Topic: ORIGINAL CB750KO EXHAUST SYSTEM REPAIRS

[1970hondacb750ko]

Hey !!! I have the original exhaust system complete, off my 1970 CB750KO. The entire systems looks pretty good but there is a little problem around where the headers meet the mufflers at the welds, some rust/rot in that area. I do not want to scrap these, would like to find someone that is very knowledgeable about these exhaust problems and has a good, solid fix for the problem. I have heard that some repairs can include filling the affected areas with BRASS and then a re-chrome of the entire system. Any ideas or offers on how to repair ? I can provide photos, if necessary.
Thanks,
Mark in  Memphis,TN

[pelicanwheel]

my experience regarding rechroming is that it will be a challenge to find a plater that will do it.  The issue is that the carbon inside contaminates thier tanks used for plating.  I searched here in Phoenix and could not find one.  When I did ask my regular plater here what it would cost for one pipe if carbon was a non issue and he estimated around $100 each.  If you look around, you can find new ones for about 200-250 each.  That may be the better way for you too.

Pelican

[1970hondacb750ko]

Hey Pelican !!! THANKS MAN !!! I have heard that account before from my own Chrome Plate Man ........................ they do not like to dip the stuff in the different tanks and contaminate the solutions, don't blame them for that !!!
Yea, I will probably have to BUY a nice new set for this bike since it is coming back up as a total resto., the original pipes look really good mounted up but I will not be running the engine with them mounted, only mount them for SHOW.
Hey, you know of any good mechanics down there in PHOENIX area ? I just bought a nice old FORD F100 truck, V8, 3 speeds, not running. The guy that sold me the truck is not mechanic inclined, he says he placed a new battery in the truck when he first got it and only getting a clicking sound, engine does not turn over.
I am planning to either ship the truck or drive it out of there, just curious if there is anyone near PEORIA,AZ area that has a good engine shop or good local mechanic that won't give me a screw job to get the truck started and driveable (?)
Any information from you or anyone else here is appreciated !!! I am planning to be down there early next week.
Thanks,
Mark in Memphis,TN
901-413-8692

[736cc]

Stuff JB Weld in the small rot holes, or mix some steel wool and JB in the big holes. SS tape for chimney repairs an ez fix. Run no diffusers because it helps prevent the repairs from blowing out.
Speaking of mufflers, to get just the right exhaust note between no baffles and stock baffles, hacksaw 1/2" off the iinside end of the HM300 diffusers. Try it, you'll like it.
If you want HM341's to breath and sound better, use a loooong 3/8" or so drill bit, remove the end caps and drill 6-9 holes. Replace the 341 end caps and mod is invisable to the eye but sounds like a 300 pipe. You can even modify the 341 caps to look like 300 diffusers

[Geeto67]

the new pipes won't be correct for an accurate resto due to that ugly paragraph thye have stamped into each one. A buddy of mine had a radiator shop dip his triumph pipes in the boil out tank to clean them and it seemed to do a good job.

[736cc]

Theres a guy in Japan selling new, no-number, unstamped HM300 pipes for $2000 a set. Apparently somebody that works at Sankei (Honda's exhaust supplier) takes the pipes off the production line and sells them out the back door BEFORE they get HM300 and epa legal paragraphs stamped on them. They also don't have the ugly brake pedal relief. As a bonus, they also have the very early "lotus root" diffusers which are AWESOMELY LOUD.

Readily available new "paragraph" HM300 pipes are beautifully chromed, and match perfectly well to a freshly painted/chromed/new gauges/spokes etc resto and give instant gratification. Sourcing a show-quality used matching set of HM300 unstamped pipes not ez, and never w/o some flaws.

Which pipes to get? Go for a set that matches the rest of the bike: nice original, fresh concours restored, or daily beater.

[Bob Wessner]

736cc,

As a bonus, they also have the very early "lotus root" diffusers

I'm not familiar with this term. What do they look like?

[Geeto67]

736cc,

As a bonus, they also have the very early "lotus root" diffusers

I'm not familiar with this term. What do they look like?

like a honeycomb but round.

[pelicanwheel]

Mark -

I don't know of a good mechanic, as I've only lived here a little while.  I know a little about engines (yikes) and my first thought about the not turning over with a new battery is that the connection is bad (coroded wires) or the solenoid is bad.

If you'r thinking of driving it to Memphis, I would have it checked out thouroughly.  Do a compression test and change fluids if you dont trust the age of whats in it.

I'll ask friend for recommendations.

