RD400 Daytona Special - RPM Question

[KANDY]

Hi All,

Newly rebuilt 1979 RD400 Daytona Special Canadian. New bore Run in finished(4 Heat cycles)

2R9 cylinders running on CDI 2.0 BTDC

2R9 Carbs with all stock settings. Filter is from Yambits ( Paper)

CDI box is from HPI Belgium. Plug : BR9ES

Running good, today I took to 140km/h but at that point the RPM was 9500. My 1977 Rd400 do not go that far for 140km/h.

And also noticed that in any point the RPM was way more than in any speed, for example 1977 would coast 70mph at the RPM of 5500, but the Daytona was RPM 6500 close to 7000

What could be the reason, is that the CDI box, should I do some setting. Please give some insight. Or is it Normal

[Organicjedi]

What's the final drive gearing?

[KANDY]

Dont know, Stock Motor.

[rodneya]

He means what are your sprocket sizes

[1976RD400C]

Clutch slipping?

[SoCal250]

Either the gearing is very different or you have something else going on (clutch slip like 1976RD400C mentioned). Are you sure it's in 6th?
The stock gearing should be the same for a RD400D and a Canadian RD400F (3J7)
Model                          Primary               Secondary
RD400D                       66/23 (2.869)     38/17 (2.235)
RD400F (US 2V0)         66/23 (2.869)     37/17 (2.176)
RD400F (CAN 3J7)        66/23 (2.869)     38/17 (2.235)

[1976RD400C]

I missed the part about it's still higher coasting. Maybe the tach is not accurate. Gearingcommander website says 37/17 = 145kph at 6650 rpm and 38/17 = 145kph at 6700 rpm in 6th gear.

[KANDY]

Either the gearing is very different or you have something else going on (clutch slip like 1976RD400C mentioned). Are you sure it's in 6th?
The stock gearing should be the same for a RD400D and a Canadian RD400F (3J7)
Model                          Primary               Secondary
RD400D                       66/23 (2.869)     38/17 (2.235)
RD400F (US 2V0)         66/23 (2.869)     37/17 (2.176)
RD400F (CAN 3J7)        66/23 (2.869)     38/17 (2.235)

Checked mine, it is 38/17. Could be the tachometer is not accurate, because for clutch slip, I could not find any drag taking off from stop.
I am sure I was in 6th Gear
Tomorrow let my friend ride, Will report here

[KANDY]

Friend could not get into any conclusion, except running very good.
But RPM I cross checked, it is high in any speed.
Any comments please.

[bitzz]

Are you basing that 140kph off the stock speedo that is notoriously inaccurate?
Check the speedo with a GPS app on your phone.

... and your almost 50 year old tach may be off too.
If your clutch is slipping, it is more apt to slip in 6th gear than in 1st.

[KANDY]

Any good source for Cluth Plates.
I will change it and see.

[m in sc]

best way to test is... ride in a higher gear. pull clutch in and dump it. if rpms stay up, its slipping. if they drop back down, its fine.

use yz250, banshee, or 1st gen fzr frictions. 

https://www.ebay.com/itm/281062515144

here you go. dirt cheap and you get spares. run this in a few of mine.

[SoCal250]

RD400F/G (3J7) OEM parts:
Yamaha 360-16321-00-00 FRICTION PLATE, (T=3.0), 7 required
       (superseded by 360-16321-09-00 then by 5Y1-16331-01-00)
Yamaha 90501-23138-00 SPRING, CLUTCH, 6 required

Alternate part (upgrade):
Yamaha 4H7-16321-02-00 FRICTION PLATE, (T=3.0), 7 required
       This part number is called out for many models including the FZR1000, YZ250, FZ6, XS400, Seca II, Raptor, Warrior, etc.

[Striker1423]

Also, clutches that are worn typically show the slipping signs at higher RPM's in higher gears. So, get it into 6th and dump the gas a few times. If you baby it you'll never slip. Give it some berries and you'll hear and feel it if it is slipping.

[KANDY]

BANSHEE Cluch plates and Friction plated ordered.
Waiting........