Commando Fork Cartridge Conversion

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cjandme said:
lcrken said:
After almost 1,000 miles on the forks, I thought it might be time for an update. Bottom line is that the front end feels much smoother on a variety of pavement, ..................... I'm planning to play with rebound adjustments, just to see how much effect they have, ............Ken
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I've been following this thread ,thanks for the update Ken. One of the guys that I work with has a little used sporster front end that I can get for cheap, so I was curious about your results. I fitted the front end from a honda hurricane 1000 to one of my old Cb750F's years ago. I need to research the harley some more to see if it is worth my time and effort to set it up on my MKIII. Anyway thanks for posting
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Harley forks have been made by Showa (owned by Honda) for some time now.
 
Danno said:
.....Harley forks have been made by Showa (owned by Honda) for some time now.
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Thx Danno, Strangely enough another guy at work offered me his old honda 400 for nothing, so we'll see. The sportster forks are supposed to be 39mm, I'll have a look at the 400 tomorrow, but I'm not gonna hold my breath. I've been down this road before, someone says that they're gonna throw something away because they don't want it. Then later after I've expressed an interest, they want to sell it. My real problem is in not having a garage though. I'm gonna be quiet now since I don't want to de-rail this thread. thanks again though for the info.
 
lcrken said:
After almost 1,000 miles on the forks, I thought it might be time for an update. Bottom line is that the front end feels much smoother on a variety of pavement, from smooth to pot-holed, and the shortened Ninja spring seems about right. I rode it for the first 100 miles, and my grandson for most of the rest, mostly at the rally. The only adjustment we made was to increase the pre-load a bit. I weigh considerably more than he does, but he rides more aggressively, with the result that we're both happy with the same pre-load setting. With the original pre-load setting, he did experience some front wheel skipping under very heavy braking. It seems better with more pre-load, but I need to do some more testing to be sure. I'm planning to play with rebound adjustments, just to see how much effect they have, but the original setting at half travel seems to work well, so I don't know if I'll see any improvement. Now I just need to find replacements for the clapped out Girlings on the rear.

Ken
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Ken,
Started reading this thread when you referenced it in your current Ohlins mod thread. Any further thoughts/comments on this mod?
 
chaztuna said:
Ken,
Started reading this thread when you referenced it in your current Ohlins mod thread. Any further thoughts/comments on this mod?
Click to expand...

Not much new to say. We had a couple of thousand miles on the conversion when I pulled the Honda (Showa) cartridges out to try the Ohlins in the same forks. I'm still hoping to get the Ohlins working well, in which case the Honda kit will go into the stock forks on a 750 Commando I'm rebuilding. I'm still trying to sort out the effect of having so little clearance between the Ohlins damper tube and the stock Commando stanchion, and determining if it is really a problem. And if it is, I want to look again at the same issue with the Honda conversion, and see why it doesn't seem to have as much effect. I think it might have to do with the Honda tube being smaller diameter, so the restriction would only be from the short length of the cap at the top of the cartridge, as opposed to being the full length of the cartridge in the Ohlins conversion. The frictional force from the thin oil layer between the cartridge and stanchion is proportional to the length of the affected area. If I make any changes to the Honda setup, I'll post it here.

Ken
 
Another update, and a bit embarrassing. On re-examining the parts I used for the conversion, it looks like the cartridges I used were the earlier 1999 - 2000 CBR600F4 style, not the 2001 - 2006 F4i. My mistake. I bought the forks on eBay, where they were advertised as F4i, and I didn't think to look any deeper. I just stripped a pair of 2005 F4i forks, and the cartridges are a little different. The earlier ones I used have a steel damper tube (with four holes, not two) and are 22.5 mm in diameter. The F4i tubes are 24 mm in diameter and are aluminum, and also have four holes. Sorry for the misinformation.

