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What does the black bracket attached with the Allen head screw on the lever over the spliced shaft do, brake light switch?

My PV is set to start opening at 5000, full open around 7000.

$600 Yambits order placed, we will see.   

Shipment history
USPS: 9400108106245537756371

Mon, Sep 14
3:59pm
Delivered, In/At Mailbox
MELROSE, NY 12121

Mon, Sep 14
9:29am
Out for Delivery, Expected Delivery by 9:00pm
MELROSE, NY 12121

Mon, Sep 14
9:18am
Arrived at Post Office
MELROSE, NY 12121

Mon, Sep 14
6:59am
Departed USPS Facility
ALBANY NY DISTRIBUTION CENTER

Sun, Sep 13
12:00am
In Transit to Next Facility

Sun, Sep 13
12:00am
Estimated delivery date updated to Mon, Sep 14

Sat, Sep 12
8:05pm
Arrived at USPS Facility
ALBANY NY DISTRIBUTION CENTER

Sat, Sep 12
4:55am
Departed USPS Regional Facility
SPRINGFIELD MA DISTRIBUTION CENTER, 01152

Fri, Sep 11
8:50pm
Arrived at USPS Facility
SPRINGFIELD MA DISTRIBUTION CENTER

Thu, Sep 10
1:46pm
Processing at USPS Facility
NASSAU, NY 12123

Thu, Sep 10
7:50am
Processing at USPS Facility
NASSAU, NY 12123

Thu, Sep 10
7:50am
Estimated delivery date updated to Thu, Sep 10

Tue, Sep 8
9:24am
Processing at USPS Facility
WYNANTSKILL, NY 12198

Tue, Sep 8
5:19am
Processing at USPS Facility
WYNANTSKILL, NY 12198

Sun, Sep 6
9:49am
Arrived at USPS Facility
ALBANY NY DISTRIBUTION CENTER

Sun, Sep 6
7:30am
In Transit, Arriving On Time

Sun, Sep 6
1:55am
In Transit, Arriving On Time

Sun, Sep 6
1:55am
Estimated delivery date updated to Wed, Sep 9

Sun, Sep 6
1:53am
Departed USPS Facility
WARRENDALE PA DISTRIBUTION CENTER

Sat, Sep 5
2:08pm
Departed USPS Facility
WARRENDALE PA DISTRIBUTION CENTER

Sat, Sep 5
11:28am
Arrived at USPS Facility
WARRENDALE PA DISTRIBUTION CENTER

Sat, Sep 5
2:55am
In Transit to Next Facility

Fri, Sep 4
9:51pm
Departed USPS Facility
GRAND RAPIDS MI DISTRIBUTION CENTER

Fri, Sep 4
5:05pm
Arrived at USPS Facility
GRAND RAPIDS MI DISTRIBUTION CENTER

Fri, Sep 4
4:46pm
In Transit, Arriving On Time

Fri, Sep 4
4:38pm
Departed USPS Facility
GRAND RAPIDS, MI 49501

Fri, Sep 4
4:20pm
Arrived at USPS Facility
GRAND RAPIDS, MI 49501

Fri, Sep 4
2:51pm
In Transit, Arriving On Time

Fri, Sep 4
12:19pm
Arrived at USPS Facility
TRAVERSE CITY MI DISTRIBUTION CENTER

Fri, Sep 4
8:42am
Departed Post Office
BOYNE CITY, MI 49712

Fri, Sep 4
8:42am
Estimated delivery date updated to Tue, Sep 8

Thu, Sep 3
2:18pm
USPS picked up item
BOYNE CITY, MI 49712

Thu, Sep 3
2:18pm
Estimated delivery date updated to Tue, Sep 8

Thu, Sep 3
8:26am
Shipping Label Created
BOYNE CITY, MI 49712

I have checked that the rotor voltage is 10 volts, lights off, kill switch off, key on.

on a 400 or 350? they work differently.

That was on a 400

I have checked that the rotor voltage is 10 volts, lights off, kill switch off, key on.

