Does anyone have a 1:1 printable template for the front disc rotor? I would like to drill it out to reduce the overall front unsprung weight. The oem disc is like a boat anchor. Thanks guys.
Swapping the stock cast iron caliper for the alloy repop caliper that EC sells will cut a pound/ 500 grams or more as well. Swapping disc and caliper fasteners for TI saves a little bit more.
Also, inner tubes and tyres vary quite a bit in weight.
Drilling/slotting rotors was because the pad material would offgass under heavy braking and make the pad "float", modern brake pad materials don't really do that so much.
Looking for weight savings with titanium fasteners and so on is like the last 5% of wringing speed out of a bike after you've done everything else, presuming that your riding ability on track is as far as you can take it.
All that being said half a pound is half a pound.
fzr or ducari rotor and blue dot caliper saves a ton of weight and increases performance better than any original style setup.
Quote from: m in sc on November 24, 2025, 06:33:58 PMfzr or ducari rotor and blue dot caliper saves a ton of weight and increases performance better than any original style setup.
Happy thanksgiving.
Thanks Mark. I guess this upgrade does require the disc spacer/flange and adapter for the dot caliper etc. that needs to be fabricated and is not plug and play, correct? If yes, are you guys fabricating your own?
yes and yes
Here is some inspiration if you are still going the OEM route. 100 3/8" holes per rotor and they were also thinned down to around 5mm.
Quote from: Tommo on November 24, 2025, 06:31:32 PMAll that being said half a pound is half a pound.
On a lightweight bike like an RD, less unsprung weight is REALLY noticeable on bumpy roads. A more extreme example is when I converted my XS650D from the oem twin 267 mm discs (more like boat anchors, really) to a single 320 mm ISR disc, and a Brembo 4 pot caliper. Combined with an alloy front fender, Ti fasteners and alloy bearing spacers, I lost around 5 kg/ 12 lbs of unsprung weight. From around 16 kg to around 11 kg IIRC. The difference was noticeable before you got into second gear.....
Quote from: Dvsrd on November 28, 2025, 09:42:21 PMQuote from: Tommo on November 24, 2025, 06:31:32 PMAll that being said half a pound is half a pound.
On a lightweight bike like an RD, less unsprung weight is REALLY noticeable on bumpy roads. A more extreme example is when I converted my XS650D from the oem twin 267 mm discs (more like boat Anchorage, really) to a single 320 mm ISR disc, and a Brembo 4 pot caliper. Combined with an alloy front fender, Ti fasteners and alloy bearing spacers, I lost around 5 kg/ 12 lbs of unsprung weight. From around 16 kg to around 11 kg IIRC. The difference was noticeable before you got into second gear.....
True dat! I've ridden a friends bike with a similar conversion and yes, the unsprung weight really makes a difference.
Quote from: oxford on November 28, 2025, 08:38:00 AMHere is some inspiration if you are still going the OEM route. 100 3/8" holes per rotor and they were also thinned down to around 5mm.
Thanks for sharing, looks great. I've now made up mind to go the blue dot way....the challenge is obtaining the specs for the flange and adaptor for the RD350B (1975 model) is a challenge as mine has the OEM fork legs with the caliper in the front unlike the RD400.....
Quote from: 350GUY on November 28, 2025, 10:14:00 PMQuote from: oxford on November 28, 2025, 08:38:00 AMHere is some inspiration if you are still going the OEM route. 100 3/8" holes per rotor and they were also thinned down to around 5mm.
Thanks for sharing, looks great. I've now made up mind to go the blue dot way....the challenge is obtaining the specs for the flange and adaptor for the RD350B (1975 model) is a challenge as mine has the OEM fork legs with the caliper in the front unlike the RD400.....
You can swap the fork legs left to right, if you don't use the oem speedo.
Quote from: Dvsrd on November 29, 2025, 06:54:47 PMQuote from: 350GUY on November 28, 2025, 10:14:00 PMQuote from: oxford on November 28, 2025, 08:38:00 AMHere is some inspiration if you are still going the OEM route. 100 3/8" holes per rotor and they were also thinned down to around 5mm.
