So i took off my gas tank to discover that there is a missing peice of the frame ( talking about the 2 side peices on the sides of the backbone). i would like to weld it but am not sure what type of metal to use. I read that the 1976 cb 750f uses Tubular Steel Duplex? Where on gods good green earth do i find that? or is there something else i can do to fix it. Thanks all
I FOUND A HOLE......YAAAAAAY!
- Thread starter dmfl
- Start date
kopcicle
antidisestablishmentarian
Re: I FOUND A WHOLE......YAAAAAAY!
Unusual but not unheard of . Usually found on lower frame tubes and generally caused by water expanding into ice .
Now for the fix .
Find a replacement tube from an otherwise unused unsalvageable frame .
Find another frame .
Take out the offending area completely , sleeve the ends of the repair and insert a new piece . Tack it all up with the engine in place . Then remove the engine to complete the repair . The reason for at least heavily tacking the repair before engine removal is to minimize distortion due to welding .
As for "Duplex" I believe Honda was referring to the design of the frame and not the metallurgy . "duplex cradle construction" was used extensively in their original advertising . The mild steel tube you are looking for is generally available and has limited carbon content with very small amounts of nickel and manganese . Easily weldable with most any process other than flux core w/o gas . Tig of course for the limited heat distortion . Mig doesn't have the penetration nor the control over deposition and placement of the filler metal . Dual shield would also be acceptable in small diameter wire in the hands of an experienced welder . Stick welding is also acceptable but would usually create quite a bit of grinding stops and starts as well as having to use 3/32" 6010 for the root and after very good cleaning of the root 7018 cover with plenty of room for grinding smooth .
YMMV
~kop
Unusual but not unheard of . Usually found on lower frame tubes and generally caused by water expanding into ice .
Now for the fix .
Find a replacement tube from an otherwise unused unsalvageable frame .
Find another frame .
Take out the offending area completely , sleeve the ends of the repair and insert a new piece . Tack it all up with the engine in place . Then remove the engine to complete the repair . The reason for at least heavily tacking the repair before engine removal is to minimize distortion due to welding .
As for "Duplex" I believe Honda was referring to the design of the frame and not the metallurgy . "duplex cradle construction" was used extensively in their original advertising . The mild steel tube you are looking for is generally available and has limited carbon content with very small amounts of nickel and manganese . Easily weldable with most any process other than flux core w/o gas . Tig of course for the limited heat distortion . Mig doesn't have the penetration nor the control over deposition and placement of the filler metal . Dual shield would also be acceptable in small diameter wire in the hands of an experienced welder . Stick welding is also acceptable but would usually create quite a bit of grinding stops and starts as well as having to use 3/32" 6010 for the root and after very good cleaning of the root 7018 cover with plenty of room for grinding smooth .
YMMV
~kop
Re: I FOUND A WHOLE......YAAAAAAY!
You have a golden opportunity to justify installing one of 'Gordon's Frame Kits'. It puts bolt-in sections of frame there so you can remove them and take your valve cover off while the engine is in the frame.
http://forums.sohc4.net/index.php?topic=115888.msg1346624#msg1346624
You have a golden opportunity to justify installing one of 'Gordon's Frame Kits'. It puts bolt-in sections of frame there so you can remove them and take your valve cover off while the engine is in the frame.
http://forums.sohc4.net/index.php?topic=115888.msg1346624#msg1346624
kopcicle
antidisestablishmentarian
Re: I FOUND A WHOLE......YAAAAAAY!
Actually Tim's suggestion in thread is the single best improvement to that bike for ease of service and something you would do if this bike was going to be around for decades .
If this is just a low budget keep it running thing then yes the engine would have to come out to complete the job as the angles and restricted space for out of position welding make it nearly impossible to complete the repair with the engine in the frame .
The engine removal and replacement isn't that difficult until everything is disconnected and it's time to take it out . It's a tight fit and more than a bit of a trick to getting it in and out . About the only thing that helps even a little is removing the breather cover on top of the engine .
