Author Topic: Quantity of Fork oil Alloy Forks RD200DX 1976  (Read 264 times)

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Online Astute Greaser

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Quantity of Fork oil Alloy Forks RD200DX 1976
« on: September 13, 2020, 01:56:26 PM »
Okay Folks
Little help and confirmation please  :) :)
Come to fit the alloy forks to my USA RD200C. Disc brake in front of forks.
The forks are very similar to the DX coffin bikes but different length springs to give softer ride.
I downloaded the RD200C Supplementary manual for the bike but then the confusion begins, typical Yamaha manual  ::) ::)
Spec says 10W/30 118cc 
Fork installation says 118cc
Fork oil replacement says 173cc
Now I tried the club tech section to see if RD200DX maintenance manual to confirm one way or other but its not there.
Can you DX boys please look up which figure I should be using  :) :)
Thanks
-Mike
« Last Edit: September 13, 2020, 01:59:35 PM by Astute Greaser »

Online Astute Greaser

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Re: Quantity of Fork oil Alloy Forks RD200DX 1976
« Reply #1 on: September 14, 2020, 06:24:33 PM »
Echo. Echo  ???

Well did what we tell everybody to do. Did a search.
http://www.aircooledrdclub.com/smf/index.php?topic=33247.0
Others have found the same problems as I  ::) ::)
Third figure comes up as 156 +-5 cc for DX
So will go with that. Guess I'm going to find out if right, the hard way  ::) ::)
Cheers
-Mike

Online tony2stroke

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Re: Quantity of Fork oil Alloy Forks RD200DX 1976
« Reply #2 on: September 14, 2020, 06:57:34 PM »
I can only go from memory here, so not really very helpful, but I am pretty sure I used 118cc (that number rings a bell) and def used 10 weight fork oil, still have a little here.

Online Astute Greaser

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Re: Quantity of Fork oil Alloy Forks RD200DX 1976
« Reply #3 on: September 15, 2020, 11:18:23 AM »
Gone through loads of different threads.
The forks for the USA RD200C although produced at same time as the 1E8 are different internally. I'm presuming that they intended a smoother ride for the USA market allowing for the state of their backroads  ::)
Alan (Gr8uncleal) helped me identify sometime back the correct seals/dust covers. Studying the parts list at the time for the 2R7, the arrangement and proportions of the internals are much closer than the 1E8.
As the threads show both the 1E8 and 2R7 using 156 +-5 cc. I'm going for that and will ignore the contradictory supplementary manual.
Thanks for replying Tony, by typing it down, its forced me to think it through.
-Mike

Online tony2stroke

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Re: Quantity of Fork oil Alloy Forks RD200DX 1976
« Reply #4 on: September 15, 2020, 11:25:00 AM »
As I remember it, it was 118ml and also measure down from the top of the fork that confirms it before spring goes in, that's how I remember it.

Offline 5port

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Re: Quantity of Fork oil Alloy Forks RD200DX 1976
« Reply #5 on: September 15, 2020, 06:12:06 PM »
Hi Guys and Gals!  I guess the correct original data would be good to use.  :)
 The 10W-30 oil spec is designed to cover a range of temperature.  Also, probably find that engine oils had better anti-frothing qualities in those days. I suspect modern 10W-30 does a similar good job.  The amount is similar, certainly must cover the top of the damper rod at full extension.  TBH, I find another 20mm or 20ml or so is a good modification these days for slightly higher gas spring rate on the 250/350/400.  Same with an additional 20mm of preload spacer.
 At the very least, you can check oil level is above the top of the damper rod with the forks fully extended.  ;)  Cheers

5port   
5port

Online Astute Greaser

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Re: Quantity of Fork oil Alloy Forks RD200DX 1976
« Reply #6 on: September 15, 2020, 07:22:08 PM »
Used 10W Castrol fork oil so no dodgy additives  :o
Filled large syringe to 120cc.
With inner tube slid fully into lower and spacer removed. Spring just reaches top of inner. 120cc was just about to spill over on first fork so assumed that was right amount. Extended inner fully out, fitted spacer and top cap.
Repeated on second fork but this time while filling, the oil must have worked its way past the damper quicker.
Bounced both forks on wooden plank and seems to match one another.
Allowing for the total movement of the inner plus the length of spacer and compression of the spring, the oil is likely to be above the top of damper  :-\, but I will strip the cap off one tomorrow and put dip stick down to the top of the damper. Its easy enough at this stage while off bike. More oil in is tempting ( 13.5 stone  :-[ ) but will report back.
Typical Yamaha!!

-Mike

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Re: Quantity of Fork oil Alloy Forks RD200DX 1976
« Reply #7 on: September 16, 2020, 04:39:59 PM »
Caps off, spacers and springs removed.
Checked using bamboo cane as dipstick. The oil was 190mm above top of damper both forks, after allowing to stand overnight.
So didn't really get a conclusive result to which figure to use.
Added additional 25cc using syringe and measured 265mm.
So works out each 1cm approx 3.4cc. Calculating using volume then that makes approx 22mm bore for 30mm dia stanchion. Seems right ball park.
Reassembled forks, bounced on planks and couldn't tell difference to previous. Its not very scientific I know  ::) Will only know when I jam the front brake on.
So now have 145cc in each.
Will leave until tomorrow then take up to 160cc inline with previous thread ie 156+-5cc. So add extra 15cc = 4.5cm. So dip stick should measure 310mm but I won't muck around with dip stick, will use the syringe for less mess.
The dip stick does confirm there is plenty of space for the extra oil without creating a hydraulic lock, thus ensuring max stroke, the bit I was really worried about.
« Last Edit: September 16, 2020, 04:42:00 PM by Astute Greaser »

Online Astute Greaser

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Re: Quantity of Fork oil Alloy Forks RD200DX 1976
« Reply #8 on: September 19, 2020, 01:54:40 PM »
Finally finished this, it took only 5 days  >:(. Problems with copper seals under holding bolts of dampers  :-[
Thankfully found at this stage and not on bike. Original washers had become solid and a recess 0.5mm deep had formed around the capheads. Re-annealing wouldn't work in this case ::)
Filled with 160cc each.
With inner fully retracted in outer, the oil comes to about 5mm below the top of the spring, which itself is about 15mm below top of inner.  :)
Bouncing on plank these feel good. You get full stroke without blowing seals.
Now if I had used the 173cc figure in the manual  :o. Nice of Yamaha to give two figures, both of which are clearly wrong :( :(
Thanks again
-Mike

Offline Lyonsio

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Re: Quantity of Fork oil Alloy Forks RD200DX 1976
« Reply #9 on: September 28, 2020, 09:26:05 AM »
I have the factory manual for the 1974 200A model (us version) and it states 157 cc per side, 10W 30 SE motor oil. Your forks may be different in some way

Online Astute Greaser

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Re: Quantity of Fork oil Alloy Forks RD200DX 1976
« Reply #10 on: September 28, 2020, 09:46:17 AM »
Hi Lyonsio.
I have two RD200A's (UK) and one RD200C (USA)
The A's have steel lowers with drum brakes, whereas the C has Alloy lowers with disc brakes, quite different.
However as the handling characteristics of the different models are similar ie weight, torque, tyres etc. It seems plausible to extrapolate that the amount of damping from the quantity of oil will be similar. Which as you point out 157cc is  :)
Thanks
-Mike