The K75 has a new bunghole.

[wmax351]

Just got this welded in over the weekend. Going to stick an oxygen sensor in for the new fuel injection.

[Motorandy123]

Nice! I'd be interested in a new fuel controller especially if it fired the injectors
separately. Looking for more MPG's...

[wmax351]

Nice! I'd be interested in a new fuel controller especially if it fired the injectors
separately. Looking for more MPG's...

sequential injection only helps at low rpm. The Pulsewidth of the injector is too large to benefit a bike like this. Its about 1%, if even that much.

What the bike really needs is better fuel control, with exhaust oxygen feedback. There is plenty of room to improve mpg on a k75 or early k100 with that.

People have an odd obsession with sequential injection. It is done primarily for emissions and very low rpm efficiency, or for a tricky to idle engine. It is of almost no utility for our use (mild cam, high rpm).

To do this on a kbike, you would need the newer version of megasquirt, as well as a way to sense the position of the cam. This is not possible without significant modification to the bike. It would be difficult for no reason.

The fuel injectors are approaching both the maximum and minimum pulsewidth that is useable or controllable. Sequential injection requires more precise injection timing, as well as shorter pulsewidths.

[Nessmuk]

What the bike really needs is better fuel control, with exhaust oxygen feedback. There is plenty of room to improve mpg on a k75 or early k100 with that.

What sort of improvement do you think might be achievable?

In years gone by I used to tinker in electronics and was once employed doing PSU and monitor repairs.  This is the sort of thing I would love to have a play around with.

Simon

[Motorandy123]

There is a provision to go closed loop with the analog Jetronic, not sure what that
would get you. The AFM can be tickled to make a better mix too. I wouldn't imagine
you would get massive gains with a tighter fuel ratio...

A lot of bikes get poor mileage. I always imagined this was due to the fuel hitting
the sides of the intake and "dripping" into the cylinders instead of going in as a gas.
Firing the injector into a closed intake would seem to make it mushroom out and
attach to the walls of the intake thus killing your mileage.

A straighter smoother intake path should give you the best gains. I am coming
from the F650GS, my 2003 got 100 MPG's at 50 MPH! The dual spark ones get
65 MPG's. That's rare for a 650!

[wmax351]

There is a provision to go closed loop with the analog Jetronic, not sure what that
would get you. The AFM can be tickled to make a better mix too. I wouldn't imagine
you would get massive gains with a tighter fuel ratio...

A lot of bikes get poor mileage. I always imagined this was due to the fuel hitting
the sides of the intake and "dripping" into the cylinders instead of going in as a gas.
Firing the injector into a closed intake would seem to make it mushroom out and
attach to the walls of the intake thus killing your mileage.

A straighter smoother intake path should give you the best gains. I am coming
from the F650GS, my 2003 got 100 MPG's at 50 MPH! The dual spark ones get
65 MPG's. That's rare for a 650!

Some of what gives the poor mileage is the air resistance. A literal Brick has better air resistance characteristics than a motorcycle.

The main place where the fuel mileage drops is above 6000 rpm. The L-jet dumps in a ton of fuel at 6000 rpm, in a "Better safe than sorry" situation. With closed loop control, especially with a wideband o2 sensor, you can set the fuel ratio to a much more optimal level.

I should be able to bump it to ~45-50 in most conditions.

You are right that the L-jet can be tweaked, but it is more work than just doing the megasquirt. Kind of amazing, imo.

The intake tract is pretty darn good on the K75. Injector is really into the port, right onto the valve.

[rbm]

Just got this welded in over the weekend. Going to stick an oxygen sensor in for the new fuel injection.

Heh Max,  Can you post a picture of where you had the bung welded?  My exhaust is off the bike at the moment, making it opportune to have a bung welded on it.

[wmax351]

Just got this welded in over the weekend. Going to stick an oxygen sensor in for the new fuel injection.

Heh Max,  Can you post a picture of where you had the bung welded?  My exhaust is off the bike at the moment, making it opportune to have a bung welded on it.

I'll put a pic up on Thursday. Finals done Wednesday at 10 pm.


The k75 and k100 will be slightly different. its on the collector, at the end of the headers. There is a nice flat spot, canted out slightly from the axis of the bike.

[wmax351]

Here you go: This is where I welded it on. Works pretty well. Its a slanted stainless bung, which I ground to the right shape. Make sure you go to someone who knows what they are doing, Stainless can be a pain to weld. Needs a TIG welder.