How To Make A Big Bang Engine With A VFR750

A video to show how to change the cam timing from standard and make a VFR750 a big bang engine.

[@Happy357mag]

Easily done on a V4! Thanks for sharing.

[@prawny12009]

With gear driven cams it is essential to align the silencing gear when tightening up the can bearing caps. If the gears jam you can snap the shaft

[@TheFlyingDuckTheory]

If you mesh the cam drive gears correctly, that will happen automatically.

[@lookingupwards8652]

This is very interesting when I’m all finished with it what will you do for me

[@vrossi2596]

I love this .. Seems simple enough to do as well, my 1990 rc36 has done 64k miles ..I'm sure she'll take it :)

[@TheFlyingDuckTheory]

This engine had similar miles on it when I did the conversion. It's a VFR it'll take it 🙂

[@vrossi2596]

@@TheFlyingDuckTheory yes, it's something to do and i just want to hear and feel it .. will certainly report back in the next week or 2. Ta

[@TheFlyingDuckTheory]

Please do. I like to hear how other people find the differences and which configuration they prefer.

[@vrossi2596]

@@TheFlyingDuckTheory i would like to ask tho, is cam reversal all that needs to be done? Nothing else, as in plug caps etc .. why isn't this more commonly done ? So intriguing .. ta

[@TheFlyingDuckTheory]

That is all you need to do. The way the ignition system is set up takes care of timing so you can leave everything else alone. It does make for a more aggressive feel to the engine and in all honesty, Honda made this bike to be a sports tourer. To that end, it does what it needs to to satisfy that role as standard. I like to explore different possibilities which is why I tried the big bang.

[@Chickendave344]

My mate has done this on is sounds a right beast going on Dyno soon see what difference is

[@xavlamela9055]

Do you have any news about that dyno run ?

[@mickleblade]

Fireblade motors have those numbers cast into the metal now.

[@TheFlyingDuckTheory]

It does make things so much easier.

[@pmncoelho]

Thank you for sharing, but... How do you manage the spark timing for the new ignition order ? Thank you

[@TheFlyingDuckTheory]

Hey, no worries. The spark timing is taken care of by the fact it is a wasted spark system so what was the unused spark automatically becomes the ignition spark.

[@BRIMATH1927]

Buenas tardes hablo desde Venezuela me gusta tu vídeo. Soy un amante de las motos de alta cilindrada. Quisiera que me ayudarás con una moto similar con respecto a la puesta de tiempo. Es un proyecto y solo falta ponerla a tiempo.

[@potheadpixi]

Presumably you could get the same result by moving the front cylinder cams by 180 degrees from their respective TDC and leaving the rear standard setting ?

[@TheFlyingDuckTheory]

Possibly but as I haven't tried it, I cannot confirm that would work.

[@fsjake]

hey, love the idea of this and debating doing it myself, just wanna confirm everything before hearing a dreaded crunch lol, your simply rotating both inlet and exhaust cams for the rear cylinder head by 180? dont do anything to the front cylinder head cams ?

[@TheFlyingDuckTheory]

Exactly that. Turn the engine over a couple of times slowly by hand to make sure you have the cams in correctly before firing it up.

[@andrewlee9090]

Did you do it fsjake? How did it go?

[@xavlamela9055]

Hy flyingduck, really good finding ! I shall try this one day, , but I just want to know if we need to do the same operation to the rear cylinder bank ? Or just the front as in the video shown ?

[@TheFlyingDuckTheory]

Hi. It's the other way round. You only change the rear cams, NOT the front ones.

[@xavlamela9055]

@@TheFlyingDuckTheory wow thanks for the insight, would love to have a sound video other than the one were your team is drag racing it, to hear what we could actually expect :) Does it sound more like a RC45 ?

[@TheFlyingDuckTheory]

@@xavlamela9055 I can't say if it sounds like an RC45 as I've never actually heard one in the flesh. It does sound angry though 👍

[@xavlamela9055]

@@TheFlyingDuckTheory I need to try this hahaha

[@TheFlyingDuckTheory]

@@xavlamela9055 go for it 👍

[@hamahama3578]

great video . I opened the other part of the engine and could not install the gears. If you can show us another video of the second part of the engine, thank you

[@TheFlyingDuckTheory]

You only need to change the rear bank of cams so I don't understand what you are asking?

