More gas, less crank? Starting problem.

Hello All,
I'm new to the forum. I've searched several threads looking for something that might parallel the issue I've had with my 2001 SV650 since the day I bought it. I know a little about mechanics, but not a lot and many of the acronyms used in the responses may be lost on me.

Issue:
When starting the bike, if I use the choke, or turn the throttle at all, the cranking power seems to drop right off. (Similar to having a weak battery) in any temperature weather. In warm weather (+15 deg C) if the bike is started daily, it usually starts with one or two cranks easily.

Bike Details:
The bike engine has been modified. According to the previous owner it has been overbored to a 750. Some custom wiring has also been done, as there is now a temperature gauge on the bike. There are no alarms on the bike. The bike runs great once started.

What I has been checked/changed:
I've put a new battery in the bike since I thought that might be the culprit soon after I got the bike - no change
I've used a multimeter to check to see if there is any current draw on the system, and it seems fine (draws current when key is on, but none when off). The regulator seems to be charging the battery, as I had no issue with it all summer.
It was taken to a mechanic and he adjusted the carbs to run a bit leaner as it was running very rich, but that had no effect on the starting ability of the bike.

I am thinking of pulling the spark plugs to see what type they are, and the current gapping on them. Possibly change to a hotter burning plug. Please respond with what you think may be the issue.
Thanks

[yorkie_chris]

I think you have a weak battery. With more air in the cylinder it will require more current to compress it.

Hmm, I've replaced the battery once, and it did the same thing. I may need to step the battery up a notch. I'll search for a stronger battery.

One thing I have also tried tho is to hook a car battery (with the car not running) up to mine in parallel and the cranking power still drops off or becomes more difficult to crank with the choke on. Could the starter be insufficient to crank the higher compression?

[yorkie_chris]

Also look at starter motor, sometimes the ceramic around positive lead can crack. Or maybe comm is dirty and worn, maybe worth stripping starter to inspect it.

The starter should be OK, I have not heard of any problems.

What about the starter solenoid, could a problem there cause this? As I have never had a problem in this area I don't know a huge amount about the starting system.
Another idea that strikes me is it could a poor earth somewhere.