81 GS550 running poorly

[Guest]

So, I'm racking my limited knowledge on this one and thought I would turn to the experts.

My '81 550 just isn't running right. The symptoms are as follows:

• Will not rev past 7k at anytime.
• Sometimes will not rev past 3k.
• Backfires when revving past 5k.
• When it will run up to 7k, I can ride it and it will top out around 55mph, but it will only maintain that for about 10 minutes at which point it starts to lose power.
• Plugs are slightly carbon fouled.

I think that is everything. I suspect the timing but seems alright when I check it out.



I welcome any and all help and thank you in advance.

[MisterCinders]

How long have you had the bike?

What mods have you done to it (pipes, pods)?

Have you brought the maintenance current on the bike (valves, legit carb cleaning, etc.)?

It sounds like carb problems in the upper circuits, but the RPM numbers are not a great measurement. Try prompting the symptoms again, but focus on the throttle position (e.g., 1/2 throttle, WoT). If it loses power after high revs, it could be a rich condition at the needle or main jet that is fouling the plugs (I am working out a similar issue on my bike).

You should also put the bike info in your signature for future posts, so you don't have to remember to include that every time.

[Spyder]

Check your air filter. Sounds to be running rich. Are you running stock air box? Stock exhaust? Are all 4 pipes getting hot? Make sure the air intake hole in the airbox isn't plugged with something.

[tom203]

So, I'm racking my limited knowledge on this one and thought I would turn to the experts.

My '81 550 just isn't running right. The symptoms are as follows:



I welcome any and all help and thank you in advance.

Plenty of helpful folks around here to help out, so don't be intimidated! Lots of stuff to check but you need to tell us what maintenance has been done.

Have you checked this out? go to #1 post to start

http://www.thegsresources.com/_forum/showthread.php?t=171846

[dueceswild883]

As far as the maintenance history goes, the PO kept all of his receipts for what he has done and I'm trying to get a handle on what he did and didn't do.

I do believe that I'm just going to start from scratch however and do all the proper maintenance to it myself so there is a baseline. With that said though, I've gone over the bike this morning to try and make a shopping list of things that I will need before doing any tear-down and I noticed that the exhaust port on the left most cylinder (I assume this is the #1 Cylinder) has only one hole for header studs...is this normal? This seems very counter intuitive to me and because it looks like the bike is blowing oil out of that exhaust port I believe something might be very wrong here.

[cableguy]

Blowing oil out the exhaust is never good. Inconsistent top end Rpms might also be electrical, like anything from coils to loose connectors. Make sure maintenance is up to snuff so folks don't have to keep asking. You're in good hands now, and you have just been promoted to head mechanic. Shops aren't worth the cost-if you can afford the labor spend the money on the best parts and pay someone on here a lot less for better work.