[@hamahama3578]

I don't know English very well. The engine contains 4 cylinders, you modified 2 cylinders. I want to modify 4 cylinders because I disassembled the engine and forgot how to install it, do you understand me?

[@TheFlyingDuckTheory]

@@hamahama3578 ah, I see. I'm afraid you will need the manual for that as it is not something I have covered. It is not the same as installing the rear cams.

[@Anti-Static_Matt]

You my friend are a genius. Any chance of a video of it running?

[@TheFlyingDuckTheory]

kzbin.info/www/bejne/e6aYaHmQbrVqirc sorry for the delay in replying. KZbin is not giving me my notifications properly. Please have a look at the link above. There is another one from Henstridge I think which has the use of nitrous as well but again, youtube is also hiding my own videos from me.

[@Anti-Static_Matt]

TheFlyingDuckTheory Nice one, thank you. I’ll take a look 😊👍🏻

[@narfi666]

I was wondering what kind of exhaust headers you have? Did the conversion to mine and I now have a big flat spot around 7-8k rpm everything is looking good so Ian guessing the stock exhaust is somehow resonating weirdly with the new firing order. Sounds awesome thanks for the idea :D

[@TheFlyingDuckTheory]

My exhaust system is 38mm diameter whereas standard and aftermarket ones are 35mm. This may have some effect. On the road bike I had a 4 into 4 system (38mm). There was always a hesitation before it came onto the cam so I just dropped a gear if I needed to get past that quickly. My race bike was never affected by it (4 into 2) but I did a fair bit of carb tuning on it.

[@narfi666]

@@TheFlyingDuckTheory Out of curiosity wich cylinder did you pair together?

[@TheFlyingDuckTheory]

@@narfi666 the two fronts together (2 & 4) and the two rear (1 & 3 )

[@leondavibe]

@@TheFlyingDuckTheory the cam lobes are apposing so rotating the cam you rotate both so you actually caused 1/2 to fire closer instead of 2/3 And Moved 3/4 instead of 1/4 closer You can't affect 1 without affecting its siblings that use the sane cam So 1 is know your 3 and 3 your 1 This is a duffus modification The exhaust will sound different as the gases move different and the balance is affected so imbalance is perceived as big bang this is so funny

[@leondavibe]

@@TheFlyingDuckTheory1/3 is on the same cam the only way they can fire together is if you cut and reweld the cam. The same with 2/4

[@RottenMatter]

Can you make a video on the correct timing positions on the rc36 1990

[@TheFlyingDuckTheory]

If you mean the standard cam settings, they are shown at the beginning of the video.

[@andrestefanowicz4486]

Thinking of trying this with my 1991 VFR750. How did you come up with this procedure?

[@TheFlyingDuckTheory]

I heard someone else mention that someone somewhere else had done it a long while ago. There was very little information available but the essential part was there so I gave it a go.

[@francescodalba7195]

Great man! There some difference on max power or torque?

[@TheFlyingDuckTheory]

It doesn't change the amount of horsepower or torque, just the way it delivers it. It feels punchier away from traffic lights and outcof corners. And on a decent end can sounds evil.

[@Timbo_tango]

Under max acceleration will this place excessive load and stress on the Crank shaft?

[@TheFlyingDuckTheory]

I had no trouble with it whilst it was in the big bang configuration. The crank is quite narrow so it can deal with any extra forces well enough.

[@danmadsen5604]

does this offer up any power gains in any way or is it just to get a more even grip on the rear tyre?

[@TheFlyingDuckTheory]

There are no power gains but it does change the way the power is delivered. It helps the tyre dig in when accelerating for better drive away from traffic lights and out of corners.

[@blackandwhitejazz]

Have you considered installing a 360 crank?

[@TheFlyingDuckTheory]

No. I like the sound of the 180 and the big bang derivative. The 360 to me just sounds like an inline 4 and I'm not a fan.

[@kalenjerome8913]

Hey guys love the video just tell me if I’m wrong but since the cans move 1/2 crank speed you moving the cams exactly 180 would seem to me to make no change at all in the cam timing, the dots in the middle still align at tdc mark on crank? No?

