Topic: Honda CB750 HM341 exhaust

[kyle750]

I saw this original Honda CB750 exhaust  for sale on YJ.  All 4 pipes have the correct Honda stamping but what I find confusing is the pipes have the earlier K0/K1 baffles    I thought the 341 pipes were later K2 - K6 and came with a different baffle design 

[kyle750]

Original Honda baffles

Photo 1 Early HM300 baffle/diffuser
Photo 2 Later HM341 baffle/diffuser

[BenelliSEI]

You are correct on all counts. Those baffles are aftermarket or modified originals. Decent set of 341’s…..

[kyle750]

You are correct on all counts. Those baffles are aftermarket or modified originals. Decent set of 341’s…..

I agree that the baffles must be aftermarket. The exhaust was listed with a buy now price of 100,000 Yen or about $675 so I went ahead and bought the set. Very conflicted as my exhaust is passable but showing it's age.   Exhaust from Japan  is certainly not perfect but looks to be in much better condition than my pipes.   Shipping from Japan to Thailand is very reasonable via DHL.    I have a set of 4 Original Honda 341 baffles that I purchased from Yamiya for my existing exhaust and will swap the baffles into the replacement exhaust once the set arrives here. My CB750 will never be a show bike with everything NOS and shiny new so parts with a little honest age and wear are OK by me. Not easy to find older original parts in decent shape and at a decent price.

https://buyee.jp/item/jdirectitems/auction/e1221641128

There are a handful of CB750 owners here in Thailand with exhaust in very poor condition so maybe sell my old pipes on to someone who needs it here in Thailand or maybe save the old set for the next CB750 project?

More photos from the seller

[kyle750]

I purchased the set of 4 CB750 HM341 exhaust pipes and they just arrived in Thailand from Japan.  Shipping cost from my proxy buying service was $125 and arrived in only 4 days (IMO a very reasonable price for shipping).  Box is Big and will be delivered to my house later today or tomorrow morning.  Very excited 

[Stev-o]

Nice find and agree, $125 to ship is a reasonable cost for those.  Do they also pack 'em up at that price?

[kyle750]

Nice find and agree, $125 to ship is a reasonable cost for those.  Do they also pack 'em up at that price?

Seller packs and ships to the proxy buying service warehouse where it sits in storage until further international shipping is initiated. From my experience sellers in Japan usually pack very well.  The proxy service will consolidate packages at a small additional charge of around $10 USD. There are 3 orders for Honda parts consolidated into the exhaust box but I am sure there is a lot of extra space in the box.    Proxy service will normally ship in the same packaging as it was delivered.  The proxy service also offers a "special packaging service" for an additional cost where they will add extra padding and more careful packaging.  I never order "special packaging" as I feel it is unneccesary.  Hopefully the seller packed the pipes well - we'll see soon!

[MauiK3]

That IS a good deal all around.

[kyle750]

That IS a good deal all around.

It's a good deal . . .  until the Tax authorities get a hold of the shipment.  Add 30% import duties on all car and motorcycle parts (new or used) in addition to 30% on all shipping charges.  And then add  another 7% on top of that for Value Added Tax (VAT).

I buy a lot of watches in Japan for many years now.  5% import duties on watches + 7% VAT.  IMO a good deal on watches.  Motorcycle parts at 30% is too much but what can you do??   

[kyle750]

Delivered - unboxing now   Seller packing was adequate with a very strong and sturdy double-wall cardboard box but internal protection was not heavy-duty and fail-safe like packaging from Yamiya.  Yamiya has specialized protection for their  exhaust during shipping with custom foam fill and this box was just stuffed with flimsy air pillows. Fortunately all the pipes arrived safely with no damage. I will be inspecting the pipes and will try to post photos later.

[kyle750]

Right out of the box all 4 pipes appear to be in very good condition but not perfect.  Pipes look much better in person than in the seller's photos.  Chrome is Beautiful - Very Happy!

Late Edit:  Seller must have cleaned the pipes very well.  No dirt or grime and squeaky clean.   Looking over the pipes I can only see  some minor scratches, small dings, small spots of rust, and minor surface discoloration (mostly visible to the frame side of the pipes and not the outside).  Maybe just a little work with chrome polish and then swap out the baffles with the original HM341 baffles I purchased earlier from Yamiya.   Seller also sent the heat shields, finned exhaust flange clamps/collars, and rear passenger footpegs with mounting bolts. 

[BenelliSEI]

Seems like that deal worked out. Those look great!

[kyle750]

Seems like that deal worked out. Those look great!

Thanks Mate.  Looking over the heat shields now and they look different than the shields on my bike.  Not a bright shiny chrome like the chrome on the pipes but a matte dull silver and looks almost like a satin blasted finish.  Not sure if they have been painted over but they look original.  It's dark now but I'll try to take some photos in the morning.

