RM 45mm Showa Performance

Questions and comments about converting to beefier forks..
Thrahl
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RM 45mm Showa Performance

Post by Thrahl »

So yesterday I picked up a parts bike off of Craigslist for $300. The PO said he was drag racing his buddy and then when he slowed down and was turning around the engine seized. When I noticed it had USDs on it I jumped on it.
This guy knew absolutely nothing about the bike but said the guy before him said they are from an RM 125.
The sticker on the back says Showa and Suzuki and the fork tubes measure 45mm. Here's some pics.

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So how did I do? I figure I should be able to part the bike out and make my money back, maybe more, and basically get a free fork swap out of the deal. :mrgreen:
Not to mention it has fat bars and dual piston calipers :rock:
It seems like most people do KX swaps or maybe CR swaps. Are these RM forks any good? It doesn't really matter to me seeing as literally anything is better than stock :lol:

One of the legs is weeping some oil so seals may be in order if I can't clean them. I plan on at least changing the oil and setting it to spec.
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KDXohio
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Re: RM 45mm Showa Performance

Post by KDXohio »

looks like you did great! Ive heard real good reviews on Showa forks. Hell you could always put the stock front end back on this one and resell it. Get some fork guards and new seals for sure. It'd be good to strip them all the way down to clean them and check bushings. I found pieces of plastic in the pistons of both my KYBs when I did my swaps but also found the fork bushings looked like they were put in yesterday! GOOD LUCK!
1990 KDX200 FMF Fatty, Answer VFC silencer, VForce 3 Cage, Wiseco Piston, KX125-J series KYB USD fork conversion, Race tech goldvalves, J series front brake assembly, air-box snorkel removed, Acerbis Headlight, KX450F Front fender, Pro Taper RM bend bars, ASV front Brake lever, MSR Clutch perch and lever, RB Head mod, 36mm PWK carb, Trail Tech Kickstand.
Thrahl
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Re: RM 45mm Showa Performance

Post by Thrahl »

KDXohio wrote:looks like you did great! Ive heard real good reviews on Showa forks. Hell you could always put the stock front end back on this one and resell it. Get some fork guards and new seals for sure. It'd be good to strip them all the way down to clean them and check bushings. I found pieces of plastic in the pistons of both my KYBs when I did my swaps but also found the fork bushings looked like they were put in yesterday! GOOD LUCK!
I think I can make more by parting it out. KDXs don't sell for much in my area. Besides I was going to strip a few parts and keep them as back ups.
I should be able to sell carb, tank, and misc. engine parts to make my $300 back I think. I know that KDX transmissions are a popular swap for KX woods projects.
Guards and seals will be ordered once I figure out what year these are from. I think the 45mm are early 90s?
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KDXohio
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Re: RM 45mm Showa Performance

Post by KDXohio »

Yeah I think they started using them in 91 till 95ish. Ill see if I can dig anything up for you two heads are better than one!
1990 KDX200 FMF Fatty, Answer VFC silencer, VForce 3 Cage, Wiseco Piston, KX125-J series KYB USD fork conversion, Race tech goldvalves, J series front brake assembly, air-box snorkel removed, Acerbis Headlight, KX450F Front fender, Pro Taper RM bend bars, ASV front Brake lever, MSR Clutch perch and lever, RB Head mod, 36mm PWK carb, Trail Tech Kickstand.
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KDXohio
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Re: RM 45mm Showa Performance

Post by KDXohio »

Here ya go found this chart first search! You have to scroll over quite a ways to the right till you see FORK INFO then look down to 91 it actually calls out showa in 92 but theyre all 45s from 91-95 same seals and gaurds. Lots of good info hope it helps.
http://www.oem-cycle.com/SUZUKIRM125BIKEID.shtml
1990 KDX200 FMF Fatty, Answer VFC silencer, VForce 3 Cage, Wiseco Piston, KX125-J series KYB USD fork conversion, Race tech goldvalves, J series front brake assembly, air-box snorkel removed, Acerbis Headlight, KX450F Front fender, Pro Taper RM bend bars, ASV front Brake lever, MSR Clutch perch and lever, RB Head mod, 36mm PWK carb, Trail Tech Kickstand.
Thrahl
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RM 45mm Showa Performance

Post by Thrahl »

I guess I should have googled harder lol. That link is really useful thanks.
$7 for seals, guards are gonna be a little more. I'll have to look around, see if other years/bikes fit these forks.