[@TheFlyingDuckTheory]

The cam marks do still align on the cylinder head but on the opposite side, at 3 0'clock instead of 9 o'clock kind of thing.

[@molak34]

You change the timing between one bank of cylinders and the other..

[@kalenjerome8913]

Ok gotcha, thank you. I just got a 97’ vfr750 w the gear driven cams, would the same timing change be necessary on this engine? I know the bike is meant more race oriented than the magna so maybe the engineers already did this to the vff series? Thanks -k

[@TheFlyingDuckTheory]

@@kalenjerome8913 I don't see why it wouldn't work on a 97 but as with all things, I can only confirm that which I have tried. Everything else is theory.

[@matthewglaze5398]

Is this changing the motor to fire 2 pistons at a time? I am unfamiliar with the big bang setups purpose.

[@TheFlyingDuckTheory]

No. It makes the firing order happen in quick succession rather than spaced out as per standard. The purpose is to give a better drive out of corners, better torque delivery away from traffic lights (if that is your thing) and less fatigue on the tyre because it is getting a 'rest' between the ignition sequences. It sounds evil too. 👍😁

[@matthewglaze5398]

@@TheFlyingDuckTheory thanks for the info. I have a 91 vfr that I love the way it is. But maybe one day if I get bored I'll give this a shot.

[@sidewaysaction9983]

Would it work on the vfr800i ? Same plug lead allocation?

[@TheFlyingDuckTheory]

I have absolutely no idea. I would guess no as being fuel injected there are sensors to dictate when fuel is added so all the timings would be wrong. It is possible you could change all that but without a lot of research, I honestly couldn't say.

[@blackandwhitejazz]

The stock firing order, with degrees of interval, is: 1--180°--3--270°--2--180°--4--90° The stock firing order, with the firing points, is: 1 @ 0° -- 3 @ 180° -- 2 @ 450° -- 4 @ 630° So your mod changes the firing intervals to: 1--90°--2--90°--3--90°--4--450° and the firing points to: 1 @ 0° -- 2 @ 90° -- 3 @ 180° -- 4 @ 270° Right? The wiki page on big bang firing order en.wikipedia.org/wiki/Big-bang_firing_order has the 2017- Honda RC213V as an example of a bike with your firing order.

[@TheFlyingDuckTheory]

As far as I worked out, yes. 90° between firing intervals and 270° after no 4.

[@blackandwhitejazz]

@@TheFlyingDuckTheory OK, I just added the Langdon Honda VFR750 to the Wikipedia page for big bang firing order.

[@blackandwhitejazz]

@@TheFlyingDuckTheory You're mixing apples and oranges. It's 90 degrees of interval between the firing POINTS, except between 4 and 1 (i.e., after no. 4), where there's 450 degrees of interval after no. 4 fires and before no. 1 fires. There isn't 270 degrees of interval AFTER No. 4 fires. Rather, no. 4 fires AT 270 degrees.

[@TheFlyingDuckTheory]

@@blackandwhitejazz yep, sorry, confusion on my part. I knew it was 90° between each from 1-4, after 4 I hadn't really thought too much about it and the 270 number was stuck in my head for some unknown reason.

[@blackandwhitejazz]

@@TheFlyingDuckTheory I just realized that on the Wikipedia page for Big-bang firing order, in the Four-cylinder section, subsection 90° V4 "Big bang," the only other entry besides yours is the 2017- Honda RC213V. You've found a very inexpensive way to make a GP replica!

[@andrewlee9090]

Silly question are you changing the timing on all 4 cams? All 4 turned 180?

[@TheFlyingDuckTheory]

Not a silly question at all. But no, as that would just put the standard spacing back in the ignition timing. Just turn the rear bank (two) camshafts and that's all.

[@andrewlee9090]

@@TheFlyingDuckTheory cheers, going in to do my valve clearances soon, i may do this then. have you encountered any problems yet? has it changed the reliability of the motor on yours at all?

[@TheFlyingDuckTheory]

@@andrewlee9090 for as long as I was running it, it was fine. The VFR crank is very strong.

[@MrGuliko]

What will this change? How much torque/hp gain?

