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Old 10-29-2013, 07:06 AM   #31
motobene OP
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Quote:
Originally Posted by Sting32 View Post
Bene, seems the 4rt concurs with gasgas, and viscosity effect of transmission oils modifications to clutch feel?

for comparison only, not trying to hijack thread at all... On the gasgas the shipment that my dads bike came in I presume, but maybe all (lol) came with totally new master cylinders for front brakes and the clutch, the clutch side piston seems to have grown in size, like you explained that you hoped was opposite on the 08 honda part. side affects concur with what had hoped for, as well, since you have gasgas... as the clutch fully disengages more now, but ever so slightly more harder pull, than my 12.

just thought I would share that, have KraZy keep practicing! see you guys at some event somewhere soon I hope.
The new hardware is likely is from the merger of AJP and (whatever it was). The slave cylinder diameter across a lot of model years was 14,2mm, so you've got something to compare with. Master cylinders have long been 9,5mm. That leaves only the lever ratio as a variable.
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Old 10-29-2013, 07:12 AM   #32
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Originally Posted by brewtus View Post
Okay. Not really sure I've seen it, but I'll take your word for it.

Any thoughts on the HRC factory mods seen on Bou's and Fuji's bikes? For instance the 315-ish slave cylinder mods seen here on the latest factory 4RT's -

And the absence of the production 4RT slave-cylinder hose and assembly on the RH cover here-
They've reversed the direction of push on the clutch and gone to the very common method of pushing a rod through the primary transmission shaft (like Sherco) and lifting the pressure plate up off the clutch stack toward the outside of the bike.

When pushing from the clutch cover side the clutch design is internally reversed. There is a fixed plate on the outside perimeter of the clutch, and the inner hub is pushed toward the center of the motor, deeper into the clutch assembly to unload the plates. It's not just a matter of changing where the slave cylinder goes, you need to change the clutch design too.

The push rod method adds a rod, but it simplifies the clutch a bit. You have a true 'lift plate' (the red center thing in the above photo), instead of pushing in on the inner hub.

That it was done at all shows that maybe they were running into some limits on what they could do with the clutch as configured before. Perhaps that new layout will show up in production some day?

motobene screwed with this post 10-29-2013 at 07:17 AM
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Old 10-29-2013, 07:15 AM   #33
motobene OP
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Originally Posted by laser17 View Post
I know, CSP make some nice stuff. I couldn't find a pic of the inner hub, but I think it has holes too. As you probably noticed, they cut slots at the top of the basket fingers to improve flow as well.
You're making an assumption about oil flow. The cutouts at top of the outer basket fingers may simply be about weight reduction. The outer basket looks like it is made from hard coated aluminum, so perhaps a strong product requirement was weight reduction?
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Old 10-29-2013, 07:24 AM   #34
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I forgot to add gearing as a very important fix on this bike.

I think KrAzy is back to, what, 48/10=4.80? This makes first through third very useable in typical lower-class sections, with first as a definite creeping gear.

The 4RTs can be very abrupt right off bottom. Higher (stock) gearing makes a twitchy throttle write more hairy, and lowering the gearing lowers the sensitivity. It's a must, in my opinion for low-to-mid skill level riders, and I personally favor lower gearing in trials when riding at higher levels too.
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Old 10-29-2013, 07:48 AM   #35
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Quote:
Originally Posted by motobene View Post
They've reversed the direction of push on the clutch and gone to the very common method of pushing a rod through the primary transmission shaft (like Sherco) and lifting the pressure plate up off the clutch stack toward the outside of the bike.

When pushing from the clutch cover side the clutch design is internally reversed. There is a fixed plate on the outside perimeter of the clutch, and the inner hub is pushed toward the center of the motor, deeper into the clutch assembly to unload the plates. It's not just a matter of changing where the slave cylinder goes, you need to change the clutch design too.

The push rod method adds a rod, but it simplifies the clutch a bit. You have a true 'lift plate' (the red center thing in the above photo), instead of pushing in on the inner hub.

That it was done at all shows that maybe they were running into some limits on what they could do with the clutch as configured before. Perhaps that new layout will show up in production some day?

Oh, I'm aware of the layout and how it works. I was a Honda technician for 15 years in a previous life. I just thought it interesting that the Pro bikes reverted back to the external slave cylinder/pushrod layout. In that same batch of photos it shows the minder bikes being prepped alongside the Pro bikes, and they have the production 4RT layout. Guesses range from the external slave cylinder/pushrod has a "feel" that Bou and Fuji prefer, or that maybe the thinking is the external cylinder layout is less vulnerable to crash damage. Either way, it's sorta neat in a retro kind of way.