Thanks for sharing, looks great. I've now made up mind to go the blue dot way....the challenge is obtaining the specs for the flange and adaptor for the RD350B (1975 model) is a challenge as mine has the OEM fork legs with the caliper in the front unlike the RD400.....
You can swap the fork legs left to right, if you don't use the oem speedo.
I thought about that Dvsrd, but I will be using the OEM Speedometer. I see that some XS650 guys had done this mod, but I guess the dims for those outer fork legs are different unless they are pre-1977.....
You need a fork leg from a TX500.
Quote from: oxford on November 29, 2025, 08:28:04 PMYou need a fork leg from a TX500.
Thank you Oxford. Just the outer or the internal/guts as well?
Quote from: 350GUY on November 29, 2025, 08:53:03 PMQuote from: oxford on November 29, 2025, 08:28:04 PMYou need a fork leg from a TX500.
Thank you Oxford. Just the outer or the internal/guts as well?
You should just need the outer leg and swap the RD internals in. I can't remember if the TX internals (or inner fork leg length) were the same or not. The fork lowers were basically the same except for the caliper lug on the left leg for dual disc.
350guy, I thought about it last night after I posted, I might be giving you wrong info on what you are wanting to do.
The TX lowers are the forks to get dual disc on a RD but I think you are going to have the same speedo problem as with flipping factory forks around for the caliper in the back. You will just gain the caliper on the same side as stock. Sorry for the confusion.
TX500 forks have caliper mounting lugs on both legs and the full assembly is roughly 1.5" longer than RD forks. The right side lower is the same part on the TX and RD. Lowers are interchangeable.
A left fork slider from a '73-74 TX500 can be swapped in to replace your OE RD350 lower. That will give you a provision for mounting a caliper on the other side (in front of the leg). As mentioned above if you swap sides with lowers to move the caliper behind the fork you're going to lose the speedo drive function.
371-23126-60-00 FORK TUBE, LOWER LEFT TX500, TX500A, XS500B
351-23136-50-00 FORK TUBE, LOWER RIGHT RD350, RD250B, TX500, TX500A, XS500B
AFAIK, the only 34 mm Yamaha forks with the calipers behind the sliders are 1976 XS650C and pre-Daytona RD400.
The XS sliders are a bit longer than RD sliders, and also have larger OD.
The RD400 sliders are also different from the 350 ones,in the top end/ seal area. So best replaced as a pair.
Quote from: oxford on November 30, 2025, 07:51:35 AM350guy, I thought about it last night after I posted, I might be giving you wrong info on what you are wanting to do.
The TX lowers are the forks to get dual disc on a RD but I think you are going to have the same speedo problem as with flipping factory forks around for the caliper in the back. You will just gain the caliper on the same side as stock. Sorry for the confusion.
Thank you Oxford guy for clarifying, know that it is appreciated.
Quote from: SoCal250 on November 30, 2025, 02:38:26 PMTX500 forks have caliper mounting lugs on both legs and the full assembly is roughly 1.5" longer than RD forks. The right side lower is the same part on the TX and RD. Lowers are interchangeable.
A left fork slider from a '73-74 TX500 can be swapped in to replace your OE RD350 lower. That will give you a provision for mounting a caliper on the other side (in front of the leg). As mentioned above if you swap sides with lowers to move the caliper behind the fork you're going to lose the speedo drive function.
371-23126-60-00 FORK TUBE, LOWER LEFT TX500, TX500A, XS500B
351-23136-50-00 FORK TUBE, LOWER RIGHT RD350, RD250B, TX500, TX500A, XS500B
Thank you very much SoCal for sharing these deets, this is extremly hepful.
Quote from: oxford on November 28, 2025, 08:38:00 AMHere is some inspiration if you are still going the OEM route. 100 3/8" holes per rotor and they were also thinned down to around 5mm.
Simply stunning