Honda GB 400 mods

**Rotter** · 15th June 2016, 21:14

Hi there,
I'm wanting to start doing some (careful and minor, at first) modifications to my GB400.

I want to try to do the work myself, and learn on the job, so stuff that's not major would be best.
I'm keen to try and get more power out of it, or make it quicker off the mark.

Does anyone have suggestions of things I would look at doing first?

**OddDuck** · 15th June 2016, 23:16

Simple mods:

Pull the bracket off the frame that sits about 20mm in front of the airbox intake snorkel. It's right in the incoming airflow path. Presumably it's there for noise control.

K&N air filter, keeping the stock airbox. You will have to check carburetion settings if you do this.

Remove the centerstand. Don't throw it away - very handy for maintenance - but first thing to go for making the bike lighter.

Lighter battery, something not lead acid.

Check condition of your chain, if bike rear wheel is stiff to turn by hand then you are losing ponies in the transmission.

TYRES. Get the absolute best rubber available. A lot of speed is confidence and if you aren't happy banked over then you'll never go fast.

Also think about the brakes. There isn't much that can be done with the rear drum but you can get aftermarket pads for the front caliper - also make sure the slide pins are clean and in good nick.

More advanced mods:

Slide carburetor, probably something with a bigger throat than the stock CV carbie.

Aftermarket muffler.

Hot cam, high comp piston, porting or pocketing work in the head.

XR600 motor (apparently it slots straight in with no frame mods).

Also think about recovering performance, if it's been a while since the bike saw serious maintenance. Worn rings / valve seats in bad condition / leaky ignition HT lead or coil / aging CDI unit, that kind of thing. Suspension pivots and the suspension itself too.

Make sure you've got working space, parts availability, and cash for tools and bolts etc. Surprising how this stuff can add up in a hurry.

**Drew** · 16th June 2016, 07:37

Pipe, carb, valve clearances, compression test, ride it like ya stole it.

**Akzle** · 16th June 2016, 13:05

Originally Posted by OddDuck

Simple mods:

Pull the bracket off the frame that sits about 20mm in front of the airbox intake snorkel. It's right in the incoming airflow path. Presumably it's there for noise control.

K&N air filter, keeping the stock airbox. You will have to check carburetion settings if you do this.

Remove the centerstand. Don't throw it away - very handy for maintenance - but first thing to go for making the bike lighter.

Lighter battery, something not lead acid.

Check condition of your chain, if bike rear wheel is stiff to turn by hand then you are losing ponies in the transmission.

TYRES. Get the absolute best rubber available. A lot of speed is confidence and if you aren't happy banked over then you'll never go fast.

Also think about the brakes. There isn't much that can be done with the rear drum but you can get aftermarket pads for the front caliper - also make sure the slide pins are clean and in good nick.

More advanced mods:

Slide carburetor, probably something with a bigger throat than the stock CV carbie.

Aftermarket muffler.

Hot cam, high comp piston, porting or pocketing work in the head.

XR600 motor (apparently it slots straight in with no frame mods).

Also think about recovering performance, if it's been a while since the bike saw serious maintenance. Worn rings / valve seats in bad condition / leaky ignition HT lead or coil / aging CDI unit, that kind of thing. Suspension pivots and the suspension itself too.

Make sure you've got working space, parts availability, and cash for tools and bolts etc. Surprising how this stuff can add up in a hurry.

or just change teeth on the sprockets., innit.