Author Topic: Concerns about rusted frame  (Read 11268 times)

0 Members and 1 Guest are viewing this topic.

Offline Kickstart

  • Expert
  • ****
  • Posts: 796
Concerns about rusted frame
« on: December 10, 2013, 04:09:37 PM »
Attached are pictures from my 72 CB750. 

I noticed the other day (while taking a brake from my other rebuild) there seems to be some significant rust on the frame around where the swingarm mounts.

The left side seems to have a little hole in the steel, and the right side has paint flaking off the welds.

Is this safe/normal, and if not is this repairable?

I was thinking about building this bike into an AHRMA race bike - not so sure now after seeing this.

Thoughts?

Thanks,
Chris
- Chris
75' CB750F Orange flake (rider)
75' CB750F Blue (Project)
75' CB750F Painted black (Project)
No Reserve Racing #171 AHRMA

Offline LesterPiglet

  • Old Timer
  • ******
  • Posts: 4,046
  • 1977 CB550F2
Re: Concerns about rusted frame
« Reply #1 on: December 10, 2013, 04:17:06 PM »
That doesn't look significant to me. Tap the rusty parts with a fine chisel or somethingto remove the scale and see how bad it is.
Oh! Is that a hole? I would weld that up.
It looks ok.
« Last Edit: December 10, 2013, 04:18:37 PM by LesterPiglet »
'Then' and 'than' are completely different words and have completely different meanings. Same with 'of' and 'have'. Set and sit. There, their and they're. Draw and drawer. Could care less/couldn't care less. Bought/brought FFS.


Les Ross.            Certified by a Professional

Offline MoMo

  • Really Old Timer ...
  • *******
  • Posts: 8,275
  • Ride like you're invisible
Re: Concerns about rusted frame
« Reply #2 on: December 10, 2013, 05:54:46 PM »
Must be the area where you live ::), my 750 red rider was way worse than that and came from your area.  I would bet the inside of the frame is filled with rusted metal flakes.  As mentioned to a lot of tap testing, any hollow sound should be an alarm.  BTW,  I had to replace the frame on mine...Larry

Offline HondaMan

  • Someone took this pic of me before I became a
  • Really Old Timer ...
  • *******
  • Posts: 13,804
  • ...not my choice, I was nicknamed...
    • Getting 'em Back on the Road
Re: Concerns about rusted frame
« Reply #3 on: December 10, 2013, 09:43:12 PM »
Those holes are the upper "breather" holes for the lower frame. The other "end" of those holes should be down by the bottom front engine bolsters, on the bottom of the frame. They often get clogged up with rust flakes.

Like Momo said, "tap testing" is a good way to check for thin spots, or put some rubber in the jaws of slip-joint pliers and firmly (not HARD) squeeze the frame along the runs to see if it crushes. The worst spots on the 750 frame are at the bottom of those engine bolsters, if they were painted or crudded shut. The frames are easy to fix, I've done several myself.

On the 1970-71 K1, many of the lower holes were forgotten in production (even some K2 bikes were this way, before it was over). There was a "quiet" service memo sent out to have dealers watch to see if the holes were missing at the lower bolsters, and the instructions were to drill a 7/32" (3mm) hole behind each one, if not present. More than one of the ones I did had water come out during this 'mod'. I usually took an oil squirt can and squirted a bunch of oil into the holes you show, until it oozed out the [new] bottom ones, hoping to extend the frame life. Now, when I have frames out of bikes, I spray CRC into the holes until it RUNS out of the lower ones, then turn the frame over and do it the other way. That will stop any rust, almost forever, right where it is.
See SOHC4shop@gmail.com for info about the gadgets I make for these bikes.

The demons are repulsed when a man does good. Use that.
Blood is thicker than water, but motor oil is thicker yet...so, don't mess with my SOHC4, or I might have to hurt you.
Hondaman's creed: "Bikers are family. Treat them accordingly."

