Well....its...running?

[exbellicus]

Here's my story. Recently got an 80 GS450. Been working on it quite a bit, mostly cosmetic and maintenance stuff. I've changed the oil & oil filter, new fuel filter and fresh gas, and "rebuilt" the carbs. I say "rebuilt" because I took them apart, spray a crapload of carb cleaner all in them, and replaced the o-rings on the bowls. <- This may be my problem...carbs.

I started the bike up today, it will idle, but is really inconsistent. Its almost like a roller coaster, have little control over it. I can turn the throttle, lets say, 1/4 turn. It will go up way above the proper RPMs, back down, back up, over and over. Does the same thing at a higher magnitude at full throttle. Tried both choked and non choked, and several different settings with the air adjustment screws on the sides of the carbs and the idle speed. No major improvements. I believe that both cylinders are working. Spark plugs are new, and it's getting good spark. I let it run and tried different throttle, air, and choke settings for a good hour total tonight, so it should have cleared up any junk.

I have not been able to balance the carbs, because I don't have the vacuum type and I can't use my other one because the airbox on this model does not come off without moving the engine.

Any ideas?

Edit: I forgot to mention, this bike hasn't been registered in 17 years, so I'm assuming it hasn't been started in at leas that long

Thanks!
Brett

[Guest]

To do a proper carb rebuild you need to dip them in a carb dip. Also replace all the o-rings inside the carbs. You'll be amazed at the difference.

[exbellicus]

Does this sound like a carb issue?

[Guest]

Have you also checked your valves? My 81 450 was doing the same thing and after dipping the carbs and doing the valves it now runs much smoother.

[exbellicus]

Have you also checked your valves? My 81 450 was doing the same thing and after dipping the carbs and doing the valves it now runs much smoother.

What do you mean by checking valves? This is my first bike, and knowledge is limited to what I've learned so far

[exbellicus]

To do a proper carb rebuild you need to dip them in a carb dip. Also replace all the o-rings inside the carbs. You'll be amazed at the difference.

I bought two sets of the 450 kit from Robert, because I knew I would probably end up redoing them. But, I was able to learn a bunch about the assembly of them and such the first time around

[Nessism]

cycleorings.com has an O-ring kit for the carbs AND new intake boot O-rings. There is a carb cleaning tutorial linked on the GSR homepage. To sync the carbs on a twin you can set the idle up to about 2000 rpm and then pull off one spark plug at a time and then adjust the balance until both cylinders idle the same.

[exbellicus]

cycleorings.com has an O-ring kit for the carbs AND new intake boot O-rings. There is a carb cleaning tutorial linked on the GSR homepage. To sync the carbs on a twin you can set the idle up to about 2000 rpm and then pull off one spark plug at a time and then adjust the balance until both cylinders idle the same.

I will need to dip the carbs this time around. I ordered a backup 450 combo kit for when I messed up the first one. I will need to follow the tutorial, although I'm not 100% sure my carbs are stock. I purchased a clymers guide and the one in there is slightly different than mine, but it is also for several different years.

Hopefully that balancing method will work for me. I actually pulled off one of the plug wires while it was running today and it died.

[Nessism]

Don't forget those intake boot O-rings while you are in there. They are almost sure to leak unless they have been changed lately.

[BassCliff]

Hi,

Perhaps you need to read your mega-welcome again. Other links you might find useful:

CV Carburetor Rebuild Guide
(Courtesy of GSR and John Bloemer)
(Click here to see the CV Carb Notes)

Valve Adjustment Video

Valve Adjustments (8 Valve)
Zip Tie Supplement(by Mr. Matchless)


Replace intake boot o-rings

Let us know how it goes.

Thank you for your indulgence,

BassCliff

[Smokinapankake]

Listen to Nessism. The guy knows what he's talking about.

[exbellicus]

So what's the theory behind valve adjustments? I'm confused on how that can effect the performance so drastically.

[jwegman]

So what's the theory behind valve adjustments? I'm confused on how that can effect the performance so drastically.

Disclaimer: answer from a newbie

The valves need to open (to allow the fuel mixture in and exhaust out) and close (to build compression).

If the distance between the cam lobes and the valve buckets are too great, the valves won't fully open (creating a restriction).

If the distance is too small, the valves won't fully close (you'll loose compression and allow excess hot gasses where they shouldn't be).

[UncleMike]

Replace your intake o-rings, put your valves back to spec, and completely pull apart and dip your carbs, replacing all the rubber with new. If it's sat for 17 years, you'll probably need new boots as well.

Do all that, do a bench sync, and then we'll be in business.

[Guest]

I'm with the others on Valves. Proper Valve clearance will work wonders on idle stability.

Also, check that the pilot jets are clear. These are the small jets under the rubber plug. These make a considerable contribution to idle function.

Finally, Make sure the stock airbox is installed, there is a good air filter in it, and there are no leaks on the carb-to-engine or airbox-to-carb and rubber boots. If any of these are not in place, valves or pilots will make no difference.