Info for an FZR400 overbore project - FZS600 Cylinder height and rod length

[ruckusman]

Hi guys,
Hello from sunny, at the moment, Sydney Australia.
I had this posted in the FZS600 section @darrsi suggested I post it here for more attention.

I'm trying to hopefully get some info on the FZS600 cylinders, rods and pistons for an overbore project on a 3TJ1 FZR400.
I'm trying to avoid ending up with a workshop full of parts just for the purposes of taking measurements, especially when many bits will need to come from OS.
As an outline, because it's essentially de-stroking a YZF600/FZS600 from 49.6mm to 40.5mm, I'm trying to avoid removing bulk material from the cylinders to maintain the gasket mating surface.

What I know for certain - Yamaha in their wisdom built an incredibly versatile crank, with many dimensions which are maintained across many many bikes.So the conrod big ends go onto the FZR400 crank - no issues. Conrod little ends are 17mm bore, so compatible with YZF600 pistons if necessary.

Regarding the FZS600 rod and piston measurements, this is only if someone has either an engine in parts or can point me in the right direction to a service manual or the like for the dimensions on the internals.

I have some of the details from another forum where the FZR600 crank was used to build a stroker YZF600, but as you can imagine it's a very old post.The measurement details are missing, however in that case they built a spacer plate.

Ideally I'm looking for just the height of the FZS600 cylinder block to begin with because the OP just says that they're 2cm (must be a typo), likely meaning 2mm shorter than the YZF600 cylinder block, the height of which I don't yet know either.

Past that he mentions that the FZS600 conrods are 3mm shorter than the YZF600 conrods.So eye to eye conrod length measurement of the FZS600 rods if available/possible.
Then there is the last element, the compression height of the FZS600 pistons.
If anyone has a reliable source for the info, or can take the basic measurements I'd very much appreciate it.

Glenn

[Gnasher]

Interesting, question is why? 

[ruckusman]

1. Well the cold rational assessment would be because the potential of more POWAH from motorcycles makes men silly and contemplate silly things.
2. More sensibly, because whilst the FZR400 engine is great, a little more poke for the easily achievable displacement increase with bolt on, readily available parts is a very attractive option - also see point 1, it also opens up the possibility of having readily available service parts, so much for the FZR400 is either NLA or only available in 'racing' versions for $$. e.g. Valves are a big issue

3. This will potentially go into an FZR250 frame, just throwing a YZF600 engine into that @ 95-100 HP isn't a sensible option - trying to avoid going the full point 1.
4. We're closer, we have the YZF600 cylinder height, also know that just due to the shorter stroke YZF600r Rods and pistons on the FZR400 3TJ crank, we're closer, know that it's 4.55m short of where it should be.
5.This has flow on benefits if we can keep a stock cylinder both the cam chain length and cam chain tensioner blades should remain unmodified hopefully from an appropriate model bike.
6. There is the possibility of other appropriately dimensioned rods in different lengths to go up in 0.5mm increments from 90.5mm - 92mm, then 93mm and 95mm, all the way up to 98.00mm

The aim is to get as close to a new bolt on top end as possible without having to resort to unobtanium of high $$ parts - sure we could just go for Carillo custom rods, but that violates the spirit of the project
You know how it goes, two blokes get to chatting on a forum...

[Gnasher]

I see

You want to muck about with the stoke to gain a little more swept area in the hope of getting more power and then shove a FZS400 engine in a FZR250, right?  Most gains are had by increasing the bore and shortening the stroke as Yamaha did with the YZF600 R6, going from 62 x49.6 for the YZS600 (Tcat as we know it) to 67 x 42.5 for the R6. Or decreasing the squash band, sort of increasing compression but gives you better mixing.  Where as, I think you want to decrease (destroking) the stroke, to increase the swept area (by using YZF conrods/pistons or a mix of FZS parts) but that could well also lower the compression and will change the squash area?  Or have I not read you right?

You make no mention of swapping the block 600 for 400?     

