Herky / jerky defined? Can this be the root cause?

Snake Ranch · 11-21-2014, 04:23 PM

In the past I have complained about the sever jerking of the engine accel or decel at part throttle, around 2000 rpm. I spent a lot of time at different dealers trying to get an explanation of what is happening and get it corrected.

The best thing that was done was to change out the throttle body which made it almost go away. I can live with it now.

But what was causing this?

Check out this web site: http://www.ivansperformanceproducts.com/fce.htm

In a nut shell its the soft wear in the ECU cutting the fuel flow off suddenly and then turning it on suddenly at part throttle. This is for emission reasons. BUT real annoying.

Its only $130.00 The only problem is Ivan does not have one to fit the 1700's. It's a wiring harness issue. He has not had the 1700 in his hands to make the wiring harness.

A fellow rider where I used to work put one on his st1300 and he reported it works and completely eliminated the lag issues and jerkiness.

If anybody lives close to: about 35 miles northwest of NEW YORK city, he said he would not charge for the fitment time.

Does anybody any info on this?

RACNRAY · 11-21-2014, 05:48 PM

The herky jerky action lots of 1700 owners were complaining about had to do with trying to maintain a steady throttle setting at low rpm/small throttle openings.

Some or most FI equipped skoots have injector cut off. During deceleration/closed throttle operation the injectors are shut off by the ecu and do not operate until the throttle is opened. I have experienced skoots that have dead injectors at different rpms, some remaining dead until the throttle is opened, some becoming active a few hundred rpm's before coming back to idle speed.

If you have a skoot with dead injectors during decel/closed throttle, then there is no fuel entering the engine, you are experiencing engine braking with no combustion occurring.

Many companies that reflash ecu's take out the injector kill during decel thus you have some combustion occurring, so when the throttle is re-opened the engine is not transitioning from dead/no combustion to power.

The 1700's are well known for intake vacuum leaks between the throttle body and manifold and between the intake manifold and heads. Insuring these are sealed and leak-free will improve the engines running quality, especially at part throttle operation.

Proper tuning will also insure proper engine operation. The 1700's don't seem to be bothered by injector cut-off as do other skoots, the new FZ-09 comes to mind. It is VERY abrupt on re-application of the throttle.

RACNRAY

11-21-2014, 04:23 PM	#1
Snake Ranch Advanced Member Join Date: Oct 2013 Location: Stockton, Ca. Posts: 568	Herky / jerky defined? Can this be the root cause? In the past I have complained about the sever jerking of the engine accel or decel at part throttle, around 2000 rpm. I spent a lot of time at different dealers trying to get an explanation of what is happening and get it corrected. The best thing that was done was to change out the throttle body which made it almost go away. I can live with it now. But what was causing this? Check out this web site: http://www.ivansperformanceproducts.com/fce.htm In a nut shell its the soft wear in the ECU cutting the fuel flow off suddenly and then turning it on suddenly at part throttle. This is for emission reasons. BUT real annoying. Its only $130.00 The only problem is Ivan does not have one to fit the 1700's. It's a wiring harness issue. He has not had the 1700 in his hands to make the wiring harness. A fellow rider where I used to work put one on his st1300 and he reported it works and completely eliminated the lag issues and jerkiness. If anybody lives close to: about 35 miles northwest of NEW YORK city, he said he would not charge for the fitment time. Does anybody any info on this? __________________ Too much fun Is never enough. You make a living by what you get, You make a life by what you give. The measure of a man can be summed up by how he treats people who are the least significant to him. Login or Register to Remove Ads
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11-21-2014, 05:48 PM	#2
RACNRAY Sr. Member Join Date: Sep 2011 Location: SOUTH FLORIDA Posts: 1,210	The herky jerky action lots of 1700 owners were complaining about had to do with trying to maintain a steady throttle setting at low rpm/small throttle openings. Some or most FI equipped skoots have injector cut off. During deceleration/closed throttle operation the injectors are shut off by the ecu and do not operate until the throttle is opened. I have experienced skoots that have dead injectors at different rpms, some remaining dead until the throttle is opened, some becoming active a few hundred rpm's before coming back to idle speed. If you have a skoot with dead injectors during decel/closed throttle, then there is no fuel entering the engine, you are experiencing engine braking with no combustion occurring. Many companies that reflash ecu's take out the injector kill during decel thus you have some combustion occurring, so when the throttle is re-opened the engine is not transitioning from dead/no combustion to power. The 1700's are well known for intake vacuum leaks between the throttle body and manifold and between the intake manifold and heads. Insuring these are sealed and leak-free will improve the engines running quality, especially at part throttle operation. Proper tuning will also insure proper engine operation. The 1700's don't seem to be bothered by injector cut-off as do other skoots, the new FZ-09 comes to mind. It is VERY abrupt on re-application of the throttle. RACNRAY __________________ "TRUE HAPPINESS IS IN THE HEART, NOT IN THE OUTSIDE FIXES" WITH OVER 46 YEARS AS A MOTORCYCLE TECHNICIAN/HI-PO SHOP OWNER I AM A PURVEYOR OF FACT NOT FICTION! "WE LIVE OUR LIVES IN CHAINS NEVER KNOWING WE HAD THE KEY"
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