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RD350 Exhausts First Baffle holes significance

Started by Pravin, September 16, 2021, 06:46:33 AM

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Pravin

#15
Yes the plates and the first one has the holes .

No usa exhaust has holes ? So all 4 plates are without holes ? Wow that's good piece of information as we cut open a 361 exhaust from uk and it has 4 holes each .

So SC why is such difference and what can be the reason Yamaha gave those holes ? Am very curious to understand if the hole vs no hole baffel plate will affect ....or change any performance

Regards,
Pravin

m in sc

all i'm saying is i haven't seen that, and i have repaired a pipe or 2 over the years. Not gospel. beats me though, there are differences on uk 350s and us models for sure.  so, if you look at this pic, you can see where the internal muffler plates would sit.  I took these pics years ago.  these are us models.















Pravin

Hi SC,

baffel is same for indian RDs too ..m trying to check there are 4 big holes in the first baffel plate to handle the back pressure ... Let me find the exhaust pics the one which we cut open to check

That will give you some idea

Regards,
Pravin


Pravin

Hi ,

Please check the pics , this ia 350A/B exhaust we cut open to check ....
The first plate from the crown nut has 4 holes in each exhaust .

So now the question we are trying to solve is what will happen if the holes are not there in that plate.

Regards,
Pravin

Pravin

It's 360 Part number ...

Pravin

These are pictures shared by my friend Mr.Gautam with whom I am doing some research on the AC RD Exhausts ..he inspected thus 350A/B in uk and he's a old time member of Uk Air-cooled forum as well ...and  I did scopy for indian 3 varients of exhausts and found that in indian exhaust we have 4 on left and 6 on right compared to 4x4 across other models abroad

Trying to share scopy videos ...


Regards,
Pravin


m in sc

honestly cant say. sill if its only in the front plate probably doesnt matter.. Id run it. carefully at 1st.


scully

My RD400 has the holes in the baffle plates....Like I said you'd never have known they were there until you burned out the pipes of carbon and oil.

Pravin

Quote from: scully on September 21, 2021, 10:38:05 AM
My RD400 has the holes in the baffle plates....Like I said you'd never have known they were there until you burned out the pipes of carbon and oil.

Agree unless you have a scope cam or burnt exhausts ..This was started when I was thinking of putting USA exhausts and dropped the plan due to costing part.

Then I wanted to try if the aftermarket ones are close to Yamaha specs ....now for that I had to study my own and few other sets externally with measurements and then I got a cheap scopy cam :) and tried to look inside and got to know about holes , baffel distancing etc ....


So all Yamaha exhausts we studied has the holes on first baffel .... But the aftermarket didn't have any holes

Regards,
Pravin

Pravin

So the question remains ....

What's the significance of 4 holes on first baffel plate in rd exhausts ?

There has to be some thought and r&d involved right ?

Cheers,
Pravin

m in sc

its still squeezing it out through the  baffle so i'm sure it really doesn't matter, especially on a bike with stock pipes. 

scully

Mine on my 400 were completely blocked with carbon and oil. I know I did at least 4k miles with them like that on the old top end and the new top end. Ran pretty good :)

85RZwade

Forgive me for asking what is undoubtedly painfully obvious to all but myself, but have you asked the manufacturer of these fine mufflers about the missing holes? Surely they have a logical engineering reason for omitting them. If they say: "the holes were hard to drill", I assume you'll have your answer.
I post waayyy too much

Pravin

Quote from: 85RZwade on September 22, 2021, 01:11:00 AM
Forgive me for asking what is undoubtedly painfully obvious to all but myself, but have you asked the manufacturer of these fine mufflers about the missing holes? Surely they have a logical engineering reason for omitting them. If they say: "the holes were hard to drill", I assume you'll have your answer.

Yes and the answer was they studied the exhausts and did not find the holes and so they did not put the holes on first baffel plate...

So to all my question is "Why Yamaha gave the holes ? What is the significance of the holes in first baffel plate ? "

I am sure Yamaha will not put something in design unless it has any significance right ? And that's the reason I am here knowing this forum and the level of extensive knowledge people have here ... .to find the answer ..

Regards,
Pravin

Striker1423

My guess is to control back pressure flow. Unlike a modern expansion chamber, these bikes distribute the exhaust gasses in a similar manner to a suppressor on a rifle. The big chambers of the exhaust allow the gasses to expand. Having holes near the front gave the best chance of expanding gasses a means of escape, which consequently distributed some of that back flow towards the cylinders. One of the reasons these have such a weird powerband when stock.