YZ USD Front End & Fork swap
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It actually didn't cost me anything to do my modification. And no messing about with stems. So you can swap back to a DTR without any faff.
Cost wise, if you've got the components then it's cheaper than barrels ported. Probably more to be gained too in terms of performance. Better braking better handling = faster lap times.
In terms of something actually educational, I wrote a guide on how to swap over the forks.
https://dt125r.co.uk/topic/17/usd-conversion-bearing-cup-method
Rather than talk of how it could be done, I show you how to do it.
@Calum said in YZ USD Front End & Fork swap:
It actually didn't cost me anything to do my modification. And no messing about with stems. So you can swap back to a DTR without any faff.
Cost wise, if you've got the components then it's cheaper than barrels ported. Probably more to be gained too in terms of performance. Better braking better handling = faster lap times.
In terms of something actually educational, I wrote a guide on how to swap over the forks.
https://dt125r.co.uk/topic/17/usd-conversion-bearing-cup-method
Rather than talk of how it could be done, I show you how to do it.
As always thank you, I’ll admit I may need to shoot you a message or something if that’s okay as that stuff would make a lot my uncle then me and I think he had a couple questions.
I have read about your bearing cup method multiple times but my main concern is it’s strength as opposed to machining the stem to fit. Both me and my uncle know how I ride sometimes...
... see I turned up to our local track recently to find they’d made a 5ft table top a couple weeks back. Few of the boys where playing on it and a couple youngens where rolling over it but nothing mad. Couple of me mates jokingly challenged me to do it and you guessed it, the DT sent it, in full road trim. In the background was all my mates on KTM’s, YZ’s, KX’s all in disbelief. Fucking priceless.
To make things better when a first turned up people clocked what the bike was and loved the old DT just couldn’t fathom that it was even going on the track in the first place . My only response was “don’t worry she gets used haha proceeds to knock it down a gear and slide the ass out”So as you can imagine I can’t chance anything like that and strength is of the importance as I do like to have a bit of a play with the boys...
With that being said though, I think you are all right about it being a very worthy mod. Better braking and handling does mean faster lap times and just generally faster bike. I’m pretty certain that alone makes up for any drawbacks caused by weight. I’m just concerned about the strength.
*its worth noting that the weight difference between an 02 YZ excel wheel and a DTR wheel isn’t anything noticeable
I’ve absolutely battered the DTR forks through all sorts and even with 15w oil, they take the punishment but at the same time, at high speed on rough terrain, you take every bit as much of that punishment across that terrain and it’s not fun. However it’s worth noting on trail and road they’re perfect and that whilst stock fork oil performs worse off road I never once suffered half as much arm pump.
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You'd be wrong to dismiss the bearing cup because of forces to great, You have to be mindful of the difference in top bearing size a YZ will use here. That is your main gain.
What you have to remember is, you can't drop the yoke down to far because you'll loose the clamping area that's clearly machined on the fork leg (You should check this first) This will occur if you use the existing DTR dimensions.
Keep it real
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You'd be wrong to dismiss the bearing cup because of forces to great, You have to be mindful of the difference in top bearing size a YZ will use here. That is your main gain.
What you have to remember is, you can't drop the yoke down to far because you'll loose the clamping area that's clearly machined on the fork leg (You should check this first) This will occur if you use the existing DTR dimensions.
@Darty hmm interesting, I hadn’t really thought about the fact I’d be using the YZ’s bearing or the impact of that.
It’s also worth noting the fit and finish would be much better as opposed to having to run a load of spacers toward the top cap if I had the YZ stem machined.
Also you’re right, much better worded but I did mention this and just as you’ve said why you can’t swap stems, at least not safely.
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Sorry? Are you worried about the strength of a bearing cup? Solid steel that's like 3cm thick?
Or machining down a spindle which is only a few mm thick?
The stems structural integrity shouldn't be compromised. The stresses on the bearing cup is minimal. The bearings give way before the headstock, by design, since they're consumerable. I wouldn't be machining the stem unless you're talking a the thou.
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@Darty hmm interesting, I hadn’t really thought about the fact I’d be using the YZ’s bearing or the impact of that.
It’s also worth noting the fit and finish would be much better as opposed to having to run a load of spacers toward the top cap if I had the YZ stem machined.
Also you’re right, much better worded but I did mention this and just as you’ve said why you can’t swap stems, at least not safely.
@Stevie-Wonder Mate you have no idea if you are talking about stacking spacers, that is just fucking dangerous.
I don't even know how you would machine the thread long enough on the stem after you've cut it down, it tapers towards the centre point away from each bearing race?!
Questionable how else it should be done in my opinion.
