PC800 modifications

Discussion in 'Road Warriors' started by 81tiger, Nov 8, 2015.

  1. 81tiger

    81tiger Been here awhile

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    I'll start this thread and we'll see how it goes.

    I have already made a few mods to my 1997 PC800 to try and get it to be a little better performer (suspension and brakes are the first priority) as a commuter bike.
    • I have swapped the wheels using NT650V wheels (imported from the UK). They are both 17" wheels, so I can now run modern radial tires on the bike front and rear.
    • I have also swapped out the front suspension to a modified (shorten) 1993 VFR750 front end. The cartridge suspension with 5wt oil was a good change; there is a RT 0.95 kg/mm lineal rate spring in there too.
    • Because I have the VFR750 fork lowers on, I am currently running 296mm discs up front. The PC800 has 276mm discs. I will probably end up going with 316mm discs... after I sort out the rear suspension.
    This is where the thread picks up. I thought documenting this on some web site might help others.

    Here is a pic of the bike with the back end apart. This was necessary to get the new swing arm in back:
    [​IMG]

    Here is a pic of the 2 swing arms. The one on the left is from a late model VT700. It was necessary to make this change to better accommodate the 17" wheel/tire. I could have had the PC800 swing arm modified, but thought the VT700 swap was cleaner. The VT700 swing arm uses the same pivot bearings as the PC800 but I had to use the VT700 final drive with the swap. The gearing is the same for both. There is no change in wheelbase with this swap.
    [​IMG]

    There is one change to the swing arm swap and that is the [long] shocks are no longer aligned up and down, but at a slight angle. That means the rear is sitting a bit lower. This will change the geometry of the bike so the steering is slower - not good. I really need a longer shock to raise the back up, perhaps enough to sharpen the steering over the oem rake of 27 degrees. The better aftermarket shocks don't have a lot of options, YSS is the only one you can get in a longer than oem length of 370mm. I have decided to try a set of the cheaper RFY shocks you can get on ebay. a 400mm set is only $90... you get what you pay for but have used these on my scooter and have been pleased with them. There is a guy that services them and actually gets them sorted out with a proper oil change (fill and quality) + he makes sure the pressure bladder is set correctly. Once done, the shocks are decent performers and are rebuildable. So on to the shock swap.

    1st, I need to characterize the oem spring rates to know I have the right springs on. Here is how I tested the oem non adjustable shock to determine the spring rate.
    [​IMG]

    Here is the adjustable shock being tested:
    [​IMG]

    Here is the plotted data:
    [​IMG]

    The green line is the non adjustable shock spring. It doesn't do much until the upper end; there, it has a spring rate of about 150 lbs/in. The adjustable preload shock is the real workhorse of the pair. it has a straight rate spring of 166 lbs/in. When you combine the two springs, you get the magenta curve. The shock bottoms out at 3.5" (non adjustable shock), so the max load before bottoming out (with no preload dialed in on the right shock) is 1,035 lbs.

    Several PC riders swap the left shock for another right shock so there are 2 stout springs on the rear. If you add the 2 right oem springs together, it looks like the dark purple cure shown in this pic. The max capacity of these springs (with no preload dialed in) is 1, 517 lbs. A good improvement over the stock set up.
    [​IMG]

    As good and cheap as the 2 right shock set up, the shocks are NOT long enough. So I bought the RFY 400mm shock (30mm / 1.15" longer) and started taking it apart. Right away, I notice they have a shorter working range, only 2.44" vs the stock 3.5". That means I need a stiffer spring vs oem rate.
    [​IMG]

    I tested the RFY springs the same way as the oem springs:
    [​IMG]

    And the results:
    [​IMG]

    They are not quite strong enough. With no preload, they can only hold up 674 lbs. With the installation preload and all preload dialed in, they are just adequate on the upper end, but really stout at the bottom end, so this would make setting the preload a challange:
    [​IMG]

    So, I will install an aftermarket spring (Hypercoil). After looking at the options, I decided to go with a 175 lb/in spring vs 162 lb/in. The 175 rate will be a tad over 5% stiffer than what I am running now but leave me some additional capacity over the oem set up. The Hypercoil spring is 10" long, so I will dial in 0.75" preload to set the install spring length as 9.25" and start with the this as the initial setting. The lighter blue curve shows a decent lower end to set the preload settings and strong enough at the top end.
    [​IMG]

    I will send of the shocks to have the oil and bladder set up properly (this Thursday) after I take the bike apart to verify swing arm movement with the new shocks on.
    Here is the link to the guy (Chris) that works on the RFY shock:
    http://chrislivengood.net/wp/rfy-shocks-rebuild-service/

    Let me know who is interested in more details...

