Vintage Dirt Bike Q & A

Anything and everything about Vintage Dirt Bikes! After you Register, email nathan@alp-sys.com and let me know so I can activate you.
It is currently Thu Aug 16, 2018 9:55 pm

All times are UTC - 7 hours [ DST ]




Post new topic Reply to topic  [ 9 posts ] 
Author Message
 Post subject: Exhaust pipe collar
PostPosted: Mon May 28, 2018 1:18 pm 
Offline

Joined: Fri Jan 19, 2018 3:40 pm
Posts: 8
Hi,

I'm re-installing the stock exhaust pipe for a 1975 MT250. I bought a new OEM gasket (GASKET, EX. PIPE 18352-358-000) and NOS collar (COLLAR, EX. PIPE 18325-358-303).
https://www.nospartsnow.com/nos-honda-m ... 5-358-303/

The NOS collar is tapered and I want to be positive which side faces into the pipe and which side faces the gasket (& engine). I can't find any information on this anywhere. Has anybody installed this same piece?

A or B?


Attachments:
exhaust collar A1.jpg
exhaust collar A1.jpg [ 154.16 KiB | Viewed 444 times ]
exhaust collar A2.jpg
exhaust collar A2.jpg [ 149.63 KiB | Viewed 444 times ]
exhaust collar B1.jpg
exhaust collar B1.jpg [ 141.35 KiB | Viewed 444 times ]
exhaust collar B2.jpg
exhaust collar B2.jpg [ 155.63 KiB | Viewed 444 times ]
Top
 Profile  
 
 Post subject: Re: Exhaust pipe collar
PostPosted: Mon May 28, 2018 6:18 pm 
Offline

Joined: Sun Nov 30, 2008 12:10 pm
Posts: 1004
Location: Connecticut, USA
The exhaust ring fits into the pipe inlet flange as shown in your picture 'A1', with the chamfer facing out. The end of the exhaust manifold has a matching chamfer, and the white ring gasket will end up sandwiched between these two chamfers. The MR175 has a very similar setup, except the ring & gasket are combined into a single chamfered ring.

Here's how I've installed these setups, with no leakage yet - it's important to have the pipe ready to go on, with all brackets on, nuts handy, etc:

1) Clean everything well, especially the pipe flange and manifold 'piston ring' groove
2) Apply hi-temp sealant to the inner pipe flange and metal ring, and insert it till it bottoms (chamfer out)
3) If the manifold is off, use the same sealant & Honda gasket to install it on the engine
4) Install the manifold 'piston ring' (not shown in your photos) into the manifold groove after coating it and the groove
5) Coat the manifold spigot and white ring gasket, then install the gasket on the manifold end
6) Coat the inside of the pipe flange, then carefully slide it straight onto the manifold
7) While keeping the pipe in place, put on the rear bracket nut loosely to hold up the far pipe end
8 ) Push the pipe onto the manifold firmly while installing both springs
9) While still keeping most of the pipe weight off the manifold end, install & tighten all mounts

You might want to try a dry run first, as the manifold / piston ring / gasket can be a little tricky to force into the pipe flange,
and it can be hard to tell if the pipe is bottomed fully onto the manifold. These pipes are heavy and have significant backpressure,
so they chafe and eventually start leaking unless sealant is used everywhere. With sealant, they neither leak nor chafe.

Ray

_________________
'74 CR125M (175cc), '75 MR175, '82 RM250Z, '08 YZ250F, '14 Zero FX electric, '14 Zero MX electric


Top
 Profile  
 
 Post subject: Re: Exhaust pipe collar
PostPosted: Mon May 28, 2018 8:49 pm 
Offline

Joined: Fri Jan 19, 2018 3:40 pm
Posts: 8
Ray,

Thank you very much. This is extremely helpful.

I have not taken off the current pipe, which the previous owner installed. The manifold is already there, connecting the current pipe. When I remove that pipe, will I need to replace the 'piston ring' also? I only got new parts from the muffler side, # 5 & 7.

Do I also need to replace, on the manifold side, #13? Is that the piston ring you refer to? I don't want to make the switch until I have all the parts I need.

When you say coat the ring and manifold groove, you are still referring to the high temp sealant?


Attachments:
muffler diagram.png
muffler diagram.png [ 85.12 KiB | Viewed 438 times ]
cylinder diagram.png
cylinder diagram.png [ 112.26 KiB | Viewed 438 times ]
Top
 Profile  
 
 Post subject: Re: Exhaust pipe collar
PostPosted: Tue May 29, 2018 6:06 am 
Offline

Joined: Sun Nov 30, 2008 12:10 pm
Posts: 1004
Location: Connecticut, USA
I don't think you'll need to replace the #13 piston ring unless it's missing. Also, if the manifold seems clear inside I wouldn't remove it, so you shouldn't need the #14 manifold gasket either. FWIW, I've replaced the piston ring with a hi-temp O-ring on my MR175 manifold; it degrades with time, but in conjunction with the sealant continues to seal fine.