Link to Hondaman Ignition: http://forums.sohc4.net/index.php?topic=67543.0

Link to My CB750 Book: https://www.lulu.com/search?adult_audience_rating=00&page=1&pageSize=10&q=my+cb750+book

Link to website: www.SOHC4shop.com

Offline MoMo

  • Really Old Timer ...
  • *******
  • Posts: 8,275
  • Ride like you're invisible
Re: Concerns about rusted frame
« Reply #4 on: December 11, 2013, 03:47:01 AM »
The result of long term neglect






Offline Toxic

  • Expert
  • ****
  • Posts: 1,200
Re: Concerns about rusted frame
« Reply #5 on: December 11, 2013, 04:59:48 AM »
I think all of the methods mentioned above are proven and valid ways to determine and repair or minimize rust would you trust it on a race bike?  I wouldn't.  The rust may not be localized to the areas you see.  There could be other areas that are weakened.  For what it would cost to pick up a frame in better shape, it would be worth it for peace of mind.

If it's to be a race bike does it matter if the frame doesn't match?

If it were a daily driver, I wouldn't have a problem with a proper repair and inspection of the rest of the frame.

Gary

Offline calj737

  • Really Old Timer ...
  • *******
  • Posts: 21,020
  • I refuse...
Re: Concerns about rusted frame
« Reply #6 on: December 11, 2013, 05:25:36 AM »
It's funny how rust is such a terrifying condition. Certainly tech/safety inspections wouldn't pass a bike with visible rust, even if it were only surface rust.

If you are hindered contemplating using the frame for racing, sandblast the entire thing to bare metal, do a full inspection to identify ANY rusted tubing or brackets, and replace it. Proper welds with quality tubing, re-weld the riveted pinch joints also, and you're good to go. These frames weren't the stiffest to begin with, but can certainly be made to very safe, very dependable, and solid platforms for any amount of HP.

Just gotta do the necessary work to be safe and sound. (I suspect you know this anyway) but it warrants stating.
'74 550 Build http://forums.sohc4.net/index.php?topic=126401.0
'73 500 Build http://forums.sohc4.net/index.php?topic=132935.0

"Of all tyrannies, a tyranny sincerely exercised for the good of it's victim may be the most oppressive. It may be better to live under robber barons than under omnipotent moral busybodies. The robber baron's cruelty may sometimes sleep, his cupidity may at some point be satiated, but those who torment us for our own good will torment us without end for they do so with the approval of their own conscience." - C.S. Lewis

Offline Don R

  • My Sandcast is a
  • Really Old Timer ...
  • *******
  • Posts: 19,846
  • Saver of unloved motorcycles.
Re: Concerns about rusted frame
« Reply #7 on: December 11, 2013, 07:49:01 AM »
I'd proceed with the race prep. If you find anything scary look for another frame. If that's out of your price range maybe a race bike isn't the best idea. They are always more $$$ than we expect.
No matter how many times you paint over a shadow, it's still there.
 CEO at the no kill motorcycle shop.
 You don't need a weatherman to know which way the wind blows.

Offline edwardmorris

  • Youngish
  • Old Timer
  • ******
  • Posts: 3,142
  • Do not cause harm, nor respond to harm with harm.
Re: Concerns about rusted frame
« Reply #8 on: December 11, 2013, 01:31:31 PM »

WHYYY did I see this? So terrified now, gotta go check my frame inch by inch, given the history of how many PO screw ups its had so far. I was planning on using Eastwood's internal frame spray on mine wherever possible to stop rusting. Seems to have worked well for people restoring cars.

Link

http://www.eastwood.com/internal-frame-coating-w-spray-nozzle-qt.html
« Last Edit: December 11, 2013, 01:33:30 PM by edwardmorris »

Offline MoMo

  • Really Old Timer ...
  • *******
  • Posts: 8,275
  • Ride like you're invisible
Re: Concerns about rusted frame
« Reply #9 on: December 11, 2013, 02:46:03 PM »
Sorry to scare you but left untended that could be the result.  Funny thing about that bike is the rest of the bike was rust-free...Larry

Offline HondaMan

  • Someone took this pic of me before I became a
  • Really Old Timer ...
  • *******
  • Posts: 13,804
  • ...not my choice, I was nicknamed...
    • Getting 'em Back on the Road
Re: Concerns about rusted frame
« Reply #10 on: December 11, 2013, 04:28:22 PM »
Sorry to scare you but left untended that could be the result.  Funny thing about that bike is the rest of the bike was rust-free...Larry

Was that one a K1? It resembles some others I saw that didn't have "the hole" drilled.
See SOHC4shop@gmail.com for info about the gadgets I make for these bikes.

