Problem engine...

[SuzukiGS]

Okay, so I just brought my new (to me) GS450LT home last night and have been having some issues with it... The engine has no problem starting up what so ever, but will rev at about 3000 RPMs with the choke at any position or die if I take it all the way down.. then if I try and throttle up on it, it only goes to about 6500 RPMs if I'm lucky and has zero power.. the bike seems to bog down the further up gears I go, and max speed is about 30 mph right now...

I then checked the spark plugs, made sure they were both getting power because I thought maybe only one cylinder was firing, but both plugs had good spark, just one was super black and what seemed to have a carbon build up.. the other super white, like it was running super lean...

When the engine is running and I put it in gear and go, what I head the most is what I think is the intake, and I can't hear the exhaust at all, and it almost seems maybe as if its blowing through the intake...? I just know the intake is what I hear the most while the bike is running..

And then... as the bike was running, the engine died, so I just figured drop the clutch and compression start it.. well when I drop the clutch, the bike just rolled like it was in nuetral until about 5 MPH and then it tried to start but it was to slow to do it... no idea what its doing there..

The only think I know right now is it needs new air filter pods.. the ones on it right now are like home made from the previous owner... but I get the same issue with the make shift pods air filter compared to just running it open..

I'm truely at a lost with this and don't even know where to start. Thanks in advance.

[BassCliff]

Hi,

Here's where to start. I know this list says it's for the 850G, but it works for all GS bikes, well, pretty much any motorcycle.

***********Quoted from Mr. bwringer************
Every GS850 [and most other models] has (or had) a set of well-known issues that MUST be addressed before you have a solid baseline for further troubleshooting. It's a vintage bike, and it's quite common (as in, every single GS850 I have had contact with) that there are multiple problems that have crept up and slowly gotten worse over the years. It's not like a newer vehicle, where there's generally one problem at a time.

These common issues are:

1. Intake O-rings (install NEW OEM or Viton only - common nitrile O-rings will quickly deteriorate from heat)
2. Intake Boots (install NEW -- these cannot be repaired)
3. Valve clearances (more important than most people think)
4. Carb/airbox boots
5. Airbox sealing
6. Air filter sealing
7. Petcock (install a NEW one)
8. On '79 models, install new points or Dyna electronic ignition (or at least verify that the old points are working correctly)
9. On all models, it's fairly common to have problems with the spark plug caps. These are $3 or $4 each, and often worth replacing if you're keeping the stock coils/wires.
10. Stock exhaust with NO leaks or holes -- good seals at the head and at the junctions underneath.

What I have noticed at the rallies is that very, very few 850Gs are actually running right. Make VERY sure it's actually running the way it's supposed to before busting out the modifications.

Brian's E-Z and fun plan for GS850 happiness:

1) Seal the airbox and air filter with weatherstripping.

2) Ensure no intake leaks. Spraying WD-40 or water doesn't tell you much, since very small air leaks can cause problems even though they won't suck in enough WD-40 to make a difference. Replace your intake boot o-rings and boots if needed, and seriously consider spending the lousy $28 for new airbox/carb boots.

3) Ensure clean carbs with correct settings, new o-rings, and original OEM jets. No, not just squirted with something. I mean completely disassembled.

4) Check/adjust valve clearances (Manual calls for every 4,000 miles. This is not optional.)

5) Ensure healthy electrical system.

6) Seriously consider upgrading coils and plug wires.

7) Install new, stock NGK B8-ES plugs gapped to .031".

8 ) Fine-tune float height and idle mixture screw to ensure best off-idle transition.

9) Clean air filter and reinstall with only the lightest oil mist -- over-oiling and/or letting the filter get dirty is a common and critical mistake, and will make the bike run funny at low speeds and run rich. This may take a few tries.

10) Make sure the exhaust seals are sealing.

11) Ooh, much better now, huh? You're gonna need upgraded suspension - Progressive or better fork springs and shocks. Set suspension sag appropriately.

12) Upgrade brakes with new pads and stainless lines to deal with all that extra speed.

13) Install new petcock, since I'm going to head to the roof with a rifle if I have to read about yet another #2 plug fouling and failed hillbilly attempts to rebuild the petcock and/or deny there's a problem.

14) Oh yeah -- check compression somewhere in there to ensure the valves and rings are reasonably healthy.

15) You'll probably need new OEM clutch springs -- the clutches last forever, but the springs get tired after 20 years or so under pressure. E-Z and cheap.

Carburetor maintenance:

Replace the intake boot o-rings, and possibly the intake boots. Here's the procedure:

http://bwringer.com/gs/intakeorings.html

Here's an overview of what happens with this particular problem:

http://cycleorings.com/intake.html

You'll also want to examine the boots between the carbs and the airbox. There's a good chance these are OK, but check them over.
And finally, if things still aren't exactly right, you'll want to order a set of o-rings for BS carbs from the GS owner's best friend, Robert Barr:
http://cycleorings.com
Once you receive these rare rings of delight, then you'll want to thoroughly clean and rebuild your carburetors. Here are step-by-step instructions that make this simple:
http://thegsresources.com/gs_carbrebuild.htm




Thank you for your indulgence,


BassCliff

[SuzukiGS]

So with just glancing that (at work) it mentions the air box a lot... so could it be as simple as just putting on a airbox or getting now air filter pods? How could that cause the engine to run all wack?

[BassCliff]

Hi,

It runs all whack without the airbox because it really throws off the fuel/air mixture. These bike are a little more sensitive to that than a car.


Thank you for your indulgence,

BassCliff

[Nessism]

So with just glancing that (at work) it mentions the air box a lot... so could it be as simple as just putting on a airbox or getting now air filter pods? How could that cause the engine to run all wack?

There are tons of threads in the archives detailing how the carbs must be properly clean, synced, and with the proper jetting to match the intake and exhaust on the bike. Stock jetting will not work with pods.

I suggest you pull the carbs, tear them down and replace all the O-rings, including the O-rings in the intake tube boots, with new parts from cycleorings.com. While you are there check the jetting and compare to stock. Again, stock jetting requires the airbox and pods require new jets or a jet kit (I don’t know what specific jets you need but you may be able to figure this out if you search the archives).

[SuzukiGS]

Okay guys.. so I called the previous owner and she said it was rejetted she thought and ran like a champ back when she was using in in '08 with the unifilter pods on it.. So I went out and bought two new Pods, new fuel line, and tighten all the screws on the carb and it runs worse now...

Now it revs at about 5000 RPMs with the choke all the way up, and then if I lower it, yes, lower, then it revs to about 7500 RPM's and wont settle down no matter what i do... I have no idea what the issue is..

And then... On top of the engine, there is like what seems to be a another fuel line that runs back where the carb is but i see no where to plug it in anywhere... What is it for and where does it go??

Thanks guys..

[SuzukiGS]

Oh, plus, when I have the carb assembly in my hand and move the choke up and down, I see no movement through the carb openings at all.. and then there are like two piston deals.. are they suppose to move at all, is that part of the vacuum system or what?

[Jimithang69]

I had this problem with my GS 450, It ran great to work one day, and the next morning it wouldn't rev and was real sluggish, I was doing like 30 on the highway. It was popping back through the carbs and what not, I replaced the CDI box with a used one and it has ran fine since.