81 CB650 Brat/Cafe Build

The rear wheel travel is larger than the clearance you have between the top of your rear tire and the seatpan. Tire will hit. If not larger, at least really close to each other. Either way, you need at least 30mm more that the total wheel travel. Just to be sure.

Sent from my SM-T900 using Tapatalk
 
dmable44 said:
I don't see a problem with the frame the way it is.
Click to expand...
Then there's not much I can say.

dmable44 said:
I simply put a loop on, something that many people have done
Click to expand...
Yes, many people have also made the same mistake.

Wanting it to be right wont be enough. The subframe needs rebuilt. I'm not going to personally involve myself in any more of this discussion, but maybe some others will continue to attempt to shed light. I've type my heart out on this subject and yet still the same mistake is made over and over.
 
dualero said:
The rear wheel travel is larger than the clearance you have between the top of your rear tire and the seatpan. Tire will hit. If not larger, at least really close to each other. Either way, you need at least 30mm more that the total wheel travel. Just to be sure.

Sent from my SM-T900 using Tapatalk
Click to expand...

Thanks for explaining. I understand I don't have enough clearance between the wheel and the seat pan but how do I correct it? Why was a loop a mistake? If it was a mistake how have so many people ran loops and changed wheel setups with no issues?

DohcBikes said:
Then there's not much I can say.
Yes, many people have also made the same mistake.

Wanting it to be right wont be enough. The subframe needs rebuilt. I'm not going to personally involve myself in any more of this discussion, but maybe some others will continue to attempt to shed light. I've type my heart out on this subject and yet still the same mistake is made over and over.
Click to expand...

I don't understand why you would say I've made a mistake but not explain how to properly correct it? Rebuild the subframe in what manner? You all have been a tremendous help with this build thus far and as I said I am new to this so please by all means explain how to solve the issue properly.
 
OK. Here's the deal.

Before you cut your frame and added the hoop, the stock seat and cross member(s) were built to allow the shocks to bottom out (or very close to it) before the tire would contact anything.

Now that you've removed the stock pieces, and added the hoop, that clearance is all gone. You've closed that gap which will now allow the tire to hit the seat area WAY before full shock compression. Pretty common mistake. I know I made it in the past.

Now, to fix it.

Remove everything from the seat area of the frame. You may not have to remove the hoop, we'll find out soon...

Without the final shocks this may be slightly difficult, so I'll lay out the process and you can do what you wish with the info.

Install the shocks.
With the wheel set up in the swinger wrap a ratchet strap around the frame and attach to both legs of the swinger (towards the end of the legs, near the axle).
Tighten it down until the shocks are as close to bottomed out as you can safely get them.
Now look at the profile of the seat area and see where the top of the tire has come to rest.
At this point, I hope to the gods that you see where we're headed here ;)

Now, when redesigning your seat are with this new knowledge keep any other parts that may be installed in the area (like a fender, please run a femder) in mind as well.

Get what we're after here now?

A couple final thoughts:

Sitting on or bouncing on the seat will NOT give you the information you need.
Fenders are good...
Safety trumps looks, but if you use your brain they work very well together.
Measure twice, cut once.
It's only metal. Fuck it up? Cut it off and fix it.

Now, get to work :)
 
dmable44 said:
If it was a mistake how have so many people ran loops and changed wheel setups with no issues?
Click to expand...

Just because you have seen others do it, doesn't make it safe or without issue. If you search "brat" in google images, the vast majority of bikes that come up are going to have the same issue. Sure they look nice, but is it a practical and logical mod or a detrimental mod to make? That's the issue with some of these trends, they're just plain stupid, given the implications on handling.

Go back and have a look at the rear end, and how much clearance there was, and where that clearance was, before you changed the rear - shouldn't be hard to see the differences.
No big deal, take on the info the other guys have offered, learn what trends should, or should not be followed - there's always a smarter solution. Then make yourself a bike that functions safely and properly, that is modified with some forethought, and also looks good.
 
I would suggest a simple series of pie cuts to progress the rear up and then add a doubler plate. It gives the illusion of an extreme race rake but the suspension works like stock.
 
VonYinzer said:
OK. Here's the deal.

Before you cut your frame and added the hoop, the stock seat and cross member(s) were built to allow the shocks to bottom out (or very close to it) before the tire would contact anything.

Now that you've removed the stock pieces, and added the hoop, that clearance is all gone. You've closed that gap which will now allow the tire to hit the seat area WAY before full shock compression. Pretty common mistake. I know I made it in the past.

Now, to fix it.

Remove everything from the seat area of the frame. You may not have to remove the hoop, we'll find out soon...

Without the final shocks this may be slightly difficult, so I'll lay out the process and you can do what you wish with the info.

Install the shocks.
With the wheel set up in the swinger wrap a ratchet strap around the frame and attach to both legs of the swinger (towards the end of the legs, near the axle).
Tighten it down until the shocks are as close to bottomed out as you can safely get them.
Now look at the profile of the seat area and see where the top of the tire has come to rest.
At this point, I hope to the gods that you see where we're headed here ;)

Now, when redesigning your seat are with this new knowledge keep any other parts that may be installed in the area (like a fender, please run a femder) in mind as well.

Get what we're after here now?

A couple final thoughts:

Sitting on or bouncing on the seat will NOT give you the information you need.
Fenders are good...
Safety trumps looks, but if you use your brain they work very well together.
Measure twice, cut once.
It's only metal. Fuck it up? Cut it off and fix it.

Now, get to work :)
Click to expand...

This is exactly what I was hoping to get. Thank you!

I think my first step is to put the wheel back on and strap it down with tension, and take some measurements. Then cut the seat pan off the frame (I have a better idea on how to mount the seat anyway). What about moving the loop forward on the frame so that the upsweep is past the center (tallest) point of the wheel. I'll have to shorten my seat obviously but that should give me more clearance right?

What do you think of that?
 
If you are considering shortening the seat so the tire bypasses the rear hoop, please make out your life insurance policy payable to "Red Willis...."

I hate this guy but here is what you can do:

PerformanceCustom+2nd+Fuller.jpg
 
redwillissuperman said:
If you are considering shortening the seat so the tire bypasses the rear hoop, please make out your life insurance policy payable to "Red Willis...."

I hate this guy but here is what you can do:

PerformanceCustom+2nd+Fuller.jpg
Click to expand...


Dont emulate anything off this piece of crap.
 
Not nearly as exaggerated, but I did sort of the same thing. Kicked the rear up just a bit to give me tire clearance.

Screenshot_2015-12-15-07-25-11-1_zpsc6rejjwu.png
 
Thats pretty much what I had in mind. Since I have the upsweep loop I think I could do that. It would give me clearance without affecting anything else right? Other than a smaller seat
 
Pie cuts are either just slits or larger slivers through 75% of the tube from the top in your case. Use a block of wood between the tire and frame, along with the ratchet strap to pretension the frame. As you make a few cuts near the bending point, the frame will auto-relax to position. Then weld.


66a3edb758f159d63df3e996faa91369.jpg
 
Ah I see. I'm in contact with a semi local custom motorcycle shop that is known for restoring, modifying and building these vintage bikes. I'll see what they have to say but I think I know what I need to do from all your input so thank you!
 
Cleaning the carbs today. They look pretty good actually but I'm going to replace the float bowl gaskets as one is torn. The jets are 124, 38, and 20 so now I know where my baseline is for when I mount them and finally run the motor and get it tuned.
 
It's an option. Depends on the look you want.

One reason to sway you away is you mentioned a passenger and this might not work with your girlfriend's butt.
 
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