Lineaway thinks the dual-plug layout is for a backup ignition system. Either that, or that thing's "got a Hemi in it".

Minor hijack over. I just thought it was neat to see the factory HRC layout. I'm glad you are enjoying your 4RT, Cowboy. This thread showed up just in time, as the clutch on my '05 4RT is beginning to slip when the bike is very hot, and it's starting to do the "ghost engagement" with the clutch in sometimes. I was getting ready to order the Sureflex clutch I told you about in Sipapu, the same one that I installed in Miss Bitters' 315R that magically transformed it into a fun to ride bike instead of the clutch dragging/grabbing rodeo bike it was. Keep up the good work fellas. I'm following this one.
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brewtus screwed with this post 10-29-2013 at 07:50 AM Reason: A g-g-g-g-g-ghost, Scooby!
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Old 10-29-2013, 07:50 AM   #36
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Quote:
Originally Posted by motobene View Post
I forgot to add gearing as a very important fix on this bike.

I think KrAzy is back to, what, 48/10=4.80? This makes first through third very useable in typical lower-class sections, with first as a definite creeping gear.

The 4RTs can be very abrupt right off bottom. Higher (stock) gearing makes a twitchy throttle write more hairy, and lowering the gearing lowers the sensitivity. It's a must, in my opinion for low-to-mid skill level riders, and I personally favor lower gearing in trials when riding at higher levels too.
How do you feel about adding flywheel weight to the 4RT?

I researched it when I got the bike. There was a Japanese flywheel available that was made with Mallory metal that was obscenely expensive and there was a guy in the UK that was able to add a small sleeve around the flywheel by moving the pickup coil out from the flywheel as far as the case would allow.
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Old 10-29-2013, 08:07 AM   #37
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Interesting, first reports of the 2014 model indicates the `bark` is much less noticeable. Post #41.
http://www.trialscentral.com/forums/...30#entry346492
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Old 10-29-2013, 08:51 AM   #38
brewtus
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Quote:
Originally Posted by lineaway View Post
Interesting, first reports of the 2014 model indicates the `bark` is much less noticeable. Post #41.
http://www.trialscentral.com/forums/...30#entry346492

LESS bark? Ooh, first chink in the armor, Ted.
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Old 10-29-2013, 10:49 AM   #39
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brewtus, I researched the Sureflex when you mentioned it many months ago, but couldn't find any availibility. If you know a source, please let me know as I would consider that possibility when or if I need to go further. For now I intend to continue working with the 4 spring mod and may try 3, and testing other oil possibilities. Its so much better I'll probably just ride it at least til its time for fresh fluid.
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Old 10-29-2013, 11:24 AM   #40
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Originally Posted by KrAzyOSUcOwBoY View Post
brewtus, I researched the Sureflex when you mentioned it many months ago, but couldn't find any availibility. If you know a source, please let me know as I would consider that possibility when or if I need to go further. For now I intend to continue working with the 4 spring mod and may try 3, and testing other oil possibilities. Its so much better I'll probably just ride it at least til its time for fresh fluid.

Dennis at Overland Trail Cycle has 'em -

http://www.overlandtrail.biz/

Tell him I sent ya!
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Old 10-29-2013, 01:32 PM   #41
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Thanks brewtus, good to know. I've spoken with Dennis extensively about this and he has not suggested the Sureflex plates. I have bought parts from him often enough that I bookmarked his website. Good guy and has an excellent working knowledge of the 4rt.
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Old 10-29-2013, 02:16 PM   #42
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This is a great thread!!!

I am loving this thread, not sure what to try first but am considering options and when I might have the time to try them.

Not to de-rail more but... FWIW: I have a BMW with there twin spark (dual-plug layout) and find the things it seems to do for me are...
1) runs smother (less pulsing)
2) better fuel economy than the single spark version
3) deceleration is less abrupt
4) and when one of the two plugs started running bad the bike ran like crap... But it still ran. (Turned out I had a failed pin coil)
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Old 10-29-2013, 05:43 PM   #43
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Bene,
When are you going to tell us about the suspension mods????

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Old 10-30-2013, 05:36 AM   #44
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OK here is the suspension part. Most of it, anyway. I will not tell all because I give away too much information instead of profiting from it. I am a statistic these days, being an engineer out of the labor force. I'm spending my accumulated wealth building a ranch. If Buffalo Dream Services doesn't make some money, I'll not be able to be charitable. If anyone wishes me to do the following, PM me.

