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Am I running the wrong carbs???

  • Thread starter Thread starter benjo
  • Start date Start date
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benjo

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So...I bought a 1981 GS450 about 4 months ago and from the get go it has had carburetion problems. I have taken them apart, cleaned them, and put them back together about 40 times (and no, that is not an over exaggeration). What tends to happen is that after running for about 10-15 minutes the bike dies when I pull up to a stop light unless I rev it really hard.

When it does die though, it won't start back up until a long while after it cools down. It felt like it was being flooded. I was successful in push starting the bike back to life after this happened once, but this required a lot of reving to keep it going and you could feel it was on the brink of death.

Today I found out that I may actually be running the wrong carbs though!! The carbs that I have on the bike are the ones here: https://static.motorcyclespareparts.eu/images/suzuki/motorcycles/CE_18574_1.JPG

A mechanic told me today, however, that these are the wrong carbs and I should be running these: https://www.cmsnl.com/suzuki-gs450ex-1981-x-usa-e03_model34205/partslist/BLCK0005.html#results

I have seen the difference of these carbs across the GS450 over the years, but I didn't think they would actually affect the performance of the bike. I thought they were both BS34SS carbs so they'd do the same thing. Any insight you can help me with would be greatly appreciated.

It might also be worth mentioning that the bike is in South Africa, so that might affect the particular carbs.

I feel idiotic but hopeful that this is what is keeping my bike back from running correctly!
 
I doubt the difference in the carbs is the cause.

Sounds like an ignition issue or maybe fuel starvation. Have you tried opening a float bowl drain screw after the issue occurs to see if there is any fuel inside? Check spark when the issue occurs?

How long since you checked the points and valves?
 
I don't think it is a fuel starvation issue. The bike is currently on a lift with the tank off, so I fill the carbs by a feeder tube and then let it run so I see from the feeder that its taking fuel. It just won't start when it gets hot.

I have also checked to see if their is a spark and it looks like a healthy blue spark.

I checked the points a little bit ago and they look pretty flat, I took some fine sand paper to file them a little bit as well.

I have checked the valve timing but have not checked the valves themselves. Can you give a quick instruction on how to do this and what I should be looking for? Maybe there is a link I can look at that can show me how to do this?

Thanks!
 
benjo said:
I have checked the valve timing but have not checked the valves themselves. Can you give a quick instruction on how to do this and what I should be looking for? Maybe there is a link I can look at that can show me how to do this?

Thanks!
Click to expand...

No valve adjustment? Scary.

Check the newbie mistakes thread linked in my signature to see if there is anything else you missed.
 
I have seen both styles of carbs on US-spec 450s, but the ones that you have did not show up until the '83 model year.

.
 
Nessism said:
No valve adjustment? Scary.

Check the newbie mistakes thread linked in my signature to see if there is anything else you missed.
Click to expand...

Ok, I'll check the valve clearance today. I just checked online how to do so. It looks pretty straight forward. The GS450s have the screw adjustments I believe so I don't have to take off the entire head right? Thanks for the info, I really appreciate it.

Just to be clear though, it won't matter what carb type I have (ie these different models won't affect the performance in any way)?Thanks for the info, I really appreciate it!
 
Steve said:
I have seen both styles of carbs on US-spec 450s, but the ones that you have did not show up until the '83 model year.

.
Click to expand...

Thanks for the info, Steve. So do you think this would affect the performance of the bike in anyway since it is an '81?
 
One last thing, since I am in South Africa it is very difficult to find parts. I am trying to find a carb rebuild kit but its been tough. I have found this one for a GS850G and it looks exactly like the components of my GS450. https://motocomp-online.com/suzuki/2125-suzuki-gs850-carb-kit.html

Did the GS450 and GS850 have the same carbs? The difference being that the GS450 has two and the GS850 has four? Can I get this carb rebuild kit for the 850 to go on my 450? The one thing that looks different is that the pilot jet is way bigger, so I would have to buy the pilot jet separately.

Thanks!
 
I buy Suzuki OEM parts from Suzuki South in Wynberg 021 761 0157 speak to Aggies. Tell him I sent you.

If you need to speak to a mechanic, an excellent guy is Allan Roberts at 10 Watsonia Street, Tygerdal, Goodwood 083 233 8681. Tell him I sent you.

Good luck with getting your bike sorted out!
 
benjo said:
Ok, I'll check the valve clearance today. I just checked online how to do so. It looks pretty straight forward. The GS450s have the screw adjustments I believe so I don't have to take off the entire head right? Thanks for the info, I really appreciate it.

Just to be clear though, it won't matter what carb type I have (ie these different models won't affect the performance in any way)?Thanks for the info, I really appreciate it!
Click to expand...

