Hello Experts ,
I have come by to a set of exhausts which are locally made as copy of RD 350 Exhausts and are quite popular as I can say ...
The main difference we found is the USA/Indian Exhausts has holes in first baffel from engine -- USA ones has 4 each - left and right and Indian exhausts had 4left and 6 right
And the copy I have seen doesn't have any holes but just 4 plain baffle plates spaced in the exhausts that too is not similar to Yamaha specs..
Now as per my understanding the holes are made to handle the back pressure and if there are no holes it may cause overheating of the engine-- STOCK ENGINE ..with Stock porting and ignition and fueling ...
Anybody can share any consequences involved in such design without any holes ?
Regards,
Pravin Dalvi
the (original) plates and holes are to allow the exhaust to flow in and out ~ between the plates and the internal baffle holes and deflectors. ie: exhaust goes in the front, gets deflected OUT the baffle holes, into a chamber between the muffler plates, then back INTO the silencer baffle to the next plated chamber in the muffler.
that being said.. you need a matching set of baffles & muffler plate spacing. or, go at the internal baffles with a drill bit.
Thanks SC ,
Just want to understand if I run the bike like this ... Without matching baffels ..say stock baffels with muffelers with out any holes ...
What are the results we expect ? Performance issues ? Damage to engine ? Yamaha must have kept some logic behind those 4 holes in first baffel right ?
Cheers ,
Pravin
would be very hard to determine without seeing it... it might be fine? but if the exhaust cant flow enough will absolutely fry a topend. I killed a motor on my 350 due to a collapsed baffle in an expansion chamber. RH cyl melted the piston.
Ever look down a rd pipe with over 10k miles on it lol... What holes ?
I feel if the gasses can pass freely then it will improve performance and engine life. If lack of holes are preventing the gasses from passing freely it is not good for the engine. It may result in overheating etc... normally such situations are rare
Quote from: m in sc on September 16, 2021, 02:37:57 PM
would be very hard to determine without seeing it... it might be fine? but if the exhaust cant flow enough will absolutely fry a topend. I killed a motor on my 350 due to a collapsed baffle in an expansion chamber. RH cyl melted the piston.
Makes sense , ideally should stay away from such designs
Regards,
Pravin
Quote from: 2t Fan on September 17, 2021, 03:40:44 AM
I feel if the gasses can pass freely then it will improve performance and engine life. If lack of holes are preventing the gasses from passing freely it is not good for the engine. It may result in overheating etc... normally such situations are rare
There's a video of a snowmobile with the exhaust can damn near on fire cause it was blocked up with mice nests I think. Was glowing cherry red at night. Guy was like, my sleds running like crap and its spitting flames. :whistle:
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Makes sense , ideally should stay away from such designs
Regards,
Pravin
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it was a straight thru baffle core. lol. just old and the vibrations broke it internally on an FPP chamber. totally my own fault as i hadn't checked it in a while. Tim (kawasakitriple freak) was actually on that ride. I think he was more upset about it than i was. :dawg:
regarding the OP:
heres the way i look at it:
measure the baffle plates in the pipes. as long as the center core internal plates on the baffles are about 1/2 way between the muffler plates, you should be ok.
Got that ....and with no holes I should be ok even ?
Regards,
Pravin
you have pictures of this baffle?
is it straight through?
Yes baffel is straight flat vertically spot welded but only no holes :(
I'll check and share pic ..
Regards,
Pravin
Quote from: scully on September 16, 2021, 03:24:13 PM
Ever look down a rd pipe with over 10k miles on it lol... What holes ?
Well that's why it's an imperative part of maintenance on these to remove and totally clean the baffles WITHOUT waiting 'til 10K miles, more like every 3K. A welding glove and handheld propane torch are your friends..........
OK my sincere apology to all !!
I think I am sensing there is mis understanding due to my lack of explaining the topic correctly .
I meant to say baffel plate and not the baffel or flute :((
So let me start over , all the rd350 250 400 exhausts have 4 bafel plates which are vertically spot welded at a distance say 120 90 90 90 from back of the exhausts and the baffel or flute slides through them via the center hole .
Now the first baffel plate from engine side has 4 holes in left and ryt exhausts .
Those holes I am talking about which are 10 or 12mm in diameter spaced evenly across the baffel plate ..
Now if those holes are not there .. what's the impact ?
Sorry again if I have caused confusion but trying to get information here whether exhausts though dimension and look wise they are same but don't habe holes in first baffel PLATE ... Should thay be okay ? I suspect not ..
Attaching the pics
Regards,
Pravin
you're talking about the plates IN the muffler body? no us model rd ive seen has the holes that ive noticed TBH.
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
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.
(https://www.2strokeworld.net/wp-content/uploads/general-tech/baffles-side.jpg)
(https://www.2strokeworld.net/wp-content/uploads/general-tech/baffles-top.jpg)
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
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
It's 360 Part number ...
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
honestly cant say. sill if its only in the front plate probably doesnt matter.. Id run it. carefully at 1st.
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.
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
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
its still squeezing it out through the baffle so i'm sure it really doesn't matter, especially on a bike with stock pipes.
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 :)
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.
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
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.
that makes sense actually, i can see that.