I've got the triples and everything apart. The lower bearing looks good but there is no upper bearing :shock:
There is just what looks like the inner race of a bearing which actually fits pretty nicely in the frame and then the nut on top of that.
I guess we'll see if there was a reason for this or what. I'll try using the upper bearing from the bike I'm swapping to.
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KDXohio
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RM 45mm Showa Performance

Post by KDXohio »

Thrahl wrote:there is no upper bearing :shock: There is just what looks like the inner race of a bearing which actually fits pretty nicely in the frame and then the nut on top of that.
I guess we'll see if there was a reason for this or what. I'll try using the upper bearing from the bike I'm swapping to.
Mind posting a picture of that? That does sound strange unless it fell apart and the PO said F*** it and put it together anyways
1990 KDX200 FMF Fatty, Answer VFC silencer, VForce 3 Cage, Wiseco Piston, KX125-J series KYB USD fork conversion, Race tech goldvalves, J series front brake assembly, air-box snorkel removed, Acerbis Headlight, KX450F Front fender, Pro Taper RM bend bars, ASV front Brake lever, MSR Clutch perch and lever, RB Head mod, 36mm PWK carb, Trail Tech Kickstand.
Thrahl
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Re: RM 45mm Showa Performance

Post by Thrahl »

Image

The one on the left is what I was referring to.
Here it is sitting in the frame.

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I would assume that whoever did the conversion pressed the KDX stem in to the RM triple so my KDX upper bearing should fit. I will probably be tearing my bike apart tonight so we'll see.
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KDXohio
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Re: RM 45mm Showa Performance

Post by KDXohio »

Oh yeah thats nasty lol you'll want to make sure none of those tapered rollers is lurking around in there when you put it back together.

EDIT* I forgot you're not using that frame so ignore that^
1990 KDX200 FMF Fatty, Answer VFC silencer, VForce 3 Cage, Wiseco Piston, KX125-J series KYB USD fork conversion, Race tech goldvalves, J series front brake assembly, air-box snorkel removed, Acerbis Headlight, KX450F Front fender, Pro Taper RM bend bars, ASV front Brake lever, MSR Clutch perch and lever, RB Head mod, 36mm PWK carb, Trail Tech Kickstand.
Thrahl
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Re: RM 45mm Showa Performance

Post by Thrahl »

There's nothing in the frame I checked there first. Idk what the deal is with that thing.
Another issue popped up though. I went to clean the forks since they were so dirty, and one of them has something wrong with it.

When I picked it up by the top, the bottom just extended all the way out until it bottomed on something, probably the seal/bushings.
I can hear something loose inside, I assume it's the damping rod. I'm going to pull it apart now, hopefully something isn't broken.
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Re: RM 45mm Showa Performance

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So I took the fork apart and found the issue. The damping rod had come unscrewed from the cap and so everything was just bouncing around inside. No problem except that all of that bouncing bent the rebound (or maybe it's compression) adjuster to the point where the damper no longer threads in. So I tried to take it out not realizing that it doesn't come out, it's part of the cap, and snapped the head off. :doh:

So now I'm not sure what the next step is because this cap seems pretty much toast and a replacement is around $120. There aren't any on eBay either.
Maybe I can drill and tap a bigger hole and make a custom bolt to fit in. Idk, I'll come back to it tomorrow and see my options.
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KDXohio
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Re: RM 45mm Showa Performance

Post by KDXohio »

Here's what I'd try and look for....a cheap fork for parts then combine the two into one good one usually thats cheaper than piecing together new and used parts when there's damage like that. I grabbed this one as an example.
http://www.ebay.com/itm/92-Suzuki-RM125 ... 25&vxp=mtr
1990 KDX200 FMF Fatty, Answer VFC silencer, VForce 3 Cage, Wiseco Piston, KX125-J series KYB USD fork conversion, Race tech goldvalves, J series front brake assembly, air-box snorkel removed, Acerbis Headlight, KX450F Front fender, Pro Taper RM bend bars, ASV front Brake lever, MSR Clutch perch and lever, RB Head mod, 36mm PWK carb, Trail Tech Kickstand.
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KDXohio
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Re: RM 45mm Showa Performance

Post by KDXohio »

that was the right fork here's a link to the left one if you go that route....
http://www.ebay.com/itm/92-Suzuki-RM125 ... 5f&vxp=mtr
1990 KDX200 FMF Fatty, Answer VFC silencer, VForce 3 Cage, Wiseco Piston, KX125-J series KYB USD fork conversion, Race tech goldvalves, J series front brake assembly, air-box snorkel removed, Acerbis Headlight, KX450F Front fender, Pro Taper RM bend bars, ASV front Brake lever, MSR Clutch perch and lever, RB Head mod, 36mm PWK carb, Trail Tech Kickstand.
Thrahl
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Re: RM 45mm Showa Performance

Post by Thrahl »

Yea I saw those. The seller is like a hour and a half drive from me too but shipping it would be cheaper than the gas to drive there.
I am probably going to see if I can do anything with these caps. Nothing really to lose at this point.
And that's assuming nothing else is broken :lol: It's true, there's no such thing as a cheap dirt bike.

