Topic: Finally found exhausts, but HMCB750 vs. HM341??

[Teddyhoeg1982]

Finally found a set of 4-4 all stamped HM341, assume they are original.

The seller then also gave me two additional pipes, only stamped HMCB750. Anyone know what they are? Condition is a little rough on those two, but they are usable.

[HondaMan]

Those are some aftermarket copies of the HM341 pipes. I have some, too. The left upper pipe may need to have a thick washer installed between it and the lower one when bolting to the passenger footpeg's  mount, in order to make them align at the little rubber coupling between the pipes at the back. Mine does. Those came out soon after Honda quit offering theirs because the mold for the #2 pipe broke and the vendor would not honor Honda's orders anymore. Someone else copied as best they could from an actual pipe, so it was/is "off" a little, but works out OK.

[PeWe]

How do the baffles look like?
I have friends with pipes marked like that.  One of them claim that German versions of CB750 had those. Maybe K0.

Those pipes have the big baffles almost like the HM300, Yamiya no numbers but smaller.

Hole inside look to flow better than the restrictive HM341 that only have an endplug as baffle.

[grcamna2]

subscribed

[PeWe]

France and Germany  got those HMCB750 pipes on K0-K1.
http://cb750sandcastonly.com/smf_forum/index.php?topic=1199.0

[ekpent]

Reading that sandcast post there were definitely two different conversations going on, pipes and carb needles. Classic thread hijack 

[PeWe]

Maybe the different pipes needed different needles?
So one guy added that in the pipe forum thread.
I got that impression.

[ekpent]

Your right Per. I was just trying to learn more on the pipes as the title stated and kept reading about needles. Interesting that they found their way over here.

[PeWe]

Yes, needles and pipes. Honda CB750 carbs differ rather much.
My brown K2 parts bike had K6 carbs, 086A.

Replaced them with a cleaner set of 064A I bought cheap in parts.
These are much richer.
086A ran fine with needles   at 4:5 + 115 mains. Yamiya no numbers 4-4.

064A, needles now 3:5 (middle), 4:5 way too rich.
I'll try smaller mains too.

So,  different pipes and different carbs. Maybe needles making most difference.

[Teddyhoeg1982]

Those are some aftermarket copies of the HM341 pipes. I have some, too. The left upper pipe may need to have a thick washer installed between it and the lower one when bolting to the passenger footpeg's  mount, in order to make them align at the little rubber coupling between the pipes at the back. Mine does. Those came out soon after Honda quit offering theirs because the mold for the #2 pipe broke and the vendor would not honor Honda's orders anymore. Someone else copied as best they could from an actual pipe, so it was/is "off" a little, but works out OK.

Interesting alternative explanation. As can be seen below, others state that these were OEM on European K0+K1, so I am not sure what is correct.