What should my rpm be for a 4oocc going 60 in 5th gear

Question

I have a Yamaha 81 400cc, and when in 5th gear going 50, it is usually at 5,000. It is the same for the other gears.

For example, at 4th gear going 40 its 5,000

3rd gear at 30 its 5,000

I don't think it's susposed to be that high , I'm just looking for some confirmation or information

Answer 1

Hi Susan,,,did You mean 6th Gear aka Hi Gear/Top Gear?

'81 XS 400 4Stroke Twins all had 6 speed gearboxes.

.................................

That bike is "advertised" at 87mph Top Speed.

Which calculates to approx 7600 rpm

Based on the bike's overall gearing & tire size,,,

Here's what the RPM @ Road speeds look like.

(approximately)

6th Gear>>>>>>>>>

8000= 91.5

7000= 80

6000= 68.6

5000= 57

4000= 45.7

5th Gear>>>>>

8000= 82.5

7000= 72

6000= 62

5000= 51.5

4000= 41.2

....................................

Considering calculation errors

*rounding off gear ratio numbers

*Unkown ACTUAL,EXACT  in-use tire radius

*Instrument Errors in Speedo & Tach...........

It appears that your bike is Geared /Tired  pretty much Stock~Original,,

And it DOES seem to be running the RPM/Road Speed it should be

.........................................

You can Re-Gear it,,,if you want to drop the RPMS per given road speed

Example,,,a 6.50 Final Drive ratio will APPROXIMATELY change 5th Gear RPM into 6th Gear RPM

Thats a 16T Front Sprocket x 32T Rear Sprkt.

Versus Original 16 x 37

You could cruise around in 5th,,,geared like High Gear,,,then 6th would be a Big drop in RPM-per-MPH

4500= 65mph in 6th with 16x32 final gearing

4500=51mph with STOCK gearing in 6th gear

5700=65mph with STOCK gearing in 6th gear

Just for example.

Get some Solid advice on ReGearing before deciding on what numbers to use,,,,if you do decide to regear it.

Too Little is almost pointless,,

a LITTLE too Much,,and bike gets very sluggish

Hope that helps

Answer 2

That sounds about right for a XS400 twin. If the clutch is slipping you would notice the RPMs increasing but the speed remaining the same (or dropping in extreme cases) while going up hill or trying to accelerate in higher gears.  You may want to check with your local bike shop, a RD400 front sprocket may fit and be one tooth larger than stock XS, this would bring your RPMs down a bit (better for highway riding, worse for acceleration)

Answer 3

if your clutch isnt slipping, those old guys are hard gears and chains, its right!