upgrading a gs400x front brake to disc

[cubanb]

Hey guys well i needed to pop my gs cherry and make a post after lurking for sometime. Anyways I purchased a 1978 Gs400x and as some of you may know it came with drums in the front and the rear. Well I love the spoke look but would feel more confident with a disc brake up front. I have done some searching but could not find the full detailed answer to this. I found a spoke rim with disc as well the brake caliper and now im left with the brake pump. I have found one for a gs 400 but it is a 1981 master cylinder. Will this be compatible? Will all i need to do is connect all of this gear up and route some power to the master cylinder ( i notice it has a power /ground wire connecting to it). I have read some of the scary posts about rebuilding the brake cylinder as well the caliber but i don't think it is out my realm of knowledge. Thanks in advance for any help.

And I added a pic of the bike so far you will notice suzuki left the mount on for the caliper for the disc model

[jfman]

Looks like a nice cafe.

The good new for you is that the drum setup you have is somwhat desirable so you will likely get some money from them to cover the mod. dotheton.com someone there will buy them from you.

Do you want twin or single rotor?

[eil]

Can't help with any specifics about the conversion, but rebuilding master cylinders and calipers is pretty simple: order up brand new OEM seals, boots, and pistons; disassemble; clean like mad; reassemble.

The wires going to the MC are for the brake light.

[cubanb]

Wow fast response time, you guys rock! Thanks for the compliment she is coming along nicely. I'll tell you putting on those led turn signals were no picnic I had to use resistors then a new relay and a heck of a lot of trial and error.The trees only have one spot for a single caliper so i figure that is what i will stick with to keep it simple/cost effective. I will prob keep the drum brake just in case I feel like going back to it in the future but thanks for the advice. Also thanks eil for the advice on the wiring i had no clue what they were for lol should be a cinch getting her wired up. All together it looks like it will come out to about 100ish for the conversion if my offers go through so not to bad for a big improvement performance/looks wise

[Steel Toed Tank]

If I'm not mistaken, You would need to switch the forks with each other in order to use the caliper.
I may be wrong, but on my single disk front end the disk is on the left side and the caliper is behind the fork.

[jfman]

You just need to find a fron end and wheel setup from this version of your bike.

Your bike might even have came like that. Some folks go back to drums when they build cafe racers.

[BentRod]

Is there any way to talk you out of it? Drum brakes can be pretty solid equipment, and at least I think they look better.
I'm pretty certain your bike has dual leading shoe up front, which I would bet is significantly more powerful than the single disk brake and one pot caliper off my old 81. Drums get a bad rap for fading due to heat, but even for the most spirited street riding, this really isn't a problem. Dual leading shoe drum brakes light weight, long wearing, all but immune to oil and grime from the road, and they provide so much stopping power it is almost silly.