Just put together 2 new 400s.  It was around 10F last night and I had trouble starting both this morning.   They labored to turn over and during the process the display would go out like the draw to the starter was too much.  They both do the same thing.  Very weird.  Load tested the new battery and Tried a jumper.  No help. Starts right up when warm but not when very cold.

Go through the electrical connections. Rub some scotch Brite on them. Someone made mention of a fuse holder near the battery on another model that was a trouble maker. If you used a jumper than I think the culprit is down stream of the battery. Does the power come off the solenoid to power the rest of the bike? If so look there. Seems odd both are like this and makes me suspect someone made a mistake. Off to a rough start..

Thanks.  I'll check for that fuse.

Just put together 2 new 400s.  It was around 10F last night and I had trouble starting both this morning.   They labored to turn over and during the process the display would go out like the draw to the starter was too much.  They both do the same thing.  Very weird.  Load tested the new battery and Tried a jumper.  No help. Starts right up when warm but not when very cold.

These big batteries require special attention during the initial acid fill.

Once you fill the acid in the battery, leave the black plastic fill cover off and let the battery sit for a minimum of 3 hours. This allows the lead in the cells to soak up the acid.

After the three hours, the batteries MUST be charged on a trickle charger (2amp or less) until it reaches a full charge.

If the batteries are not filled and charged correctly they will have issue.

Just received a service bulletin from cf Moto.  Some of the 400s may have caused me through with a decompressor issue.  Causes hard starting with n the cold. Just a heads up.

Can you post the TSB for us? It would be nice to see exactly what they put out.