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The boys on the old site pressed out the stem from the DTR. Pressed out the stem from the YZ. Made a collar for the DTR stem to fit into the YZ bottom clamp and pressed that back into the yoke.
Okay yes fine, but you are still left with the DTRs ball bearing, instead of a taper bearing, and you still have to do machine work.
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@Stevie-Wonder Mate you have no idea if you are talking about stacking spacers, that is just fucking dangerous.
I don't even know how you would machine the thread long enough on the stem after you've cut it down, it tapers towards the centre point away from each bearing race?!
Questionable how else it should be done in my opinion.
@Darty said in YZ USD Front End & Fork swap:
@Stevie-Wonder Mate you have no idea if you are talking about stacking spacers, that is just fucking dangerous.
I don't even know how you would machine the thread long enough on the stem after you've cut it down, it tapers towards the centre point away from each bearing race?!
Questionable how else it should be done in my opinion.
Aye hear me out, not my idea my uncles. I wasn’t 100% what he meant, after a lot of talking we where both sceptical on what the best way to do things was. I also wasn't 100% on what he meant, I thought he meant about machining the threads. We got the idea after seeing this bike however we could’ve just interpreted things wrong
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The boys on the old site pressed out the stem from the DTR. Pressed out the stem from the YZ. Made a collar for the DTR stem to fit into the YZ bottom clamp and pressed that back into the yoke.
Okay yes fine, but you are still left with the DTRs ball bearing, instead of a taper bearing, and you still have to do machine work.
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@Darty said in YZ USD Front End & Fork swap:
@Stevie-Wonder Mate you have no idea if you are talking about stacking spacers, that is just fucking dangerous.
I don't even know how you would machine the thread long enough on the stem after you've cut it down, it tapers towards the centre point away from each bearing race?!
Questionable how else it should be done in my opinion.
Aye hear me out, not my idea my uncles. I wasn’t 100% what he meant, after a lot of talking we where both sceptical on what the best way to do things was. I also wasn't 100% on what he meant, I thought he meant about machining the threads. We got the idea after seeing this bike however we could’ve just interpreted things wrong
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@Calum That's the most common way I've seen it over time, trouble is your fork legs don't sit properly in the clamps anymore.
But it works, alot more leverage over the top bearing which I hate.
It's not optimal.
@Darty said in YZ USD Front End & Fork swap:
@Calum That's the most common way I've seen it over time, trouble is your fork legs don't sit properly in the clamps anymore.
But it works, alot more leverage over the top bearing which I hate.
It's not optimal.
Which is what I mentioned earlier and the first thing my uncle noticed. I never realised the upper fork legs tapered, not something I ever noticed before however instantly we both expressed great concern about it not clamping properly.
I just couldn’t commit to or trust itAnd @Calum yeah however at a glance it doesn’t look to bad and the forks used are newer spec YZ/WR forks, which is kinda important because I noticed how most people that have done a USD swap have just opted for early 89 YZ/WR200 forks, something I wanted to avoid as I actually want to get a decent upgrade for the price I’m paying. Not to mention aftermarket support
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@Calum RIP Roller bearings
@Stevie-Wonder It's pretty important to take the time and do this properly.
Make a plan and draw your measurements out, mock it up and take some photographs.
Pre 1996 YZ forks use the same spindle size as the DTR, that's the appeal.
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time to continue this old donkey...
First and foremost, I hope everyone’s well and what’s everyone been up to with their projects?
So since tearing down my entire front end this is what’s happened
•Rebuilt the 02 YZ forks
•Noticed the gigantic difference in stems and tapering on the upper stanchion
•Not a lot elseUnfortunately being at home at university without an income and also coming to the realisation this is going to need quite a bit of work halted things.
During a storm she also took a bad hit, being knocked clean sideways off, knocking bearings out and taking everything else with it.
I was very lucky as there was no panel damage and no glass or anything smashedAccording to my phones camera roll, she’s not been started or rode in over 2 months. Devastated. On the bright side keeping them miles down and rebuilds away
Anyway... I’ve spoke to a lot of different people about the way they did their USD fork conversion, I even found the guy who’s bike I posted and got chatting to him and the general consensus is some people having been using Dremels and buying replacement modern taper bearings. @Calum if you’re reading, don’t worry mate I’m taking your advice on this one. Bearing cup method all day. I think of about 8-10 people I’ve spoke to online only one person has used that method. Everyone else had made their own kind of diy jobby. Worst of all, 95% of the time they’re fucking weirdos and act all secretive about it. Not a fan tbh. Sounds very sketchy
I don’t think a single one of the people I spoke to who’s done a USD fork swap has actually done so with any intent of using those forks like they where designed for. £500 on a WR200 front end just to supermoto it and look cool?
That's bad 
