Frustrating running issue
Frustrating running issue
It seems I have developed a low speed hesitation I cannot get rid of. Only when engine is good and warm does it become an issue. When accelerating from a prolonged stop the engine spits and sputters and falls on its face. Ive had it to the dealer and get told they cannot duplicate it. I even rap the throttle a couple times just before the light changes but it does not seem to help. The issue gets worse the hotter the engine gets.
Bike runs great at speed.
Bike details:
09 with 103 upgrade
SE255 cams
True Duals
SERT
Bike runs great at speed.
Bike details:
09 with 103 upgrade
SE255 cams
True Duals
SERT
Extreme HDF Member
Joined: Sep 2010
Posts: 14,744
Likes: 402
From: Phoenix '53, '88, '09 Big Twins
possible the MAP sensor in the intake?
when we open the throttle, the motor goes momentarily lean, and the vacuum in the intake drops
carbs use an accel pump to compensate.
efi uses a sensor in the intake to recognize the drop in pressure and to let the ecm know to add fuel.
what you describe, could be this
older motorcycles i have with out accel pumps do this, they stumble and may even sneeze out the carb if the throttle is opened suddenly...I have to open the throttle fairly gradually*.
so I'd suggest you check out the threads on cleaning the sensor, a specialized spray cleaner will do it.
also check that the intake nipple ( on the top of the intake manifold ) either has a cap on it ( 49 State) or a hose to the charcoal canister ( Cal.) and that the hose is in good shape, no cracks
mike
*the linkert on the '53 is like this ( and also the honda trail 90), and most riders would set the idle over-rich to try to smooth out this transition...so idle might be over-rich, stinky and sooty.
the Keihin "butterfly" carb which pre-dated the 1990+ keihin CV carb could also be problematic in the same way. even the first CV carbs lacked an accel pump- as introduced in '88 on the sportys
when we open the throttle, the motor goes momentarily lean, and the vacuum in the intake drops
carbs use an accel pump to compensate.
efi uses a sensor in the intake to recognize the drop in pressure and to let the ecm know to add fuel.
what you describe, could be this
older motorcycles i have with out accel pumps do this, they stumble and may even sneeze out the carb if the throttle is opened suddenly...I have to open the throttle fairly gradually*.
so I'd suggest you check out the threads on cleaning the sensor, a specialized spray cleaner will do it.
also check that the intake nipple ( on the top of the intake manifold ) either has a cap on it ( 49 State) or a hose to the charcoal canister ( Cal.) and that the hose is in good shape, no cracks
mike
*the linkert on the '53 is like this ( and also the honda trail 90), and most riders would set the idle over-rich to try to smooth out this transition...so idle might be over-rich, stinky and sooty.
the Keihin "butterfly" carb which pre-dated the 1990+ keihin CV carb could also be problematic in the same way. even the first CV carbs lacked an accel pump- as introduced in '88 on the sportys
Last edited by mkguitar; May 11, 2014 at 01:07 PM.
Extreme HDF Member
Joined: Sep 2010
Posts: 14,744
Likes: 402
From: Phoenix '53, '88, '09 Big Twins
When i was taking auto trades over 20 years ago the instructor, NHRA Bracket Racer Mike Brandt, encouraged students to buy service manuals and read up on stuff.
He had about 20 "Wally" trophys in his office and a 40+ year automotive career
I have a stack of manuals for stuff i don't even own
my post above is my best guess
Mike
He had about 20 "Wally" trophys in his office and a 40+ year automotive career
I have a stack of manuals for stuff i don't even own
my post above is my best guess
Mike
Last edited by mkguitar; May 11, 2014 at 01:38 PM.
Grand HDF Member
Joined: Jan 2012
Posts: 4,445
Likes: 2,810
From: Oklahoma
Have you pulled the plugs to see if they are showing, rich, lean or about right? What is the gap? How many miles on the plugs and fuel injectors, and have you been running brand X gas or a name brand with a good detergent package? Have you tried an injector cleaner yet, Techron, Berryman Chemtool or Sea Foam? How recent is the air filter element? Any codes? Have black soot coating the inside of the exhaust pipes?
Road Warrior
Joined: Apr 2010
Posts: 1,648
Likes: 37
From: Monroe, Louisiana
If none of the above fix it you can richen the idle in the VE tables by increasing the VE 5 to start with. You only need to richen the throttle position 1 thru 10 and rpm 750 thru 1500. The acceleration enrichment can be richened around 0.3 from top to bottom. The 255's like to be a little rich at idle. In fact the ones that work right will give a slight black puff from the exhaust if you rap it from idle. The VE in this area should be around 90 on rear and 85 on the front cylinder. Just estimated. All above is assuming you have cables and software and know how to use it. I would check all of the above first as the bike won't just start doing this if it were right at one time and nothing changed, like pipes or mufflers or intake.
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Thanks Mike I will give that a look.
To answer others: Pugs replace 1K ago at last service. A/C serviced as well
Intake gaskets were recently replaced as well.
Ive been putting Lucas Fuel Additive in tank.
I do not have the CD or program to make adjustments on the SERT.
No it is not the way I let out the Clutch
To answer others: Pugs replace 1K ago at last service. A/C serviced as well
Intake gaskets were recently replaced as well.
Ive been putting Lucas Fuel Additive in tank.
I do not have the CD or program to make adjustments on the SERT.
No it is not the way I let out the Clutch
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Tourer
Joined: Oct 2013
Posts: 368
Likes: 3
From: pennsylvania
Aint that the truth he is always postin in these threads with knowledgeable no bs comments. Maybe mr knownledge is what the mk stands for haha. If you sir are not a mechanic sounds like you should be you could probly make some decent money at it.
Update:
I took a look at the Purge hose on top the Induction Module as I do have a Ca. bike with charcoal canister. I found this hose was not a tight fit on the metal tube from the Induction module, I was able to slide it off and on with no resistance. Not sure if this was an issue Mike eluded to but. I was able to get a Zip Tie on it and clamp it down. We will see.
Mike, could that hose cause somewhat of a vacuum leak?
I took a look at the Purge hose on top the Induction Module as I do have a Ca. bike with charcoal canister. I found this hose was not a tight fit on the metal tube from the Induction module, I was able to slide it off and on with no resistance. Not sure if this was an issue Mike eluded to but. I was able to get a Zip Tie on it and clamp it down. We will see.
Mike, could that hose cause somewhat of a vacuum leak?