FJ1100 vs FJ1200

[Flying Scotsman]

Why do they show the 1100 and 1200 as making the same hp at the same rpm when the 1200 has bigger pistons more compresion and a more advanced ignition system.Logic would indicate that the 1200 has to make more power.The 1100 makes up for less power by being lighter and having less drag so they should be fairly equal in performance.Spec sheet shows the same hp for both motors at 125 bhp.
I just bought 1200 pistons and cylinders I plan on turning my 1100 into a 1200 and should make 120 hp at the rear wheel later when i get the head done.Not a lot of hp but more than I have now.

[Pat Conlon]

Peak horsepower does not tell the whole story. You need to look at a dyno sheet and look at the difference in the torque curve between the 1100 and 1200 engines. You will see more available torque, early in the rpm's, with the larger displacement motor.

For everyday street riding, more torque is a good thing....In fact so good, I'm gonna replace my 74mm pistons with these:


82mm Wiseco's; Yummy!

[Flying Scotsman]

Nice looking piston Pat.What comp are you going to run.What would you say the max comp would be that you could run on 93 octane pump gas without any detonation ?.I wouldnt mind buying 93 but I dont want to have to spend the extra $$ for 100 or 110 octane.My 99 GP1200 runs on 100 octane its got 155 psi  comp.(2 stroke)
I know the 1200 makes more low end torque but it has to make more peak power too.I have never ever raised displacement and or comp in any of my 2 smoke motors without making more torque and peak hp.Either way I am going from 1097 cc up to 1202 cc,that and a head port and  shave  should  be a big improvement.I am sure if you took a stock 1100 motor and a stock 1200 motor the 1200 will make more peak hp it might be at a lower rpm as well.
I do plan on going up to a 1250 or bigger  later as well when I can afford to do so.Got some other things to do first like a EKZZZ chain and a few other little things.

[Pat Conlon]

Yea, that's a big concern, compression ratio, especially here in Kalif where we can only get 91 octane piss water.
With a old school air cooled, carburetor'ed inline 4 motor, the highest compression I would run for the street on this piss water, would be ~10.5 to 1... I don't want to have to carry around cans of octane booster to add to the gas every time I fill up.

Of course the new water cooled fuel injected engines run 12 to 1 all day long with no problem. There is a Wiseco kit for FJ's that has 12 to 1 pistons, I don't know of anyone running these on their street FJ's. So in answer to your question I would opine that 10-11 to 1 would be the highest compression ratio I would feel safe to run on the street on our air cooled motors. Access to 93 octane is a plus.

Randy @ RPM is building my motor and he tells me that the new short skirt 82mm Wiseco's, left alone, stuffed into a FJ motor would have a compression ratio close to 14 to 1.....No good for the street.
So, he is shaving the crown down and then doing some work in the combustion area of the head, adding about 20cc's of volume to bring down the compression to ~10.5 to 1. A spin off benefit on this head work, will be unshrouding of the big valves going into the head.
Cheers!

[andyb]

The other key note is that's factory rated horsepower, so it's measured before losses on an engine dyno.  Really silly way to do things.  The reality is closer to around 102rwhp for the 1100 and 108 for the 1200 (depending on the dyno, air, and correction factors used).  Depending on where you find the numbers, the factory specs were 125 and 130hp respectively, though many places list both as 125.  On a FactoryPro dyno, the reading is more like 90 and 93 between the two.

Still seems strange that the engines were released in such a soft tune from the factory, for what was originally their top tier sportbike they left an awful lot of performance on the table.

The reality, by looking around this site a pinch, is that neither made enough power, and it's fortunate that it's an easy mill to improve dramatically

[Mark Olson]

Yea, that's a big concern, compression ratio, especially here in Kalif where we can only get 91 octane piss water.
With a old school air cooled, carburetor'ed inline 4 motor, the highest compression I would run for the street on this piss water, would be ~10.5 to 1... I don't want to have to carry around cans of octane booster to add to the gas every time I fill up.

