GS500FU BK4221 K4 derestrict

[the mole]

What did I say.
Sledge, you're the man!

[noworries]

What does Suzuki mean by the FU suffix? 

[ujtordai]

What does Suzuki mean by the FU suffix? 

As I know:

F it means full fairing
U it means restricted model,
In the engine is same as in the unrestricted models, but the carburetors differ between the jets from K4 and newer by the supplemental manual.
By the difference the overall performance is 25Kw 34Hp.

[sledge]

I wouldnt term it as a restricted model, more like a lower power model.

Restricted suggests its a full power model with non OEM mods to reduce its power.............. but the U`s never had full power to start with 

[007brendan]

I wouldnt term it as a restricted model, more like a lower power model.

Restricted suggests its a full power model with non OEM mods to reduce its power.............. but the U`s never had full power to start with 

So, does that mean it's a different engine?  What exactly are the design changes that reduced the power?

I think the question here is if there is a simple mod that can turn an FU in to an F.  If the engine is the same, I can't imagine it being that difficult.

[mister]

I wouldnt term it as a restricted model, more like a lower power model.

Restricted suggests its a full power model with non OEM mods to reduce its power.............. but the U`s never had full power to start with 

So, does that mean it's a different engine?  What exactly are the design changes that reduced the power?

I think the question here is if there is a simple mod that can turn an FU in to an F.  If the engine is the same, I can't imagine it being that difficult.

To quote Sledge's post at the bottom of page one...

The FU`s were low powered versions built in the factory to comply with the various learner laws that are in place in certain European countries, they are not full power versions with restricter kits fitted......they are just low power versions that have never seen more than 30 or so hp.

The carbs differ in the way of jetting and slide design, the exhausts are more restrictive and the ignition timing is slightly different so I would guess if you replace your carbs, exhaust system and the ignition advancer from a full fat GS500 you might see some gains 

The FU was never sold in the UK or the USA, Germany was/is the biggest market for the FU`s , perhaps you might get more info you need in one of their forums.

Michael