cb750s are naturally wide bikes. What makes it easier stock is that the seat taipers as it rises so it conforms to meet your groin. If you just cut the foam in half and throw a cover over it it is going to feel flat and wide.
Here is the advice I give newbie to old bikes in real life. Rather than take a shotgun approach to old bikes and just see what's cool and for sale - pick a few models you really like and actively seek them out. be patient and look at a lot of bikes - you'll know the right deal when you are in the middle of it. I started riding these bikes when they were just 15-20 year old used bikes nobody wanted and therefore cheap. Now they are 35-40 year old bikes and have a lot more issues and good ones cost a decent amount. So it pays to do your research in this regard so you know what the issues are, whether they have been addressed, and whether quality parts have been used. The cb750 is an excellent commuter bike, I have owned mine since the mid 90's, put a ton of miles on it, and used it as my daily commuter. But i got it in really nice condition and always kept it that way. There are deals to be had out there, but you just might have to put some leg work in.
The one semi good piece of advice I can give you - any time you see an emgo pod filter know that your seller doesn't know the difference between good parts and a good deal (emgo filters are neither). I don't mean to be so judgmental on one part but those are usually a sign that whomever put them on is unabashedly cheap and didn't look at the part before he installed it. If he says it is a performance upgrade you can add not knowing his ass from his elbow to the list. Its a nice clear big red flag.
Final thought - vintage performance bikes are kind of personal to the owner. so if you are buying someone else's hot rod know that change is inevitable. You just want a good foundation. In this rush to be "cafe cool" people forgot or didn't realize there should be a good solid performing motorcycle underneath. The modifications should make sense to you from a functional standpoint not just aesthetic. Some other red flags are:
- Knee dents on a stock tank: you can lose up to a gallon of fuel capacity and adds weight - all for "racer style", blegh. Serves no functional purpose and tries to hard to make an old bike look older. The exception is if the tank capacity has been increased to 5 gallons or larger because you need that space to clear your legs.
- Fixed clubman bars with stock pegs: clubman bars were designed for small european and british twins in the 50's, not big fat japanes 4 cyl leg burners. as such 90% of the fixed ones out there are a poor fit and the ones that aren't cost real money. a good sign a clubman bar is a poor fit is if the master cylinder is turned in an uncomfortable wrist breaking angle to clear the gauges. Also look for clubman rash - spots where the bar hits the tank (esp a problem on the F bikes). if you see that bar with a set of stock pegs know that whomever installed them doesn't understand ergonomics. That position forces you to bend your back into an arch as the ass to seat position tries to hold your body upright while you bend forward to reach the bars. I personally call this the crapping in the woods riding position because without the bike that's what it looks like you are doing.
- open pipes: If loud pipes saved lives, imagine what training and proper gear would do. People think motorcycles should be as loud as possible. However if you are a long time rider you know that volume leads to rider fatigue and also being treated like an arsehole by everyone around you. A little music is fine, a 4" open meg is just obnoxious and crude.
- changed master cylinders: if you see a new master on old calipers be wary. 1) the person probably can't rebuild the master so they just bought a new one off ebay, 2) they probably didn't understand what those little cast numbers mean underneat, 3) you might not have a front brake light switch. If you see one, check that the piston is the same size as stock (or appropriate size if upgraded to dual disc) by reading the cast numbers on the underside. Also check for a brake switch. If it has both those things take comfort in the fact the seller/builder was using his head. If not - be very cautious a the bike may have spongy or wooden brakes.