Yes, all the 'coating' I mentioned was with hi-temp sealant (usually silicone based). I used to assemble the pipes dry, and they either leaked immediately or within a few months of use. It also makes for easier disassembly later, as the sealant is much softer than baked-on carbon.

Ray

_________________
'74 CR125M (175cc), '75 MR175, '82 RM250Z, '08 YZ250F, '14 Zero FX electric, '14 Zero MX electric


Top
 Profile  
 
 Post subject: Re: Exhaust pipe collar
PostPosted: Tue May 29, 2018 9:12 am 
Offline

Joined: Fri Jan 19, 2018 3:40 pm
Posts: 8
Thank you, Ray.


Top
 Profile  
 
 Post subject: Re: Exhaust pipe collar
PostPosted: Fri Aug 10, 2018 3:16 pm 
Offline

Joined: Sat May 24, 2014 7:19 am
Posts: 20
Michaels wrote:
Hi,

I'm re-installing the stock exhaust pipe for a 1975 MT250. I bought a new OEM gasket (GASKET, EX. PIPE 18352-358-000) and NOS collar (COLLAR, EX. PIPE 18325-358-303).
https://www.nospartsnow.com/nos-honda-m ... 5-358-303/

The NOS collar is tapered and I want to be positive which side faces into the pipe and which side faces the gasket (& engine). I can't find any information on this anywhere. Has anybody installed this same piece?

A or B?


Part number 5 is only listed for 74's, and used up to frame serial number 1002746 only see pic. The pipe in your picture appears to have an existing beveled section made into it, do not use 18325-358-303. Just my opinion.
Attachment:
parts.JPG
parts.JPG [ 13.44 KiB | Viewed 69 times ]


Attachments:
gasket.JPG
gasket.JPG [ 26.13 KiB | Viewed 69 times ]
Top
 Profile  
 
 Post subject: Re: Exhaust pipe collar
PostPosted: Fri Aug 10, 2018 6:20 pm 
Offline

Joined: Sun Nov 30, 2008 12:10 pm
Posts: 1004
Location: Connecticut, USA
Quote:
The pipe in your picture appears to have an existing beveled section made into it, do not use 18325-358-303. Just my opinion.

IMO the metal ring's 'OD bevel' shown in pic B1 (as opposed to the inner ID chamfer/bevel) is designed to fit into the pipe flange's ID bevel you mentioned, for a better seal there and more lengthwise 'crush' on the white gasket against the manifold bevel. It should work without the metal ring - especially with sealant - but if I had the ring I'd definitely use it, fwiw.

_________________
'74 CR125M (175cc), '75 MR175, '82 RM250Z, '08 YZ250F, '14 Zero FX electric, '14 Zero MX electric


Top
 Profile  
 
 Post subject: Re: Exhaust pipe collar
PostPosted: Fri Aug 10, 2018 7:15 pm 
Offline

Joined: Sat May 24, 2014 7:19 am
Posts: 20
Hello Ray, I'm using the original graphite/steel mesh gaskets which are pretty tuff, that being said I have to fight these pipes on both of my bikes just to get the studs into the tabs on the muffler. Neither of them have ever leaked a drop yet, do not ride them much either. Ordered some of those new soft white ones to try. Will report back if they make things easier to assemble.

Mark


Top
 Profile  
 
 Post subject: Re: Exhaust pipe collar
PostPosted: Fri Aug 10, 2018 7:35 pm 
Offline

Joined: Sun Nov 30, 2008 12:10 pm
Posts: 1004
Location: Connecticut, USA
Quote:
I have to fight these pipes on both of my bikes just to get the studs into the tabs on the muffler.

One thing I've done was to leave the shock bolt a little loose so the rear mount could move a little. It might also help to heat the rubber on both mounts with a heat gun on low, just to get that last bit of flex to help get the studs in.

I'm using a new mesh ring gasket on my MR now. I worked it into the pipe flange with the manifold quite a bit to get it pre-shaped to fit the pipe & manifold bevels before mounting, and it still needed a lot of pressure to align with the frame mounts. Thankfully they're pretty durable.

_________________
'74 CR125M (175cc), '75 MR175, '82 RM250Z, '08 YZ250F, '14 Zero FX electric, '14 Zero MX electric


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 9 posts ] 

All times are UTC - 7 hours [ DST ]


Who is online

Users browsing this forum: No registered users and 3 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
Powered by phpBB® Forum Software © phpBB Group