Some years ago a few of the stalwarts of the SOHC4 forum put together a step by step engine R&R thread howto . I suggest you find it and read it several times before asking additional questions there or here . At least you will seem that you know something about what you're talking about .
The good thing is you wont need anything but common hand tools . A 1/4" dr set helps for the tight places and a 1/2"dr set helps with the frame bolts but most can be done with 3/8" dr deep and shallow sockets . The wrenches other than the countershaft sprocket are 8 , 10 , 12 , 14 , 17 ,19(3/4") in box and open end . No specialty tools needed .
The only hard parts you need to replace are the exhaust gaskets and possibly the rubber connections to the carbs .
YMMV
~kop
Actually Tim's suggestion in thread is the single best improvement to that bike for ease of service and something you would do if this bike was going to be around for decades .
If this is just a low budget keep it running thing then yes the engine would have to come out to complete the job as the angles and restricted space for out of position welding make it nearly impossible to complete the repair with the engine in the frame .
The engine removal and replacement isn't that difficult until everything is disconnected and it's time to take it out . It's a tight fit and more than a bit of a trick to getting it in and out . About the only thing that helps even a little is removing the breather cover on top of the engine .
Some years ago a few of the stalwarts of the SOHC4 forum put together a step by step engine R&R thread howto . I suggest you find it and read it several times before asking additional questions there or here . At least you will seem that you know something about what you're talking about .
The good thing is you wont need anything but common hand tools . A 1/4" dr set helps for the tight places and a 1/2"dr set helps with the frame bolts but most can be done with 3/8" dr deep and shallow sockets . The wrenches other than the countershaft sprocket are 8 , 10 , 12 , 14 , 17 ,19(3/4") in box and open end . No specialty tools needed .
The only hard parts you need to replace are the exhaust gaskets and possibly the rubber connections to the carbs .
YMMV
~kop
Re: I FOUND A WHOLE......YAAAAAAY!
isn't that what a forum is for? im in no way shape or form a motorcycle fabricator or even a mechanic. But I am trying to figure out how to do things on my own ( hence opening an account on THETON, information gathering before I decide on a course of action) . There is only so much one can do without getting frustrated and having to ask a couple questions. Sorry if my questions aren't to your liking. Feel free to not put fingers to keypad if my questions are so offensive.
isn't that what a forum is for? im in no way shape or form a motorcycle fabricator or even a mechanic. But I am trying to figure out how to do things on my own ( hence opening an account on THETON, information gathering before I decide on a course of action) . There is only so much one can do without getting frustrated and having to ask a couple questions. Sorry if my questions aren't to your liking. Feel free to not put fingers to keypad if my questions are so offensive.
VonYinzer
Over 10,000 Posts
Re: I FOUND A WHOLE......YAAAAAAY!
Glad to hear it. First and foremost though...
Can you weld? Do you own a welder? Are you friends with or related to a welder? Are you sure (enough to bet your life) of your or their skills?
When it comes to heavily modifying, rebuilding, or fixing the frame of your motorcyle you need to remember that it only takes a couple shit welds to ensure that at some point your face and the pavement are going to start dating. And trust me when I say that she's a real asshole.
Keep safety at the absolute forefront when deciding on your next move.
And Kop may seem like he's fucking with you, and that's because he is. But if you just let him (and listen) I promise you'll learn something useful.
Glad to hear it. First and foremost though...
Can you weld? Do you own a welder? Are you friends with or related to a welder? Are you sure (enough to bet your life) of your or their skills?
When it comes to heavily modifying, rebuilding, or fixing the frame of your motorcyle you need to remember that it only takes a couple shit welds to ensure that at some point your face and the pavement are going to start dating. And trust me when I say that she's a real asshole.
Keep safety at the absolute forefront when deciding on your next move.