    Cheers
    Jerry
    #1
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  2. Dave W.

    Dave W. Yea Sportball!

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    Great work! Keep us posted!
    #2
  3. 81tiger

    81tiger Been here awhile

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    Some work today; it is clear the reservoir shocks will not work even in the upside down position. The close molded truck is in the way no matter which side the reservoir is mounted.

    A pic of the PC800 once the truck is out of the way:

    [​IMG]

    You can see the oem shock is at a slight angle vs straight up and down.

    [​IMG]

    Fully extended, the lower shock mount is 16" from the floor

    [​IMG]

    The RFY shock fits with a little work, here is the left side.

    [​IMG]

    Here the lower shock mounting point is 15 6/16 from the bottom, so the 400 (vs 370 oem length) drops the lower shock mounting point 10/16".

    [​IMG]

    But, when I go to put on the rear trunk it will not fit! So, I have to get a different shock that is about 400mm long. I have ordered a pair of YSS RZ366-395TR-03 shocks. They have an additional 10mm that can be adjusted to give 405mm ETE length. They are pricey, but they also come with rebound adjustability.

    [​IMG]

    The RFY shocks will get mounted on the Frankenstein naked PC800 I am making from another bike. On that bike, there will be no trunk to get in the way.

    Jerry
    #3
  4. 81tiger

    81tiger Been here awhile

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    I'm waiting for the YSS shocks, so I've started the front brake upgrade going from the oem 276mm discs to 316mm disc + fixed 4 pot NISSIN calipers from a 2001 CBR600F4. Here is a pic of the stock 276mm discs vs 316mm disc (from a ST1100):

    [​IMG]

    Here is a pic of the current set up which has 296mm discs:

    [​IMG]

    Here is a pic of the bike with the left 316 mm disc on, it fills up the wheel, the polished caliper is near the wheel.:

    [​IMG]

    A pic of the bike with no trunk:

    [​IMG]

    I will have to fabricate an adapter to match up the fixed caliper to the fork leg. We'll see how far I get tomorrow.

    Jerry
    #4
  5. maydaymike

    maydaymike Fearless Commuter

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    How are you going to make those fancy new shocks squeak like the stock ones do? :dunno Great looking bike! Cool to see someone bringing a PC800 up to date performance wise.
    #5
  6. 81tiger

    81tiger Been here awhile

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    How are you going to make those fancy new shocks squeak like the stock ones do?

    Easy, just over tighten the top nuts just a bit.... Its just like wearing jeans that are too tight in the crotch. :imaposer
    #6
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  7. Ultra54

    Ultra54 Been here awhile

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    http://www.ebay.ca/sch/i.html?_from...+cat.TRS0&_nkw=fox+shocks+arctic+cat&_sacat=0

    I wonder if you could find a set of fox shocks off an older Arctic Cat sled on Ebay? Don't be deterred if their overall length is slightly longer as a simple fix is to put a spacer behind the piston to modify the overall length. Many of them are an internal floating piston design, meaning no reservoir. If you want a reservoir you can add one easily using steel braided line to allow you to choose where you want it. I rebuild them as a sideline job so you could consult with me on things to look out for when buying. They are completely rebuild able and every part is available for purchase.
    #7
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  8. RedRocket

    RedRocket Yeah! I want Cheesy Poofs

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    There's an idea!
    #8
  9. 81tiger

    81tiger Been here awhile

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    You should have posted earlier Ultra54! The YSS shocks are about built and will be coming within the week.

    But, for the next rider, how long are the shocks ETE? I needed a 400 mm length, are the Artic Cat shocks that long?

    I am on to the front brakes, any inputs before I start cutting and making the adapter that locates the calipers on the disc and bolts to the fork?

