Thank you bigbwb for taking the time to test fit and photograph the HM shock on the bike. I know from experience that can be time consuming.
I can’t help but notice how similar the HM shock looks to the generic eBay shock I installed on an SSR 70 I was repairing this summer. The one I used was 250mm (stock CRF50 is 235mm) but can be bought from eBay, Amazon, and AliExpress for around $20-25. Unfortunately, I already sold the bike so cannot install it on my chinese CRF50. Here is the one I used from several different sources.
I also stumbled upon a 260mm one while on eBay while looking for the one I bought. It looks identical to the HM one to me.
Bigbwb’s efforts to help the forum encouraged me to do some testing and research also in hopes of helping others.
Here is my FastAce BDA01 mounted on my Chinese made CRF50:
Despite reports that it won’t fit, you can clearly see that it does.
The shock must be mounted with the lock rings closest to the seat and the adjustment knob at the bottom. If you reverse the direct the lock rings will not pass thru the frame and will block it from compressing. I think this might be where the idea that it does not fit originated. The spring DOES touch the frame and over time may rub the finish from the shock or the frame but with my 200+ lbs butt on the bike it compresses and rebounds without issue.
I also have an older iShock (no longer available new). The iShock is less than 45mm at the widest point so it will also work and easily pass thru the frame.
There is also the blue Kitaco Shock. Another forum member was kind enough to measure his Kitaco shock for me and at 51mm wide at the spring it will pass thru the Chinese frames. Here is cool video of a stunted 2014 Chinese built CRF50 running a Kitaco shock:
Kitaco also has an updated (red) version of the shock which I am willing to bet will also fit just from the photos, but I am having a hard time finding the pricing, availability, and specs except that it is a 220lbs shock with 8 clicks of adjustment.
I am guessing there are probably quite a few other shocks that will fit, but I just don’t have the time and money to buy and test fit them all.
So it appears we have options for all types of budgets:
$365 Fox Float MXR - air shock with lots of adjustability but requires notching the top mounting bracket
$110 Kitaco (blue) - approx 200lbs spring with 5 adjustments, direct bolt on
$103 FastAce BDA01 - 250lbs spring with adjustable rebound, must be mounted with lock rings on top
$50-100 (used iShock) two versions (reservoir and non-reservoir) adjustable dampening, Mount the reservoir at the bottom unless you want to notch the seat base.
$85 Honda Mini shock - unknown manufacturer with unknown spring rating and no adjustments for dampening or rebound (appears to be a generic chinese shock)
$20-45 generic Chinese shocks - spring ratings from 200lbs to 1200lbs with no adjustments for dampening or rebound. Ask seller to confirm spring rating before buying.