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.

 

[exbellicus]

I disassembled the carbs today, one of them is currently soaking in dip, the other will replace it tomo morning. Quick question: I was not able to get the air adjustment screw to come out. Is this normal? Again: 80 GS450...Mikuni 34mm carbs

Another one: My carb float needles seemed to have a little damage near end of the needle. I have heard these needles should be replaced any time there is doubt they are perfect. Is this accurate and why?

Thanks for all the knowledge as always, you guys have been extremely helpful

Next on the list: valve adjustments!

 

[Steve]

If you could not get the adjustment screw out, the carb should NOT be in the dip.

There is a rubber o-ring around that screw that will get turned to mush.
You will now have a much harder time getting that mush out and the carb will not work right until you do.

Sorry you are having to "clean" your carbs again, but this just emphasizes the point that we keep trying over and over again,
do it right the first time, you will only have to do it once.


By the way, jwegman's view on valve adjustment is rather simplistic, but surprisingly accurate. :clap:
The valves control how much air is admitted into the cylinders and when. If the clearance between the cam (the bumpy stick that opens the valves) and the valve/shim/bucket assembly is not correct, the efficiency of the engine can be greatly reduced. If the clearance is neglected long enough to be reduced to zero, the valves can actually be damaged because they are not closing long enough to transfer heat to the cylinder head. This procedure is important enough that Suzuki recommends that it be done every 4,000 miles.

.

 

[exbellicus]

Just one is in the dip, so I'll go give the other another shot. I unscrewed it all the way and it seemed to just keep turning and turning

 

[exbellicus]

No luck yet, I tried pulling straight out with tweezers, prying, and pulling it out with a strong magnet. Any other ideas? There is what looks to be a sealed pin of some sort in the center of the mold between the air spring hole and the "blocked" hole that would be used if the carb was on the other side. Does that pin have any significance to getting this screw out? I tried pushing on it a bit, nothing.

Brett

 

[exbellicus]

I just took the first set out of the dip....wow! Just looking at them I can tell a huge difference from my "cleaning" the first time around.

Now if I could just get that air adjustment screw out....