Real answers about converting f75-f90 please?

[boscoe99]

I don't think that an "expert" would make a partial half ass modification to a motor without fully understanding it.

Sounds like you got away with it. What about the next guy that follows your ill advised lead and does not get away with it?

[rodbolt17]

so much of the previous story is BS it aint funny.
that motor should turn 6000 RPM out of the box if propped correctly.

that being said.

can someone post a part number of this mythical air restrictor ?

[99yam40]

we went through this with him before, I just gave up on posting to him.

But yes it is a shame this kind of stuff gets allowed on forums as it messes with some peoples way of thinking.

If some read it on the internet they believe it is true without any logical thought or proof

[boscoe99]

[QUOTE=rodbolt17;85707]so much of the previous story is BS it aint funny.
that motor should turn 6000 RPM out of the box if propped correctly.

that being said.

can someone post a part number of this mythical air restrictor ?[/QUOTE]

No. Because there isn't one.

[almetelo]

Hi!

In fact that part is not listed anywhere and acording the manual parts all 4 models F75_F80_F90_F100 EFI may have the same intake (have a look on attachment) maybe you Rod and Boscoe perhaps (for sure) handled with F75 and F90 EFI and can tell us if you checked that suposed air restrictor on F75 and not on F90 listed on the attachement pics. I know in US you dont have the F80 and F100 EFI but the principle should be the same used by some members to convert a F75 to F90.
My F100 is carbed so I've never seen it at all unless on the following pics but once again my opinion is that isn't possible without an ECU remap and like Rod so many times explained before with facts and knowledge, even without that suposed air restrictor on F90!

Yes, its possible on carbed models convert a F80 to F100 by changing the complete set of carburectors because everything else is the same (its not my opinion, is what manual parts show" never checked F75 vs F90 carbed carefully but must be the same") About a year ago I tought that just changing the jets would be enough to convert a F80 to a F100 but isn't because the F100 carb is large "have a large intake"

My closest experience with this was remove a plate on F50 EFI intake and the gain was minimal (100rpm and 1 kts) so I dont think it became on a F60 like many people claim and on my opinon dont worst the risk of damage something.

99yam40 I think the purpose of the foruns are also discuse this... but I admire your persistence because when someone doesn't want to understand it with logicians and theoretical arguments not only based on some experience is useless and I give up easily than you. In Portugal we have a saying that is something like this: "Is useless take the dunkey to the fount/spring if he doesn´t want to drink" (the translation may not be the best but this must be universal using other words) with due respect for all members.

After all we are free to think what ever we want and belive what ever is convenient for us...

I think is boring when we are talking all the time about the same things but would be even more boring if we didn´t discuse this...

[rodbolt17]

and the picture tells the story.
remove the air restrictor and with NO other ECU mapping all you get is extra air, no real power gains.
add air and you MUST add fuel.
same principle with adding an No2 (nitros oxide) kit.
as it combusts and the N02 releases the additional Oxygen then you MUST add fuel or bad,very bad, things happen.

unlike diesel which will burn from about 7-1 up to about 160-1 A/F, gasoline can only burn from about 15.5/1 to about 12.5/1 with 14.7/1 being optimal.

doesn't matter what you do, super duper turblow charge or whatever you still MUST have a gasoline to air ratio at about 14 parts air to 1 part gasoline or it simply cant go.

at the end of the day the articulated rod internal combustion engine running on gasoline works today just like it worked 100+ years ago.

suck, squeeze,bang and blow.

it aint me folks, its a simple physical law.

[99yam40]

It just gets to me that some people will just play with these things they do not understand or refuse to try to do the research before doing things. And the stuff some people post points them in the wrong direction.

