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Discussion Starter · #1 · (Edited)
I recently purchased a 85' Shadow 700C and I Believe there is an issue with the idle.

At a cold start I put half choke on and start it up. After ~ 20 seconds, I put off choke and the bike idles at 1.3 - 1.5k RPM. The bike warms up and may slightly drop over time but it doesn't really fall until I start moving the bike (even physically pushing the bike can drop it).
Then once the bike is warm and I drive around and come to a stop sign the bike drops to 600 + or - 100 RPM.

Some info that may help about this bike. I noticed (not sure if normal) that the choke has a slack in the first millimeter or so. I also ran some seafoam into the tank and it did not have an effect (I used 1/4 - 2/5 bottle)
 

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If you have not done so already follow the procedure in the repair manual on adjusting the choke, after that let the engine fully warm up into the normal zone slowly turning the choke off to keep the RPMs at 1,100 rpms, once the engine is warmed up into the normal zone and the choke is all the way off then adjust the idle knob to set it at 1,100 rpms.

If you still can't keep the idle at a steady 1,100 check the couplers between the bottom of carbs and the intake tubes and the couplers for the air snorkel above the carbs that they are not out of place and the clamps are on tight.
 

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Discussion Starter · #3 ·
Thanks for the info. As a side note; your 700c is awesome.

The thing that is confusing is that the bike doesn't have a steady idle > this leads me to believe its not the idle adjusters doing. The bike can be at 1100 RPM all day if it is kept on its center stand. Once it starts moving (maybe it just becomes warmed up fully) then it drops . This led me to believe that the choke was still slightly engaged (causing the lower engine revolutions) but I'm not sure. But then again sometimes it drops when I just push it off the center stand. I'll check back soon about the choke.

I was also wondering if non-stock exhaust tips can cause this. The bike is not jetted properly and backfires at decel.
 

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Suggest you pull the choke out of the carb and inspect/clean. Sometimes they get gummy or the spring poops out. You could also have a sticky float that unsticks when the bike moves.

On all five Hondas we have owned, there is a 'no mans land' during warm up when you keep pushing in the choke to reduce rpm, and you finally push it in and the bike suddenly doesn't want to run at all. Have found a hand on the throttle keeps it from dying, then it settles down.
 

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Discussion Starter · #5 ·
Thanks for the info. I'm going to check the choke and maybe open the carburetors up for a clean. I was also thinking that maybe the fuel filter is clogged because it probably hasn't been changed and the bike has 18k. What kind of fuel filter do these bikes use?
 

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Discussion Starter · #7 ·
I'm taking off the tank to check the choke, I should be able to come from above and the side.

Do I just take the filter off and bring it to any auto place and match size, diameter, and size of intakes? Or do I purchase OEM? Any experience on this?
 

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You do not need to remove the tank to get the choke cables out of the sides of the carbs you will just need to raise it up a couple of inches, remove the two bolts on the front of the tank and loosen the one at the back and then it should raise up. There is also a vent tube on the bottom front left hand side of that tank that you may need to remove in order to raise the tank up.

The filter is your basic tube with two male connectors on each end, any filter that fits should work I would get something made out of plastic that you can see through so that if you are having a no-start situation you can see if there is any fuel in the filter or not.

I would not get one made from glass, I had one in a car I had once it cracked open and sprayed gas all over the engine compartment, why my car didn't burst into flames is beyond me guess I was lucky that day.
 

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Discussion Starter · #10 ·
OK, I set the idle and it now calms down around 1100 fairly consistently. The only concern is that when the bike is rev'd up and then it sets it will fall to about 900 +- 100 then back to 1100 RPM but it takes ~4 seconds. I am planning to use some seafoam in the tank on my next tank to clean out some pipes.

Any second opinion?
 
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