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Bike runs way better cold than warmed up - ideas?

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15K views 3 replies 4 participants last post by  Aussie Steve  
G
#1 ·
ok, this is getting weird. took the bike for a ride around town and to the provincial park last night (some decent curved roads), and noticed that when warmed up, the bike has this lurching hesitation at steady-throttle and during acceleration. but when 'cold', like after being parked for 30-45 minutes, it runs great and smooth.

so, why in the hell would it run WORSE when it's fully hot than when it's just barely warmed up?

do i need to run higher octane fuel to keep detonation out of the pic? been running 87 all the time (and put in 89 around a week ago), but lately it IS kinda hot around here, and the coolant is reading 90C / 194F or a bit higher during most non-highway riding.

is the chain heating up, expanding a bit much, and causing the whole thing to feel so jittery?

other stuff to check into?
 
D
#2 ·
Check the choke adjustment. If it is not correct, the bike will run fine cold but poorly once it warms up.
This could also be cause by poor routing of your fuel lines, placing them too close to a heat source.
Or you could have a slight lean condition, which will cause the bike to run hot and surge at steady throttle. Pull the choke out a tad and see if it runs better when you richen it up.
 
E
#3 ·
DrBob said:
Check the choke adjustment. Pull the choke out a tad and see if it runs better when you richen it up.
Click to expand...
My bet is that it gets worse. Usually a bike that runs better cold than hot is running rich. If it IS rich, then check air filter, obstructed exhaust, and choke adjustment mentioned above. Those are the easy things. After that, it gets tricky. Could even be an electrical component that is sensitive to heat or a crack opening up in the carb boots when hot.

And the answer to all of your other questions is: NO!

An inspection of the plugs should answer the rich/lean question.
Oh, yea, and check that gas cap vent !!!
 
#4 ·
I tend to agree with ER if the mix is rich you will get hesitant running. I have had similar problems and I figure it is general wear and tear on carb componants...after all the major problem with most modern bikes and Japs especially is they are very suseptable to even the slightest change because of the super fine tolerances used.
 
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