Throttle body choice '88 FZR 1000

[Designer_Mike]

Will the fuel rail parts from the 750/1000 TB fit the injectors from the 600?
If so, that would make it easy. They are plastic junctions with orings and metal tube between (easy)....
The original 600 looks to be a solid casting with machined ports (not so easy)

I know the bodies on the 600 still come apart so that will be easy for spacing changes...but you are correct. I really don't want 45 psi gas spraying out onto a hot engine between my legs (call me silly I guess)

[tubular]

I am afraid I cannot give a definite answer to this. I assume (but assumption is the mother of all f**** ups) that suzuki uses injectors from the same manufacturer and same line but with different flow rate. So it will fit.

Also check the link I posted above. The guy is working on GSXR600 TBs but utilizing the fuel rail bits from a 750. The injectors are coming from the 600 and are perfect fit. At least this is my understanding.

[24c]

I'm with you tubular, the injector profile/fit will be the same, it just wouldn't make sense to change it.

[Designer_Mike]

Just looking at pics of the two different TBs the fuel rails are much different. I agree that I doubt the injectors would be any different on the connection so I SHOULD be able to take the rail off the 1000 and modify it to fit the 600 TB with my new spacing.
Time will tell

AH>...found a good photo and the way the rail bolts to the TB is completely different. It will take some extra mods for sure....damn...nothing is easy

[tubular]

...found a good photo and the way the rail bolts to the TB is completely different. It will take some extra mods for sure....damn...nothing is easy

and you'll probably need to fabricate some link extensions for linking the TBs, but you'll work it out... no doubt...

go on man, have fun!

[EWflyer]

I'd like to interject a little perspective into this throttlebody sizing discussion to help you understand what's been going on in the motorcycle industry over the last decade and why I believe it has created a bit of a confusing situation for those of us trying to pick the correct size of throttlebody for our project bikes.

I think you need to be realistic about whether you're building a "sport" bike or a "supersport" bike.

All the major motorcycle manufacturers are in an arms race to generate "showroom grade" horsepower for their Supersport bikes, which is what people (think they) want, even if they never use all of it or kill themselves with it when they do, and the manufacturers have engineering departments with the resources to deliver.

My project bike is a Kawasaki EX-250. It is a two cylinder engine, so each cylinder is 125cc. The EX-250 is a "Sport" bike not a "Supersport" bike and that distinction will make more sense in a few paragraphs......

The European Kawasaki EX-250 is fuel injected and it uses 28mm bores in its throttlebody. So that's a 28mm bore on a 125cc cylinder. The Kawasaki Ninja 650R is also a two cylinder engine and is also in Kawasaki's "Sport" category. The Ninja 650R uses 38mm bores in its throttlebody. So that's a 38mm bore on a 325cc cylinder. The industry views both of these bikes as "Sport" rather than "Supersport."

Now let's move up into Kawasaki's "Supersport" world. When you go up to their "Supersport" level the ratio of throttlebody size to cylinder size goes crazy. As an example, the ZX-6R uses 38mm bores on its 150cc cylinders. Obviously Kawasaki can make this combination work, it's a huge seller in the 600cc market, but it takes some real careful engineering to pull it off. The ZX-6R has a very technically advanced airbox, it also has a set of ECU-controlled butterflies in its throttlebody and it has an exhaust system that the sales brochure describes as "contributing to superb low and mid-range performance while maintaining high-RPM performance." If it didn't have these features it wouldn't idle and it would stall when you gave it throttle from idle or low RPMs (off-idle response).

Let's compare the Kawasaki Ninja 650R to the ZX-6R. They both have a 38mm throttlebody bore and the Ninja 650R's cylinder displacement is over two times the size of the ZX-6R's cylinders. Do you think the Kawasaki engineers had to perform some serious magic to get that bike to idle and respond well in low RPM conditions? Are you capable of replicating their efforts on your XJ-700 engine?

If you look at the throttlebodies that Honda/Suzuki/Yamaha/Kawasaki are using on their "Supersport" class bikes you'll see that when you go "oversize" on the throttlebody bores you have to put in a set of ECU-controlled secondary butterflies (although some of the earlier FI bikes actually used vacuum-controlled slides just like you find on carbs) and you have to have an advanced intake and exhaust system. Really big throttlebody bores (oversized for the cylinder) are great for making insane levels of horsepower when the engine is at high RPMs, but they're a real big problem at idle or coming up out of idle RPM or when you roll on power down low in the engine's RPM range, which is why these bikes all employ high-dollar engineering technology like variable/multiple intake tracts, variable airbox volumes, more than one injector per cylinder, and valves/flow trickery in the exhaust tract.

Yes, if you do a little research on the Kawasaki "Sport" level bikes (EX-250 and Ninja 650R) you will find that they also have ECU-controlled secondary throttlebody butterflies. But the truth about these sport level bikes is that they don't really need them. I did some research both before and during my project and eventually managed to correspond by email with a Kawasaki engineer who simply said it has become "standard practice" to have secondaries on every fuel injection system so they just don't design a bike without them.

I just think that your XJ-700 project is probably "sport" rather than "supersport." But I'm fully prepared to be told that I am wrong.

Greg

[dontz125]

I'm gonna say Greg has a good point. Quite frankly, for your 2-valve cruiser engine, I might be so bold as to suggest that you might want something akin to the 28mm TBs he's using for his EX250 project ...

[EWflyer]

Now that I look back at this thread I'm wondering about the difference between the thread title and your signature line. Is your project an FZR1000 or an XJ700?

[24c]

...Is your project an FZR1000 or an XJ700?

Which is why I was curious about the crank triggering, because I saw the FZR1000 bit, and know that won't work with B&G code, as it doesn't have a supported trigger wheel, and if you can fit a toothed wheel without pulling crankcases apart or machining them I'd be surprised.

The XJ has two VR sensors IIRC and a plate that locates onto the end of the crank, so I assume this is where the toothed wheel would fit, but I know folks on this forum who had problems converting these twin VR sensor setups who suffered noise, interference etc.

[tubular]

The thing is that, whatever D_Mike is converting, he does not have many options to pick from. If he is looking to use what is already available on the market for an I4 engine and unless engine's intake spacing permit him to use two sets of readily available casted TBs, then his standard options are separate casting TBs. Up to my knowledge, this limits to: Suzuki GSXRs K1 - K3, or Yamaha R6 02 - 05, or early Kawa GPZ1100B2.

If anybody knows other I4 separate casting TBs, please add to the list.