Preface: I don’t claim to be an experienced machinist. More like a hopeless starving artist DIY guy. But I love to tinker and try new ideas, make things and learn stuff along the way. So no, you don’t get to critique the finishes and various mistakes. Hahahah
Design brief: I’ve been a small bore guy most of my life (now 60) and you know how those bikes are- you are wide open and working the clutch. Adding to that is that I have always had a hard time with the whole re-grip thing. My wrist just seems to like to work in a more limited range. No injuries or anything, just more of how it naturally works.
So for decades I have wanted a shorter turn throttle. And I’ll use the term “short turn” as opposed to “quick turn” because the idea is NOT to open the throttle quicker, but more that it takes less rotation to go full open. Most throttles are about 70°. I wanted one around 45°. Doing the math, that means the cam needs to be about 2.00”R. There is nothing out there even close to that. It would require a whole new housing.
Short version: This project is (or was) way out of my skill set so I spent a fuck ton of hours destroying chunks of aluminum, various cutters, re-drawing, re-measuring, re-doing. Learned a whole lot. Finally came out with a workable version to establish a proof of concept. Went riding at Pala today . . . I frigging love it!!!!!! Man, I was stoked! It works just like it did in my mind. Takes very little rotation to get wide open. On my 144 it is awesome. I don’t think I would try it on my 250 big bore but for the small bike, I am amped!
It is still rough around the edges and sealing the unit is an issue. But does it work? For me- hell yeah. I’m amped.
The throttle tube itself is one off of ebay. I think it was a Moose. It was $12 and it was just what I was looking for. It uses tabs to hold in the cam so I could make different cams as needed. It made no sense to try and make a tube myself. One less hassle. Whew!
Making that deep groove for the pulley was a bitch. I used a super long end mill but made a shank to make more rigid. Shocked I didn't break it. I broke and ruined lots of other cutters, though!
Had some pretty sketchy work holding set ups as I was learning. Only once did a part fly out of the fixture. Luckily into the wall and not into me. The set up here is actually really solid and worked great. The lens distortion is what makes it look like it is not all square and tight.
That relationship of the cable in, meeting the roller wheel, and then feeding onto the pulley is critical, obviously. It took a few tries to get right but came out perfect. I realized the mistake I was making initially was measuring off of one of the key outer surfaces. (top right corner of the squared block.) It would just not work out. I finally realized I had to start all my measurements from the CENTER of the block. Then it became more consistent and I could hold my dimensions. It's all about learning new stuff.
I Love seeing People Make Their Own Things!
Brilliant stuff FWYT !
You've a preference, and you Made something to match that preference.
I see it's on a 144 - 125. And, you noted that you'd probably Not want such a set up on a 250. I can't imagine what such a throttle would be like on, say a 500...........
I make my bikes suite Me, and my weirdness. Thus, an enormous amounts of mods done, by Me. For Any of my bikes. My throttle mods for my 500 consisted of getting a G2 throttle, running it, not liking a few aspects of it, and then welding and machining another profile to one of the cams. Making the first part of the throttle opening Quick, then slowing the pull. Plus, modifying it so it could actually get Full Throttle - With the slow turn cams, You couldn't get the last few mms of slide opening at the time - I can only assume G2 sorted that out, though, I'd not be surprised that people putting on the slow action cams, don't realize they aren't getting full throttle, on many bikes.
Once again, Brilliant work, FWYT !
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Thanks, Bearuno! Yeah, it was a lot of fun and learned a ton. Got better with my janky little rotary table which was really confusing at first. Learned that a lot of time is spent making little pieces to align or hold the part before you even begin cutting the part! Also trying to get down the most efficient order-of-operations. That seems like it just has to come with experience. Heck, the first couple I tried to make, I got about 1/4 way in and realized I had no more surfaces to be able to safely clamp it. So it was make notes, and start over.