[@TheFlyingDuckTheory]

It changes the firing order and brings the ignition sequences closer together but then leaves a bigger gap between the last ignition of one sequence and the first ignition of the next. It doesn't change hp or torque values, it changes the way it is applied. The idea is to allow the rear tyre to grip better under hard acceleration.

[@bp-d8264]

Are you using stock pistons with the blower? Looking to do something similar

[@TheFlyingDuckTheory]

Yes. Unfortunately, there isn't anything available off the shelf to replace them with for this model.

[@bp-d8264]

@@TheFlyingDuckTheory I'm finding out that quite rapidly. I have contacted dp pistons, and it's close to £1500 for kit

[@TheFlyingDuckTheory]

@@bp-d8264 ouch!

[@simongroot7147]

@@TheFlyingDuckTheory You can use CBR 900rr pistons. 92 to 95 are 70mm bore, 919 (96 to 99) are 71mm bore so you get the chance to over bore the cylinders for wear. The are the same pin height to crown but they are flat topped.

[@TheFlyingDuckTheory]

@@simongroot7147 if the 92 to 95 pistons are the same dimensions except for having flat tops, that would be an advantage as lowering compression would be a bonus on the race bike. Unfortunately, I cannot use the later (919) pistons as that would take me over the class capacity limit and into the next class up which is not where we want to be at this time.

[@RottenMatter]

Do you have a video of this running ?

[@TheFlyingDuckTheory]

kzbin.info/www/bejne/e6aYaHmQbrVqirc

[@RottenMatter]

@@TheFlyingDuckTheory hi chap do you have a way I can contact you as I have some questions on the rc36 engine as mines in the correct positions and getting fuel,spark and compression but still not firing just back fires through the exhaust

[@TheFlyingDuckTheory]

@@RottenMatter you can contact me through the messenger via Facebook, Team Flying Duck Theory Motorcycle Sprint Racing.

[@junzunft2060]

Correct me if I'm wrong but if the original firing order is 1-3-2-4 (0-180-450-630-720/0 degrees) then doing this would make the new firing order be 1-2-3-4, each cylinder firing every 90 degrees then a full 360 degrees of the crank with nothing and starts again (-----------------360-450-540-630----------------). I would love to see this run but not sure how well.

[@TheFlyingDuckTheory]

It runs and pretty good too. See the video .. kzbin.info/www/bejne/e6aYaHmQbrVqirc

[@junzunft2060]

@@TheFlyingDuckTheory Sounds great but is this a sprint only bike. I thought I heard you say the torque delivery is great for the track as in out of corners.

[@TheFlyingDuckTheory]

@@junzunft2060 this is a sprint bike but an acquaintance did the conversion on his track bike.

[@NovatoCustom]

What about ignition timing and firing order? Isn't it affected?

[@TheFlyingDuckTheory]

Yes, that the point. It brings the ignition events closer together in an even pattern which is what defines it as a big bang. Instead of 1-3-2-4, it will then be 1-2-3-4.

[@NovatoCustom]

@@TheFlyingDuckTheory I understood the point, I was talking about the ignition itself only, you couldn't do that on an 800 without a custom ECU, I reckon?

[@TheFlyingDuckTheory]

@NovatoCustom no, you couldn't. The 750 is lucky in that it runs catbs so nothing the change there and as it runs a wasted spark system there is nothing to change there either. The 800 running fuel injection needs the timing for that changing and possibly the ignition timing (I don't know if it runs a wasted spark) neither of which you can do on a standard ecu so you are correct.

[@roy7602]

Do you only change the front cylinder bank, or also the rear in the same way? And really no changes to the ignition system, is it really "that" simple?

[@TheFlyingDuckTheory]

You only change the rear bank of cams, NOT the front. The ignition is a wasted spark system which makes it really 'that' simple.

[@roy7602]

@@TheFlyingDuckTheory Damn, that is unbelievable. It's alsmost as if honda made it so easy intentionally. I guess this works on the RC36/2 as well, basically for all gear driven carbed VFRs?

[@TheFlyingDuckTheory]

@@roy7602 I honestly couldn't say. I would assume so but not having done it on a 36-2 I'd only be guessing. It didn't work on my RC24 though. Don't know why but it didn't like it at all.

[@roy7602]

@@TheFlyingDuckTheory alright, gotcha! Thanks for taking the time to get back to me, man!

