and while this will address piston clearance issues, it will still increase the compression ratio because while the combustion chamber volume at TDC will be identical, the combustion chamber volume at BDC will be greater. If we want to maintain the same compression ratio, it is necessary to shim the cylinder block or reduce the connecting rod length slightly more than 1/2 the additional crankshaft stroke.In my build, I will be using 78mm (overbore but accounted for by the piston manufacturer) JE pistons with a compression ratio of 13.5 and a +2mm stroker crankshaft (NOT accounted for by the piston manufacturer). Therefore, to maintain the manufacturer's intended compression ratio of 13.5 (and simply to know the compression ratio without tedious volume measurements), I will need a 1.16mm spacer.
It may not seem like much, but 0.15mm is the difference between a compression ratio of 13.5:1 vs 14:1.
APE's website states that "the height of the cylinder base spacer plate needed is EXACTLY half the stroke of the crankshaft." According to this equation, wouldn't a thicker spacer plate would be required? No, because this extra height comes from the additional cylinder base gasket required (stock base gasket + 1.0 mm spacer + 0.15mm HRC base gasket).