GS400 bored to GS448

[droyce]

Pete, it appears the carbs are identical with the exception of the float bowl trench, gasket, and jets. The new set I got has 110 main and 20 pilot. The set im using is a 117.5 main and 22.5 pilot (from memoery). What does the gs450 run? Im thinking that may be a better option with being bored over to 448cc.

 

[Guest]

117.5 and 22.5 are the stock jets for the 80 - 82 450 carbs

They should have a 4C3-3 needle too if memory serves me right.

In fact here's my link to the dirt on the 80 - 82 450 carbs...

http://www.thegsresources.com/_forum/showthread.php?t=204475

 

[droyce]

I'll have to check the needles when I get home.

But according to the parts fiche on boulevardsuzuki dot com, the 1978 GS400 did indeed come with the 110main and 20pilot.

My '77 should have come with a 112.5main.

However, the needle and needle jet part#'s match between the '77 and '78, so I should be good to go there.

I'm wondering why they would switch jets though, I would think the tuning would be identical between the two years. The engine and carbs are the same. My only guess would be the design difference in the float bowl, in which case, I'll need to switch to the later jets of the '78 to match my bowls.

Now if I want to match the jets more to the gs450. The parts fiche shows the 1980 GS450's with 115main and 17.5pilot. But according to your research I'd just need a 17.5pilot.

 

[Guest]

One reason for the difference could be that the 77 and 78 are A,B or C models. Each had different cam's with different performance level's.

 

[droyce]

One reason for the difference could be that the 77 and 78 are A,B or C models. Each had different cam's with different performance level's.

I thought only the german models came with a different camshaft profile, and the model designations were for the options (electric start, etc.)

 

[Guest]

Check the back of the clymer or haynes manual. They have an upgrade section that says of you want more power to get the cam's from a gs400 C model.
A,B and C refer to the revision of the engine not the whole bike I thought.

 

[Chuck78]

Will GS450 cams swap onto a GS400/425, particularly the 76-79 models? Any idea the duration and lift on those?

 

[Chuck78]

How did this build turn out? How much in performance gains did the new engine produce??