CB450 cut seat mount rear, will the frame flex??

[joevirus563]

If I cut the old seat mount of a cb450 like so:

And leave it like that, will the frame flex?

The thing is that I've soldered a flat bar between the 2 posts but I'm worried now that if the shocks bottoms, my wheel will hit it... I already bent it forward on a big bump.

 

[SONICJK]

Yes.

 

[joevirus563]

Ok if I solder my 1/4 steel plate here instead will that prevent it to flex?

 

[johngofast]

Solder or weld?

 

[joevirus563]

Weld

 

[Rich Ard]

It'll help - but not as much as a proper hoop. Before you do anything, pull the rear down all the way to bottom out the shocks to make sure it won't contact.

 

[joevirus563]

What do you mean... Push on the bike to force it to bottom... I have some hagon on it and pretty worried about braking the seat of if give it a big push on it. I was thinking about measuring the shock dampening rod hand try to see if this is gonna work.

Pretty sure that it's almost fine with my setup right now so if I install the bracket on it that would do it.

 

[cqyqte]

You need to weld a hoop that arches up to clear the rear tire at maximum deflection. Nice pic if I do say so myself ;D, the CB450 frame has spot welded sleeve joints that will begin to flex with age. Removing the fender arch bracket weakens the frame further, which will induce further unwanted flexing.

When people give you helpful opinions don't ignore them, they are passing on valuable information which they have learned through experience or education. If you read further on in my project thread you will see what I did to correct the manufacturers short comings, such as seam welding, bracing, or you can choose to ignore and try short cuts because you are in a hurry or cheap. The choice is yours!

 

[Rich Ard]

^ +1

You can use ratchet straps to pull the bike's rear end down

 

[cqyqte]

Don't think he's listening Rich

 

[joevirus563]

^ +1

You can use ratchet straps to pull the bike's rear end down

Awsome! Good idea I'll give it a try.

 

[joevirus563]

Don't think he's listening Rich

? Of course i'm listening... I'll plan to put a rear hoop on it.

But for now I'll weld a bracket to it.

 

[joevirus563]

You need to weld a hoop that arches up to clear the rear tire at maximum deflection. Nice pic if I do say so myself ;D, the CB450 frame has spot welded sleeve joints that will begin to flex with age. Removing the fender arch bracket weakens the frame further, which will induce further unwanted flexing.

When people give you helpful opinions don't ignore them, they are passing on valuable information which they have learned through experience or education. If you read further on in my project thread you will see what I did to correct the manufacturers short comings, such as seam welding, bracing, or you can choose to ignore and try short cuts because you are in a hurry or cheap. The choice is yours!

I don't understand the last part of your post...

What tells you that I ignore helpfull informations?

 

[cqyqte]

Pretty sure that it's almost fine with my setup right now so if I install the bracket on it that would do it.

Nothing, nothing at all...

 

[Flugtechnik]

Yes, since shocks and tires vary, I would definitely check as they suggested.

My seat and fender are basically lined up at the top of the frame rails and my tire has a very small amount of clearance when my shocks bottoms out.

 

[joevirus563]

I was talking about the clearance between my wheel and the bracket.

I like all kind of opinions, it makes me think right on a subject.

How about that post of rick: "It'll help - but not as much as a proper hoop." well thats about right.

 

[joevirus563]

Yes, since shocks and tires vary, I would definitely check as they suggested.

My seat and fender are basically lined up at the top of the frame rails and my tire has a very small amount of clearance when my shocks bottoms out.

Thanks.

Hangon's have 2.5" of travel so I'll need about that.

 

[cqyqte]

My point Joe is that frame flex in the CB450 is a known issue, depending on the state of the bike when you start a project can make the flex issue into a problem. Cutting out OEM bracing can make it worse, although the rear fender arch brace doesn't look significant it's shape and placement helps stiffen the frame reducing pitch and yaw between the shock towers. Remember the swing arm mounts to the same fame rails, movement of those shock mounts will affect the swing arm pivot points as well.

Rich said your bracket will help but not as much as a hoop, or in my opinion the original fender arch. To run with just your bracket until you get a hoop installed is not ideal. Just saying

 

[Rich Ard]

Re: Re: CB450 cut seat mount rear, will the frame flex??

Rich said your bracket will help but not as much as a hoop, or in my opinion the original fender arch. To run with just your bracket until you get a hoop installed is not ideal. Just saying

Agreed. I pushed my CB450 with a stock frame to the best of my meager abilities and could feel the frame flex.

 

[joevirus563]

I have to pass safety tomorrow. I'll put a braket on it but i'm looking for a hoop right now. What diameter is the stock frame tubing?