Suzuki GN400 Thumper

[ILoveThumpers]

Suzuki GN Thumper: Fuel & Air

I've nearly got the frame modifications and suspension changes planned out so I turned to fuel and air last week. I had already done a cursory cleaning of the carb and it was relatively clean. No varnish on anything and there wasn't any gunk anywhere that I could see.

Two things I didn't do (and paid for it later) were: 1) pull the emulsifier tube and 2) pull the fuel flow screw.

So I ended up pulling the carburetor again tonight to do it right. And here's what I found on the emulsifier tube:

I didn't think the fuel flow (some people call it the pilot air screw but it adjusts fuel, not air) screw was adjustable or accessible but I found a tutorial for the BS Mikuni carbs on BikeCliff's website that explains how to get to it.

So after a dip in the Gunk dip and liberal cleaning with nearly a whole can of Carburetor cleaner, I decided that rather than put it back together with factory finish that I would paint it. So I taped it up and I'm ready to soda blast it tomorrow. I also polished the bowl and the top plate.

Since I'm leaving the stock airbox and exhaust (those will be some of the last things I change) I'm leaving the jetting for now.

-Deek

 

[ewpurdy]

Geometry Question

Hi,
I've recently started a GN400 build myself and find the geometry discussion here invaluable. I've been playing with the geometry calculator and have a question about what effect lowering the triple trees has. Does this have the same effect as shortening the shocks with respect to the geometry calculator? So, the shortened length entered needs to be the amount the triple trees are lowered PLUS any internal shortening of the shocks?
Thanks everyone for the discussion,
Eric

 

[ILoveThumpers]

Eric,

Man, I can't believe I missed your post. Sorry about that.

What do you mean by "lowering the tripple trees"? The position of the trees is fixed as it is a function of the length of the neck that the stem and bearings go through. The top tree can't be lowered as it sits (basically) right on top of the neck. The lower tree could possibly be lowered through some kind of stem extension and a collar between the neck and the tree but I cant imagine that would be useful.

-Deek

 

[ILoveThumpers]

I didn't want to leave anyone hanging who might be watching this thread; I've decided to go a slightly different route with this bike. It won't be anything like a racer of any kind but instead a simple commuter to get me from A to B and occasionally take a dirt path or two.

I'll continue updates here as I work on the bike but this season is mostly going to be riding the GN and re-assembling the GN.

-Deek

 

[MattL9]

I'm in the same boat as you man. I'm attempting to rebuild/modify a suzuki gn400, but being a college student, it's difficult to find time. What are you doing for the seat?