Want to change front chainwheel and need advice

[Old timer]

The chainwheel on my E bike is a single, 48 teeth, length from pedal spindle centre to BB centre is 170mm. It`s ali and looks like it`s the same as my Evans crank that is a centre nut pulling the chain wheel onto a sq drive. I have the removal tool becuase I removed my evans Shimano crank wheels recently. What is that type called? for ordering?
The rear mech is shimano tourney indexed(cheap i know but seems to work fine for me and they came with the bike)

The rear gears are 6 speed. I don`t ever use below the first four gears 6-3 inclusive but I do find that the top gear along with the pedal assistance is at times just a bit too low. I know that if I jump up a touch in size I might get to the point where the assistance tails off (15mph is supposed to be the upper limit) but I can always drop down one gear and hopefully be back where I was with the old chain wheel thus leaving the top gear as a bit of an overdrive.(if you know what I mean)

So! can you see any problems (chain length etc) and if I went up to say a 53 tooth would that make much of a difference. I notice that a lot of chain wheel sets are at least doubles but I only want a single and besides the inner wheel might interfeer with the pedelec magnetic disk that is on the inner part of the BB spindle. If I had to purchase a double could I remove the inner smaller wheel?
One other thing(sorry) the existing single wheel has a chain guard (slightly larger than the chainwheel on both sides) is that a chain guard to keep clothes off of the grease or is it to help prevent the chain from jumping off and is it required?

Something like the chain reaction sale set 11275 and do you get the left hand arm in the set. I can`t tell if it is the sq drive fitting.

Sorry about all the questions

Thanks

Dave

 

[Old timer]

The chainwheel on my E bike is a single, 48 teeth, length from pedal spindle centre to BB centre is 170mm. It`s ali and looks like it`s the same as my Evans crank that is a centre nut pulling the chain wheel onto a sq drive. I have the removal tool becuase I removed my evans Shimano crank wheels recently. What is that type called? for ordering?
The rear mech is shimano tourney indexed(cheap i know but seems to work fine for me and they came with the bike)

The rear gears are 6 speed. I don`t ever use below the first four gears 6-3 inclusive but I do find that the top gear along with the pedal assistance is at times just a bit too low. I know that if I jump up a touch in size I might get to the point where the assistance tails off (15mph is supposed to be the upper limit) but I can always drop down one gear and hopefully be back where I was with the old chain wheel thus leaving the top gear as a bit of an overdrive.(if you know what I mean)

So! can you see any problems (chain length etc) and if I went up to say a 53 tooth would that make much of a difference. I notice that a lot of chain wheel sets are at least doubles but I only want a single and besides the inner wheel might interfeer with the pedelec magnetic disk that is on the inner part of the BB spindle. If I had to purchase a double could I remove the inner smaller wheel?
One other thing(sorry) the existing single wheel has a chain guard (slightly larger than the chainwheel on both sides) is that a chain guard to keep clothes off of the grease or is it to help prevent the chain from jumping off and is it required?

Something like the chain reaction sale set 11275 and do you get the left hand arm in the set. I can`t tell if it is the sq drive fitting.

Sorry about all the questions

Thanks

Dave

Also! how do I measure the chain size (width)

 

[totallyfixed]

I think you will find it's a Shimano crank extractor you are looking for. Regarding the chain wheel the most important measurement you will need is the Bolt Circle Diameter [look it up] as there are several different ones out there. I would be looking at a 50t or 52t chain wheel from what you have said about the gearing on your bike.
The chain guard has nothing to do with keeping the chain on it's just there to stop you getting oily clothing, I personally prefer bikes without them, just a nuisance when or if your chain needs fettling.
If unsure about any kit a shop is selling always email or ring them to check, oh and don't bother with a double, just buy the single chain wheel.
Hope that helps a bit.