So something from the past got me to thinking, and not that I'm in a position (or have the determination) to attempt such a feat, but I remember a guy from here in Alberta that put stock CBR900 pistons into a CBR600 (hurricane) a waaaaay long time ago.
IIRC, he wound up with a "CBR654" for his efforts.
Seeing as how the price of bigbore kits for the VFR is sky-high, I was wondering if it would be even remotely possible to use a set of CBR929 pistons in a VFR800?
They are 74mm, which through a handy web displacement calculator, yields 825cc's (954 pistons would give 848cc's, but there's probably not enough room)
Now I know it's just not that simple, there are things like piston pin diameter to consider, also the distance from the pin center to the top of the piston, the dome shape, the skirt configuration, etc, etc, etc.
But it would be fun to have one example of each on hand, plus a set of calipers to play with, yes?
If all the stars aligned, perhaps a set of real low miles 929 pistons, a set of rings, a couple of new gaskets, and a trip to the machine shop later, and voila! (or maybe not?)
Discuss......
I once dug into the world of big bore kits for the 800s. I was told by Dynamo Humm (Canada) that since the block has a Alum Ceramic composite liner(ok it might be alum silcon nitride?), but composite none the less, that the block first has to be bored out, replated, then finish bore and honed. Millinium Tech in Wisconsin is expert in that area. So just getting any 800 block for a bigger bore was a major expense. - There was/is an english kit (TSA?) that punched it to 825cc.
http://www.mt-llc.com/
Link --
- So after digging deep into the big bore thing, I decided it wasnt gonna be worth it. So I'm thinking that a port, polish, 4 angle valve job, and maybe decked would be about the only value add without super major hassle.
Like your thinking... thought about a big bore kit before. probably best to start with a spare engine to measure compare. IIRC the wall on the 5th gen engine isn't very think hence big kit sizes are limited.
ill keep an eye out for fireblade pistions still... :goofy:
The TTS kit for the VFR800 is "supposedly" 74mm bore, which is why I mentioned the CBR929......
http://www.tts-perfo...products_id=472
And the cost!
Quote
VFR800 98-01 837cc Big Bore Kit
£587.50
That's $918 USD just for the piston kit! (that is what got me thinking about used CBR pistons)
BUT they say it's a 4mm overbore, which is incorrect, as the 800 has a 72mm bore size. Typo methinks.
AND they cannot be 74mm either, as to get 837cc's with 48mm stroke, you need 74.5mm.
72x48=782 (stock)
74x48=826 (CBR)
74.5x48-837 (TTS)
http://www.web-cars....gi-bin/displ.pl
I remember reading somewhere that fireblade pistions have been used before... can't remember where though!
The grasstrack racing guy I know has bored out a susuki RF900 to nearly 1000cc before I'll ask how much it cost to do next week... off to look if I can find fireblade piston on fleabay..
I wonder if there's any tricks that can be played here. Like putting 1985 VF700F pistons in a 1983 VF750F motor - same bore, but the 700 pistons had a higher dome to "de-stroke" the motor to 700cc after 1984's higher import tariff. Installing 700 pistons in the 750 nets you higher compression, according to Dave Dodge, and in combination with a Stage 1 cam should give a nice power boost.
So, all that makes me think that there might be a Honda piston somewhere that has the same general dimensions as your 5th gen piston, but with a higher dome that gives higher compression?
That's a lot of homework! :comp13:
I've never looked at dimensions on the vf1000 motors, but AIR the 1000 is a stroked 750, which kept the size down. Don't know if you could actually bolt a 1000 motor in a 6 gen frame, but with a PCIII and FI, that would be 20% more displacement 110hp*1.20 = 132.....
This reminds me of something Lamborghini did many years ago when they didn't have the cash to design a new engine from scratch. They wanted more displacement out of their V12 but had already bored out the cylinders as much as they could. Do you know what they did? The put spacers in between the block and heads to increase the stroke (and got additional displacement that way.)
I don't remember the specifics about this next case but I once read about a guy that had a Camaro with, I think, a 327cid motor. He got the idea to drop some pistons from a 350 into his 327. While he successfully bored out the cylinders, got the pistons in place, etc., he said his "new" engine just didn't have the punch he thought it would. To make a long story short, the 350 pistons didn't sit as high (on the rods) as the 327 pistons. Consequently, he wasn't getting as much compression. ***If you're a car buff and are reading this, please don't quote me on any of this because since I only recall the basics, I may not recall the exact engines he was dealing with.***
Going back to motorcycles, I once talked to this guy that built I-4 race engines (for track bikes) and he showed me an engine he had just worked on. He said he shaved a little bit off the base of the head and was able to increase compression from something like 12.5:1 to 12.7:1. Again, don't quote me on the specifics but that's the gist of what he did.
