Greetings, Your advice was perfect. (Machine would not idle) I changed the idle settings to 3 3/4 open and installed the air filters. It idles perfectly. ANOTHER QUESTION: When riding the RPMs do cone back to idle when shifting. The throttle snaps back properly. Any suggestions? A SECOND QUESTION: I did custom tank and side cover painting. (about 7 photos) If anyone is interrested and you tell me how to post photos, I will do that. Thanks, Lew
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1978 XS 400 Carburetor Problem--Follow up
- Thread starter Lew11
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revs are supposed to come back down
I use a third party web based photo site such as photobucket. they allow you to copy the IMG tags of you picture. then you just copy and paste into the same text box you currently write in.
more than 1 photo, just keep pasting the relevant img (image)tags
there is a facillity to upload to the site but they are not very detailed, quality wise.
drewps
If it sounds like it idles perfectly but hangs try adjusting the idle rpm screw (not the fuel screws); it looks like a cog and is on the air filter side. You'll want to turn the idle rpms down a little (counter clock-wise I believe). Anywhere from 800 to 1200 is fine; it doesn't really matter as long as the engine sounds like it is running strong and steady. If you get too low it may sound like it wants to die.
Just above the #5 in this pic:
View attachment 3926
You have the idle mixture set, so get it warm and adjust the idle speed with that screw to 1200-1400 rpm, then balance the carbs and reset the idle speed if necessary.
View attachment 3926
You have the idle mixture set, so get it warm and adjust the idle speed with that screw to 1200-1400 rpm, then balance the carbs and reset the idle speed if necessary.
Ah yes---the idle adjustment. I have been using that. I was not clear at describing my problem. When I shut the throttle down, the RPMs are slow to return to idle. As an example when shifting the RPMs will hang around 3000 then slowly bleed back to idle. The carbs are snapping immediately back to the stop. Any suggestions??
Well, I hate to say this, but if the idle mixture screws are at 3 3/4, I would say there is still some level of schmutz in the idle circuit. Not returning to idle quickly is a classic sign of a lean idle condition which, at 3 3/4 turns, is not due to the adjustment itself, but some stubborn particle of dirt in there.
The bad news is that these carbs have to be surgically clean to run correctly. the good news is that once they are clean and if you run an external fuel filter, they will stay clean and hold a tune for a good long time.
The bad news is that these carbs have to be surgically clean to run correctly. the good news is that once they are clean and if you run an external fuel filter, they will stay clean and hold a tune for a good long time.
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