The demons are repulsed when a man does good. Use that.
Blood is thicker than water, but motor oil is thicker yet...so, don't mess with my SOHC4, or I might have to hurt you.
Hondaman's creed: "Bikers are family. Treat them accordingly."

Link to Hondaman Ignition: http://forums.sohc4.net/index.php?topic=67543.0

Link to My CB750 Book: https://www.lulu.com/search?adult_audience_rating=00&page=1&pageSize=10&q=my+cb750+book

Link to website: www.SOHC4shop.com

Offline lucky

  • Really Old Timer ...
  • *******
  • Posts: 6,717
Re: Concerns about rusted frame
« Reply #11 on: December 11, 2013, 04:35:37 PM »
That doesn't look significant to me. Tap the rusty parts with a fine chisel or somethingto remove the scale and see how bad it is.
Oh! Is that a hole? I would weld that up.
It looks ok.

You cannot weld rust.
The frame is only 1/16 inch thick.

Offline edwardmorris

  • Youngish
  • Old Timer
  • ******
  • Posts: 3,142
  • Do not cause harm, nor respond to harm with harm.
Re: Concerns about rusted frame
« Reply #12 on: December 11, 2013, 06:59:43 PM »
Oh thank goodness, looks like my frame is alright. I will update my build thread and pix there and stop hijacking this one. !!PAGING HONDAMAN!! mine's a super early K2, mind showing me where I can drill a hole from the "quiet" memo? I sprayed CRC in the holes I found and it didn't run anywhere, came out the same hole when I flipped the frame. My build thread in my sig.

Offline Kickstart

  • Expert
  • ****
  • Posts: 796
Re: Concerns about rusted frame
« Reply #13 on: December 11, 2013, 07:47:04 PM »
No worries about the thread hijack edwardmorris.

I believe the holes should be drilled here (see attached - this is a picture of my F0 frame - without holes.)

I believe it's a couple of inches before the front mounts (or behind?)
- Chris
75' CB750F Orange flake (rider)
75' CB750F Blue (Project)
75' CB750F Painted black (Project)
No Reserve Racing #171 AHRMA

Offline Kickstart

  • Expert
  • ****
  • Posts: 796
Re: Concerns about rusted frame
« Reply #14 on: December 11, 2013, 07:53:01 PM »
Well... Argh!

I guess I paid too much for it.  It's a K2, so it should have the drain holes.

Anyone know a good frame repair shop near the Philadelphia area?
- Chris
75' CB750F Orange flake (rider)
75' CB750F Blue (Project)
75' CB750F Painted black (Project)
No Reserve Racing #171 AHRMA

Offline MoMo

  • Really Old Timer ...
  • *******
  • Posts: 8,275
  • Ride like you're invisible
Re: Concerns about rusted frame
« Reply #15 on: December 11, 2013, 07:53:36 PM »
Sorry to scare you but left untended that could be the result.  Funny thing about that bike is the rest of the bike was rust-free...Larry

Was that one a K1? It resembles some others I saw that didn't have "the hole" drilled.


No,  a 75.   I found a frame that had the same serial numbers except for two digits.  I changed the digits :-X

Bike with new frame


Offline edwardmorris

  • Youngish
  • Old Timer
  • ******
  • Posts: 3,142
  • Do not cause harm, nor respond to harm with harm.
Re: Concerns about rusted frame
« Reply #16 on: December 11, 2013, 08:32:19 PM »
No worries about the thread hijack edwardmorris.

I believe the holes should be drilled here (see attached - this is a picture of my F0 frame - without holes.)

I believe it's a couple of inches before the front mounts (or behind?)
Interesting. So the holes in the pix from your first post, you spray CRC there and its supposed to come out through these? Pardon the noobness, trying to make sure I stop rust in its tracks.

Offline Kickstart

  • Expert
  • ****
  • Posts: 796
Re: Concerns about rusted frame
« Reply #17 on: December 11, 2013, 08:47:47 PM »
Hmm... I'm not sure exactly what spot Mark (Hondaman) is referring to as the Upper vent holes.