Edit - took a look at the forks again. The adjuster bolt in the cap actually broke off inside of the damping rod. It looks like a new fork leg for me :sad:
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Re: RM 45mm Showa Performance

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OK so a little update. I have decided to just buy two fork legs because I can get two for just a little more than the price of one.
But other issues have come up. It turns out this was a very half assed conversion. Whoever did it didn't press in a KDX stem to the RM triple, they just left the RM stem in place. :cry:
This causes a couple issues, the largest being that the stock KDX upper bearing does not fit the RM stem. The RM stem is also shorter and the bottom bearing doesn't actually fit the frame.

But I have taken some measurements and it looks like I can sort this out without too much of an issue.
The KDX stem and RM stem seem to be the same size where they press into the bottom triple, though it's hard to say without removing both of them.
If they are the same then it should be a simple stem swap, if not then I will have to have a machinist work a little magic. Either way they bottom should be fine. :cool:

The RM top triple is larger than the KDX stem, so I will need to have a spacer in there to take up the slack. I was thinking of opening up the RM triple a bit and then just pressing in a sleeve but we'll see what ends up happening. :pop:

With the proper stem in place and a good set of forks I should be set.
I will be talking to a machinist I know to see what he thinks. I should be able to do the pressing myself but I will need any sleeves/spacers made by someone else.
The forks don't cost too much and hopefully any machining I need won't be expensive and I should have my front end set up properly. :boogie:
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KDXohio
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Re: RM 45mm Showa Performance

Post by KDXohio »

Sounds good man looking forward to the outcome
1990 KDX200 FMF Fatty, Answer VFC silencer, VForce 3 Cage, Wiseco Piston, KX125-J series KYB USD fork conversion, Race tech goldvalves, J series front brake assembly, air-box snorkel removed, Acerbis Headlight, KX450F Front fender, Pro Taper RM bend bars, ASV front Brake lever, MSR Clutch perch and lever, RB Head mod, 36mm PWK carb, Trail Tech Kickstand.
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KDXohio
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RM 45mm Showa Performance

Post by KDXohio »

On another note let me know if you decide to part the bike out I may be good for a part or two
1990 KDX200 FMF Fatty, Answer VFC silencer, VForce 3 Cage, Wiseco Piston, KX125-J series KYB USD fork conversion, Race tech goldvalves, J series front brake assembly, air-box snorkel removed, Acerbis Headlight, KX450F Front fender, Pro Taper RM bend bars, ASV front Brake lever, MSR Clutch perch and lever, RB Head mod, 36mm PWK carb, Trail Tech Kickstand.
Thrahl
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Re: RM 45mm Showa Performance

Post by Thrahl »

Except for a few small parts (powervalves, petcock, gascap, rear caliper cover) everything will be for sale.
It's mainly complete too aside from the plastics. If you want something email me at ericguest@ymail.com

I haven't torn in to the engine yet but going by how badly seized it is right now it's probably going to be ugly.
I will start really getting in to disassembly once my front end is taken care of and my work space is clear.
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Re: RM 45mm Showa Performance

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It's been a while, but I pretty much finished the conversion today. :supz:
I ran in to more issues than originally planned (as it always goes).
The KDX stem is a little bit smaller than the RM one so I got it knurled and pressed in with some loctite.
But before I had it pressed in I had the RM lower triple milled down where the bearing sits. The RM one is a little taller than the KDX which would cause the bearing to sit higher, effectively shortening my stem.
With the milling taken care of and the knurled KDX stem pressed in to the RM triple I installed the lower bearing and thought I was on the home straight.

It turns out that during the pressing, there was so much force (15 tons even after heating it) that it mushroomed the upper threads for the top nut. :sad:
I ended up reworking the threads with files for hours until the nut fit nicely. Had I taken it back to the machine shop they probably could have fixed it in no time.

With the top nut now fitting well, I made my own shim for the upper triple out of a little strip on galvanized steel sheet. With a little work everything fit together like a glove.
So I regreased the bearings (yes I am reusing the old ones, I'm cheap and they aren't totally shot just yet) and put it all together. Fits beautifully.
My new fork legs required a little cleanup (cleaned seals, changed oil, etc.) but should be perfectly functional now.

Now the only issue left to deal with is the steering stops which are too far apart causing the upper triple to contact the tank at full lock. (it never ends does it :roll: )
I am probably going to get the frame stop welded to widen it so it contacts earlier, we'll see.

I will hopefully take it out for a light ride tomorrow to see how it handles.
I haven't taken pics yet, they will also be up tomorrow.
Last edited by Thrahl on 10:32 pm Aug 07 2013, edited 1 time in total.
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KDXohio
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Re: RM 45mm Showa Performance

Post by KDXohio »

Sounds good can't wait to see it
1990 KDX200 FMF Fatty, Answer VFC silencer, VForce 3 Cage, Wiseco Piston, KX125-J series KYB USD fork conversion, Race tech goldvalves, J series front brake assembly, air-box snorkel removed, Acerbis Headlight, KX450F Front fender, Pro Taper RM bend bars, ASV front Brake lever, MSR Clutch perch and lever, RB Head mod, 36mm PWK carb, Trail Tech Kickstand.
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