Fitting a 35mm muffler to a 32mm pipe

[moto]

I bought a V50 recently that came with a second set of mufflers that turned out to be the OEM V50 iii version built for 35mm exhaust pipes instead of the 32mm on the V50.

Any tips on mounting them? I can make new hangers, but am not finding 32x35mm reducing sleeves.
A simple sleeve would be just right, allowing the full length of the 32mm pipe to fit inside the muffler as intended.

I bought 32x35 aluminum pipe before thinking about the difference in the expansion coefficient compared to steel.

32mm is about 1 1/4 inch (1.260 vs. 1.25) and 35mm is 1 3/8 (1.375 vs. 1.378) but so far no luck with inch-sized sleeves that small.

I could buy Mistrals but the price is getting near $1000 with the tariff, I believe. The V50 iii ones I got look very nice.

[jcctx]

Muffler shop can "swell" the pipes up size needed??

[Antietam Classic Cycle]

Maybe a set like this and trim the ends so that they work with small I.D. pipes?
https://www.partzilla.com/product/aftermarket/2154-EMGO-80-47310

[DoubleGuzzi]

Maybe a set like this and trim the ends so that they work with small I.D. pipes?
https://www.partzilla.com/product/aftermarket/2154-EMGO-80-47310

That is exactly what I was thinking of (I've just been searching Aliexpress for them for you). Alternatively, go cheapskate with some kitchen 'tin foil' (actually aluminium). You'll likely require some exhaust assembly paste to provide a decent seal.
UK link: https://www.feked.com/exhaust-reducing-bush-set-of-3.html

[bronzestar1]

Another option would be to remove the head pipe, take it and the muffler to a good muffler shop, and have them "flare" the end of the header pipe to match the muffler inlet.  A little more work, but having the two ends slip fit into each other would be better than using reducers. 

[normzone]

32mm is about 1 1/4 inch (1.260 vs. 1.25) and 35mm is 1 3/8 (1.375 vs. 1.378)

Do some creative engineering with about twenty aluminum beer can walls ...

 

[PeteS]

I have made my own out of steel and later aluminum on my lathe but I think the EMGO set is your best option.

Pete

[moto]

I have made my own out of steel and later aluminum on my lathe but I think the EMGO set is your best option.

Pete

So how have the aluminum ones worked out? Were they simple pipes or did they have a split in them? No problems with differential expansion compared to the steel pipe and muffler? I've got a suitable pipe ready to go that will need a bit of sanding.

[PeteS]

So how have the aluminum ones worked out? Were they simple pipes or did they have a split in them? No problems with differential expansion compared to the steel pipe and muffler? I've got a suitable pipe ready to go that will need a bit of sanding.

They lasted over twenty years but I used them on my Norton for original Dunstall Mufflers. Probably less than 20,000 miles. I used solid bar stock and bored it out and tuned the OD to fit. The steel ones were chrome plated. This done back in the ‘70s before plating costs shot into the stratosphere.
These days I am into the K.I.S.S. principle so if you can buy it then buy it.

Pete

[bigbikerrick]

I have made my own ,using aluminum flashing material available at most hardware stores. Just cut it to the length you want,and wrap it around the pipe to fill the gap. I also use a smear of clear silicone RTV to further seal the joint,and it makes dis assembly easier too.
Rick

[Perazzimx14]

I bought a V50 recently that came with a second set of mufflers that turned out to be the OEM V50 iii version built for 35mm exhaust pipes instead of the 32mm on the V50.

Any tips on mounting them? I can make new hangers, but am not finding 32x35mm reducing sleeves.
A simple sleeve would be just right, allowing the full length of the 32mm pipe to fit inside the muffler as intended.

I bought 32x35 aluminum pipe before thinking about the difference in the expansion coefficient compared to steel.

32mm is about 1 1/4 inch (1.260 vs. 1.25) and 35mm is 1 3/8 (1.375 vs. 1.378) but so far no luck with inch-sized sleeves that small.

I could buy Mistrals but the price is getting near $1000 with the tariff, I believe. The V50 iii ones I got look very nice.

Strips of HD aluminum foil wrapped around the "male" pipe until you reach the desired diameter. I fold it slightly over the edge so it sort of rounds over making sliding the female end over it easier w/o pushing or balling up the foil.

[Antietam Classic Cycle]

Strips of HD aluminum foil wrapped around the "male" pipe until you reach the desired diameter. I fold it slightly over the edge so it sort of rounds over making sliding the female end over it easier w/o pushing or balling up the foil.

In a pinch, I've used "duct tape" (not to be confused with cloth-based duck tape) - the adhesive-backed thin aluminum tape used to seal HVAC ducting.

[Bill W]

I also have used the aluminum duct tape on some Emgo's I put on a Honda and it worked fine though it did smell for a little awhile until all the adhesive burned off.

[Huzo]

For heaven’s sake, just take the damn headers off and get them flared to suit.
Anything else is just a hotch potch heap of junk, no wonder some bikes are rough as guts.

[DoubleGuzzi]

For heaven’s sake, just take the damn headers off and get them flared to suit.
Anything else is just a hotch potch heap of junk, no wonder some bikes are rough as guts.

You have obviously missed "the devil is in the detail". I suggest that you look at the standard header pipes on a V50 - they extend far into the silencers. So you want to butcher the standard pipes? Each to their own. 

