Problems with top speed of a 1980 GS 550 L

[valentin]

Hi everybody:

I have a 1980 GS 550 L and runs great at low speed, but when I go up to 100 km/h (62 mph) it cost a lot of work for the bike reach the 120 km/h (75 mph). The top speed of my bike is 133 km/h (83 mph). I think that the bike can do more than that, near to the 150 km/h (94 mph). Do anyone know what will be the real top speed of this model?

The carburation is OK and I have put a 16 tooth sprocket on the front and 52 on the back. I can't get the original ones: 15/48 so I have to put the ones that I can get at that moment.

Regards from Chile
Valentin

[zuty13]

I have a 1982 GS 550LZ so it's basicaly same model like yours..
Recently rebuilded(changed piston rings,cam chain..etc)
Compression in range 140-145psi. sprockets 15/50
It grabs very well untill it riches 120km/h after that need some time untill 140km/h ...I've never pushed it more than that...after all it's 24 year oldbike...
The top speed shoud be 157km/h by the Suzuki(new bike)...that means 150km/h in real conditions..flat track... so 140km/h is more than solid and I'm not gonna pu**** more since it's not racing bike( more a cruiser from 80')
Need more speed buy a bigger bike and newer too.. it's illegal any way(it\s not designed for that much speed thats for sure)

[robinjo]

Hi everybody:

I have a 1980 GS 550 L and runs great at low speed, but when I go up to 100 km/h (62 mph) it cost a lot of work for the bike reach the 120 km/h (75 mph). The top speed of my bike is 133 km/h (83 mph). I think that the bike can do more than that, near to the 150 km/h (94 mph). Do anyone know what will be the real top speed of this model?

The carburation is OK and I have put a 16 tooth sprocket on the front and 52 on the back. I can't get the original ones: 15/48 so I have to put the ones that I can get at that moment.

Regards from Chile
Valentin

How many rpm does it run when it's at maximum speed? If your engine isn't worn out with bad compression I suspect one or two faulty (either ripped or badly fitted) diafragms on your throttle slides.

I did the same repair to a GS1150 yesterday and the top speed went up from 150 km/h to somewhere well over 210 (ran out of room/nerve).

[valentin]

It reaches 5.700 rpm at the top speed.

[DimitriT]

A well tuned the 550 should have no trouble seeing the 150 km/h. Assuming your the compression is ok. My the 550 has no trouble according to GPS. You need to open up carbs and clean. Other things you can check are air filter, plugs, chain, brakes (maybe the dragging). What is your gas the mileage like? Good the luck.

[valentin]

15 km/lt on city and 18 km/lt on the freeway at 100 km/h.

The ring is OK (it have only 6 months). The air filter and breaks seems to be OK, also the plugs. The only thing I don´t know are the carbs, but I think they are Ok too because the bike runs great until it get 100 km/h, before that take to much distance reaching 120 or 130 k/h.

Passing a car on the freeway is so hard for the bike, but finally she does.

Maybe I have to follow the advice of Zuty13 and buy a bigger bike. Or a faster bike, like a Bandit or a Honda NT Hawk.

[DimitriT]

It does sounds like the carbs. Different things in the carbs will work at different speeds. Your carbs may work fine until you try to pass and then they stop. You need to open them up and pay special attention to the slider which controls the needle jet. This is what works at the speeds you are having a problem with. Make sure they are not stuck and that rubber parts are not leaking. Read the part of this web site which talks about carb cleaning.

When I got my 550 it had poor idle and was slow after 100 km/h. I cleaned the carbs, replaced some rubber parts, and now it is like an animal. The power between 100 km/h and 140 km/h is nice, even in 6th gear.

[valentin]

Maybe you're right and the carbs needs a clean: yesterday I went on a ride with some friends. Make over 300 kms and at 110-120 km/h. The gas "mileage" was 12.7 km/lt at that speed... a lot !!!! and I can't go over 120km/h, the bike have "asthma" (¿that's the spelling?) at that speed.

[KEITH KRAUSE]

If you have good compression???...sounds like carburetion to me.
Either not enough air or not enough fuel.
Did the bike sit awhile?
You can try removing the air filter, re-install the air box lid and test.
If you still have the problem, focus on fuel starvation.
Any rust in the tank? Good petcock flow? Any in line fuel filter? Carb cleaning and check float levels would be next.

[Nerobro]

yeah, something is definitely off. My 80 550E was doing 110mph before I started modifying it. And you should be turning something like 8500rpm when you're topped out.

[valentin]

Yes, it was the carbs. My mechanic cleaned and now the bike is riding so well !!! 9.000 rpm at second gear and 90mph !!! the bike brings to life again.

Thanks all of you for your answers and advices. And sorry my english (but all of you understand me).

Regards

Valentin

[KEITH KRAUSE]

Glad your bike is running good! Enjoy it.