hot and hard to start

[vern]

I've got a shovel on the rack that start and spins nice when its cold but after it warms up for a few minuets the starter has a tough time turning it over, it has an oil cooler but it just seems to hot. intake leak, pistons to tight, it has after market cases and is 93 inch.

[Hillside Motorcycle]

Starter issue??
Scott

[76shuvlinoff]

  What I have found with the stock (prestolite) starter is the brushes and springs deteriorate and it's capability slowly goes down hill. New brushes and springs, clean armature greased bearing can make a world of difference. On my 93"er I also installed hi torque field coils from JP  You need a heavy soldering iron for changing brushes not your hobby store 25 watt unit.

I just went to an All Balls starter, the jury is still out on that.

If you think you have an intake leak, you need to address that first.

Good luck

[vern]

it's got a new starter in it and I'm happy with the way it spins. I was thinking forged pistons in a cylinder bored for cast pistons.

[Lew]

Good battery?  Is the battery getting charged when the motor is running?
       

[vern]

The alt charges at 14.4 volts. I don't think its electrical. the motor gets so hot that it seems to sieze.

[HogMike]

What cam? High compression?
Had a similar problem with my 93"....went to a different cam, cause I didn't want to lower compression.
Just me.

[vern]

would a cam affect hot or cold starting?

[HogMike]

To a degree.....with different overlap, and lower cranking pressure the motor will spin over easier. Just depends on the build, compression, etc.
If the forged pistons are set too tight they will seize. I would sure check all the other stuff first....check your battery cables, connections (most common cause) and work out from there.
I had a similar problem running forged (all I could get at the time) in a '38 flathead.
Had to keep boring until the bike would run while hot. Made a terrible clatter when cold!

[vern]

I checked in side the sparkplug hole and the cylinbers were starting to score and the work order said they were forged, so I guess it will be an other rebuild.

[Older-twin]

It sounds like it is not bored correctly and it is seizing up the pistons when warmed up.  I just read that this condition can be caused by spark knock detonation.  Check out this article.

http://www.streetrodstuff.com/Articles/Engine/Detonation/index.php

[dusty1]

I dont know the clearances off the top of my head.I do know that forged pistons need more clearance than cast pistons.Cast=.002" and i think forged need twice that

[stray]

New pistons require that the bore be checked against the piston manufacturer's recommended fit and re-bored for correct fit.
Joe