RPM Dropping all the way down only after nearly coming to a stop | GTAMotorcycle.com

RPM Dropping all the way down only after nearly coming to a stop

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il3dsm

Well-known member
Hello,

I have an odd problem with my bike.

When I pull in the clutch and coast to the stop, my RPM drops to ~2500 and only after I come to a stop decreases all the way down.
I checked the cable and the throttle movement to make sure it doesn't stick, it doesn't.

I can coast pretty far with fast idle and clutch pulled it and it starts to drop all the way down only after I start applying brakes (front or back, doesn't matter, however brakes may not be related).

Here's a video of this happening. (Fast idle at 13 seconds, goes down at 16 seconds)
(WARNING: TURN DOWN THE SOUND)

https://www.youtube.com/watch?v=hyvxCIAj0m4&feature=youtu.be


Does anybody know why this is happening?
 
Do you know when the valve clearances were last checked?
 
il3dsm said:
Nope. Planning to do it soon...
Click to expand...

Valves out of whack can affect/cause hanging idle, air leaks around the carb intake boots, carb sync is a big one ( on multi-carb bikes, does not apply to your drz).
It sounds as though you have an aftermarket exhaust, if this was done without jetting it can cause issues with idle as well.
Fwiw, the valves are easy to check/adjust on the drz. First time I did it, I was 5 hours, including replacing all 4 shims and a trip to St Onge to get the required shims.
 
What bike ? There are a couple of machines were the throttle cable hangs up in the right handlebar switch housing and doesn't release properly.
 
Iceman said:
Valves out of whack can affect/cause hanging idle, air leaks around the carb intake boots, carb sync is a big one ( on multi-carb bikes, does not apply to your drz).
It sounds as though you have an aftermarket exhaust, if this was done without jetting it can cause issues with idle as well.
Fwiw, the valves are easy to check/adjust on the drz. First time I did it, I was 5 hours, including replacing all 4 shims and a trip to St Onge to get the required shims.
Click to expand...


Thanks for the response.

I have stock exhaust but 3x3 mod and it has been jetted.
It sounds louder in the video since camera must be vibrating in the case or something... Or maybe I just go deaf when I ride it after a while.

The bike starts and runs fine. Has lots of torque and can do highway fine, no performance problems.
I've watched numerous videos on it, it seems okay as long as it's just clearance check. Adjustment on the other hand... Need to buy shims.

I'll look into air leaks.

TK4 said:
What bike ? There are a couple of machines were the throttle cable hangs up in the right handlebar switch housing and doesn't release properly.
Click to expand...

It's a DRZ400sm
I checked the movement, seems fine.
 
Last edited:
It's a DRZ400sm
I checked the movement, seems fine.[/QUOTE]

Spray some WD40 (or similar) on the intake manifold between the carb and the cylinder head - sounds like its sucking air...
 
If it only does it while you are coasting and it goes away when your road speed drops, check your clutch lever free play. The clutch may not be completely disengaging
 
Run some seafoam through the system, may be a plugged jet causing a lean condition.
 
Put some carb cleaner into the fuel + spray.
It looks like it's idling faster now since I can roll around 1km/h faster on idle.
Hard to tell otherwise with no tachometer.

I noticed it sometimes revs down immediately, but sometimes not. Hard to tell since I only rode it around hard for 20km after putting all sorts of **** into the system. Time will tell.

In a few days I'll receive a package from canada's motorcycle so I can do valve clearance check + change oil + take off the carb and actually clean it.

...And also should have ordered a new air filter. Oh well.
 
hard time idling without maintaining throttle opening is a classic symptom for issues with carbs. You have to clean them. Running seafom or similar cleaner /may/ remedy your situation, but unlikely.
 
If the bike is not stock ... the jetting is probably out of whack, or it's simply a carb issue period.
 
Update: After cleaning the carb using seafoam and spray, issue persisted.

Fixed it by turning down idle (was idling a bit too fast after cleaning)
RPMs drop down as expected now.
 
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