GS450 1981 won't redline, missing 20hp

[Gorminrider]

I know that It's not very helpful to say, but Maybe the 35 year-old tachometer is tired....they use magnetized steel to move the needle and this can lose its charge over time...so From this reader's perspective, "not redlining" is not much of a symptom .

But "lack of power" seems to be the kernel.

The bike makes it to 120km/h

Is that the limit? Yes that's truly gutless . I expect that's what the de-powered (german) bikes would do....I'd look up what they did de-powering (as to jets?) and doublecheck your own against it. It might be a clue as to how to improve yours.
add: or maybe someone replaced the original carbs ...

Given the weights are working, and your strobelight test looks decent, but you have pods, carburetion still seems to be a possibility too. Might just be the air filters on the pods themselves....

[Thefidel]

I haven't ruled out carburetors. Pods are k&n with 135 main jet. I tried a 145 jet but that only made it worse. This made me think that it ran rich but since there's no black smoke and plugs look good I let it go. Since the lack of power is through the whole register my suspicions point towards ignition.

I also have a GSX400f from '82 and that one runs amazingly well compared to the GS. (Same bhp)

[Thefidel]

This thread can be put to solved!

Tacho was as someone stated not working properly, after 6800~ it wasn't following the engine speed the same anymore. Recleaned carbs again and checked compression. Everything was fine!
I got annoyed by not finding the issue so I looked up another gs wich was for sale, I contacted the owner and got a test ride. They ran exactly the same. So I guess I was expecting too much from the old sack

Thanks for all the input in the thread!

[John Park]

You could get some US spec camshafts. They are cheap, easy to install, and as far as I know that's the only difference. You would [probably] have to go bigger on the main jet.

I don't think that year is a critical factor, but you'd probably be safer with cams made in the 80 - 84 period; I think everything from '77 to '94 fits, but there may be slight differences in endplay, etc. to contend with.

[Gorminrider]

yes, it's very common the old tachs get tired...

[pete]

Good news! You can also go with the GS500 camshafts for a little boost especially in the midrange.

[John Park]

Good news! You can also go with the GS500 camshafts for a little boost especially in the midrange.

The early ones with the tach drive gear, yes. I don't think the differences are all that great, but if you're making a choice, a bit more lift?, why not? I'd tend to go for condition first.

[Thefidel]

I sold the bike yesterday and got myself a yzf750 street fighter. No need to switch cams in that one

Thanks again!