My circular saw, Riobi, tracks to the left. Even with a guide clamped to the work piece I can't cut a straight line. What's up with that?
I started out with a cheap Ryobi circular saw, and I had the same issue. I eventually realized that the base plate was not parallel to the blade.
I would suggest taking a measurement from the edge of the base plate to the front of the blade and comparing it to the distance from the edge of the base plate to the back of the blade. (For the most accurate measurement make sure you rotate the blade and measure to the same tooth both times.) If they're not identical then you know that is the problem.
My solution was to throw it out and buy a track saw.
As already mentioned in the Comments above this may be a duplicate of a previous thread and the replies there could help you solve the problem.
This isn't a diagnosis or a solution but a workaround that you may be able to take advantage of with the saw running exactly as-is.
- If your saw tracks to the left clamp the guide on the left side of the saw.
That way the current drift of the saw will pull it firmly against the guide board and not away from it, almost ensuring a straight cut. I believe a similar idea is used by some jigsaw owners, although jigsaws are lower in power and cut more slowly the basic principle may still work here.