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Hello all.
Got myself this here motorcycle...
Untitled by Kayak23, on Flickr
....a 1982 Suzuki Gsx400f (not even sure I'm allowed on this forum with my extra letters after GS).
It's been about fifteen years since I last had a bike and I'm a little rusty, as is the bike
Anyway, I'm having some running issues and hoped this place might suggest a few avenues to try.
I'm having charging issues but I reckon I can figure that one out (tested reg/rec, seems fine, not sure about alt)
The main issue I'm having and can't seem to suss is a 'hanging idle', in other words, the revs will often not drop and stay at or climb to about 5-6k and stay there until I nudge the clutch out in gear. It's obviously not ideal when you're trying to slow down and the bike wants to keep going.
It appears to be worse when the engine is hot.
The first thing I checked for was vacuum leaks. With the bike idling, I sprayed carb cleaner around the rubber boots to the engine. No change in revs.
I checked the throttle cable which seems to run very smooth and has a small amount of play at the carb end when under full lock either way so I don't think it's that.
Then two days ago I stripped and cleaned all the carbs, using carb cleaner, blowing out the jets with air and cleaning gently with a toothbrush. There was evidence of yellowing deposits in the float bowl but obviously I cleaned the whole shebang.
I inspected the diaphragms and the sliders. Diaphragms looked fine and although the sliders seemed to move up and down pretty freely, there was some degradation of the black coating on them, some of it coming away very easily under my thumb.
Untitled by Kayak23, on Flickr
When I reassembled the bike and started it, the hanging idle was briefly there, but after it settled it seemed good. I took it for a long run of about fifty miles and it seemed to be running great. I'd blip the throttle and the revs would stop right down again like they should. I even had engine braking!
So that was the day before yesterday. Yesterday I took it for a run again and almost immediately I had the hanging idle again.
Again this morning I've started it up, and hit each carb boot in turn with carb cleaner and seemingly no change in revs.
Today I plan to take the sliders out and polish the bore to see if I can get them running any better.
I'm hesitant to touch the coating on them as it seems very fragile.
Saying that, they do push up and drop down fine. Putting a finger over the slot thing makes a vacuum and they drop slower too.
After reassembling the bike today following checking float height and polishing up the bores a little and wet and drying the slides very lightly to get rid of any flakiness, the hanging idle is back, and if anything, worse than before.
Checked for vac leaks again but it all seems fine.
Can anyone suggest what else I might try?
Bear in mind I've been away from bikes for a long time and I may not know what you're on about...
Got myself this here motorcycle...
Untitled by Kayak23, on Flickr....a 1982 Suzuki Gsx400f (not even sure I'm allowed on this forum with my extra letters after GS).
It's been about fifteen years since I last had a bike and I'm a little rusty, as is the bike
Anyway, I'm having some running issues and hoped this place might suggest a few avenues to try.
I'm having charging issues but I reckon I can figure that one out (tested reg/rec, seems fine, not sure about alt)
The main issue I'm having and can't seem to suss is a 'hanging idle', in other words, the revs will often not drop and stay at or climb to about 5-6k and stay there until I nudge the clutch out in gear. It's obviously not ideal when you're trying to slow down and the bike wants to keep going.
It appears to be worse when the engine is hot.
The first thing I checked for was vacuum leaks. With the bike idling, I sprayed carb cleaner around the rubber boots to the engine. No change in revs.
I checked the throttle cable which seems to run very smooth and has a small amount of play at the carb end when under full lock either way so I don't think it's that.
Then two days ago I stripped and cleaned all the carbs, using carb cleaner, blowing out the jets with air and cleaning gently with a toothbrush. There was evidence of yellowing deposits in the float bowl but obviously I cleaned the whole shebang.
I inspected the diaphragms and the sliders. Diaphragms looked fine and although the sliders seemed to move up and down pretty freely, there was some degradation of the black coating on them, some of it coming away very easily under my thumb.
Untitled by Kayak23, on FlickrWhen I reassembled the bike and started it, the hanging idle was briefly there, but after it settled it seemed good. I took it for a long run of about fifty miles and it seemed to be running great. I'd blip the throttle and the revs would stop right down again like they should. I even had engine braking!
So that was the day before yesterday. Yesterday I took it for a run again and almost immediately I had the hanging idle again.
Again this morning I've started it up, and hit each carb boot in turn with carb cleaner and seemingly no change in revs.
Today I plan to take the sliders out and polish the bore to see if I can get them running any better.
I'm hesitant to touch the coating on them as it seems very fragile.
Saying that, they do push up and drop down fine. Putting a finger over the slot thing makes a vacuum and they drop slower too.
After reassembling the bike today following checking float height and polishing up the bores a little and wet and drying the slides very lightly to get rid of any flakiness, the hanging idle is back, and if anything, worse than before.
Checked for vac leaks again but it all seems fine.
Can anyone suggest what else I might try?
Bear in mind I've been away from bikes for a long time and I may not know what you're on about...
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