Pelican

[Bob Wessner]

736cc,

As a bonus, they also have the very early "lotus root" diffusers

I'm not familiar with this term. What do they look like?

like a honeycomb but round.

Were they glass wrapped?

[nippon]

If you want to rechrome your exhausts, ask the companies when they are going to change the fluids in their tanks.
Probably, then you have a chance to get them rechromed as last part w/o contaminating their fluids.

nippon

[736cc]

Quote
As a bonus, they also have the very early "lotus root" diffusers


I'm not familiar with this term. What do they look like?


http://www.yamiya750.com/muffler%20english.html
 
 
 

[Jugghead]

WOW, 736, I have said it once and I will say it again, your bikies are the cat's meow, and make many an enthusiast drool
Hats off to you and I hope you really get some serious enjoyment out of those machines!

[jaknight]

Hey Mark; About Your Truck,

     It sounds like your starter to me or you solenoid.  I have had times when one or more of the bolts holding the starter in position came loose and the starter would not function; only clicking sounds as you described.

     Get down in there and check out the bolt tightness.  While at it, check the cable connections for tightness or corrosion........  check the connection going to the battery and the frame/motor connection for ground.........that can mess it up too.

     Good Luck to you......... it may be something simple.

     ~ ~ ~ jaknight ~ ~ ~

[jwurbel]

Quote
As a bonus, they also have the very early "lotus root" diffusers


I'm not familiar with this term. What do they look like?


http://www.yamiya750.com/muffler%20english.html
 
 
 

[jwurbel]

Are the root diffusers available for purchase separately from the entire system?  I have a comlete HM300 system for a K1 and am wondering if they would work.

Thanks

[Bob Wessner]

Quote
As a bonus, they also have the very early "lotus root" diffusers


I'm not familiar with this term. What do they look like?


http://www.yamiya750.com/muffler%20english.html
 
 
 

Hmm, have unmarked pipes (well three anyway) on my K0, but the diffusers don't look like that. They have a recessed area to take glass cloth wraps.

[736cc]

The "lotus root" diffusers came on the very low-serial number sandcasts. They have a very large outlet and are LOUD.
http://www.yamiya750.com/

[mrbreeze]

Theres a guy in Japan selling new, no-number, unstamped HM300 pipes for $2000 a set. Apparently somebody that works at Sankei (Honda's exhaust supplier) takes the pipes off the production line and sells them out the back door BEFORE they get HM300 and epa legal paragraphs stamped on them. They also don't have the ugly brake pedal relief. As a bonus, they also have the very early "lotus root" diffusers which are AWESOMELY LOUD.

Readily available new "paragraph" HM300 pipes are beautifully chromed, and match perfectly well to a freshly painted/chromed/new gauges/spokes etc resto and give instant gratification. Sourcing a show-quality used matching set of HM300 unstamped pipes not ez, and never w/o some flaws.

Which pipes to get? Go for a set that matches the rest of the bike: nice original, fresh concours restored, or daily beater.

Hey!!!!.....Hold the phone!!!!! One of them 750's is missing!!!!! I'd sure hate to misplace one of them and break up the set

[Bob Wessner]

The "lotus root" diffusers came on the very low-serial number sandcasts. They have a very large outlet and are LOUD.
http://www.yamiya750.com/

Thanks. Honda must have seen the light, or gotten some neg. feedback on the loudness. The slightly later glass wrapped diffusers are anything but loud, more mellow/throaty.

[bwaller]

I have a set of 341's that I removed at least once a summer to clean & polish and are in great shape except that the chrome is partly worn off the mufflers and has a gold tinge to it. I checked with my local plater and he asked $175 (cdn) to redo. He was going to send them out to be cleaned before plating. I shyed away but will hang on to them just in case, plus I had another set.

[BobbyR]

I had the same problem of rustout where the pipe eats the muffler. A friend of mine with a MIG welder filled it in, we ground ot flush and it looks fine for a rider. For show, you would need new pipes.

[BobbyR]

Theres a guy in Japan selling new, no-number, unstamped HM300 pipes for $2000 a set. Apparently somebody that works at Sankei (Honda's exhaust supplier) takes the pipes off the production line and sells them out the back door BEFORE they get HM300 and epa legal paragraphs stamped on them. They also don't have the ugly brake pedal relief. As a bonus, they also have the very early "lotus root" diffusers which are AWESOMELY LOUD.

In Asia there is very little back door selling by employees. The companies themselves engage in "Graymarket" and everyone looks the other way. It is a cultural thing.