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Discussion Starter #1
Hello Everyone. Last summer I bought a GS 450L. This is my first motorcycle, and so far I have been able to get it running. I do have a few questions however. My first question on the bike is pretty simple. Does anyone know the model number on the carbs? I know they are Mikuni Carbs, but I don't know the model number. My second question is about the choke lever: is up choke or is down choke? My last question is a bit more complicated. I am able to start the bike and it will idle around 1.5k-2k rpm which is alright, but once i give it even a little throttle It revs up to 3.5k-4k rpm, which is too high. it does not idle down, and I have to shut off the bike in order to get it back down. This happens while the choke lever is down (the bike backfires and dies if the choke lever is up). I am really excited to get this bike ready, and it really helps when people share their knowledge. Thank you!
 

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Best option would be to go on one of the spare parts sites that has an exploded view of your carbs The carb number should be stamped on it somewhere, some have the specs on the air intake, while others have a small flat info panel with the information stamped there. A bit of cleaning may expose this.

If the spluttering and backfire is when the engine is hot I would suggest the choke is on...ie the choke butterfly is restricting the air flow....or in the case of an enriching circuit this is active making the fuel ratio richer.

The hanging idle may be a stiff linkage, blocked jets/passages, one or more return springs not working properly....sometimes the springs get tangled up when the slide is removed then replaced causing it to jam, stiff throttle cable...or in the case of CV carbs a blocked vacuum passage.

The first thing to do would be to clear out any old gas, check all filters then run some good quality carb cleaner through.....let the engine run for a short while to get the stuff into all the little circuits etc then leave it overnight. You may need to do this more than once.

Check the mechanics of your carbs...if you twist the throttle and then let go it should snap back cleanly with no resistance or delay....you should also hear the slides snapping closed with a click. If this doesnt happen it indicates a fault/problem with either the cable, the slides/return springs or the mechanism. Further investigation will be needed.....you may get away with spraying some WD40 into where the cables attach but be warned any build up of crud etc will probably not be dislodged and come back to cause the problem at a later date.

If you dismantle anything take lots of pictures of the components and how they are assembled before so you have a reference for later.

Good luck
 

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Discussion Starter #3
I put new pod filters on the bike, and they get pretty close to the holes at the intake side of the carb. Do you think this is my blockage?
 

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I put new pod filters on the bike, and they get pretty close to the holes at the intake side of the carb. Do you think this is my blockage?
No.....but they WILL make it run too lean and that alone might explain part of your problem.

You should always get it running good with EVERYTHING stock before you start changing things; and then make the changes ONE thing at a time.

As for the choke....LOOK down the throat of the carb(s). When you see the little plate closed, that is when the choke is active.
 

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The bike did not come with the factory air box so I went straight to pod filters. I increased the jet size by 2.5 to compensate for the increased airflow. The choke does not move the throttle plates, I think it just adds fuel this richening the mixture
 

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The bike did not come with the factory air box so I went straight to pod filters. I increased the jet size by 2.5 to compensate for the increased airflow. The choke does not move the throttle plates, I think it just adds fuel this richening the mixture
Of course it won't move the THROTTLE plate but if it is a real choke, it will move a choke plate, which is upstream from the throttle.

You are right that an enricher type choke doesn't have a plate in the throat.

Where did you come up with that number for the jet increase ??

And what you describe with the fast idle sounds like a vacuum leak......at a point where it sucks in extra air AND extra fuel too.

You are so far away from stock now that it might be hard to determine exactly what the problem really IS.
 
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