And Kop may seem like he's fucking with you, and that's because he is. But if you just let him (and listen) I promise you'll learn something useful.
Re: I FOUND A WHOLE......YAAAAAAY!
yeah I have a family friend who owns a shop. the main reason why I was because I don't really like asking people to take a decent amount of time out of their day to help. I do weld but not good enough to be confident in my abilities for the sake of me and the lady taking a sunday ride. My friend also says the same thing about taking the engine out to weld it so it looks as if my options are taking the engine out or buying the kit Tom suggested. Ill prob go the route of removing the engine so I can learn a bit more. Thanks for the normal response! have a good one.
VonYinzer said:
yeah I have a family friend who owns a shop. the main reason why I was because I don't really like asking people to take a decent amount of time out of their day to help. I do weld but not good enough to be confident in my abilities for the sake of me and the lady taking a sunday ride. My friend also says the same thing about taking the engine out to weld it so it looks as if my options are taking the engine out or buying the kit Tom suggested. Ill prob go the route of removing the engine so I can learn a bit more. Thanks for the normal response! have a good one.
Re: I FOUND A WHOLE......YAAAAAAY!
It is a common thing to see thos 750 frames cut like that it look like a shortcut for a valve adjustment to quite a motor befor a saleget a short section of thick wall tubing that has the same id as you fames od and cut it long ways so you have two half circles then put them over the bad section and have them welded solid thus creation a full wrap....follow me? the stress will them be transfered through the frame correctly
It is a common thing to see thos 750 frames cut like that it look like a shortcut for a valve adjustment to quite a motor befor a saleget a short section of thick wall tubing that has the same id as you fames od and cut it long ways so you have two half circles then put them over the bad section and have them welded solid thus creation a full wrap....follow me? the stress will them be transfered through the frame correctly
Re: I FOUND A WHOLE......YAAAAAAY!
Yeah. that is almost like one of the plans but id cute it right out then take the new pipe, cut in half, then weld from the inside for the first bottom half, then weld the second half onto the first half. The one thing I learned from this thread is that I don't think I should cut the piece that needs to be welded as to not mess with the integrity of the frame. I may work with it instead of removing the engine. So maybe angle grinding the area smooth so I can weld a puzzle piece on it or do as you suggest. So I did learn a little something. and I appreciate all the advice. Collectively I think I can come up with a plan of action! Thanks all who were usefull!
bradj said:
Yeah. that is almost like one of the plans but id cute it right out then take the new pipe, cut in half, then weld from the inside for the first bottom half, then weld the second half onto the first half. The one thing I learned from this thread is that I don't think I should cut the piece that needs to be welded as to not mess with the integrity of the frame. I may work with it instead of removing the engine. So maybe angle grinding the area smooth so I can weld a puzzle piece on it or do as you suggest. So I did learn a little something. and I appreciate all the advice. Collectively I think I can come up with a plan of action! Thanks all who were usefull!
VonYinzer
Over 10,000 Posts
Re: I FOUND A WHOLE......YAAAAAAY!
I'm not sure why removing the engine keeps getting brought up. At some point you WILL remove the motor. The point of keeping ot in at the moment is to ensure that the frame is "straight" when you begin to fix the issue. The motor will hold the frame in the correct position while you do that. But after you get it properly tacked together, you WILL have to remove the engine to finish weld it all.
I'm not sure why removing the engine keeps getting brought up. At some point you WILL remove the motor. The point of keeping ot in at the moment is to ensure that the frame is "straight" when you begin to fix the issue. The motor will hold the frame in the correct position while you do that. But after you get it properly tacked together, you WILL have to remove the engine to finish weld it all.
rockcitycafe
I make things.
Re: I FOUND A WHOLE......YAAAAAAY!
this is such a good reason for proper registration and background checking purchases of angle grinders...
dmfl said:
this is such a good reason for proper registration and background checking purchases of angle grinders...