Of course the new water cooled fuel injected engines run 12 to 1 all day long with no problem. There is a Wiseco kit for FJ's that has 12 to 1 pistons, I don't know of anyone running these on their street FJ's. So in answer to your question I would opine that 10-11 to 1 would be the highest compression ratio I would feel safe to run on the street on our air cooled motors. Access to 93 octane is a plus.

Randy @ RPM is building my motor and he tells me that the new short skirt 82mm Wiseco's, left alone, stuffed into a FJ motor would have a compression ratio close to 14 to 1.....No good for the street.
So, he is shaving the crown down and then doing some work in the combustion area of the head, adding about 20cc's of volume to bring down the compression to ~10.5 to 1. A spin off benefit on this head work, will be unshrouding of the big valves going into the head.
Cheers!

Umm , Father Pat,

I recall our first meeting at the petaluma rally over 5 yrs ago now where you preached the awesomeness of the fj engine and how it needed no improvement other than a jet kit.

you preached "spend your money on suspension and wheels and brakes because the engine has more than enough power".

I have done as thou hath commanded and am quite happy with the results. 

Is this a new commandment?  thou shall increase thy horsepower and torque with an overbore kit.


all kidding aside , what are the projected numbers after it is all done?

[Pat Conlon]

Umm , Father Pat,

I recall our first meeting at the petaluma rally over 5 yrs ago now where you preached the awesomeness of the fj engine and how it needed no improvement other than a jet kit.
you preached "spend your money on suspension and wheels and brakes because the engine has more than enough power".
I have done as thou hath commanded and am quite happy with the results.  

Yeppers, I clearly remember saying that, between mouthfuls of your most excellent cheeseburgers...What I didn't mention was that once you start down the modification road....well, you know the rest.
Question: What do you do when your suspension is done? Pipes and jets are nice but.....DAMN Frank Moore! It's ALL his fault.

....all kidding aside , what are the projected numbers after it is all done?

The engine will be tuned for torque. Other than the larger valves and some light blending, I'm leaving the intake ports alone. I do want to continue to run the CV36 carbs, what final jetting I don't know until we put the bike on the dyno with O2 sensors plugged in...
Final rwhp (as Andy correctly points out, depending on the type of dyno) should be around 130-140 but the torque numbers should be quite high around 105 to 110 ft.lbs of torque.   We shall see.....

After this I'm done. No kidding.

[Yamifj1200]

"After this I'm done. No kidding. "

Yea right... let me know how that works out for you... lol

Eric M

[Flying Scotsman]

Just got in from an hour on the bike.She is running good but I need more power and another gear would be nice.I got this email from the person I bought the 1200 cylinders from and it seems like a good base line to follow.

Dear 97red1200,

Hi,
First off, what's your first name?
You'll laove the change going to 1202cc will make with your bike.
It's the lmost dramatic difference that you can do to these bikes.
while you've got the head off, do a pocket port and have it milled at least .010" and put new valve seals in.
You then want the pistons as close to level with the top of the cylinder. Have it milled if needed to bring the pistons to .005" below the top of the cylinder.
slot your cam sprockets and degree the cams to 104 intake and 106 exhaust.
Jetted stock carb with a pipe and this setup will make 120 rear wheel HP, and aprox 85 lb/ft of torque.
You'll love it. Most of these bikes were so poorly tuned and low on compression that they made 90 RWHP.
The difference is phenominal

I can go bigger later 

[racerman_27410]

The engine will be tuned for torque. Other than the larger valves and some light blending, I'm leaving the intake ports alone. I do want to continue to run the CV36 carbs, what final jetting I don't know until we put the bike on the dyno with O2 sensors plugged in...
Final rwhp (as Andy correctly points out, depending on the type of dyno) should be around 130-140 but the torque numbers should be quite high around 105 to 110 ft.lbs of torque.   We shall see.....

After this I'm done. No kidding.

LOL.....I think you are going to wind up with just a bit more HP than that.

Depending on your current jetting you may actually have to lean the carbs out!

good move on just cleaning up the ports and de-shrouding the valves.

you 're gonna L O V E the torque! 

you have super nice hot rod ... it's the logical progression to have a hot rod engine !

KOokaloo!

[Flying Scotsman]

Cylinders and pistons had to go back they needed a sleeve.