[@helloslayer666]

@@TheFlyingDuckTheory cause RC24 have a cam sensor, and they making impulse for ECU. May be ECU making wrong ignition timing, on this bigbang mode

[@andrewlee9090]

Andrew, I would like to contact you about this, is there a way I can email / phone you?

[@TheFlyingDuckTheory]

If you are on Facebook, look up Team Flying Duck Theory Motorcycle Sprint Racing. You can message me through that. 👍

[@TheFlyingDuckTheory]

Andrew did you contact me as facebook notified me of a mention but have no actual message or details?

[@JPSporTT]

Works on the 800 Rc46??

[@TheFlyingDuckTheory]

That's where I first saw it done to a VFR. Look up supercharged VFR on KZbin.

[@pecoraropeppino3169]

have you tried to change the carburetor rail? guaranteed power gain!

[@TheFlyingDuckTheory]

Change it to what?

[@molak34]

@@TheFlyingDuckTheory EFI ?¿

[@TheFlyingDuckTheory]

@@molak34 no. Modified standard carburettors.

[@molak34]

@@TheFlyingDuckTheory meant to change the carburators for EFI . I'm switching my uncle's vrf750f rc24 to EFI

[@TheFlyingDuckTheory]

@@molak34 I have a plan to do that sometime in the future but I have targets to achieve in the meantime with carbs. I would be interested to see how you do it though.

[@fouedbaccar9555]

Alors là aucune idée, ça doit être possible mais avec pas mal d’adaptations, par ce que le cadre du vfr800 est bien différent du 750

[@TheFlyingDuckTheory]

Hi, sorry I don't speak French and the translator doesn't seem to make complete sense. If I understand correctly, the frame makes no difference as all changes happen inside the engine. I have no idea whether it would work on the 800. It might if it has a wasted spark ignition system but I cannot claim that to be the case.

[@Anti-Static_Matt]

Is it firing 1-4 2-3 now?

[@TheFlyingDuckTheory]

To be honest I haven't tried to work that out yet.

[@johanqq]

Stock is 1-3 4-2 So most be 3-1 4-2 now right ?

[@johanqq]

Okay and then he change it to 3-1-2-4 ?

[@buni7340]

I like crazy english people for this kind of ideas))

[@ElMyggo]

Your video inspired me to fix my modified lawnmower with VFR750 engine, check my channel for the testrun clip

[@TheFlyingDuckTheory]

Do you have a link?

[@thejdmguru621]

Well then lets hear a sound clip

[@TheFlyingDuckTheory]

If you go onto my uploaded videos, there is at least one onboard one there 👍

[@TheFlyingDuckTheory]

kzbin.info/www/bejne/e6aYaHmQbrVqirc

[@mickeymouse4897]

Yes this will defo change the valve timing 180 degrees & it'll still run, but it's defo not turning it into a so called "Big Bang" engine ... do some engineering research & you'll discover you'll need a "Cross Plane Crank" to achieve the generic "Big Bang" motor.👍

[@TheFlyingDuckTheory]

Considering the firing pulses are very much closer together than on a standard VFR, it's close enough to be called a big bang. It comes down to definition. And this ran pretty damn good. Look up the Henstridge Airfield big bang test video on my channel. Proof is in the pudding, as they say.

[@user-ic1kg1qj4b]

Очень интересно что он тут зделал и какой с этого толк?

[@TheFlyingDuckTheory]

I apologise but I am unable to translate your comment and therefore cannot give a response 😞

[@sts9567]

@@TheFlyingDuckTheory Тёма Басов says "Interesting what you have done, but what is the use?"

[@TheFlyingDuckTheory]

@@sts9567 it changes the character of the engine and the way the power is delivered. Very good for roads with tight corners.

[@blackandwhitejazz]

Have you listened to the 2022 RC213V? According to that Wikipedia page, in 2017 it was changed to 180 and 90-90-90-450, same as yours. But there have supposedly been big changes since then. Have a listen. Does the 2022 model sound like yours? kzbin.info/www/bejne/ZmWcg6J3rM13hKc

[@TheFlyingDuckTheory]

Can't say that I have. I'll look on KZbin and see if I can find a video of it.

