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GS650GL Pod Filters

  • Thread starter Thread starter Anonymous
  • Start date Start date
A

Anonymous

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My girlfriend has a 1981 GS650GL. I would like to remove the airbox and install pod filters. Has anybody doen this or does anyone know if it can be done. I can't look at the bike right now so I can't remember how much room there is behind the carbs. Any suggestions on if this can be done and as to what filters to get?
 
I looked in my Dennis Kirk catalog and found a set of UNI filters for '81-'83 GS650 for $34.99 a pair. And they also have the K&N stage 3 jet kit for the same model for $113.99, which is necassary if going to pod type filters. The website is www.denniskirk.com
 
She probably won't like the change. The GS650 has CV carbs and removing the airbox will severely hamper midrange response. The jet kit will be necesary to get back some of the response, but it usually takes serious tinkering to get the jetting close. The carbs will have to be removed to get the airbox out, and you will probably have to replace the carb to motor boots after pulling the carbs (the boots are a rubber/metal combination - the rubber hardens with heat/age and seperates from the metal when disturbed - the set is $104 from Suzuki). Doesn't the bike seem fast enough already? Mine seems darn quick for a 650. If it doesn't seem to run well, I'd check a few things first and make sure there isn't some problem. Check the plugs, oil, compression and air filter. It is also possible that the carbs do need cleaned.
 
I realize I would have to tinker with the carbs, jetting, etc. I probably won't do it, it was just a thought sitting around on a rainy day. You are also right that she probably wouldn't want it or like it. Just a guy sitting around thinking too much and trying to find trouble where it isn't LOL
And you ar right, that 650 is pretty quick. Not that she really jumps on it either.
Thanks for the reply though.
 
If you get rid of the stock airbox and filter you not only have to rejet, you have to change the carby spring as well. The CV carbs work by having a fairly high pressure drop (vacuum) in the venturi. It is the vacuum that draws the piston in the carb upwards. And that vacuum is kept up (or down?) by having a fairly restrictive airbox entry boot. This allows lots of still air in the box which is easily taken into the motor, but it sits there at a reduced air pressure. It obviously flows enough air as the stock bike is quick enough, but it can be freed up.

When you put on pod filters you no longer have the level of vacuum in the venturi as the air flows too easily through the pod and fills be vacuum before it builds up enough energy to draw the piston up. Therefore you need weaker springs under the diaphragm.

And the next thing you need to do is replace the stock needles. With more air going through the venturi you need to allow more fuel to flow. This means not only larger jets but needles with a steeper taper.

The jet kits generally have the springs, the needles, as well as the jets, and it is these extra bits that make the price seem so high.

And then..... when you have set the thing up there is no guarantee that the jets are right for that particular bike/pod/pipe combination. So they sometimes give you a couple of sets of jets so you can experiment.

My bike came to me with pods but all the previous owner's mechanic had done was set the needles up beyond their normal top position. The bike ran hopelessly rich at normal running and faltered through the mid range on acceleration.

I put the needles back to normal mid-position, paid $40 Oz for a used airbox, made up my own oiled foam filter, and the bike runs magic.

Kim
GS1000G
 
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