In actually riding, it was reaffirmed that all this time, I had rarely ridden at WOT. Where I could actually feel the cable topped out. Damn, all this time . . . Even at 60, still learning how to ride! hahahahahha The main riding difference was a few corners I would be bogging because whereas before I might have been at 85%, now it was a 100%. So it just forced me to carry a little more corner speed and/or a little more clutch. Overall I am just amped. Wish I had this 30 or 40 years ago.
Something I’ve thought would be useful before as I also have difficulties with re-grip and limited wrist movement. Not an issue on my 450 where I ride, but I’ve noticed some times I couldn’t go WOT without elbow drop or re-grip, mostly while standing.
Nice job! I'd have killed for one of those on my 125! Is it noticeably harder to twist?
No, not at all. Exactly the same as stock.
Fabulous and satisfying.
I need to make the same, except with a double pull (2 cables) for my 2 cylinder 2stroke 250cc road race project.
That's awesome work!
I've recently started riding an 06 RM125, coming off an 08 RM250, and that was the first thing I noticed was how hard it is to ride full throttle with good arm/wrist position. Immediately starting browsing for shorter turn throttles and was disappointed to find nothing.
There really is a gap in the market here.
Do you think the 45 turn will be suitable for year round/all track use? Or will you experiment with 50/55/60 degree throttles?
I think there is a lot to gain performance wise from the throttle itself, as I've had good experience going the other way using the G2 throttle tamer on aggressive bikes
Splitter boxes exist aplenty, AzureHog ......
Yes they do.
But I want a twin cable setup. For adjustment, low binding and reliability. The twin cable setups are not uncommon. But I want short throw like this project. Potentially available commercially.
I've a genuine TZ twin cable throttle that I've used on various bikes over the decades.
I've not found anything that was as Quick Action (relative to other twin cable RR throttles of the era) as that, though I haven't tried for a long, long time.
It's a bit of an heirloom now - any carb'd Dukes I set up now for track days, I run with a modern 2 stroke throttle and splitter boxes. The TZ unit is a bit 'precious' to risk in an 'off' with nowadays. Though, I'm sure I bought 2 of them back in the 80s, but I'm buggered if I know the 'safe place' that I put it, and many other 'precious' things in.............
So, what is the 250 2T Twin you are building?
I'm pretty pumped with how the 45 degree turn works so I won't be trying other ratios.
Though I have not gone trail riding yet, in my mind it seems like it would be just fine for the small bike. They don't really have any power down low anyway. Not sure if that would be the case on a bigger bike but ever the idiot, I will definitely be trying the throttle on my YZ250 big bore, just to see what it is like. :D
Awesome stuff!!
Freakin' wild ride, I'm sure!
Motion pro vortex , and G2 have similar throttles to what you made here, but not as extreme. Nice work. I was just thinking about a 3d printed throttle cam that is more aggressive to work with ODI grips might be an easy way to make changes for different riding conditions.
Anything that fits in the stock housing is only going to be marginally bigger/quicker. No where near the scale of FWYT's setup. The only thig commercially available that gets pretty quick is the Motion Pro Rev-3 setup. It replaces the entire housing and comes with reels up to 50mm in size. The reels are also ODI lock on compatible. But even 50mm is still relatively tame compared to what we're seeing here! haha Oh, and it's only available for 4-strokes.
Pit Row
Im into vintage strret bikes too. If you made one for the 72-75 Z1 you'd make a fortune.
Very nice work. That was a major undertaking to go from a drawing to a finished part. The quality of your work is not hobbyist at all. For a prototype on a manual machine with limited tooling it looks professional. You should be very proud of that part. I have been in the machining business for decades and am not sure I could have done any better using what you had to work with.
I’m putting a Suzuki RGV250 together for Historic Road Racing.
The class I’m targeting is “Pre December 1990” known as “Period 6”.
If the bike is stock enough, it can run in “Production”, mainly against the 4 cylinder Honda CBR250RRs (20,000 rpm!).
And in the open 250cc class - trying to keep up with TZ250’s etc.
I have a lot of “good bits” (Suspension, custom chambers, “kit spec motor”). I have to fabricate an AL subframe and start putting it together.