[@blackandwhitejazz]

@@TheFlyingDuckTheory Try searching: Day 1 Testing Misano|Marc marquez back on track

[@leondavibe]

i think this is BS yes you changed the firing order ie 1 will fire when 3 was suppose to and then 3 will fire when 1 was suppose to here (link below) is a reresentation of vfr (180 degree crank) firing instead of firing in a cross pattern now it will fire 2 on the left and 2 on the right, ie you just stuffed up the x balance a bit , it is impossible to get a big bang without taking the crank out cutting it and rewelding it in 360 fashion , that is according to stories where the rc30 comes from, a privateer team actually did this with a vfr750 and whipped the buts of the factory teams and then the RC30 was born or so the story goes kzbin.info/www/bejne/qou8f41-odOie5Y google the different cranks rc30 and other 360 variations you will see the two wide journels point the same direction and the 180 variations they point opposite directions it is techinically impossible to make a big bang by just rotating the cam that is exactly why we have wasted sparks ie 1/3 spark together but only one of them is on the ignition stroke and the other wasted , that is why the bike still runs when you do this since you just moved the ignition stroke to the wasted one and the wasted one to the ignition stroke also adding the 360 big bang notice how the two cylinders fire so close together and then nothing for a while because of the way the crank is built the 1/4 fire close together and the the crank has to go all the way around before those 2 can fire again hence the big bang, same applies to 2/3 kzbin.info/www/bejne/Z2KTqmuLa7OIq9E

[@TheFlyingDuckTheory]

2+2 =4, so does 1+3, so does 0+4. There is more than one way to create a big bang engine. Simply, given the fact that the RC36 is a 180 degree crank as opposed to a 360, there's no need to cut it up and reweld it, it already lends itself to the configuration. The ignition pulses are brought to 90° intervals the way I did it, with a firing order of 1-2-3-4. I don't know what the RC30 spacing/firing order is but I'm willing to guess it isn't any closer than what I've done. So you can call it whatever you like but you'd still be wrong.

[@leondavibe]

@@TheFlyingDuckTheory i don't get what you think you are doing, the firing order is already 90 apart swapping one bang for another doesn't create a big bang ie you don't create a dead spot by rotating the cam on 180 you just swap which one is ignition stroke ie you swopped 3for 1 and 1for 3 Moving when the bangs can happen creates a big bang Rc30 2 cylinders fires close together ie the cylinder 3 fires then as that journal reaches top om 2/4 90 later, 4 fires then because the crank is 360 On the next 90 there is no piston that is tdc the next one will only be tdc again 270 later , thus the bangs have been moved creating what is regarded as big bang because longer break Ie the cams follows the crank if you want to change bangs or the space inbetween you must change the crank

[@TheFlyingDuckTheory]

​@leondavibe there is so much wrong with that comment, I'm not even going to bother trying to explain it to you.

[@leondavibe]

@@TheFlyingDuckTheory yea we both made mistakes There isn't a spark every 90 there is a piston tdc every 90 napkin math dumb mistake it will only fire every 2nd time it gets there though, and i had the order wrong 1/4 follows closely and 3/2 on the next crank rotation Now yes i get you think you spaced the bang by 180 by rotating the cam 180 but the cam makes one rotation while crank does two so technically you just swopped the strokes of the two pistons And thus the combustion stroke is still happening just on a different cylinder Ie spark/ignition is happening when that cam rocks wether it is on piston 1 or piston 3 it happens so the bang characteristics hasn't changed at all You just messed with the balance for no gain

[@TheFlyingDuckTheory]

​@@leondavibe​@leondavibe I haven't made any mistakes. I have changed the firing order by utilising the wasted spark system. That's what make this work. Rotating the cams moves the original ignition events of cylinders 1 and 3 to what would have been the exhaust stroke so that it is now the compression/ignition stroke. It subsequently changes the firing order to bring the ignition events closer together in a regular 90° crank rotation pattern. It's as simple as that. Big bang doesn't mean all the cylinders ignite at the same time. It can, but it doesn't have to. In this case it just means there is a significantly short ignition sequence compared to a much larger non ignition period. As for no gain, you have never ridden a VFR with this configuration so how would you know? Stop speculating, ignorance is not a good look.