[My comments are frequently ignored on this forum, so you may do the same.  ]

[moto]

For heaven’s sake, just take the damn headers off and get them flared to suit.
Anything else is just a hotch potch heap of junk, no wonder some bikes are rough as guts.

You should read a thread before you post in it. Here is what I said my first message:

... A simple sleeve would be just right, allowing the full length of the 32mm pipe to fit inside the muffler as intended....

The pipe goes into the muffler about a foot, maintaining the velocity of the escaping gas that much further, and increasing the (quite notable) torque at lower RPM. I am being careful not to change that part of the exhaust as I switch the outer chrome shell. Your suggestion would require cutting off that foot of pipe and so butcher Guzzi's design.

Your angry use of profanity is contrary to the policies of this board and offends me and maybe others. I suggest you think before you rant.

Big shout-out here to DoubleGuzzi for his on-point comment.

[PeteS]

I believe you are overthinking the use of an aluminum sleeve. Expansion would be minimal and I am assuming you would be using a clamp to hold it on. If the sleeve is a bit tight on the ID and won’t easily slide onto the head pipe just cut a slit in it lengthwise. If the slit is too wide when placed over the headpipe just put a dab of high temp silicone in the groove.
FWIW the after market mufflers made for Guzzis come with an opening for larger after market pipes but also include a sleeve to fit on the stock pipes.

Pete

[Perazzimx14]

One could also source a split muffler bushing.

[moto]

One could also source a split muffler bushing.

This is a good suggestion, but I am finding that bushings this small and thin (1.5mm) are rare on the ground. Do you know a source?

[Antietam Classic Cycle]

This is a good suggestion, but I am finding that bushings this small and thin (1.5mm) are rare on the ground. Do you know a source?

Buy a sheet of 1/16" thick aluminum and make your own, a good set of shears will cut it. For example: https://www.mcmaster.com/8975K199-8975K379/

[DoubleGuzzi]

Before I sourced a near complete stainless Keihan exhaust for my '50, I messed about with various methods, to fit very cheap 'universal' silencers. They are supplied with the 3 bush reducers but are still too large.

• I wrapped some adhesive backed aluminium, that was lying about in the garage, around the headers at the silencer junction.It wouldn't stick enough to prevent the tape bunching up. Otherwise seemed like a good plan.
• I wrapped some thicker aluminium - cut from a food container - around the headers but just couldn't get it to sit right. (Very fiddly)
• I bought some (eventually) suitably sized exhaust gaskets from my usual cheap Ali place but these were so flimsy they split apart when trying to slip them on - even after cleaning/lubing the header pipes.
• I tried filing back the S-shaped cut on one of the reducers, to reduce its diameter - didn't quite get around to perfecting the dimensions.

Then I acquired the aforementioned stainless pipes.. so that was that. ;-)

Options & Conclusions:
Cut back bush reducers are a possibility.
Heat proof duct tape, as mentioned by Charlie.
DIY 1.5mm approx. 40mm long, aluminium sheet formed into a tube, as previously mentioned.

Aluminium is softer than steel so it will 'give' before the steel will.
Exhaust Assembly Paste is easier to work with to get a seal, clean up residue and remove when attempts fail, rather than silicone, for example.

[DoubleGuzzi]

I bought 32x35 aluminum pipe

Sorry, I forgot about that bit. D'oh! A narrow slit along its length of approx. 40mm long (Italian measurements  ) and "Bob's yer uncle". 

[moto]

This is a good time to report on my current project plan, which is still not set in concrete. Constructive comments are still welcome, and all the preceding constructive comments are really appreciated. As usual asking this group for advice has changed my own ideas for the better.

The EMGO reducers Charlie first suggested are a great design. They must be 1/16 inch thick, given the description. This is 1.59mm, only a little more than the 1.5mm required. I am making similar items out of the 1.5mm-wall aluminum tube (32x35), since I already have the tube and would have to make similar modifications on the Emgos.

I originally planned to use a simple ring cut from the tube, but this does not seem to be a good design. A solid circular ring is the strongest shape to resist compression, which is why it is used in submarine hulls. So pressure exerted on it from the muffler clamp would not be transmitted to the exhaust pipe, leaving the possibility of a leak there. Simply splitting the ring would allow it to be compressed onto the exhaust pipe. The trick is to not leave too big of a gap in the split, since air could leak in at idle, causing backfires. Rick's initial suggestion of using a high temperature silicone to seal the gap is the one I'll try. (No doubt Emgo carefully sized the gap for the intended application to inch-sized pipes.)

A second consideration about the gap is that it not be so small that it disappears when things heat up. This would make it act like a solid ring so far as the ability to transmit compression to the exhaust pipe goes. This is the same consideration that goes into ring gaps on pistons. It will take only a moment of Internet consultation to make sure the gap is big enough, but I won't bore everybody with that.

The EMGO adapter has a wavy profile where the two ends come together. This no doubt leaves the appropriate gap between them. The waves help locate the two ring ends, and maybe give at least the impression of retarding any gas leak through the gap. I'm not going to try to cut a wavy profile. Instead, I figure I'll cut a simple chevron, using two straight saw cuts, to achieve both features.

Might work. 

EDIT: Thanks to DoubleGuzzi for making two more posts while I wrote this. I'll take them into account.

[DoubleGuzzi]

Instead, I figure I'll cut a simple chevron, using two straight saw cuts, to achieve both features.

I like the V-slit idea and would help to maintain the tubular shape, though for this application I reckon a straight cut is fine.