Does your bike have the lower holes?
- Chris
75' CB750F Orange flake (rider)
75' CB750F Blue (Project)
75' CB750F Painted black (Project)
No Reserve Racing #171 AHRMA

Offline edwardmorris

  • Youngish
  • Old Timer
  • ******
  • Posts: 3,142
  • Do not cause harm, nor respond to harm with harm.
Re: Concerns about rusted frame
« Reply #18 on: December 11, 2013, 08:57:37 PM »
Hmm... I'm not sure exactly what spot Mark (Hondaman) is referring to as the Upper vent holes.

Does your bike have the lower holes?
Don't think so, some pix here

http://forums.sohc4.net/index.php?topic=126735.75

Offline HondaMan

  • Someone took this pic of me before I became a
  • Really Old Timer ...
  • *******
  • Posts: 13,804
  • ...not my choice, I was nicknamed...
    • Getting 'em Back on the Road
Re: Concerns about rusted frame
« Reply #19 on: December 11, 2013, 09:35:30 PM »
No worries about the thread hijack edwardmorris.

I believe the holes should be drilled here (see attached - this is a picture of my F0 frame - without holes.)

I believe it's a couple of inches before the front mounts (or behind?)


You can make them anywhere in that area, at the lowest point. Honda's old recommendation was just behind those bolsters. The general idea is: if moisture gets in there, it must have 2 holes for some flow-thru to help dry it out. The engine heat also helps.
See SOHC4shop@gmail.com for info about the gadgets I make for these bikes.

The demons are repulsed when a man does good. Use that.
Blood is thicker than water, but motor oil is thicker yet...so, don't mess with my SOHC4, or I might have to hurt you.
Hondaman's creed: "Bikers are family. Treat them accordingly."

Link to Hondaman Ignition: http://forums.sohc4.net/index.php?topic=67543.0

Link to My CB750 Book: https://www.lulu.com/search?adult_audience_rating=00&page=1&pageSize=10&q=my+cb750+book

Link to website: www.SOHC4shop.com

Offline edwardmorris

  • Youngish
  • Old Timer
  • ******
  • Posts: 3,142
  • Do not cause harm, nor respond to harm with harm.
Re: Concerns about rusted frame
« Reply #20 on: December 11, 2013, 09:41:34 PM »
You can make them anywhere in that area, at the lowest point. Honda's old recommendation was just behind those bolsters. The general idea is: if moisture gets in there, it must have 2 holes for some flow-thru to help dry it out. The engine heat also helps.

So, if my frame tubes have no holes on the top side by the steering stem, then the tubes are sealed and I don't need the new holes? Or are there for sure holes in the steering stem area that I can't quite see?

Offline HondaMan

  • Someone took this pic of me before I became a
  • Really Old Timer ...
  • *******
  • Posts: 13,804
  • ...not my choice, I was nicknamed...
    • Getting 'em Back on the Road
Re: Concerns about rusted frame
« Reply #21 on: December 11, 2013, 09:54:39 PM »
Hmm... I'm not sure exactly what spot Mark (Hondaman) is referring to as the Upper vent holes.

Does your bike have the lower holes?

There are usually holes near the web that is shown above as the rusty spot. On mine, for example (not visible to a camera, now that I just repainted it) there are holes in the frame tubes where they go up from the web plates, where the rear tubes are joined to the rear downtubes. The rear (footpeg/pipe mount) tubes meet the rear downtubes and the holes that were probably cut into those downtubes to receive the rear tubes are bigger than those tubes, so there are unfilled openings ('holes') above them, near the little holes in the sideplates (gusset plates). I admit to not looking at every frame I see here, but those I can think of where I have oiled them up with CRC had the holes to spray in at this junction.

This raises a good question for some of the really rusty frames I've seen, though: I wonder if some of these holes were not so big where the rear tubes meet the main "loop", and this caused a non-vented situation altogether, or even more: if these holes got welded shut in the process, before the gusset plates were added, and no further work was done? The early frames often were not treated with quite the respect of the later ones, particularly the beefier New Factory frames.

