Yamaha RD400F Daytona original carbs, any good?

[old-too-smoker]

Yamaha RD400F Daytona original carbs, any good?
Hello Smokers, So far I have used only original carbs in my RD400 and RZ350's and they work well. Just acquired a Daytona project bike, will be getting a set of pipes, originals are MIA, not sure about the oem carbs. I assembled many new out of the crate and did not like the stock bike performance. The previous unrestricted RD400 were better IMHO. So should I use the OEM or find a set of aftermarket. End goal is an original stock bike with chambers, jetting and air filters.

[SUPERTUNE]

No, Stock carbs are for show bike in a museum.
Put a set of VM 30's carbs and bare minimum, re-machine head.
Ive done at least 15-20 Daytonas this way.

Chuck

[Alain2]

If you could find a cheap pair of 360 or 1A1 carbs that would free some money for better heads/chambers. Not sure if you are on a budget or not...but I would also prefer a CDI upgrade before spending money on new VM30s.

[SUPERTUNE]

If you could find a cheap pair of 360 or 1A1 carbs that would free some money for better heads/chambers. Not sure if you are on a budget or not...but I would also prefer a CDI upgrade before spending money on new VM30s.

Not a real bad idea...but would have to have about nothing invested in the carbs as they would need rebuild kits and all new rejetting to work well.
Still need cables, still need air filters... unless going to use the stock air box, if still stock, go to a uni. Sometimes this is not a great option as you'll still have 45 year old carbs...
Chuck

[old-too-smoker]

Hey Chuck,
This is a Florida bike, he had everything modified 10 years ago, then it sat in his garage un-assembled, not sure if you did it though but he mentioned your name, Chuck, what is this hole above the exhaust port, have not seen that before? I found a set of new looking 32mm Mikunis in my treasure chest, is that a good choice? The crank was rebuilt by Falicon in st pete, it looks new. Regards Dave

[old-too-smoker]

Here are my carbs, the 32mm and the originals, the originals gave me a headache after I looked at them. Which should I use?

[old-too-smoker]

Chuck, Here is the head, what do you do to it? This one does not look modified, the depth on the edge of the dome is about .03 inches.

[RDFL]

Hey Chuck,
This is a Florida bike, he had everything modified 10 years ago, then it sat in his garage un-assembled, not sure if you did it though but he mentioned your name, Chuck, what is this hole above the exhaust port, have not seen that before? I found a set of new looking 32mm Mikunis in my treasure chest, is that a good choice? The crank was rebuilt by Falicon in st pete, it looks new. Regards Dave

Yamaha introduced the RD400, a stroked and refined evolution of the RD350, in late 1975. The RD400 featured a redesigned clutch hub and different transmission gear ratios to complement the engine's powerband. Yamaha engineers improved the porting and added a bypass hole that ran at a 45-degree angle directly to the exhaust passage. This hole eased starting, reduced low rpm surging and quieted the exhaust note at low speed --- From here -- https://www.motorcycleclassics.com/classic-japanese-motorcycles/yamaha-rd400f-daytona-special-zmsz13jazbea

[pdxjim]

Yup. 

And on the first run of RD350LCs in 1980, they tackled the same "problems" with a little notch at the top of the exhaust port, like this:

[SUPERTUNE]

Jims pic didn't post for some reason...
I have pics somewhere on my computer.
I'll look for them to post.
C

[SUPERTUNE]

Hey Chuck,
This is a Florida bike, he had everything modified 10 years ago, then it sat in his garage un-assembled, not sure if you did it though but he mentioned your name, Chuck, what is this hole above the exhaust port, have not seen that before? I found a set of new looking 32mm Mikunis in my treasure chest, is that a good choice? The crank was rebuilt by Falicon in st pete, it looks new. Regards Dave

Dave,  it looks like they have decompression holes drilled in them...
Yeah... Falicon was here in Clearwater, they're gone now. My long time friend Jan was Tom Falicons 1st full time employee and was there for 42 years until it got bought out and dis-assembled last year for the name only.
I work with Jan a lot as he now works out of his home shop and does all my Cryogenics, piston coatings and TSP process (micro-polishing) I do to my race engine builds.
Chuck

[SUPERTUNE]

Here are my carbs, the 32mm and the originals, the originals gave me a headache after I looked at them. Which should I use?

Without a doubt the Mikuni 32's. Stock carbs are very close to junk.
Chuck

[SUPERTUNE]

Chuck, Here is the head, what do you do to it? This one does not look modified, the depth on the edge of the dome is about .03 inches.

That is the stock problem child 2V0 head. It has not been modified.
Here is a modified 2V0 head I did...Split it in half and modernized the chambers.
Chuck

[Alain2]

Without a doubt the Mikuni 32's. Stock carbs are very close to junk.
Chuck

Why are you saying the VM28 are close to junk, I don't understand. I know new and/or bigger carbs are "better", but that doesn't necessarily mean VM28 belong in the spare bin.

I use stock carbs on my bikes and they work great, am I missing something?

[SUPERTUNE]

I'm not saying all VM28's...
Well,  I think your not familiar with 2V0 carbs are you? That is the subject here.
C