Took me close to a year to finally figure out someone had drilled out the main jets in a C40 to try and make it a C50 I guess.
Finally replace with new ones and she is running as it should again. Running too rich at top end is a tough one to find when you are not looking for someone drilling out jets

[madharchod]

thanks Almetelo
at least you have posted the pictures for some to see as we in the pacific have lot of time to spend for free so we experiment with these things as we dont wear watch and time dosent mean money to us ,this pictures is from the carburated model but for EFi they have like a sieve type of plate and to my knowledge and experience the companies aint stupid to give part numbers of these plate so people will replace them, this is a company secret which i was not supposed to reveal when i worked for them ,now iam retired and enjoying i can at least say something
these parts are only put in the motors make them less hp and you remove them it becomes a higher hp .i have done it and there is no 2ways about it ,believe it or not ,it has been done and its democracy so everyone is entitled to their opinion
ch

[almetelo]

This pics are from a carbed model !?!?!?
I don't know what mods are you doing or you say you on F80/F90 do but this is EFI !!! If you have lot of experience like you say "working" on this motors how do you don´t know them???

The sieve plate is used on F50!

[boscoe99]

Is there a difference between a carbureted F50 and a fuel injected F50?

[almetelo]

Is your question if are diferences on between a F50 carbureted and a F50 EFI?
What do you mean?
On the intake?

[rodbolt17]

both make 50 HP at the propshaft at about 6000 RPM.
the difference is in how fuel is introduced to the cylinders.
carbs rely on air pressure.
EFI relys on pressure in the fuel rail and the ECU con*****ed injector on time.
injector on time is a calculated time the ECU opens the injector based on various inputs to the ECU concerning RPM,air density and throttle angle and some use an intake manifold pressure sensor to determine engine load as well.

which is why you cannot remove mythical air restictors and gain 15 HP.
cannot happen with a speed density EFI setup.

[madharchod]

to clear everyone's mind about this saga is iam talking about F80 to F100 DETl models and F75 to F90 detl models as i have done these models by removing the air restrictor and they work ,so if you haven't done it might as well not even comment on it as these things are company secrets ,to avoid costly economies of scale manufacturing .big companies do this without changing production lines for big profits is just by inserting this restrictions in for smaller hp and when mass producing they avoid putting these in ,this is from the horses mouth as i basically worked on these motors on assembly lines during production to testing and then marketing and became a technical expert
cheers,now iam enjoying my retirement
cheers

[boscoe99]

to clear everyone's mind about this saga is iam talking about F80 to F100 DETl models and F75 to F90 detl models as i have done these models by removing the air restrictor and they work ,so if you haven't done it might as well not even comment on it as these things are company secrets ,to avoid costly economies of scale manufacturing .big companies do this without changing production lines for big profits is just by inserting this restrictions in for smaller hp and when mass producing they avoid putting these in ,this is from the horses mouth as i basically worked on these motors on assembly lines during production to testing and then marketing and became a technical expert
cheers,now iam enjoying my retirement
cheers

What did you do for the CDI change?

[rodbolt17]

once again.
I call B S.
the F75 at 6000 RPM makes about 75 HP at the prop shaft while burning roughly 7.5 gallons of gas per hour.
the F90 at 6000 RPM makes about 90 HP at the propshaft while burning roughly 9 gallons of gas per hour.

the ECU CANNOT and WILL not add extra fuel based on a mythical resrictor.

the ecu does not monitor air flow.
to date all Yamaha EFI systems are speed density based NOT mass air flow based.

basically the engine is an air pump.
x amount of fuel must burn with X amount of air.
to much fuel and its rich and power suffers.
to much air and its lean and not only does power suffer but mechanical damage starts occurring due to the excessive heat generated by the lean burn.

google it if you don't belive the A/F ratios that gasoline burns at.
you will find its about 13.5/1 to about 15.5/1.

its a simple law of physics.

the F75/90 motors don't monitor O2 levels in the exhaust nor do they monitor mass air flow.
the ECU is mapped for that particular engines airbox and throttle valve size.

which is why I call BS.

you cannot tell me you just added air without adding fuel and made a magical 15 HP with air.