I installed the UFO inserts in my 34mm carbs and WOW, they transformed them to be ultra smooth and crisp. You really notice the improvement at 1/4 throttle. I got them from Niche and they came with the slide. You can get them without the slide, but you must modify the cutout to match the insert.

are there enough rod kits, bearings and seals available out there for rebuilding personal cranks that aren't trashed beyond repair?

You can get the 4 main bearings from Yambits for about $100 a set plus shipping and tarriff. OEM is double that. The rod kits are about $100 each. No problem getting that stuff.

I'm not too hip on drilling the jets because now you don't know what size you have and the number stamped on them is wrong. How about going to a local dealer, they normally have jets. Bikes with chambers may not pull well at 5000 rpm in high gear. Have you ridden other RD's that seem to run better?

I asked what's the gearing on a RD400. Read it all for a laugh. BTW those ratios for 1-6 are also wrong.


Copilot Search Branding




Gear Setup for a Yamaha RD400
The Yamaha RD400 is a 400cc air‑cooled two‑stroke with a close‑ratio 6‑speed transmission designed for sport riding. Its gear ratios are optimized for throttle response and acceleration, with a slightly lower 6th gear than many other 400s for better cruising efficiency.

Stock gear ratios (RD400C, 1976 model)



1st gear: ~2.55:1

2nd gear: ~1.85:1

3rd gear: ~1.50:1

4th gear: ~1.25:1

5th gear: ~1.05:1

6th gear: ~0.90:1

These ratios give the RD400 a quick 1st‑5th shift and a slightly overdriven 6th for cruising, which is typical for Yamaha's sporty setup.

Adjusting the gear setup

For more throttle response: Use slightly smaller rear sprocket (e.g., 13T instead of 14T) or larger front sprocket (e.g., 17T instead of 16T) to increase the 1st‑5th ratio. This can make the bike feel more aggressive in acceleration but may reduce top speed.

For smoother cruising: Use a larger rear sprocket (e.g., 14T) or smaller front sprocket (e.g., 15T) to lower the 1st‑5th ratio, improving highway feel but slightly reducing acceleration.

Close‑ratio modifications: Some riders swap in 400‑specific gears from a close‑ratio RD400 transmission to fine‑tune the 4th‑6th ratios for track or long‑distance use

.

Maintenance & inspection
According to the RD400 service manual, periodic inspection of the transmission includes checking for wear on gears, shafts, and bearings, as well as ensuring proper lubrication intervals

. The RD400 uses a shaft drive with a 14T rear sprocket and 16T front sprocket in stock configuration.

Tip: Always match sprocket changes to your riding style and road conditions. For track days, a close‑ratio setup with smaller rear/larger front sprockets is common; for commuting, a slightly wider ratio improves comfort at higher speeds.

If you want the exact OEM sprocket sizes and their effect on ratios, consult the RD400 service manual or a Yamaha parts catalog, as sprocket sizes directly affect the gear ratios and riding characteristics.

I bought this motor that the previous owner said had a leaking neutral switch causing low oil level. Two of the shift forks galled in their channels on the gears. The gears turned black and blue and seized on splined shafts making it unable to shift. I guess the lesson learned is keep an eye on oil level and if you see smoke coming out of the breather hose, shut 'er down. 

When mine broke the motor just suddenly changed pitch and the power dropped off. It had a very light HPI rotor, modified ports, big reeds, 34mm carbs, chambers. Wound out in 3rd gear at 9500 rpm. I kept going poking along, using very little throttle, for 5 miles to get home.

The 400 Daytona crank is known to have not been hardened as much as the other 400's and those are the ones that break most often. I think it might just be old age and hard use doing it. Maybe also if the crank gets out of true it stresses it more in the middle. 

That is a problem with the tapered bearing sets. It will also cause the distance between the upper and lower triple clamps to be more, making the headlight mount ears, that fit over the fork tubes, to slop up and down. Putting O rings on there can take up the slop. Keep in mind once you have the upper triple on there and tighten the acorn nut the adjuster nut isn't going anywhere.

I had that happen once also.