Problem: The 4RT suspension settings are old world. They are too slow on the front and way too slow on the rear. You can make 4RTs fully modern without compromising compliance control, and the quality of the suspension will then more fully compliment the bike. You will have among the best suspension of ANY available bike up to 2014! Lively, responsive, and certainly less heavy feeling.

SUSPENSION

The 4RT is blessed with excellent quality Showa suspension. The forks on the 2005+ models are a bit dated in design, being early 2000s, but they work well. I'd bet on Bou's and Fugigas' you will find sophisticated dual close-cartridge forks. Perhaps on the 2014 models for the rest of us are just tweaked versions of the 2005 forks:

Left-Side (Brake Side):

A low-tech damper rod for fixed compression damping. This side has the one and only compression spring. It also has the only top-out spring. (The other side will extend down free when you remove the front wheel axle). When there is only one spring it is in the leg with high-speed compression damping to reduce the force imbalance during fork compression. (I'll add the spring rate when I get around to calculating it).

The original oil was the stuff from the factory. At 120 hours it was not as dirty as I expected, but it was grey (metallic particles), and about the same in the left and right forks.

The only adjuster-based adjustment is a minor one, a few turns of added spring preload from the blue adjuster beyond the ~17mm of spring preload due to fork cap compression. Ride height and steering characteristics with respect to preload are minor in the adjuster, and much more significant through fork position in the triple clamps. We have been positioning the forks low in the triple clamps, from stanchion rod tops level to the top surface of the top triple clamps to sticking up no more than 4mm. This helps reduce over steer and hyper active handling.

The fix to slow compression is within the range of available oils. KrAzy's bike now has Red Line Like Water in it, and that is working well in colder temps. We can now make use of the adjusters! I'd bump up oil in this leg to 100% Red Line Extra Light 2.5 for a year-round oil. Keep in mind there is a compression adjuster in the other leg, so you have some range of adjustment beyond oil.

Oil level should be close to 3.5", spring out, fork fully collapsed.

Right Side:

No spring (other than the secondary or air spring). Inside is an older-type so-called 'open' cartridge system. Open means the oil pumps through on each stroke and ejaculates out a little hole in the top on fork extension. Closed cartridge systems are a pain in the ass to bleed. I prefer the older style open cartridge units regarding servicing.

The cartridge rod is attached to the fork cap, with fork compression and extension providing the pumping action to create resistance or damping (BTW 'dampening' is to wet). There are two adjusters, the top knob that controls a portion of the rebound resistance beyond that which is set by cartridge valving, and a compression adjuster, a flat-head screw in the center of the head of the damper rod retainer bolt in the bottom of the fork. Having two adjusters is a very good thing because you have a wider selection of oils you can use and still tune the compression and extension responses inside the more optimal window.

The cartridge valving spec is old world, so if you use the recommended Showa SS5 (a medium-light oil) you'll be wondering who turned up the gravity?

We were able to bring the rebound side into modernity without re valving buy using the very low viscosity Redline Like Water oil. The fork now responds quickly and the adjuster is useable instead of having to be set at full minimum. At last adjustment we were half way into the adjustment range with the Like Water oil. At a second iteration I'd use 50% Redline Like Water and 50% Redline 2.5 Extra Light.

I'm not religious and dogmatic about oils and spark plugs. But this is a case where I'd recommend a specific oil because you can't go by what oil sellers say on the bottle. One brand's light suspension fluid is another's medium. You can try what you want, but to repeat these results, I suggest sticking with the Redline. It is a full synthetic so you're getting a very high quality oil. Then once you know what faster feels like, you can try other oils, but keep in mind most brands start at SS5 thickness and go up from there.

Oil level, cartridge pumped through cleanly, is reported by KrAzy to be spec'd at only 1-1/2" or 38mm! with cartridge rod fully collapsed. Given there is no spring there, the level can be higher without over pressuring. We set this side at 3-1/2" not knowing better, and that softened the overall spring resistance fully compressed a bit.

You can speed up the forks nicely, but proportionally the bigger problem is the slow shock. To really transform this bike you need to re valve the shock.

SHOCK

This Showa shock is very large compared to many brand's shocks! It uses a larger-diameter body. Nertz! I forgot to measure the piston diameter. It's substantially larger than Ohlins and especially Reiger pistons. Here is Little Miss Piggie:



I'll provide the spring rate when calculated. Note the spring is long with respect to the preload nuts. Not enough adjustment to easily remove the spring collar clip! It reassembles easy enough, but getting the spring off requires some extra hands and tools.