    Since this is my commuter bike, any thoughts on adding an AC? I was thinking of taking one apart to integrate it into the tail section of the PC so it doesn't walk away.
    http://entrosys.com/

    Jerry
    #9
  10. RedRocket

    RedRocket Yeah! I want Cheesy Poofs

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    It looks like Snowmobile shocks are pretty similar, and there are plenty of options.
    #10
  11. Ultra54

    Ultra54 Been here awhile

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    There really are three individual things to consider regarding length. Firstly, overall length. Secondly, the shock body length. Lastly is the length of the shock rod. All this being said, there are literally hundreds of different variations available for this application. I would look at front suspension shocks as they are coil over and are not used with a linkage, hooked directly to the a-arm to chassis similar to the PC 800 actually. I would use the stock bike stock springs as they are in the ballpark for rate and probably play with the valving. You see one shock absorber on the front a arm set up does all the damping on a sled where the work is shared for a bike as two dampers per one swing arm (same concept as an A arm really). One warning I would like to add is beware of buying the shocks as a common issue is the shock shaft chrome will pit/peel if they were abused, and by abused I mean they weren't cleaned or sprayed down after being trailered on an open trailer as salt will sit on them and damage them. Many times they are delivered to me and the first thing I check is for pitting on the shaft. This isn't the end of the world though as you can purchase a new shaft and seal kit.
    As I said, you can make up any length you can imagine. I buy all my parts through Carver

    http://www.carverperformance.com/
    #11
  12. panhead_dan

    panhead_dan This aint jo daddy's Grundle.

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    I've never been a fan of this bike but I gotta say, this is a great thread!
    Nice work man!
    #12
  13. L.B.S.

    L.B.S. Long timer

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    Wow, the attention to detail is most humbling regarding the shock graph charts and the Mr. Thingy spring weight measuring device :eekers :bow :D
    #13
  14. 81tiger

    81tiger Been here awhile

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    Thanks guys.

    A little progress as the YSS shocks came in! I disassembled one of the shocks to measure a few things, here is a pic of the shocks:

    [​IMG]

    The asked for a 395mm (15.55") ETE length; 25mm longer than stock length, so I will have almost a inch longer shock. That should raise up the rear just a tad over oem height. I see the working range of the shock is only 3 2/16", so shorter than the 3 8/16" oem length. The spring has a free length of 9 8/16" and once mounted for my application it has a 9 1/16" length - this means the preload compression is 7/16". I plan on calibrating the spring tonight and will report back the progressive spring curve. Once I know this, I can see how much preload they put on the shocks.
    Note: The blue spring at the top of the pic is the Hypercoil spring I had ordered. It is 10" long and has a 175 lb/in working range, so I will put this on the graph to see how it compares to the YSS/oem set up.

    Tomorrow I will set up a little jig to characterize the rebound damping curve. This shock comes with a 60 click adjustment, so I need to know what that means. It has been my observation that this is one of the most unclarified aspects of suspension tuning once you buy an expensive shock that comes with rebound and/or compression damping adjustability. Once I get through the testing, I will have an idea on how to set the rebounding starting point and understand how to adjust the damping during the riding phase. As I post this information, I would be interested in how others do this.

    Jerry
    #14
  15. 81tiger

    81tiger Been here awhile

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    I put the YSS spring into the weight lifting equipment and loaded up a 45 lb weight and measured the amount the spring compressed and continued this until I couldn't add anymore weight on the spring. Here is the [green] curve of the weights. You can see it is a progressive spring. Since the shock only has a 3 2/16" working range, I can see the max capacity of this spring is ~ 414 lbs with no preload. Another way to look at the spring; its about equal to a 133 lb/in linear rate spring as shown by the dotted red line.

    [​IMG]

    You will recall, the YSS spring has a 9.5" free length but once installed, the spring is only 9 2/16" long, so the spring is compressed 6/16". This preload shifts the green curve to the right as shown below. Now the max capacity is 462 lbs for a single spring.

    [​IMG]

    Now, we project the total spring capacity by doubling the weight potential to get this curve. You can see with the preload they set the initial spring at, the max capacity is 924 lbs.

    [​IMG]

    How does this compare with the oem spring set up by the factory... it looks to be about the same as the curves essentially overlap each other! For now, I am ignoring the nitrogen charging of the YSS shock. That preload adds about 20 - 25 lbs of additional capacity per shock. If I added it in, it would even closer to the oem set up initial capacity.

    [​IMG]

    But, I am running 2 right side OEM springs, so I should be comparing this configuration to the YSS 2 spring set up. Here is how they compare. The 2 rightside springs have much more capacity (an extra 467 lbs) or about 51% more capacity. This makes for a stiffer rear end if you are riding solo; good if you 2 up.