Ken
 
A few changes to the conversion. I was unable to get the Ohlins cartridges to work properly in the small inside diameter Commando forks, so I've put that project aside until I can sort out either a way to bore the stock tubes for more clearance, make new tubes out of thinner wall tubing, or adapt other stanchions. I need to get the grandson's bike back in service, so I'm going back to the Honda F4 internals, but with a couple of changes. I've made up a couple of spring seats and guides, similar to what Onlins used, out of Delrin, with a smaller outside diameter and some clearance slots for better oil flow. I'm also switching to some Race Tech springs in place of the shortened Ninja 250 springs. The Ninja springs are progressive, and I prefer straight rate springs, like the RT items. I also now have a collection of different rate RT springs from the Ohlins effort, so if I need stiffer springs, I have plenty. I also fitted the Cosentino bushing and seal kit from NYC Norton, and made a one piece aluminum top spacer to limit travel, replacing the two bronze bushings I had used previously.

This is a picture of the bits with the new pieces.

011821 Mods 1200.jpg


I should have the bike back on the road in a couple of days, and will report on whether there are any improvements.

Ken
 
Just took a short test ride, after adjusting preload to get reasonable sag measurements. There is noticeably less friction/sticktion in the forks. Also, we had earlier concluded that we couldn't reduce the damping (both compression and rebound) quite as much as we wanted, even with both adjustments at full soft. We had been using 10W fork oil, but discovered that Honda recommended 5W, so we switched to that. It does seem like a better choice. The rebound seems about right with the adjuster backed out about a third of it's range. Compression is maybe a little soft now, but we need to ride on some more challenging roads before we change it. It's a bit of a pain to pull the axle to adjust it, so we want to be sure before we go there. The .70 kg/mm springs seem about right for street use.

Ken
 
I think we are at the end of this project. My grandson put in some serious test rides while we tweaked the preload settings a bit, and I think we're done. We added a little preload on the front, and took out a turn on the rear Ohlins, and he's very happy with how well it rides and handles now. With the higher preload on the rear spring that suited my heavier weight, the front end felt to him like it was starting to feel twitchy at high lean angles, enough that we worried about it tucking if he pushed it any harder. Adding some preload at the front and taking out some at the rear changed the rake angle of the bike slightly, increasing the trail enough to make that twitchy feeling go away. The Ohlins rear shock is slightly longer than the stock Commando item, which acts to reduce the bike's rake angle and trail enough that it was a little more sensitive to the preload adjustments. It's been a fun adventure. Time to get back to trying to make the Ohlins cartridge conversion for the front forks work properly.

Ken
 
You can't beat the law of Physics, you can use a set of F4i forks with 43mm stanchions coupled with early Yamaha R6 yokes, conversion bearings needed for the headstock. These are the only modern forks long enough to directly replace Commando forks, get rid of the paint, polish the lowers, fit gaiters and they look period but will take the ohlins cartridges.
 
kommando said:
You can't beat the law of Physics, you can use a set of F4i forks with 43mm stanchions coupled with early Yamaha R6 yokes, conversion bearings needed for the headstock. These are the only modern forks long enough to directly replace Commando forks, get rid of the paint, polish the lowers, fit gaiters and they look period but will take the ohlins cartridges.
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More info please. When you say Yamaha R6, do you mean YZF-R6? What is the last year of the "early" yokes?
 
kommando said:
I see it but it disappears if I click on it.

Here it is on postimage

Commando Fork Cartridge Conversion
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Sorry I should have been clearer. I see it in the thread, but if I click on the image to get a closer look (which this bike deserves), it opens another tab to imgur but it's just a blank black page.
 
Works ok for me
cliffa said:
Sorry I should have been clearer. I see it in the thread, but if I click on the image to get a closer look (which this bike deserves), it opens another tab to imgur but it's just a blank black page.
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works OK for me
JD
 
cliffa said:
weirdly, if I "Right click" and copy the link then paste it into a new tab it works - NICE BIKE !!
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Sorry guys , I am a newbie in posting pics , first time , I had used imgur , now I think I, had understood .........may be , will try with another bike with R6 forks ..............
 
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