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Post by rebelron on Mar 22, 2012 15:24:38 GMT -5
Took apart the fork on my 1980. The damper rod appears to have been drilled out. It has 4 holes at the bottom of about 3/16" in size along with a single 1/16" hole near the top. The biggest concern is the missing parts. From the schematic I am missing #10 rebound spring and #11 sealing ring. On the 80 model it is equipped with spring pre-load adjustment.
Has this fork been modified in some way or are the holes correct? Does the spring pre-load model have part #10 & #11 installed? If the fork has been modified does anyone have any knowledge of any reference material? It doesn't really fit a Minton mod.
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Post by 10ecjed on Mar 22, 2012 17:59:09 GMT -5
I think the holes are stock. I had mine apart about 2 years ago to put the emulator in. I remember there were holes as you described. But there should be a spring and sealing ring. Even with the preload adjusting caps.
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Post by preston on Mar 22, 2012 18:08:21 GMT -5
and do that that Minton Mod drill the 3/16th holes, to 1/4" ,, and the one 1/16'' use same size or tad bigger, drill bit, and run out the other side, bevel or file the new holes,, clean it and clean it,,, and add the missing parts,,,
Or buy my 75 fork set..., and look vintage-cool.
Preston
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Post by 5twins on Mar 24, 2012 10:07:27 GMT -5
You probably have the seal ring. The parts diagram doesn't illustrate it's location very well. It's the red bakelite ring fitted in the groove on the damper rod top .....  #10, the rebound or top out spring, may be stuck down in the bottom of the fork tube. |
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Post by rebelron on Mar 24, 2012 19:49:40 GMT -5
My buddy had the spring in the big tank with my fork lowers. Would drilling out the damper rod help without the use of emulators? I'm not planning on adding any to the forks.
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Post by 5twins on Mar 25, 2012 0:11:28 GMT -5
Yes, that is the "Minton Mods". Enlarge the 4 bottom holes to about 1/4" and drill the one small one at the top through the other side to create a 2nd hole up there. This will help the overall performance of your forks and in particular make them respond better and nicer to the little bumps. Also use about 7 ounces of oil instead of the stock just under 6.
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Post by pablosixfivezero on Mar 25, 2012 14:10:25 GMT -5
why does no one ever post pictures of these mods? pictures are worth a thousand words and better understanding of what the mod is to look like in the end.
less mistakes people!
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Post by preston on Mar 25, 2012 15:17:31 GMT -5
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Post by rebelron on Mar 26, 2012 8:35:29 GMT -5
Minton wrote the original article for an early version of the fork. I have the pre load model and was not planning on using any emulators. Would it be wise to add the additional 2 holes for a total of 6 plus drill out the top hole? From my reading I have not seen information on this modifications effect on the pre load model fork.
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Post by tomterrific on Mar 26, 2012 9:35:47 GMT -5
I don't know but Minton likely did the original mod to get less compression damping and more rebound damping. The writers for the magazines contantly complained of harsh compression damping and too little rebound damping back then. This was most all Japanese bikes and focused on both ends. The majority of these guys had chances to ride the same bikes with custom shocks and fork setup to make a comparison.
With the above in mind, what changes in damping are you looking for? A lighter fork oil will provide lighter damping, both compression and rebound. Converse for heavier oil. Less spring preload will give a softer ride and more preload a firmer ride. An over fill of oil will lessen the air space at the top of the forks and give a progressive springing effect where the forks get quite firm at the top of the stroke. Drilling out the compression holes and then using heavier oil to bring back the compression damping will give stronger rebound damping due to the heavier oil.
A mix and match of changes will have forks perfect or ruined so the end result should be thought out before hand.
Tom
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Post by 5twins on Mar 26, 2012 16:03:42 GMT -5
I think the bike featured in the Minton Mods article was a '78 Special. All the forks from '78 on were the same. The '77 forks (1st year for the 35mm fork) differed slightly. They didn't have the adjustable preload caps, instead using tube preload spacers and slightly shorter springs. The damper rods differed slightly but had the same amount of holes. The holes were beveled and the rods polished. You can (and I recommend you do) polish the later rods. It takes just a few minutes using some 600 paper .....  The fork part of the Minton Mods article has errors in it and no one has ever bothered to correct them. All the 35mm fork damper rods have four 3/16" holes at the bottom, none have two 1/4" holes as he states. Simply enlarge the 4 existing holes - don't drill 2 more. All have one small hole at the top but it's already bigger than the #54 drill he says to use for enlarging and drilling through. Use a #45 instead.  |
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Post by rebelron on Mar 27, 2012 10:27:52 GMT -5
Tom, The ride has basically been okay. What I really want to change is the excessive dive under braking. I have new springs and am going to put in heavier oil to firm things up a bit.
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Post by 5twins on Mar 27, 2012 10:58:48 GMT -5
Using one ounce more oil will help a lot with the dive, so should the new springs. You can try heavier oil but that may make the ride harsher everywhere. Stock spec is 10 wt. I would try 15 wt. 20 is probably too much.
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Post by preston on Mar 27, 2012 11:40:54 GMT -5
on my 81 forks, with the minton mods, 15wt fork oil , i could not be happier with my new ride..
Preston
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Post by tomterrific on Mar 29, 2012 8:37:39 GMT -5
5T already answered but I'll step in for support. I think you should try the more oil trick. This is a time honored trick and many have been using it successfully for a long time. Doing the trick right will preserve your nice ride and limit the fork dive. Simple idea but may do just what you want.
Rather than just pour in more oil, I'm going to suggest an accurate measurement.
Center stand
Remove top caps (use a towel on the tank and pull the handlebars clamps. lay the handlebars on the tank)
Remove the springs
Collaspe the forks all the way
Fill the forks with oil to 6" - 7" from the top of the fork. (spring out and collasped all the way) (move the fork up and down to remove air pockets for an accurate reading if you drained the old oil.)
Put the bike back together, carefull with the fine threaded caps, and go for a ride.
The distance from the top of the forks determines how fast teh progression of spring rate increases, 6" allot, 7" not as much. Since you are complaining about dive why don't you start with 6" but I wouldn't go any less or the fork seals may suffer.
You can use a device to suck out the fluid to the proper level. Try the pump off a lotion bottle. Cut the tube to length, fill the forks to a higher level and suck out the excess.
Tom
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