Rear Sprocket info needed

[Joe6v6]

I bought new sprockets & chain for a 77 rd400. The RD has a spoked rear wheel with drum brake. The rear sprocket I purchased has a 110mm bolt pattern, the existing sprocket & wheel has a 92mm bolt pattern. What sprocket fits this wheel? Is this an RD400 rear wheel? I purchased rd400 rear brake shoes & they were correct. I cant find any info as to an RD with this bolt pattern. Any info is appreciated.   .   

[SoCal250]

Rear spoked wheel with drum is not stock for a RD400.
Sounds like your rear wheel is from a RD350. Here's a sprocket diagram from JT


Not sure what shoes you got for a RD400 as they all came with rear disc so only used pads, not shoes.

[Brad-Man]

I thought you could get spoked 250's and 400's in Europe...

[rodneya]

I thought you could get spoked 250's and 400's in Europe...

You are correct, but they are disk hubs.
Never heard of a 400 with rear drum brake.

[IR8D8R]

There's another possibility. Spoked wheels were standard on an RD400C but everyone picked the cast wheel option because cast wheels were the cool new thing. The RD400 was the first motorcycle from a major manufacturer with cast alloy wheels on the C model. The RD 400D, cast wheels and rear discs were standard.

In the U.S. if you purchased an RD 400C in early '77 it could be titled as a 77 even if considered a "1976" production by us today. Not all manufacturers introduced a new model every year like the U.S. They changed type designations periodically, and the U.S. tried to fit that into our system. I've seen this before on imported European cars. If it is original, it is a RD400C bought with the standard spoked/drum, imported and titled as a 77.

Another question is why they went back to rear drums on the RD350LC for 2 years. Are they the same shoes as an RD250/350 aircooled?

IR8D8R

[Joe6v6]

Yea , after spending several hours last night I came to the determination that the rear wheel is from an RD350. It has a 40 tooth sprocket so it makes sense. I had previously read that, as IR8D8R mentioned, Some 77 400's did come with spoked wheels, but I dont think thats the case here. I wanted to stick with the 400 stock 17-38 sprocket set so it took a minute but I did find a 38t rear that will fit. It is a JTR & matches the dimensions posted by SoCal250.  .  The brake shoes I bought were from MikesXS , discerption says 350 & 400.  .
 

[dgorms]

6v6, DeLuxe Reverb?

[SoCal250]

All RD400s were disc brake rear, whether cast wheels or spoked. The 400 did come with spoked wheels in some markets, however the drum rear was never a factory option in any market on the 400. (I have never seen a stock RD400 with a drum in back regardless of country of origin.)

The brake shoe part description at Mike's XS is an error because it lists the shoes as fitting RD400C, RD400D and RD400E. It will not fit any of those models on a factory original bike.

@Joe6v6 if you're unsure of the year of your bike, if your frame and engine numbers begin with 1A1-30xxxx or 1A1-31xxxx it's '77 RD400D. (If 1A1-0xxxxx it's a '76 RD400C)

[1976RD400C]

Both my 2 1976 RD400s have a serial number 1A1-00****   

[Yamanatic]

Both my 2 1976 RD400s have a serial number 1A1-00**** 

From the Cyclerestorer web page:
1976 RD400C    Chappy Red, Geneva Green    1A1-000101--017310

Cyclerestorer Yamaha Serial Numbers

Warren

[pdxjim]

6v6, DeLuxe Reverb?

That's what I thought, too.

... and yeah, what Russ said. 400's all had a disc in back, never drum, regardless of market. And all US market 400s had cast wheels, no spokes.

[m in sc]

also remember.. the large axle nut is on the opposite side from 350 to 400. so it -may- have a 350 swing arm in it as well.

[SoCal250]

Both my 2 1976 RD400s have a serial number 1A1-00****   

Sorry, you're correct. First digit after the dash is a 0 on '76 model 400s. It's a 1 on first year 250s & 350s.
I'll correct my previous post

[IR8D8R]

Lol. "The brakes were single disc front and rear. These were optional on the RD400C as it came standard with spoked wheels and a drum rear brake. Picking the cast wheel option gave a disc rear brake as well." 
"The RD400C was the first motorcycle by a major manufacturer to be fitted with cast wheels." -Wikipedia main article on the RD400.

OK I admit. You can't believe everything you read on Wikipedia, but it is peer reviewed and cites references. The reference is Bike Magazine issue 71, 1979, (which is also a British publication). I don't have a copy. Doing a parts search also does give you rear drum brake parts for an RD400. That's why I was curious. Why would they? I'm not gonna die on that hill because I'm no expert, I don't care that much, and you guys know more than I do on the subject. If there's a better way to confirm it I wouldn't argue.

I personally prefer spokes to cast wheels on motorcycles, but I would not consider giving up a rear disc just to get spokes. I probably wouldn't put cast wheels on my RD350 to get a disc brake. Some people would for the weight savings. Just etceterini. Not trying to be difficult. 
FWIW, I assumed that it was a 350 rear wheel also. I still think it is. A quick search indicated that it was possibly OEM. I thought that was interesting but I knew what y'all would say...
It also says that the RD400 has self-canceling turn signals. I don't recall my 77 having that feature. Maybe it was broken or my memory is bad after 40 years? My 2020 Yamaha doesn't even have that feature. Would sure be nice...

IR8D8R

[Joe6v6]

@Joe6v6 if you're unsure of the year of your bike, if your frame and engine numbers begin with 1A1-30xxxx or 1A1-31xxxx it's '77 RD400D.

1A1-30277 , so yes 77 400D . This bike wasnt quite a basket case when I got it but very close so several areas had mismatched parts. I should have looked into the wheel situation a little better before procuring parts.  .

also remember.. the large axle nut is on the opposite side from 350 to 400. so it -may- have a 350 swing arm in it as well.

The swing arm, where ever it came from was lengthened 3" so I didnt want that. I found a nice one on Ebay.  . 

6v6, DeLuxe Reverb?

Ive been building Tube Amps for 20 years or so, just a hobby these days.  . Blaze Amps