    [​IMG]

    Since I ride solo almost 100% of the time, I could use a different spring. I checked the Hypercoil Springs (175 lbs/in) I ordered for the RFY shocks. They are on this graph. With only a 0.25" preload dialed in, I can see they look good. They offer ~257 more lbs (~28 % more capacity).

    [​IMG]

    So, for tomorrow, I will characterize the damping on the compression and rebound side; then install the Hypercoil springs; then get the new shocks installed. Class is over for the night....

    Jerry
    #15
  16. phillyrube

    phillyrube Leading Chief

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    But since half of what yer telling us is going right over our heads, yer gonna tell us what shocks to get, right?

    Great thread so far......
    #16
  17. freediver73

    freediver73 Adventurer

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    good job man ! :thumb
    #17
  18. 81tiger

    81tiger Been here awhile

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    Thanks for the + feedback.

    The YSS shock is advertised to have 60 clicks of rebound adjustability which sounds impressive.... but my experience is that the medium to lower end rebound adjustability are linear tapered rods that pass through a hole. This kind of set up doesn't deliver a linear adjustment. That is, if you dial in 30 clicks and it doesn't feel right, you might move it 5 more clicks...then try that... My opinion is that you are kind of wasting your time doing it this way. You need to know what what the curve looks like.

    Here is my test set up, an older spring compression tool (black frame) set up to be a vertical test jig. The shock is placed in it with 0 clicks, the handle is raised up, then allowed to fall. Using a stopwatch, I measure the time it takes to go from the start to stop position. I do this 10 times, then throw out the highest and lowest reading and average the remaining 8 times. I do this for 0, 5, 10, 20, 30 and 60 click positions. Here is the test jig:

    [​IMG]

    Here are the test results... You can see even though the shock has 60 clicks of adjustability (3 full 360 turns), it really is only effective over the first 20 clicks! SO, when I get the shocks on, I will start with 10 clicks and go 1 click at a time heading to 0 to find the best sweet spot.

    [​IMG]

    If I had started with 30 clicks (middle) and didn't know what the curve looked like, it would take me a while to get the shock dialed in... Or worse yet, I started at 40 or 50, it would take a long time to get it dialed.

    Tomorrow I get the nylon washer on the shock to measure load on the spring.

    Jerry
    #18
  19. 81tiger

    81tiger Been here awhile

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    Working some of the little bits now.

    Getting the flat washers on the shock shaft. I use the washer to help me understand how much of the suspension travel I'm using + helps me set sag. I use 1 1/4" outer diameter nylon washers (Lowe's) and drill the center to be just shy of the shock shaft. For these YSS shocks, I use a 5/8 bit to enlarge the inside hole, then cut the washer so I can slip it onto the shaft. The washer hugs the shaft, so it stays in the place it was last pushed to.

    [​IMG]

    When setting sag, this is what I would expect to see (left pic). I will increase or decrease the spring preload so the gap is only about 20%. Then, after riding I will check to see how far down the shock body has pushed the washer down the shaft. With any luck, I will have about 5-10% gap left. This tells me I am not bottoming out and using most of the working range of the shock.

    [​IMG]

    I'll paint the reference marks for the rebound damper and wait for the spring centering spacers ordered a few days ago. I am sure by next weekend, I can put the shocks all back together setting the initial preload and rebounding settings. Feels like its taking forever, thank goodness I have other rides...

    Jerry
    #19
  20. 81tiger

    81tiger Been here awhile

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    The spring guide parts came in from the Can Am dealer. I had done some front and rear suspension set up on my 2012 Spyder RTS. When I disassembled the rear shock, I ended up using a coil over sleeve and Eibach spring so I didn't need the oem spring guide part that centers the spring on the lower perch. Since I always save old suspension bits, I had it handy to verify that's what I needed to mount the Hypercoil 1.87" ID spring on the YSS shock. The part number is # 503191872 and costs $1.99 each. You need 4 to mount up 2 shocks. Here is a pick of the part:

    [​IMG]

    Here is a pic of 1 shock still disassembled, and one put together. I'll start with and initial 0.5" installation preload on the spring to set the sag. I show this tomorrow when I get the shocks mounted up and verify/adjust for final sag.

    [​IMG]

    I don't know if I mentioned it, but there is a test at the end of this thread, so you should be paying close attention.

    Jerry
    #20
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