Racerboy Posted October 9, 2012 Share Posted October 9, 2012 Hi, Has anyone else got any dyno graphs for comparison? VFR750FV 1997 VFR750FK Link to comment Share on other sites More sharing options...
Member Contributer Dutchy Posted October 9, 2012 Member Contributer Share Posted October 9, 2012 top end speed 174mph on a VFR750F with 100 horses? The highest I got (GPS) was some 145mph.... Link to comment Share on other sites More sharing options...
Member Contributer slowbird Posted October 10, 2012 Member Contributer Share Posted October 10, 2012 90.35 RWHP Mods: PAIR Removal Slip On Can. Can you guys post your modifications too? Interested to see where the big difference is. Wow. Even the power curves are wayy off. That first one has a big drop at the start! Link to comment Share on other sites More sharing options...
Racerboy Posted October 10, 2012 Author Share Posted October 10, 2012 top end speed 174mph on a VFR750F with 100 horses? The highest I got (GPS) was some 145mph.... Thats with no load against the red line, subtract about 10% said the operator. Have seen 160mph on the speedo so probably 155mph, the 86 VFR's did 152mph out of the box. You need to make them breath, rip out the stupid snorkel its only there to pass the noise tests but it restrics the carbs. Next stage on the FK (89) is to put the tuned motor together. Link to comment Share on other sites More sharing options...
Member Contributer YoshiHNS Posted October 10, 2012 Member Contributer Share Posted October 10, 2012 You need to make them breath, rip out the stupid snorkel its only there to pass the noise tests but it restrics the carbs Not sure about it being there to pass the noise test. It doesn't get THAT much louder without it. I thought it was there to tune the airflow into the box to match the pulse of the desired air intake at mid-revs. Not all that different of a function than the velocity stacks. What else did you do to it? Or maybe your bike was put together with more love and has some more power on it. Don't get picks at work, but what was done to the FK motor? Link to comment Share on other sites More sharing options...
Racerboy Posted October 10, 2012 Author Share Posted October 10, 2012 The induction noise is quite loud without the snorkel and it also has foam inside to absorb the noise, My RC30 has a foam dome filter and no airbox, the intake is as loud as the exhaust when riding it. The FK has nothing else at this stage, the pictures are some heads which have just been gas flowed but not tried yet. The next job is to skim the cylinder block to get the compression up from a measured 9.6:1 to +11:1 Link to comment Share on other sites More sharing options...
NakedViffer Posted October 10, 2012 Share Posted October 10, 2012 You wanna deck down 1.4 points worth of compression? Thats quite a bit.. And you may have already considered this but, I'd be seriously concerned about critical clearances for piston to valve, and also your clearances for your cam drive gears. While also allowing for heat expansion. The valves I'm not clear on.. But in theory, the factory wouldn't have those cam drive sprockets meshed very loose, so I would expect to see some interference there. I would also be concerned with the amount of decking possibly biting into your valve seat area. You should just make a casting of your combustion chamber with devcon and have JE forge you some custom slugs. EDIT: I noticed now that you said deck the block, so valve seat area won't be a problem. Link to comment Share on other sites More sharing options...