Other than point 1 of your list, it makes no sense, the gains will be a minimal for the work and you'll more than likely have to play about with the fueling to get it to run right and produce power across the rev range.  The power increase in the Tcat (15hp ish) over the FZS is all mainly in the head and intake (the block is angled forward slightly and the intakes are 90* to the ground i.e. straight down and in) plus the T cat revs faster.  Basically from the crankcase up the YZF is a completely different engine. The R6 is totally different in all areas.

Unless it's all about point 1 I'd be more inclined to shove an R6 into the 250 frame now your talking, quite a bit a fabrication but it will go 

[b1k3rdude]

What about wedging a FZS600 engine in..?

[ruckusman]

I see

You want to muck about with the stoke to gain a little more swept area in the hope of getting more power and then shove a FZS400 engine in a FZR250, right? 

Partially correct, we're planning to basically overbore the FZR400 from 56mm to 62mm with either YZF600 or FZS600 cylinders & YZF600 cylinder head - various rod/piston combinations/choices to get compression height spot on - this may go into an FZR250 or an FZR400 - TBD

Most gains are had by increasing the bore and shortening the stroke as Yamaha did with the YZF600 R6, going from 62 x49.6 for the YZS600 (Tcat as we know it) to 67 x 42.5 for the R6. Or decreasing the squash band, sort of increasing compression but gives you better mixing.  Where as, I think you want to decrease (destroking) the stroke, to increase the swept area (by using YZF conrods/pistons or a mix of FZS parts) but that could well also lower the compression and will change the squash area?  Or have I not read you right?

Correct a straight bolt on would drop compression.
We're taking an FZR400 crank for the 40.5mm stroke, then a possible combination of cylinder block and conrod and pistons @62mm bore - fortunately there's quite a few pistons available in 62mm, because a straight swap of say YZF600 top end, with the same squish band with the reduced swept area would see compression fall from 12:1 -> 9.78:1 - not good!
Just on the numbers before any actual measurement of the combustion chamber volume there's a 2.3cc combustion chamber volume change (reduction) required to keep the same compression ratio
YZF600 @ normal bore/stoke ratio has 12.5cc combustion chamber volumeYZF600 @ 62mm bore 40.5mm stroke needs 10.18cc combustion chamber volume to maintain 12:1 compression ratio
Fortunately we know the basic FZR400 crank as deployed in other bikes is good for well over 120HP, crank mains and conrod big end diameters remain consistent for ~30 yearsI've read of people, taking the YZF600 stroke to 54.8 with first release FZR600 cranks and 64mm bore for something well over 700cc and over 120HP
Silliness?

You make no mention of swapping the block 600 for 400?     

The YZF600 and FZS600 blocks are essentially the same for our purposes, the 62mm Nikasil bore, cylinder head will be YZF600, as will carbs airbox etc

The difference in cylinder block height is of interest, we know with some accuracy that the YZF600 cylinder block is 87mm high, apparently the FZS600 cylinder block is a few millimetres shorter - TBD - this difference may assist us with a rod/piston combination that doesn't need any sillyness further in.
Hogging 4.55m off of the YZF600 block will mean cam chain tensioner blades become a problem as well as cam chain length coming into play, not to mention re-timing cams, which will get done anyway further in, but let's keep the mods, and potential problems to a minimum to start with...

Other than point 1 of your list, it makes no sense, the gains will be a minimal for the work and you'll more than likely have to play about with the fueling to get it to run right and produce power across the rev range.  The power increase in the Tcat (15hp ish) over the FZS is all mainly in the head and intake (the block is angled forward slightly and the intakes are 90* to the ground i.e. straight down and in) plus the T cat revs faster.  Basically from the crankcase up the YZF is a completely different engine. The R6 is totally different in all areas.