Decking & spacing the heads is not an option for the 2nd/3rd/4th/5th gens, due to the gear driven cams. I was going to suggest a cam regrind for more power as well, but that could get pricey by itself, let alone the added cost of working with the gear drives.
"cubic inches rule"
If you want a wide torque band and good bottom end = drivability
I'm impressed with Honda, they've done well with 800 cc, just don't understand why they never went to a liter??????
[image: View Post]PLCGuy, on 07 February 2010 - 09:52 AM, said:
"cubic inches rule"
If you want a wide torque band and good bottom end = drivability
I'm impressed with Honda, they've done well with 800 cc, just don't understand why they never went to a liter??????
A lot of people have wondered the same thing. Given the 6th gen.'s size and weight, 1000cc's would be the way to go. If Honda built a 1000cc V4 with the same power:displacment ratio as the 781cc engine it currently has, it would put out about 140 rwhp. Sure, the bike would weigh even more but it would still be an improvement.
[image: View Post]Veefer800Canuck, on 07 February 2010 - 04:31 AM, said:
BUT they say it's a 4mm overbore, which is incorrect, as the 800 has a 72mm bore size. Typo methinks.
AND they cannot be 74mm either, as to get 837cc's with 48mm stroke, you need 74.5mm.
72x48=782 (stock)
74x48=826 (CBR)
74.5x48-837 (TTS)
http://www.web-cars....gi-bin/displ.pl
Rob, I'm sure that back in the day (when Dynamo Humm was turning these things out regularly), the 750 went to 837cc and the 800 went to 870cc?
I'm still loosely interested in boring mine out... :lurk:
But the cost of even a low buck overbore is still going to make the A&A supercharger kit look very attractive, and you're not messing with Honda's precise machining and assembly with the blower... or are you thinking of doing both? :491:
Who, me? Just wondering aloud. :unsure:
If I were truly interested, I'd just order some lightly used CBR pistons and measure it up! :comp13:
I just want to get my bike running in 1 piece again and I'll be happy with that. :)
Surgery tomorrow, so I'll be out of action for awhile again. :pissed:
BUT BY ZEUS, AS SOON AS I'M WELL, THE WRENCHES WILL BE FLYING! :fing02:
(pictures to follow) :warranty:
Who knows, if/when I get a decent settlement for my accident, I'll think of a ToroCharger. :idea3:
OK, haven't done it for the VFR, but piston vendor catalogues will give you enough data to keep you awake plotting and scheming for a long time. Wiseco was the catalogue I used, IIRC.
Glenn
[image: View Post]Veefer800Canuck, on 07 February 2010 - 03:51 AM, said:
So something from the past got me to thinking, and not that I'm in a position (or have the determination) to attempt such a feat, but I remember a guy from here in Alberta that put stock CBR900 pistons into a CBR600 (hurricane) a waaaaay long time ago.
IIRC, he wound up with a "CBR654" for his efforts.
[snipped...]
Now I know it's just not that simple, there are things like piston pin diameter to consider, also the distance from the pin center to the top of the piston, the dome shape, the skirt configuration, etc, etc, etc.
But it would be fun to have one example of each on hand, plus a set of calipers to play with, yes?
Discuss......
Unfortunately the catalogs I've looked through don't list anything beyond the bore and compression ratio.
Wrist pin bore, and height of the crown above the pin centerline are never shown as far as I could see.
ISTR that Tony Scott once built a VFR engine (possibly RC30 type of VFR...) using 900RR pistons, achieving some sort of big bore displacement, though I can't remember what it was.
Honda does seem fond of using similar parts on different models--even pistons. For example, the NC30 and NC29 use the exact same pistons--and that's in a V-4 and an I-4. I wouldn't be surprised at all if one of the 900RR pistons worked well as a big-bore piston in a VFR, but which 900RR engine would that be? (Also, this doesn't apply to the 800s, given their different cylinder wall materials.)
Ciao,
900RR pistons are 71mm, 800s are 72mm.
Would dropping in shorter pistons (thereby lowering compression) then getting a Torocharger allow you to run more boost out of the blower? Would this simply take you the long way around to being back where you would have w/ the Toro alone?