The frames on the Old Factory bikes, in particular, were subject to these sorts of vagaries much more than the later ones. My first K1 had obviously been dropped after it was tacked together in the jig, and the welds (somewhere) broke: the gussets were then added to the now-misaligned frame and it was welded up sidesaddle, so to speak. When they got to the part where they installed the engine, lo, the bolts did not meet the holes in the engine cases. Their solution was to oval out the lower frame mount hole and widen the ones on the right-side triangular engine mount plates. When I got the bike, I could barely pull it up out of a deep turn on one side, and on the other I could not push it down and hold it down: it turned out to have the rear wheel about 1/2" out of line with the front one. I have some of those details mentioned in the chassis section(s) of my book, to help others watch for these sorts of things: this was the mad rush to build these bikes, in their day. ;)
See SOHC4shop@gmail.com for info about the gadgets I make for these bikes.

The demons are repulsed when a man does good. Use that.
Blood is thicker than water, but motor oil is thicker yet...so, don't mess with my SOHC4, or I might have to hurt you.
Hondaman's creed: "Bikers are family. Treat them accordingly."

Link to Hondaman Ignition: http://forums.sohc4.net/index.php?topic=67543.0

Link to My CB750 Book: https://www.lulu.com/search?adult_audience_rating=00&page=1&pageSize=10&q=my+cb750+book

Link to website: www.SOHC4shop.com

Offline HondaMan

  • Someone took this pic of me before I became a
  • Really Old Timer ...
  • *******
  • Posts: 13,804
  • ...not my choice, I was nicknamed...
    • Getting 'em Back on the Road
Re: Concerns about rusted frame
« Reply #22 on: December 11, 2013, 09:57:58 PM »
You can make them anywhere in that area, at the lowest point. Honda's old recommendation was just behind those bolsters. The general idea is: if moisture gets in there, it must have 2 holes for some flow-thru to help dry it out. The engine heat also helps.

So, if my frame tubes have no holes on the top side by the steering stem, then the tubes are sealed and I don't need the new holes? Or are there for sure holes in the steering stem area that I can't quite see?

No, not at the steering stem: back by the gusset plates where the rear loop(s) meet the triangle of the rear footpeg/pipe mounts. There is a small hole on each side of the gusset area, and there should be a small opening in the downtube of the rear loop there, normally seen above the points where the rear triangle (horizontal) tube meets the frame. It will look intentional, like they made the hole in the downtube too tall as compared to the diameter of the tube from the footpeg/pipe horizontal tube (does that make sense?).
See SOHC4shop@gmail.com for info about the gadgets I make for these bikes.

The demons are repulsed when a man does good. Use that.
Blood is thicker than water, but motor oil is thicker yet...so, don't mess with my SOHC4, or I might have to hurt you.
Hondaman's creed: "Bikers are family. Treat them accordingly."

Link to Hondaman Ignition: http://forums.sohc4.net/index.php?topic=67543.0

Link to My CB750 Book: https://www.lulu.com/search?adult_audience_rating=00&page=1&pageSize=10&q=my+cb750+book

Link to website: www.SOHC4shop.com

Offline edwardmorris

  • Youngish
  • Old Timer
  • ******
  • Posts: 3,142
  • Do not cause harm, nor respond to harm with harm.
Re: Concerns about rusted frame
« Reply #23 on: December 11, 2013, 10:06:12 PM »
No, not at the steering stem: back by the gusset plates where the rear loop(s) meet the triangle of the rear footpeg/pipe mounts. There is a small hole on each side of the gusset area, and there should be a small opening in the downtube of the rear loop there, normally seen above the points where the rear triangle (horizontal) tube meets the frame. It will look intentional, like they made the hole in the downtube too tall as compared to the diameter of the tube from the footpeg/pipe horizontal tube (does that make sense?).
Yea, I think I know where to look. I'll try and take pix if when I find them, then I'll drill the "quiet memo" holes. Thanks for the info! There is just sooooo much to learn about these bikes. Fun!

Offline edwardmorris

  • Youngish
  • Old Timer
  • ******
  • Posts: 3,142
  • Do not cause harm, nor respond to harm with harm.
Re: Concerns about rusted frame
« Reply #24 on: December 13, 2013, 08:18:00 PM »
I looked real close, no luck finding them yet. I sprayed a lot of CRC in the holes showin in the first post pix here, and it started to overflow out the same hole. I guess I will have to bring it out in the daylight this weekend and look with a mag glass.