[BenelliSEI]

Kyle….. Those dull finish heat shields belong on very early bikes.

[kyle750]

Kyle….. Those dull finish heat shields belong on very early bikes.

Thanks Brother.  I wonder why the seller had dull finish heat shields with later HM341 pipes.  Strangely the heat shields were wrapped in a thick bundle of newspaper and it looks like the seller cut the newspaper and removed 1 shield to photograph for the YJ auction and then stuffed the shield back in the newspaper.  The shield bolts were taped to the underside but 1 set had fallen out and I found the bolts and washers loose in the bottom of the box just bouncing around.

I'll take a photo in the morning     

[Stev-o]

Kyle….. Those dull finish heat shields belong on very early bikes.

 I wonder why the seller had dull finish heat shields with later HM341 pipes.   

We've asked ourselves that question a thousand times when buying a vintage bike [or car]:

"Why did the previous owner do that?!!"

[kyle750]

1 of 2 dull finish heat shields, shield bolts and washers, and finned exhaust flange clamps/collars (no bolts provided)

Can original Honda chrome plated exhaust flange/collar bolts still be purchased?

[kyle750]

Exhaust collar bolts are not so simple or easy to find Lots of 8 x 32 for sale  but my understanding is the correct bolts are a special chrome plated alloy metal??  First photo is one of the newly arrived collars with an old collar bolt removed from my bike.  2nd photo looks like the correct Honda replacement with 8 symbol stamped to the head.  $3.99 each or $16.00 plus $6 shipping.  I've bought original Honda bolts from this seller before and he sells real deal Original Honda

[Don R]

  I have a set of 341 pipes and they don't sound as good as 300's. With the smallest tube in the baffle cut off they sound a lot better, probably the reason for the baffle swap.

[kyle750]

  I have a set of 341 pipes and they don't sound as good as 300's. With the smallest tube in the baffle cut off they sound a lot better, probably the reason for the baffle swap.

Thanks Don.  An excellent suggestion.  Install the pipes with the current baffles and give them a listen.  I truly love the Rumble of the CB750 pipes. The more Roar the merrier!  Let's Go!

[kyle750]

I highly suspect that the Autosol I purchased is FAKE from China.  I'm scrambling now to try to find authentic Autosol so I can lightly polish the pipes

[HondaMan]

Exhaust collar bolts are not so simple or easy to find Lots of 8 x 32 for sale  but my understanding is the correct bolts are a special chrome plated alloy metal??  First photo is one of the newly arrived collars with an old collar bolt removed from my bike.  2nd photo looks like the correct Honda replacement with 8 symbol stamped to the head.  $3.99 each or $16.00 plus $6 shipping.  I've bought original Honda bolts from this seller before and he sells real deal Original Honda

They were chromed: they also begin losing that plating around 15 years ago, though. I find them with corrosion under the plating, making the chrome lift off. That means the bolts weren't fully acid-cleaned, probably were just done in dump batches  before the chroming. The bolts are usually very annealed by now, sometimes the heads will snap off from being very soft if the chrome in the grooves of the clamp are real rusted.

Today I use stainless steel bolts in their place, if needed. I polish them up a little first. It seems to stay? It's only the heads, so it's not a lot of work.

[kyle750]

Removing the old exhaust collars and pipes.  I sprayed the threaded ends with WD-40 yesterday and lightly tapped the bolt heads with a hammer and left overnight.   I was anticipating a struggle with the old bolts but this morning all 4 bolts came out easily and old rusted collars slid down the header pipes.  I also have new OEM Honda copper exhaust crush gaskets  so I will remove and replace the old gaskets but leave the old flanges in place.   If it Ain't broke

[HondaMan]

Removing the old exhaust collars and pipes today  I sprayed the threaded ends with WD-40 yesterday and lightly tapped the bolt heads with a hammer and left overnight.   I was anticipating a struggle with the old bolts but this morning all 4 bolts came out easily and old rusted collars slid down the header pipes.  I also have new OEM Honda copper exhaust crush gaskets  so I will remove and replace the old gaskets but leave the old flanges in place.   If it Ain't broke

You might have figured this out already, but...those crush gasket go behind the exhaust spigots. So, then you have to remove their crosspoint screws.
They don't often leak, though, so they might be fine?
This was the great advantage of the HM300/341 pipes: you could remove/reinstall them without any gaskets needed, almost unheard of back then.

[kyle750]

You might have figured this out already, but...those crush gasket go behind the exhaust spigots. So, then you have to remove their crosspoint screws.
They don't often leak, though, so they might be fine?
This was the great advantage of the HM300/341 pipes: you could remove/reinstall them without any gaskets needed, almost unheard of back then.

Thanks HondaMan. I believe the old gaskets might be fine so I'll leave them. If it Aint broke!