Hey all, awhile ago i got a 1200 kit put in my bike. i have about 1400 miles on the conversion. Everythings been running well. Lately when i start my bike, soon as the starter engages i hear a loud clunk. It's right when i start it and does it most of the time but not all the time. Sometimes it even stalls-stops turning over. When it does start everything runs good tho. Im assuming its my starter going out but wanted to know what all ur opinions were. Thanks guys

 

Does it typically just happen when the motor is hot, like when you shut it off and then crank it back up a few minutes later?

 

Now that i think about it cHarley, thats the only time i notice it..so yes, just when its warm and i fire it right back up.

 

This is not an uncommon problem with 1200s due to their higher compression ratio, especially in warmer weather and climates.

The short answer is that the stock HD starter doesn't quite have enough torque to handle some hot starts. When you shut off a hot motor, one of the pistons will often come to a stop on a compression stroke, meaning that there will be pressure built up in that cylinder. That pressure pushing against the piston creates more dead load than the starter has torque to overcome. The end result is often a loud clunk or bang sound, which is the motor kicking back against the starter, specifically the starter clutch gear. When you let the bike sit for a while and cool down, the pressure in the cylinder will eventually bleed off, escaping past the rings, valves, etc, and the motor will start fine.

The end result of this kickback, will over time, result in the teeth of on the starter clutch gear being sheared off. I had this happen twice in the first ~24,000 miles.

After the second starter clutch failure, I replaced the whole starter with a 1.4kw "All *****" (brand) starter which I got from Eastern Performance. I think it was around $160.00. I haven't had anymore problems in the last 35,000+ miles.

 

Make certain you check your battery and battery cables before guessing it's the starter. That is an older bike and could have a battery with low cranking amps and I have seen brand new bikes with bad battery cables.