Bike pedal stop front wheel from turning
 

We know nothing about bicycle other than how to ride it. We bought a used 26" bike. I hurt my leg and cannot test the bike and I was stupid to trust the seller because he was ridding it towards me. That gave me the impression that it is in working condition. When I am home, I found out that the cranking pedal is stopping the front wheel from turning when it is parallel to the ground. If I had tested it, I definitely detected the problem right away. But it is too late now. I think the bike may be a scam by putting different parts together. BTW, all the parts looks good. I am trying the get some suggestions on how can I get it to work again. I can think of 3 options.
1. Replace the crank arm with a shorter one.
2. Replace the front wheel with a smaller wheels (not sure what's the impact by having difference size front and back wheel)
3. Replace the frame with a bigger frame.
I am not a bike mechanic. But I am handy and have some tools at home. Can anyone suggest what is the easiest way to fix the problem.

Your post makes little to no sense.
Take it to a bike shop.
I'd say post a pic but as it is your first post you can't for a bit.
If the person who sold it to you rode it to you it is likely working.

Photos. The ONLY way this could happen is if the fork is backwards OR the bike has had a large frontal impact and the frame is bent.

Not an unusual problem with many bikes. "Toe or Pedal Overlap" is the term. Of course your front fork could have been bent rearward from a head on crash causing this or making it worse but most likely just the way the bike was made. You can learn to stop pedaling when you have to turn the steering a few degrees, just another cycling skill many have learned. We need photos first to determine what the issue is.

Pedal/wheel overlap, as @Crankycrank suggests, is not uncommon, but is only an issue with very sharp turns at very low speed. Front-end damage, as @cxwrench suggests, is also a possibility. Look for ripples in the tubing and/or paint damage adjacent to the head lugs or welds. Examine the bike from the side to see if the fork blades have been bent back toward the frame. If you can post some pictures, e.g. side views and close-ups of the head tube joints, we may be able to help determine if that is the case.

If we’re talking about TOE overlap with the front wheel, that’s perfectly normal, particularly on bikes with smaller frame sizes. Unless you try to pedal during a very sharp or low speed turn it’s seldom an issue, and everyone deals with it.
If we’re talking about actual PEDAL into tire overlap, that’s less common unless the Acme Clown Shoe Company also made your pedals, though I have seen it with normal pedals. We really will need a picture, and for that you’ll need 10 posts. Replies here or a thread/replies in the new user section are both easy ways to get your post count past 10.
Putting on tiny cranks or mismatching the wheels is not the solution, though if your fork is on backwards that might be. I’ve seen my share of backward forks on brand new department store bikes, so it’s quite possible the seller rode on in it because it’s always been that way and they just didn’t know better.

I wouldn't do that regardless, but is it a one-, two-, or three-piece crank?

Absolutely not. The frame was designed for a specific wheel size. The next size smaller is 24" -- the brakes won't line up correctly and it will handle weird.

Maybe ... but getting all the old parts to retrofit might be a challenge, as seat tube diameter, bottom bracket dimensions, headset, brake type, etc. all have to be the same as the old frame.

Take it to one and let them have a look before you do anything else. I suspect this is either a routine toe overlap issue or the frame and/or fork are damaged.

You can upload pics to the Gallery here on BF. Someone will find them and post them in this thread for you.

https://www.bikeforums.net/g/

Or you can put the pic's on https://imgur.com or other hosting site and just simply type the sharing URL for them in the text of your message here. But you have to obfuscate the URL so the SPAM filters don't pick it up.

Sort of a test to see if we are getting decent quality noobs! <grin>

Thanks, you are right. The fork was installed backward.

More common than you might think. I have seen a photo of New York City mayor Eric Adams riding his bike with a backwards fork. This might be a sign that there are other problems with the bike that should be checked over

:thumb: Glad you got it sorted!

I've seen this fairly often with department store bikes. The bikes are boxed with the forks reversed, to save a little space. Inexperienced assemblers assume that this is the proper orientation, and leave the fork reversed when they complete assembly. On larger frame sizes there is generally enough clearance between the tire and the down tube to allow this, but with smaller frame sizes the tire can abut the down tube, as you discovered.

Fork can't be installed backwards, handlebars were installed backwards...

I see what you did there.

I will point to the elephant in the room and mention that assembling a bike with the fork backwards (and assumably the bars and stem properly forward) and not knowing that a potential buyer might see that and thus bicker the price down seems to me a mark of someone who would do other no nos with assembly and adjustments. Some possibly more safety related then fork trail is:) Andy

What if the brake is backwards in the fork and the QR lever is still on the left side of the bike? Less common, but I’ve seen it.

LOL. Then the brakes and the q release (or possibly the whole wheel) were installed "backwards", fork can't be installed backwards. We see some of this from department stores and big box bikes that are assembled by hired companies that assemble everything from furniture, grills, and what have you.