Racerboy Posted October 11, 2012 Author Share Posted October 11, 2012 You wanna deck down 1.4 points worth of compression? Thats quite a bit.. And you may have already considered this but, I'd be seriously concerned about critical clearances for piston to valve, and also your clearances for your cam drive gears. While also allowing for heat expansion. The valves I'm not clear on.. But in theory, the factory wouldn't have those cam drive sprockets meshed very loose, so I would expect to see some interference there. I would also be concerned with the amount of decking possibly biting into your valve seat area. You should just make a casting of your combustion chamber with devcon and have JE forge you some custom slugs. EDIT: I noticed now that you said deck the block, so valve seat area won't be a problem. Std compression is 9.6:1 not the quoted 10.5:1 which is too low for a performance engine so I have investigated ways of increasing to 11:1 to 12:1. the simplest way is to use 700 pistons which have a higher crown because Honda only changed the pistons, stroke and rod length, the 700 heads are same as 750 therefore the compression would be too low hence the domed crown. Problem is that this is a very bad shape for the flame front to get a complete burn, the best shape is a flat top. The pistons on a 750 at TDC are 0.035" short of the top of the cylinder plus the gasket is 0.059", and the compression gain is greater by removing metal here due to the dia being larger than in the head. I will probably use 0.030 - 0.040 squish for safety. Speaking to Tony Scott (engine tuner for HRC in the RC30 era) he runs 0.024" (head gasket thickness) squish clearance, this is tight but ok on a regularly rebuilt race engine You are right about the cam gears but fortunately on RC24 engines the cams run in separate cam carriers like and RC30 and cam be shimmed up to the correct gear mesh. . PTV clearance is more of a problem as the std motor is very tight on the inlet valves at 0.035” in places, however this is on opening so the valve is under positive control unlike closing which is reliant on the valve springs.. Will have to machine the valve pockets slightly deeper to overcome the clearance issue. Link to comment Share on other sites More sharing options...
Member Contributer slowbird Posted October 11, 2012 Member Contributer Share Posted October 11, 2012 Degression! Link to comment Share on other sites More sharing options...
Racerboy Posted October 11, 2012 Author Share Posted October 11, 2012 OUCH! Bye x Link to comment Share on other sites More sharing options...
Member Contributer YoshiHNS Posted October 11, 2012 Member Contributer Share Posted October 11, 2012 So was Tony's solution to run a thinner head gasket to get compression up, or did they do some machining as well? Link to comment Share on other sites More sharing options...
Racerboy Posted October 11, 2012 Author Share Posted October 11, 2012 Std gasket and machine top of cylinder block. The std engines are designed to run on unleaded so they are low on compression and a tight squish isnt so important. Better carry on in the 1st generation forum or I will be in trouble. LOL http://www.bikersoracle.com/vfr/forum/showthread.php?t=119524&page=4 Link to comment Share on other sites More sharing options...
Member Contributer YoshiHNS Posted October 11, 2012 Member Contributer Share Posted October 11, 2012 Read through that other thread. Guess as a sort of reference, someone from Germany posted here about his highly modified 94-97. Bored engine with redone cams with custom exhaust among other things. Was a bit above 120HP. Don't remember a torque figure, but it improved. Link to comment Share on other sites More sharing options...
Member Contributer kgsmotorcycles Posted October 11, 2012 Member Contributer Share Posted October 11, 2012 Heres a run from my 92 some years ago.. 93 horses was about as good as it got with a race can with a K and N filter only. I do notice the dip around 4/5000 was partially eliminated once i added a race can, as i had a previous fully standard bike run.(no idea where that dyno sheet has gone?) Will get my latest 96 on the dyno at some point as there are a lot more rotating weight items with air box mods to gauge. Would love to get things jetted also... have a 3rd gen jet kit here, not sure would suit the 4th gen. Then again have been informed the earlier kit needles were not great for the carbs? Be nice to see if the change in ignition has any effect also. sooo, without the relevant cam carriers its a no go on the 4th gens? :-( At least the porting is accessible if i ever get the exhaust off soon... I do remember looking at suspect weld on the exhaust ports :-/ Would these mods not accompany/suit a big bore as well, especially as so much work has gone into the engine already? How would simply loosing a good few kilo from the bike itself effect performance on a mildly tuned engine, compared with the gain of a few horses from the engine alone? Good work chaps, be great too see how things pan out once the 89 has been rebuilt. Link to comment Share on other sites More sharing options...