[image: View Post]2fast2young, on 10 February 2010 - 06:48 PM, said:
Would dropping in shorter pistons (thereby lowering compression) then getting a Torocharger allow you to run more boost out of the blower? Would this simply take you the long way around to being back where you would have w/ the Toro alone?
Lower compression and greater boost pressure would most likely create a "lag" situation if taken to a point where it actually can create more power. I'd leave all that alone and instead focus on some basic flow work done to the heads on a flow bench, a really good full exhaust system including a Motad or similar header, and then go after having the cams reground lightly for a little more lift and duration. This also assumes that there's proper fuel & ignition control going on but that should be a given.
Has anyone ever ported and polished the heads on a 5th or 6th gen bike? It would seem that that would be the nect most reasonable step after the basic header,slippon,PC3, and depairing that most of us have done. It is supprising that no one has any data on this.
[image: View Post]Veefer800Canuck, on 07 February 2010 - 03:51 AM, said:
So something from the past got me to thinking, and not that I'm in a position (or have the determination) to attempt such a feat, but I remember a guy from here in Alberta that put stock CBR900 pistons into a CBR600 (hurricane) a waaaaay long time ago.
IIRC, he wound up with a "CBR654" for his efforts.
Seeing as how the price of bigbore kits for the VFR is sky-high, I was wondering if it would be even remotely possible to use a set of CBR929 pistons in a VFR800?
They are 74mm, which through a handy web displacement calculator, yields 825cc's (954 pistons would give 848cc's, but there's probably not enough room)
Now I know it's just not that simple, there are things like piston pin diameter to consider, also the distance from the pin center to the top of the piston, the dome shape, the skirt configuration, etc, etc, etc.
But it would be fun to have one example of each on hand, plus a set of calipers to play with, yes?
If all the stars aligned, perhaps a set of real low miles 929 pistons, a set of rings, a couple of new gaskets, and a trip to the machine shop later, and voila! (or maybe not?)
Discuss......
One Word....
NOS :goofy:
Now if you blow it up.... big bore kit.. :biggrin:
[image: View Post]steven113, on 10 February 2010 - 07:07 PM, said:
Has anyone ever ported and polished the heads on a 5th or 6th gen bike? It would seem that that would be the nect most reasonable step after the basic header,slippon,PC3, and depairing that most of us have done. It is supprising that no one has any data on this.
That's what I want to know. There have been three or four "how to make more power threads" and we keep speculating on this. Has anyone done it?
:fing02:
[image: View Post]Ryanme17, on 10 February 2010 - 10:47 PM, said:
[image: View Post]steven113, on 10 February 2010 - 07:07 PM, said:
Has anyone ever ported and polished the heads on a 5th or 6th gen bike? It would seem that that would be the nect most reasonable step after the basic header,slippon,PC3, and depairing that most of us have done. It is supprising that no one has any data on this.
That's what I want to know. There have been three or four "how to make more power threads" and we keep speculating on this. Has anyone done it?
In process :fing02:
http://www.vfrdiscus..._1
A member from another forum I frequent was very helpful to supply the following info on his 750 out to 837cc big-bore kit from TTS Performance in the UK. Unsure if will aid the quest but could useful none the less.
Red.
Quote
Here are all the details taken from the label on the box of my 837cc JE Pistons...
TTS PERFORMANCE ENGR LTD
ACCT 6916
CUSTOM ORDER
PO 5317
HONDA M/C 750cc VFR750
Bore 2.913
Comp Height .900
Forging 75M
Pin Dia .669
Pin Length 2.050
JE .050 Wire Locks
Dome .155
Top Ring .8mm
2nd Ring .8mm
Oil Ring 1.5mm
Piston weight 176
PART 150871
JOB 421787
I believe that these pistons are made by JE to a specification set by TTS Performance Engineering here in the UK.
I may be correct in saying that JE also offer another set to their own spec, but I may be mistaken - Havn't checked their website.
More useful might be to find out if they'd make you some sets of 870cc pistons to Dynamo Humm's spec, and if not, who owns that spec now (following the demise of Picotte Performance--it's possible the spec did not go with the business Brian Law sold to Picotte). Having done two big bores (TTS), I would say it is an expensive route, so you may as well get the most cubes you can!
Ciao,
End of thread · 25 posts recovered Wayback Machine snapshot 17 Jun 2011