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81 GS550 feels slow / wont rev past 6K

  • Thread starter Thread starter chrsjcb
  • Start date Start date
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chrsjcb

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Having real trouble getting the bike to have any kind of power on anything but totally wide open throttle, it almost feels as though it's been restricted but i've had the carbs apart and there's nothing unusual in there.

It also won't rev past 6K really.

I read on here that it could be the signal / pulse generator?!

Also, something that is strange but maybe related... the speedo only goes up to 80MPH?! It is a US import (I'm in the UK)

It's annoying, I'm used to riding my ZX6R but i'm pretty sure the GS isnt meant to be this slow! I struggle getting to 70!

Help Please?!
 
Hello, good evening and welcome to the good ship GSR.

You're right - your 550 should be a lot quicker than that. Where are you along the basic maintenance line - valve clearances, plugs etc? Will it rev up to the red line when parked? If so it's probably carb or airbox related.

By the way - the 80 mph speedo. In the early 80s the Yanks thought that the world was flat or something and if you went more than 80 mph you would fall off the edge. Well, it was either that or they had a daft politician who thought you could slow bikes down by putting a speedo that only went up to 85 on it - yes, it really was a law over there.

By the way - what part of the UK are you in?
 
Last edited:
chrsjcb said:
Having real trouble getting the bike to have any kind of power on anything but totally wide open throttle, it almost feels as though it's been restricted but i've had the carbs apart and there's nothing unusual in there.

It also won't rev past 6K really.

I read on here that it could be the signal / pulse generator?!

Also, something that is strange but maybe related... the speedo only goes up to 80MPH?! It is a US import (I'm in the UK)

It's annoying, I'm used to riding my ZX6R but i'm pretty sure the GS isnt meant to be this slow! I struggle getting to 70!

Help Please?!
Click to expand...
Well, you didnt say what the mileage is on it, but I would imagine that you will need to do 30 years of neglected maintenance.
Do a compression check first, might need valve clearance set. And all those rubber carb parts and inlet o-rings are all dried out and leaking.
Post more of the symptoms of what the bike feels like wide open at 70.
85 mph speedos were standard for us bikes of that age.
 
Aha cheers!

I knew i should never get overtaken by a mum in an Astra, I thought the speedo was wrong and i was riding through some sort of time warp.. Wishful thinking.

Not much you can say to that really.... the mind boggles.

It won't rev to the redline when parked.

When trqavelling along, if I really open the throttle to the max it kind of feels like it bogs but then doesn't... and I get slight judders of power and then the gutlessness, still refuses to rev past 7K max. You really have to give it some beans to make it move.

It wouldnt start for a while so me and a friend have done the following:

Fully charged battery.
New plugs.
Taken carbs off completely, opened them up, sprayed a load of cleaner in there, wiped out.

This made the bike start fine.

Could fuel starvation / clogged petcock cause it?

And i'm from Basingstoke, what about you mate?
 
I'm not far away - just the other side of Farnham.

I would guess carb problems. If your strip down got the bike going then they were probably gunked up. However, you really need to strip these things down and clean them 100% and then do it again. Many have tried to take short cuts and many have failed.

Have you had a look at: http://www.mtsac.edu/~cliff/storage/gs/Mikuni_BS-CV_Carburetor_Rebuild_Tutorial.pdf

You really need to do that before you go any further plus check valve clearances.
 
That's quite a guide!

I'll get round to that when i next feel brave!

I hate taking them apart.
 
I would order up new O rings as well while they're apart. They're 30 years old and well past their sell by date. This guy is a member here and his service is first class:

http://www.cycleorings.com/

By the way - your bike isn't the one with the red frame that sold on Ebay recently is it?
 
gearhead13 said:
Well, you didnt say what the mileage is on it, but I would imagine that you will need to do 30 years of neglected maintenance.
Do a compression check first, might need valve clearance set. And all those rubber carb parts and inlet o-rings are all dried out and leaking.
Click to expand...

+1, Don't even bother running it until all of the maintenance is done.
This is why God created Winter.
 
tkent02 said:
This is why God created Winter.
Click to expand...

He's just forgotten to send it here yet Tom - still good riding weather, it's been the warmest October and November since.....the last warm October and November (which was apparently a long time ago according to the papers)
 
It's strange, the carbs really werent that dirty inside and the screws on them had obviously been moved at some point because there was the usual rounding.

Once of the carbs was actually spotless.

The only thing we noticed was a slightly brown dust / colouration on 3 of the 4 bowls, it came straight off with cleaner.

We sprayed cleaner in all of the holes mentioned in that tutorial.

The gaskets in the carbs didnt look very old at all, they were still black, I think the previous owner or owner before serviced them.

I think that the new plugs and making sure the vacuum system was on properly made a difference more than the carbs?

I have a feeling it could be fuel starvation as full throttle at low revs gives lots of power but as it gets up the rev range all power just goes and it gives up at 6K.
 
There are no short cuts to cleaning the carbs. There must have been a 1000 guys on here who shot carb cleaner up all the holes and the thing never ran right.

That and checking /correcting valve clearances sorts 99% of reasons why the bike won't run properly.

Did you see my question about your bike having a red frame by the way?
 
Fair enough, I shall brave them once more at some point.

Will look at clearances after.

No red frame, standard gs550, going to bobber it.
 
I can't tell if that's sarcasm or the fact that a hardtail with a tiny seat is a bad idea at 80mph?

I would like it to get to 80mph though aha
 
I only asked about the red frame as a guy over your way was member on here with the same problem recently. His bike had a red frame. He wouldn't believe he should clean the carbs properly and after a dozen attempts at not doing the job right gave up and sold the bike.

A 550 will romp way over a ton easily though as a bobber I wouldn't want to go over 50.
 
That's comforting to know that it will actually move a bit.

A "proper" carb clean is in order then... I'll print that guide off and follow it.

Will service the petcock first.
 
The power on a 550 only starts to kick in above 6k rpm so you haven't felt what she should run like yet.
 
Brilliant, it's frustrating how you have to be so meticulous with the carbs.

It runs really badly and they appeared fine, frustrating!

Hopefully it will fix it!
 
Have you tested for air leaks? the boots from the air box to the carbs need to seal well. The BIG one is the seal between the carbs and the head. There are O-rings on the head mating surface of the intake tubes there that are almost always bad. An easy test is to have the bike running and carefully spray the areas around the boots and such with starting fluid. If the engine changes rev at all, you have a leak.

Are the air box and exhaust pipes stock on this bike??
 
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