That bulge at the bottom end (they run he shock with the body and bulge down) is the cavity for the reservoir, a rubber bladder accumulator hidden from view when disassembling the shock. The body threads into the cast aluminum bulged end, and shuts off against a bore inside. The only thing connecting the body to the reservoir cavity is one small hole in the side of the body, way down in there.

The shock is a conventional Japanese affair. That is, held together with one wire clip and gas pressure, which is around 200 psi (1380 kPa) of nitrogen. Air is 78% nitrogen, but it is common to use pure nitrogen in shock reservoirs, whether DeCarbon (piston) style or by rubber bladder. Not having ~18% oxygen in air at higher pressure may be the reason.

If you were to lose gas pressure, the seal head would back off and the shock would begin a process of falling apart. Thankfully there is no weird pressurization port. Showa used a conventional Schrader valve to charging the shock with nitrogen.

The Showa shock is oriented rod-side up. The positive is the body and reservoir are not closer to the radiant and convective heat from the exhaust. The negative is water and corrosives will get past the gap between the shock rod and the cap over the seal head and be trapped instead of running out under gravity, as with the flipped orientation. Bikes with lots of hours and run in wet and corrosive environments can have lots of dirt and corrosion in the space under the cap, right where the retainer clip for the seal head lives. If the corrosion is severe enough, the shock may not be able to be disassembled. After de gassing, the seal head has to be pushed about 10mm into the shock body to get access to the retainer clip to remove it. Oftentimes a good cleaning and oil soak will free things up, but sometimes not. But as long as you don't stroke a shock de gassed, you will not get air in it and you can re charge it and just keep using it.

Inside is a conventional powder metal or PM piston with low-friction sealing band, and a conventional set of shim valve stacks. One set of shims for rebound damping, and another for compression damping. The lawyers unfortunately got to the valve stack nut and rod interface, as they swaged the end of the rod over the nut. It takes careful work to remove rod material such that the nut can be removed without destroying the red threads. Here is what the bits from the inside look like after I did the necessary work to remove the M12X1.5 valve stack nut:



In this photo, the rigid rebound stack washer is at top left (the nut clamps the stack together there), then follows the rebound stack to the right. The round thing with ports is the piston, then right of that is the compression stack. I altered these parts to re valve the shock.

I used the Redline Like Water in this rebuild, and we ended up about mid way in the rebound adjustment range, so we have more adjustment to dial in when it gets hot again. But the next iteration I'd use Extra Light 2.5 to thicken the oil slightly. That should put the adjuster closer to mid range in hot weather, leaving plenty of room to back off in cold weather.

A fellow could simply change the shock oil for Redline Like Water and speed the shock up some, but the real magic is in the revalving, and I'll not be disclosing that.

I will say this about this shock. It is quite large and the rising rate linkage is apparently well thought out. This shock revalved on KrAzy's bike has produced the most plush rear end I've ever felt on a trials bike, and it is very controlled and responsive. When I switch back to my Reiger GasGas it feels really good, but not as plush.

We have fairly little preload on this shock spring. The rear end squat significantly under a 185-pound rider, but if you use too much preload you get oversteer. The 4RT will get hyper unless the overall ride attitude or bike pitch is a little head high and butt low. The preloaded shock length we are using was 5.06" (128,5mm) before the rebuild and we lowered it to 5.08" (129mm) after the rebuild. The fork position after the rebuild ended up with stanchions sticking up about 8mm.

SUPPLEMENT

As part of the overall handling related to bike pitch and suspension preload, it is VERY important on the 4RT to rotate the bars more forward than one might think should be. The cross bar on the 2005 will end up forward of and with clearance given a 6mm hex key stuck into the front handlebar clamp screw. While inclining forward is going toward oversteer, the bike just won't handle as well if the bars are back. KrAzy, we need photo from the side showing bar rotation, or getting from you what the distance between a 6mm hex and the cross bar is.

Rider above ~190 pounds (86kg) can up the shock preload, but don't overdo it!

motobene screwed with this post 10-30-2013 at 07:01 AM
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Old 10-30-2013, 07:23 AM   #45
Sting32
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Quote:
Originally Posted by motobene View Post
The new hardware is likely is from the merger of AJP and (whatever it was). The slave cylinder diameter across a lot of model years was 14,2mm, so you've got something to compare with. Master cylinders have long been 9,5mm. That leaves only the lever ratio as a variable.
We still suspect that master cylinder piston grew in size, uses same levers as my bike, dad took them to this one. Havent investigated, I assume the clutch cover is same part#, and specs. I dont know that.
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