Racerboy Posted October 11, 2012 Author Share Posted October 11, 2012 Heres a run from my 92 some years ago.. 93 horses was about as good as it got with a race can and a K&N filter alone. I do notice the dip around 4/5000 was partially eliminated once i added a race can, as i had a previous fully standard bike run.(no dyno sheet am afraid) Will get my latest 96 on the dyno at some point as there are a lot more rotating weight items with air box mods to gauge. Would love to get things jetted up also... have a 3rd gen jet kit here, not sure would suit the 4th gen. Then again have been informed told the earlier kits were not good for the carbs? sooo, without the relevant cam carriers its a no go on the 4th gens? :-( At least the porting is accessible if i ever get the exhaust off soon... I do remember looking at suspect weld on the exhaust ports :-/ Would these mods not accompany/suit a big bore as well, especially as so much work has gone into the engine already? How would simply loosing a good few kilo from the bike itself effect performance on a mildly tuned engine, compared with the gain of a few horses from the engine alone? Good work chaps, be great too see how things pan out once the 89 has been rebuilt. No cant skim 3rd or 4th gen models, only different pistons or weld the heads up I was thinking about a big bore for the other bike 74mm 929 pistons Difficult to gauge performance of power vs weight, Thunder bikes run a weigh to hp limit to even up the racing. I alway thought it odd that all car an Kart racing have a minimum weight including driver but bikes dont? http://www.thunderbike.org.uk/rules_overview.php Link to comment Share on other sites More sharing options...
Member Contributer kgsmotorcycles Posted October 11, 2012 Member Contributer Share Posted October 11, 2012 Thanks for the Thunderbike series link, as my friend who runs a vtr1000 keeps trying to get me to join him. But i dont think my vfr750f is competitive enough. Am still dialing in the suspension, hoping to work it better. Might just be im a pants track rider... a quick dispatch road rider is a very different thing altogether! lol.. Traveling from the isle of man is a real mission especially as the boat discount for racers is not as great as it should be. Will see how things go. Just looked at your thread on the vfroracle site mentioning the rs125 and 45 hp will run rings around all with the weight next to nothing. How true that is after my last track outing left me long behind such a machine.. My excuse is that session was mainly for testing new fitted components and learning the local track again after new tarmac patches. Without the use of tyre warmers its a waste of time even trying to compete with any hot machine. The VFR-F hits the 'under 105hp' limit no problem so would have hoped to reach class1, but the regs read -VFR 750F up to and including 1999 , class 2. Which is the Extreme class up to 130 horses among RC45's and 996's no less. The rc30 hits either class 1 or 2 for some reason? I can only guess either standard or TT ready?.... A TTS bore kit might be the cheapest way to go, especially if there is a lack of engineering tools to hand? A fresh weight in and a dyno test is imminent... i may be under weight.. Link to comment Share on other sites More sharing options...
Member Contributer slowbird Posted October 19, 2012 Member Contributer Share Posted October 19, 2012 This Thread is a mess. All these random Dyno sheets posted with no info. How can other VFR members benefit from this thread if people aren't posting their Dyno sheets with info on their Bike and what mods have been done to them? Link to comment Share on other sites More sharing options...
Racerboy Posted October 19, 2012 Author Share Posted October 19, 2012 OK Slowbird, 97 FV - 102hp (see earlier graphs) K&N Filter Removed snorkel Viper high level can Stainless replacement headers (make unknown) 86 FG - 100hp (89 FK engine) No airbox lid Std filter Rubber bellmouths shortened and FL aluminium bellmouths shortened and inserted into rubbers Jets #136 Std headers with welds inside flange removed Motad link pipes Viper can Neoprene heat shield under carbs Heat shield above radiator trimmed with HRC style ram air inlet duct made of Plasticard Barnet Clutch springs Link to comment Share on other sites More sharing options...
Member Contributer Dutchy Posted October 19, 2012 Member Contributer Share Posted October 19, 2012 standard 1997 with a Akrapovic slip on. no rejetting. Link to comment Share on other sites More sharing options...
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