Am I running the wrong carbs???

[gustovh]

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

[Spyder]

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...

[benjo]

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?

[2BRacing]

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?

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!

[Gorminrider]

also, because I am running pods

Why,oh why wouldn't you include that in your first post?
That would seem to be a salient point....

[benjo]

Why,oh why wouldn't you include that in your first post?
That would seem to be a salient point....

Haha dude, the issue I specified was happening before I switched to AirPods. It now only starting with the choke is the issue with the new AirPods despite rejetting and shimming needles. I am at a "f#ck it all" phase with this bike. I am going to take 2BRacing's advice and step away from the bike and let an expert get it to a good place. I have been working on this bike every day for the last 3 months, reading posts on gsresources that could probably fill a library.

So far, with being a newbie I have:
- had to combine two Carbs together to make twins due to defects in a few cv carbs I have come across in South Africa. One had a stripped jet casing, another had a broken air/fuel screw jammed into it for example.
- rejetted carbs to 30 on the pilots, 127.5 on the mains, and shimmied needles with three washers on both sides due to AirPods
-adjusted float bowl levels to 26mm (by turning the carbs upside down and measuring it from gasket to highest edge of float)
-thoroughly cleaned the carbs at least 5 times
- replaced all gaskets
-replaced intake manifold boots
-replaced all cables and hosing
- re-wired the entire bike by myself. When I say re-wire, I mean buying each wire by the meter and soldering every little connection from ignition switch to rear brake light (previous owner took out the 15 amp fuse housing, straight from starter solenoid to all positive outlets and did a hack job with indicators!!)
- tested voltage/conductivity on my Stator, r/r, coils
-installed a new, handmade muffler and wrapped my two-to-one exhaust headers
-corrected timing on my cam chain (18 links between 2 &3)
- replaced my ht leads, spark plugs, and caps
-replaced petcock and checked that my petrol tank is being properly ventilated from the cap key hole

and a few more cosmetic things...I just don't think the bike gods are smiling down on me haha

i am trying but feeling extremely discouraged...

[Spyder]

Why,oh why wouldn't you include that in your first post?
That would seem to be a salient point....

That is indeed a very important variable. Take 2BRacing's advice and go to his mechanic...

[2BRacing]

..... I am going to take 2BRacing's advice and step away from the bike and let an expert get it to a good place.

So far, with being a newbie I have:
- had to combine two Carbs together to make twins due to defects in a few cv carbs I have come across in South Africa. One had a stripped jet casing, another had a broken air/fuel screw jammed into it for example.
- rejetted carbs to 30 on the pilots, 127.5 on the mains, and shimmed needles with three washers on both sides due to AirPods
-adjusted float bowl levels to 26mm (by turning the carbs upside down and measuring it from gasket to highest edge of float)
-thoroughly cleaned the carbs at least 5 times
- replaced all gaskets
-replaced intake manifold boots
-replaced all cables and hosing
- re-wired the entire bike by myself. .......
- tested voltage/conductivity on my Stator, r/r, coils
-installed a new, handmade muffler and wrapped my two-to-one exhaust headers
-corrected timing on my cam chain (18 links between 2 &3)
- replaced my ht leads, spark plugs, and caps
-replaced petcock and checked that my petrol tank is being properly ventilated from the cap key hole

I am trying but feeling extremely discouraged...

Actually I think that as a newcomer, you have done a great job so far on a 36 year old motorcycle! [I am just unsure of the items I marked in bold print above - as far as I know, the washers go only on one side when you shim the needle; and when measuring float level, you measure from carb base without gasket to the "step" on the float, and not the highest part of the float (not sure if the 450's floats look like the 850's, so maybe the 450's do not have the "step") ]. I am glad that this excellent site has provided many hours of reading matter to help you along - I spend a lot of time reading the technical posts, and still learn new things quite often!

However, even though I have been wrenching on my own motorcycles for 44 years, I know that every now and then something pops up that really stumps you and makes you feel discouraged, hence my suggestion to take your bike to Allan. Tell him everything that you have done to the carbs so far - the information will help him to narrow things down, just like the suggestions made here on GSR. Print the "carb specifications" page on BassCliff's website, and take it with you, so that Allan can see what the baseline jetting for a standard bike is supposed to be.

Unfortunately my bikes have always been standard, without any changes to filters/exhausts, so I do not have experience in jetting recommendations required for those modifications, and therefore cannot help you myself.

Please keep us posted on the progress with your bike - good luck!

[benjo]

Hi all,

So I am taking my bike to Allan on Thursday, but just wanted to ask a quick question about something I just noticed. So we've established that my 1981 GS450 is running a newer set of carbs from the 1983 model and said it shouldn't be a big deal. However, I just noticed that my carbs have a nipple that has that been capped off with a short piece of hose and a bolt. It is #58 on this diagram https://www.cmsnl.com/suzuki-gs450l-...5.html#results

Is this by chance a vacuum line that is intended to be attached to my petcock? (I don't really know if my petcock has a vacuum outlet) Would this explain the fuel starvation symptoms I am getting after 10 min of riding?
thanks.

[2BRacing]

Yes, that is the vacuum line to the petcock. On the petcocks that use a diaphragm to shut off fuel flow when the engine is not running, there will be a vacuum nipple on the rear (square end) of the petcock. There will be two nipples on the petcock - a larger one for the fuel feed hose to the carbs, and a smaller one for the vacuum hose to the carb.

I am not familiar with the GS450, so not sure what type of petcock is fitted. However, if the petcock on your bike does require vacuum to turn it "on", but the hose is blocked off, your carbs would not get fuel at all, unless the petcock lever is set to "prime".

I really hope that your experience with Allan will be a positive one and that your bike will be sorted out. Just tell him everything about how your bike runs/does not run. I will feel bad for recommending him if your experience turns out to be anything like dealing with the spares guy Ryan.

Please keep us informed and let us know what he found wrong with your bike!