Or these 79' front axle I found cleaning the garage. Again ugh.

Again just what is expected? If the machine is to be raced vmx then i think only 4 inches of travel is allowed. However if he just wants to stop loosing his dentures then a swap is in his interest.

I have swapped forks on a 77 Honda CR125 (AHRMA P-V Historic Class) for the forks and front wheel off an 82 Honda XL250. I did shorten the travel of the forks, so the bike would remain “legal” for the class, but upgraded them with Race Tech cartridge emulators and fork springs. It now has a full 9” of travel up front and 7” in back with Works shocks. Another swap I did was putting 31mm forks from an 83 Honda CR80 onto an 83 Honda XR100. That one required using the triple clamps from a 77 Honda MR175. Damping rod forks are pretty simple to take apart and upgrade with emulators.

This is just what I am trying to point out but you seem to have left out a large detail. The need for a fork swap to increase travel. The emulators dont do that by themselves alone correct ?

For vintage class (pre-75), suspension travel is limited to 7” front, 4” rear. Yet some forks do not have 7” of travel. Also some people upgrade to larger diameter fork tubes.

Emulators offer a way to control compression damping. Basically you modify the damping rod to increase oil flow. The emulator is a spring loaded valve that sits on top of the damping rod. Compression damping is controlled by the preload and the spring on the emulator. Rebound damping can then be more easily tuned with different weight oils.

Bike has to remain balanced in my experience. If you put long forks on front then you need long shocks on back.

Swingarm angle gets too steep... rear of bike "jacks up" under acceleration and "squats" under braking. Rear traction sucks under power. Chain tensioning becomes an issue. It just doesn't work well if you go beyond a modest increase... maybe an inch or two... on these old bikes. Pre 79 monoshock forks are a good choice as mentioned. You can put emulators in them too.

Just good shocks (stock-ish length) and improved stock forks is a HUGE improvement and you don't mess up geometry.

Ok, just to clarify.... I'm not doing any triples or even jumping my RT3. The goal is to have decent suspension for running enduro or harescramble type trails and not get beat up. Don't get me wrong, the rider needs to do a lot of work to get better himself, but a suspension upgrade would help me with control of the bike.

Not sure what, if anything, you have done to the forks already. Sometimes just taking them completely apart, cleaning the internals, installing new springs matched to your weight and ability, new seals and fresh fork oil is all you need to improve handling. Many older manuals call for using ATF in the forks. It works, but not as good as fork oil which comes in several viscosities, from 2 to 20.

The compression and rebound damping is controlled by the damping rods and can be only be tuned by the fork oil viscosity and volume of fork oil. Cartridge emulators allow for more precise tuning of the compression damping. This in turn allows for better control of rebound damping using different weight fork oils.

If your compression and rebound damping are too fast it will feel like you’re riding a pogo stick and you’ll have less control the faster you ride. If your compression and rebound damping are too slow you end up with what’s called packing. The forks become hydro-locked and do not absorb small bumps at speed.

While emulators are a wonderful item to have, for fine tuning, your best bang for your buck comes from having the correct fork springs for your weight/ability. Essentially you want the forks riding high in their stroke and let the damping soak up the terrain. Most fork springs are sacked out leaving you with much less travel.

Yamaha used very soft fork springs on most models too... Even on a "competition" model like the IT175.

I agree that getting the correct single rate springs for your weight and riding style will make a big difference.

I use `75 MX250B forks on my trackmaster honda. They work great.