Everything from the engine cases up will be YZF600 - with the cylinder block dependent upon deck height and TBD
BTW, R6 rods share a common bottom end bore diameter @33mm, rod width unknown at this point and fortunately some of our potential candidate pistons for recovering the compression ratio are 16mm diameter also

That's the beauty of Yamaha, basically the FZR600/FZR400 engine cases were so well designed they're been deployed with all manner of crank throws for ~30 years in various bikes, and there's also consistency among those various cranks, with the stroke variations
I'm seeing someone in the early to mid '80's with the foresight to plan a roadmap that has advanced for decades and build accordingly
The only limit in there is the bore spacing, consider that the original FZR600 was 59mm bore and the only thing preventing them going larger than 64mm is bore spacing of adjacent bores

Unless it's all about point 1 I'd be more inclined to shove an R6 into the 250 frame now your talking, quite a bit a fabrication but it will go 

See now, this is what happens, a few guys get to chatting on a forum...

Not motorbike specific, but definitely related, part of what reinvigorated this was project binky on youtube - I am assuming you may have seen it, fair warning, if you haven't it's addictive

I won't post a link so that I can remain blame free

[ruckusman]

What about wedging a FZS600 engine in..?

We're close to that, wanting to keep the FZR400 stroke for high RPM and YZF600 head for that performance

[darrsi]

I think you should design a space rocket that can safely land without blowing up instead.
It sounds like a lot less hassle. 

[Gnasher]

Partially correct, we're planning to basically overbore the FZR400 from 56mm to 62mm with either YZF600 or FZS600 cylinders & YZF600 cylinder head - various rod/piston combinations/choices to get compression height spot on - this may go into an FZR250 or an FZR400 - TBD

then a possible combination of cylinder block and conrod and pistons @62mm bore - fortunately there's quite a few pistons available in 62mm, because a straight swap of say YZF600 top end, with the same squish band with the reduced swept area would see compression fall from 12:1 -> 9.78:1 - not good!

Now it's starting to make more sense

Don't quote me, as I may be wrong as it's been some years since this kind of thing was asked.  Back in the day many tried all manner of ways to get more power out of an FZS600 motor, including using parts from the YZF, like heads and blocks, I don't know of anyone succeeding.  The FZS is one of those bikes that was already getting close to it's limit out of the factory and any real power improvements required major engineering, which just wasn't worth the costs.  As mentioned the YZF is a very different beast to the FZS and I seem to remember someone trying to fit a head to a FZS block and it wouldn't, due to cam chain issues, water/oil galleries don't align and the same sort of issues when a YZF bloc was tried to a FZS cases.  Not to mention pistons, con rods etc. 

The other drama was with mounting the airbox in the FZS frame, as the YZF doesn't have a traditional tank layout like the FZS.  The YZF uses the tank area to mount it's airbox because the intakes are at right angles to the cases i.e. from traditional 9 O'clock position to the YZF 12 O'clock.

Now anything can be done, if your prepared to throw enough money and time at it.  But from what you saying money isn't something your prepared to spend much of, if it is then I hope you've got deep pockets.  Personally I would look at the R6 option I mentioned earlier, with the 08 -09 (127bhp ish) being the most powerful next was the 06 - 07 (125bhp ish), quite why the later models produce less power and torque, emissions probably.  Although the latest 17 - on produces less power but more torque than 06 - 09 models.   Shoehorning one of these into a 250 or FZS 400 would be a real hoot and would require just fabrication work to the frame, tank etc but you'd need the, fuel system and electronics from the R6.  Again unless it's just to prove you can and for fun there's little point just buy a R6.   

I wish you the very best of luck mate and please do keep us posted, its a very interesting project.       

 

[ruckusman]

I will definitely document the process.
The 490cc FZR400 has been done, there's forum members on fzronline that have done it successfully, however that forum itself seems to be languishing unattended, trying to register doesn't send the verification email
Onto the FZR400, their formula was YZF600 cylinders and pistons and FZS600 rods, with some choosing to use an FZR600 cylinder head, others make mention of using the YZF600 cylinder head - those posts however don't mention all of the details, which is where the devil usually resides

Interesting that you mention the water gallery - I will cross reference head gaskets and cylinder base gaskets between them all - many parts are common
Cam chain replacement is anticipated, length yet to be determined