The 450 has shim valve adjustment. There is tons of info about how to adjust the valves including youtube videos.

Do not purchase "carb kits" other than maybe some O-rings. You best take an inventory of what jets are inside your present carbs so you can baseline what's going on.
 
Nessism said:
The 450 has shim valve adjustment. There is tons of info about how to adjust the valves including youtube videos.

Do not purchase "carb kits" other than maybe some O-rings. You best take an inventory of what jets are inside your present carbs so you can baseline what's going on.
Click to expand...

Does this mean that I can just remove the valve cover to make the adjustments? Or do I have to take off head to make the adjustment? Thank you!
 
It very well might not be the carbs. Maybe a petcock problem, floats etc etc etc
especially if the bike ran alright with them in the past.

but STILL, if these aren't the carbs that came with the bike You have to get the manual for your bike and investigate the jet sizes for one thing. They should be listed in there. I think you can get various jets for these carbs online. .But there's more to investigate when you think on it.....Having BS34SS carb does not mean they fit every bike. There's right and left for instance. and Variations in the "enricher" mechanism....and more
 
2BRacing said:
I buy Suzuki OEM parts from Suzuki South in Wynberg 021 761 0157 speak to Aggies. Tell him I sent you.

If you need to speak to a mechanic, an excellent guy is Allan Roberts at 10 Watsonia Street, Tygerdal, Goodwood 083 233 8681. Tell him I sent you.

Good luck with getting your bike sorted out!
Click to expand...
Thanks a lot! Will do.
 
Just in case you have a second or two to spare, you might check and clean the vent on the gas cap, a plugged one can cause fuel starvation and symptoms similar to yours.

V
 
Most of these bikes have a vacuum activated petcock, (not sure about the 450's). If it does, it could be sucking fuel in through the vacuum line. If it's not too much, the bike will like this when cold, and flood when warmed up. Have you pulled the plugs when this problem happens? Are they soaked with fuel, or dry? You could possibly have an enrichener circuit leaking as well, again will like the extra fuel when cold, but flood when warmed up. It sounds like you haven't done 2 very key things to this engine. Properly clean and rebuild the carbs, and adjust/check valve clearances. You need to go here, http://www.thegsresources.com/_forum...d.php?t=171846 and make sure to cover everything there to ensure all is right and tight. Also, get an O-Ring set from CycleOrings.com this will seal everything up in the carbs. Good luck. Listen to that Steve guy, he has mental-GS telepathy. He can sense when your bike isn't right from the other side of the world...
 
Thanks guys. So I just checked my valve clearance and the two outlets are within spec (.03-.08mm) when the cam lobe is pointed vertical away from the bucket on top dead center One inlet (right side) fits a .04mm gauge but the other does not. I don't have a .03mm gauge to measure it,but should I adjust nonetheless? If so, how do I go about doing valve adjustment to increase the clearance? Do I need to buy a new shim?

also, because I am running pods (I know, I know) I just increased my jets to 30 on the pilots and 127.5 on the mains per a thread on here. But it's still not running unless I have the choke on. (When I switched from airbox to pods this was what was happening, not running without the choke). Any advice?
 
benjo said:
Thanks guys. So I just checked my valve clearance and the two outlets are within spec (.03-.08mm) when the cam lobe is pointed vertical away from the bucket on top dead center One inlet (right side) fits a .04mm gauge but the other does not. I don't have a .03mm gauge to measure it,but should I adjust nonetheless? If so, how do I go about doing valve adjustment to increase the clearance? Do I need to buy a new shim?

also, because I am running pods (I know, I know) I just increased my jets to 30 on the pilots and 127.5 on the mains per a thread on here. But it's still not running unless I have the choke on. (When I switched from airbox to pods this was what was happening, not running without the choke). Any advice?
Click to expand...

No, you do not have to buy a new shim. However, you need to know the thickness of the shim that is in there at the moment, in order to get one size (maybe two sizes?) thinner. You probably do not have the special tool to depress the bucket in order to get the shim out. The thickness is stamped on one side of the shim (for example 2.75). Search on this site for "Ziptie method" for adjusting valve clearances for an alternative to the special tool. Do not turn the engine over when a shim has been removed, it will damage the edges of the cam lobe.

If you are new to wrenching on bikes/cars, I suggest you speak to Allan, the guy I recommended above. He has a selection of shims (and jets), so you do not have to buy new. He is also a real fundi with carbs. Perhaps let him do the work to get your bike running properly now, instead of chasing your tail with something new to you and maybe getting discouraged because you cannot get it right. Then you can learn to do the maintenance required in future to keep your bike running well.

Good luck!
 
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