Leo wrote:

Later type KH500 inners offer more rebound damping which is a plus.

You can further improve fork action by reducing diameter of small bore to 1.8 mm and thus increase rebound damping. On top of that, you can reduce compression damping by drilling trough aluminum top of inner rod with 8 mm drill bit.  One should close two of the four holes on the lowest part of the inners.

H-forks have stock springs that are close to OK. Just increase oil level to keep it from bottoming out under severe braking. btw, severe braking is not possible with stock brakes. 

Only if you are way over 130 lbs you will need to change to a stiffer spring.

I have found the 18 inch front wheel to work well up to speed of 100 mph. Past that it becomes unstable. Reduction of triple clamp off-set by 5 mm helps some.   Best thing to do would be to drop an engine into an S-frame. Your worries are over right away.

Per John Aylor:

Here are side by side pics of the aluminum vs steel H2 damper rods.

The recommended modification for the bottom of the steel rod is to weld up two of the four holes and drill the other two out to 1/4".

The damping hole in the side of the rod about 2" down from the top. It is about 5/64" diameter (2mm) and is in the same place on both style rods.  It should be 1.8mm, might be a small hole but the size % difference is pretty big. Almost 20%.

Polish and check after welding to make sure the fork slides smoothly on the damper, as well as the damping parts on the rod after filling the small damping hole.

Pic 1: Steel late model on top with bottom being early aluminum


Pic 2: Same as pic 1 except the items are dissasembled.


Pic 3: Early model aluminum bottom hole close up


Pic 4: Early model aluminum top portion of rod close up.


Pic 5: Late Model steel bottom portion of rod close up.


Pic 6: Late Model steel top portion of rod close up.

 

Emulators

Jim C. wrote:

John's mod to the alum rods is really good when you are not using the Race Tec cartridge emulators. He is not removing nearly as much material as Race Tech. I have sets of both alum. and steel and felt that the R.T. mod for aluminum was a potential structural issue.

 Here's the article I wrote for the UK Club Magazine awhile back:

Fork Improvements for the H Series Triple
by Jim Crenca

First off, this mod is the greatest thing since sliced bread; my H2 now has real hydraulic damping with great dynamics over rough streets, speed bumps, hard front brake use, etc.

Second, special thanks to Dr. James for explaining that cartridge emulators are not designed for a specific bike but rather a fork tube I.D.
I had called Race Tech a few years ago and asked if they had or would make an emulator for my H2; they did not have one and would not make.
While searching their site, they do offer a set for a late model H1 and the directions are very good.

http://racetech.com/

1. You MUST have a late model H series bike with steel front fork damper tubes. The aluminum tubes are too small in diameter IMO after you drill 6ea 5/16" holes. Race Tech doesn't say this but I can't believe that there is not enough structural integrity with the small diameter soft aluminum tubes.

2. Order 1ea. FEGV S3001 pair of emulators ($169.99) as well as 2ea. FPEV AD3003 adapters ($9.98 for the pair)
The HMWC copper washers for the bottom bolt seal are the wrong size and I didn't opt for their fork oil at $30 per quart

3. Order 1 quart of Torco RFF Synthetic blend 15wt. fork oil; this stuff does not feel like regular fork oil and I believe it to have much less stiction; about $10 per quart.

4. 2' of schedule 40, 3/4" PVC plumbing pipe to replace the original metal spacer for pre-load (or cut up the original; I wanted the ability to adjust pre-load after more testing)

5. The fork dampers have 2 sets of clear holes over top of each other. Drill the bottom set out to 5/16". The set that are directly above need to be sealed; I threaded this hole and installed Allen set screws, mig welded and ground flush; then decided this might not be strong enough and brazed around the perimeter. Not the prettiest work by my hands and would have tig welded the holes closed in hindsight.
Now drill a 5/16" through hole 10mm (centerline to centerline) above your lower holes and at 90 degrees. Then drill another set 10 mm CL to CL and again at 90 degrees. You should have 3 clear holes or 6ea holes and might look something like this:

6. You will not use the original damping disc assembly and the new damper sits on top of the adapter which sits on top of the rod.

7. Here's a close up of the emulator; not terribly complex but not worth trying to copy (steal) for a lousy $170. Hey, if it's so simple, how comes you didn't think of it? (John Jacob quote)

8. I weigh 175 lbs and my bike weighs 430 lbs with fluids. I tried a number of different weights and race vs. street applications with their "digital valving search" and always come up with 140 mm of 15 wt oil and 20 mm of preload. They measure preload as the distance from the top of the top tube to the top sealing surface of the fork cap. In my case I ended up with something like 88.8 mm spacers. I'm using the stock springs but Race Tech and Sudco offer progressive wound springs; not so sure if this mod will add that much but would be interested to hear from anyone who can A/B the two different springs although new spacers would probably need to be made.

9. During assembly the adapters are dropped onto the modified rods from the top and then emulators drop on top of this. I used a high powered LED flashlight and a magnetic parts pickup tool to get these parts lined up. Once in place the PVC spacers and fork caps will hold it in place.

10. Take the bike for a ride and please post your results. As of this writing I’ve put down approx 250 miles with this mod and there may be more improvements with some experimentation. BTW, I'm using Redwing Hammerhead shocks and the overall handling improvement was nothing short of great. The stock shocks may not allow you to get the full benefit as I've never believed these shocks to work that well.

Best handling improvement for the buck and is added to my personal list of "must do" mods along with chambers, pods, and Sytec release.
(Still need to rubber mount the H2 after doing this mod to the H1)!

Edit Note: Racetech now lists FEGV 3004 emulator w/adapter for both H2 & Late H1.

When I bought mine a few years ago they only listed the H1 and couldn't offer any fitment advice to similar bikes other than they are adjustable. Would be interested to hear what they say about these new part numbers vs. what they suggested I use.
While these units will not transform the bike into anything close to modern, they do help damping performance. I've only used them with the oil suggested in the article.

- Jim Crenca