What “splitter boxes” do you recommend?
Thanks, Alien!
Yeah, I'm stoked for sure. Particularly since it actually worked. The actual machining of the part I know I can get better at and I am happy to have gotten a decent working prototype. Now I can fine tune the part and trim it down here and there. What was really fun was learning the order-of-operations. The first block I cut into, pretty soon I realized I had no more surfaces to clamp onto. Then realizing I needed to make my measurements from the center. That was a big help. Things like that. When I get around to it, won't be anytime real soon, I'll make another one and post a photo.
An RGV sounds like a fantastic thing to campaign in that class!
As an aside, I've thought of getting one, but, bloody hell, the prices on them are starting to get Way up there, and, I've other 'toys' in front of them to acquire. Though, I've asked my mate that gets bikes from Japan to keep an eye out for one : I don't know much about the various 'race kitted' ones they may have done - when I see (usually Pommie) bike mag stories on Japanese 250 2T proddie racing bike models, it gets pretty bloody complicated....
As to Splitter Boxes : I'd use Venhill , Tomaselli or Domino ones, years ago. They'd be Aluminium units. I've seen Amal Junction boxes for sale on the net, and I think they may be Aluminium ones, and they go for $42 - not sure if AUD or USD.
I also saw an Elvedes cable Splitter - That it has a threaded cap, and 3 Orings that go into grooves on the outside of it ( for protection / vibration ? - I think it may be Bicycle Brake related ) indicates it may be of high quality / Aluminium. Listed as $70.99 AUD.
My very quick check, only on my phone, came up with ones ranging from $9.95 / 15.99 Asian made (one assumes), through to Venhill's Kit that has cables , splitter, ferrules etc , etc. The splitter box in that kit looks to be the same thing as a few individual splitters sold separately by quite a few 'sellers' for around the $36 AUD mark, and, it looks to be plastic. Now, plastic Can be great, and, Venhill should still tend to have reasonable quality, but, I can't attest to that. Kenma Australia sell the Venhill kit for $79.40, AUD, by the way
I made a few myself, out of Box Aluminium, many years ago, after my bought alloy tubular ones 'ran away', but, if I needed another one myself now, I'd do some research and just buy one. My time is worth more to me now, with such things, and the 2 I've still got, will last me forever.
I noticed MXStore have a Domino Dual cable throttle for around $170 AUD, but I doubt it's particularly fast turn - it is listed only as have a 45mm 'pull'. You could give them a call to see if they can confirm it has a quicker pull, than the seeming 'endless turn' ones .
Have fun with that RGV. It will be intersting to see how it goes up against those Screamer Fours, and the TZs. I had the last model reverse cylinder PT TZ 250 for a short time, many, many moons ago. I've been thinking of doing some 'period' RR, when I'm all repaired, putting that new to me 900 engine to my own chassis. It will be a TT2 type, of my make, with many improvements ( longer swingarm than the short arse original, with, decent rear wheel travel, not sweet FA, removable subframe / adjustable footpeg plates etc to suit my buggered up body etc ) - though, I'm not sure how that would be accepted by the 'period' rules people though......... But hang on, they allow Harris (or replica) XR69 Chassis FJ1100 /1200s that I don't remember ever existing in the XR69 Suzuki years, don't they?
Oh, as an aside, I wonder if the OP took note of the time he spent making that Genius Throttle of his - it can be Frightening! Good grief I've spent days making 'one of' things for myself - all while tearing my hair out / having a wonderful time doing such madness. There's Nothing better than making your Own Things!
You can get a stock throttle to deliver stock peak HP by an 1/8th turn, at a lower RPM. Works every time with a STIC Super X carb or their PWK meter block. By a 1/4 turn you're into a new level and wider peak HP. The carb has an unmatched accelerated fuel uptake. I run the slowest turn G2 cam, as to gain back a std range of use/control.
The X carb is leading a national 250cc carting series. Last year it also captured the world 2t 500cc drag race championship and the CR placed 2nd in the 750 class.
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