Starter kickback fixed cheap!!! i think....
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Cruiser
Joined: May 2013
Posts: 128
Likes: 3
From: NJ
Starter kickback fixed cheap!!! i think....
Since ive owned this bike its had the all to common issue of starter kickback when its got a good heat soak on it. i recently rebuilt the motor with the FM107, tw555's and bigboyz heads w/releases. it went away.... or so i thought.
Down here in Mobile,AL it gets a lil toasty in the afternoon. on top of that traffic kinda sucks too depending on where you are. theres plenty of opportunity for this thing to get real hot especially when running errands. in the past two weeks ive had 6 starter kickbacks and im done with it. i know that you can change the compensator with a screaming eagle one for a few hundred bucks but i dont have the time or money for that so i did something else.
The main theory behind these kickbacks is cylinders getting hot building pressure and "pre-detonating" during starting sequence causing the piston to "kick back" right? Anyways that's how i've thought about it.
2 THINGS I DID:
So i used my PCIII to RETARD THE TIMING in the lower RPM and throttle range. i went to -5 in the lowest range and in the first three throttle settings. making sure that it was back to normal by the regular idle rpm.
I also regapped my plugs down to .35 from .40 as i heard that higher compression pistons require a closer gap.
So far its had no issues. it actually starts up VERY quickly now when its got a soak on it. its been a couple hundred miles and im happy with it. Figured i would pass this along and maybe some other folks will have some good luck as well.
Shiny side up yall
Down here in Mobile,AL it gets a lil toasty in the afternoon. on top of that traffic kinda sucks too depending on where you are. theres plenty of opportunity for this thing to get real hot especially when running errands. in the past two weeks ive had 6 starter kickbacks and im done with it. i know that you can change the compensator with a screaming eagle one for a few hundred bucks but i dont have the time or money for that so i did something else.
The main theory behind these kickbacks is cylinders getting hot building pressure and "pre-detonating" during starting sequence causing the piston to "kick back" right? Anyways that's how i've thought about it.
2 THINGS I DID:
So i used my PCIII to RETARD THE TIMING in the lower RPM and throttle range. i went to -5 in the lowest range and in the first three throttle settings. making sure that it was back to normal by the regular idle rpm.
I also regapped my plugs down to .35 from .40 as i heard that higher compression pistons require a closer gap.
So far its had no issues. it actually starts up VERY quickly now when its got a soak on it. its been a couple hundred miles and im happy with it. Figured i would pass this along and maybe some other folks will have some good luck as well.
Shiny side up yall
Grand HDF Member
Joined: Jan 2012
Posts: 4,458
Likes: 2,877
From: Oklahoma
I was told by a Harley service writer that couldn't be done. Your ability to change that alone makes a PC worth having. Will have to go to the web site and see what else it can change. Having any advance during start seems illogical to me, a little retard seems like a great setting.
Outstanding HDF Member
Joined: Dec 2008
Posts: 2,007
Likes: 353
From: Ohio
The releases should have cured the problem. Are you sure yours are working?
Extreme HDF Member
Joined: Sep 2010
Posts: 14,744
Likes: 402
From: Phoenix '53, '88, '09 Big Twins
A motor always stops on the compression stroke.
( always- when the spark is turned off, the motor rotates until the stored rotational energy cannot overcome the compression in the cylinders)
the TC motor does not have much of a flywheel to store forward motion
when the starter is pressed, the starter will attempt to push the piston past top dead center- and start the motor turning in the correct direction
the starter may not be able to produce enough power- and the piston may rebound back down the bore, turning backwards.
On a kick start bike, this may throw the rider's knee out...
on an electric start, the primary drive and the starter drive take the hit.
this is all affected by compression
a hot motor has more compression, as the pistons have expended into the bore for a tighter fit.
a hot motor will also have more resistance in the starter motor windings and the cabling- (so less force available to turn the bike over)
cam timing/duration/overlap
and comp releases (if any)
all factor into this.
some versions of the motor are programmed to turn a few revs before starting
I find that giving the starter a quick flick will either push past TDC, or compress and rebound the piston back down the bore.
In either case, the piston has a chance to take a run, build some momentum before hitting compression again and will almost always crank and start smoothly the 2nd time the starter button is pressed and held.
Mike
( always- when the spark is turned off, the motor rotates until the stored rotational energy cannot overcome the compression in the cylinders)
the TC motor does not have much of a flywheel to store forward motion
when the starter is pressed, the starter will attempt to push the piston past top dead center- and start the motor turning in the correct direction
the starter may not be able to produce enough power- and the piston may rebound back down the bore, turning backwards.
On a kick start bike, this may throw the rider's knee out...
on an electric start, the primary drive and the starter drive take the hit.
this is all affected by compression
a hot motor has more compression, as the pistons have expended into the bore for a tighter fit.
a hot motor will also have more resistance in the starter motor windings and the cabling- (so less force available to turn the bike over)
cam timing/duration/overlap
and comp releases (if any)
all factor into this.
some versions of the motor are programmed to turn a few revs before starting
I find that giving the starter a quick flick will either push past TDC, or compress and rebound the piston back down the bore.
In either case, the piston has a chance to take a run, build some momentum before hitting compression again and will almost always crank and start smoothly the 2nd time the starter button is pressed and held.
Mike
Last edited by mkguitar; Oct 10, 2013 at 01:32 PM.
Thread Starter
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Cruiser
Joined: May 2013
Posts: 128
Likes: 3
From: NJ
I thought the same thing. I think mine are too sensitive maybe. Sometimes they would close before the motor had started causing it to retain the compression. The backed out timing has done the trick so far. My next step was going to be pullin the releases and opening up the ports a bit
Road Warrior
Joined: Jan 2008
Posts: 1,995
Likes: 2
From: Land of 10,000 lakes
I was having the same issue. Now along with the c.r.'s I always make sure it is in Neutral. It really makes a big difference. If I ever have another hard start I'll check on doing what you did. What did you end up for numbers on your FM 107 with big boyz heads?
Road Captain
Joined: Jun 2006
Posts: 723
Likes: 62
From: Cape Cod, Ma.
Neil
RDMC
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Thread Starter
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Cruiser
Joined: May 2013
Posts: 128
Likes: 3
From: NJ
Mine didnt care if it was in neutral or not she just did it anyways. As for the numbers for the build i dont know yet. im takin it to my local shop to get it dynod and fine tuned in the next few weeks. FM gave me a map for the 107, 555s, and their heads. its workin really well. only thing i changed was the starting timing. i can say that it PULLS LIKE CRAZY. The bike is a monster now for sure. totally worth the money if you are on the fence. and as for the bigboyz heads it was less than 400 bucks for the porting and the releases shipped back to me ready to rock so id say it was worth it.
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Outstanding HDF Member
Joined: Dec 2009
Posts: 2,502
Likes: 6
From: Lapeer , Mich
Mine never kicks back , when I am at the dealer . Did the 96'' come with CRs ? Mine blows smoke out the top end someplace when it kicks back , bought mine used so I don' t know what has been done to it
Tourer
Joined: Aug 2009
Posts: 368
Likes: 22
From: southwest Iowa
I have the FM107 kit with the same issues on hot start. My question is regarding flicking the starter button. Do you just tap it quick to make the starter spin then full press right away or wait for it to quit spinning? To me, this seams as it could be harder on the starter than not turning at all??