Topic: Cb550 cafe/brat rest/mod

[work9to5]

Hi guys, this is one of the bikes I’m biulding at the moment. It’s actually my original vintage bike (or at least the frame and bottom end is) that I purchased 9 years ago. She’s been through it all, a lot of good times and good rides, and a lot of sitting neglected in the corner while I work on other people’s bikes or just other things. Well she’s been sitting for about three years currently and I’m gonna change that.

So far-
1.) gsrx750 front end conversion
2.) cb650 swingarm and rear wheel conversion
3.) cl360 headlight and mounts
4.) tip end rebuilt, cb650 cam, standard bore
5.) hooped and de-tabbed
6.) built a 4 into 4 exhaust system using the stock headers, some ingenuity and some reverse cone mufflers
7.) “pill style” oil tank which I welded up to serve as a battery box
8.) cb200 gas tank

It’s a pretty awesome looking build. Still really rough, but she’s up and rolling and fires.

[SOHC4 Cafe Racer Fan]

Why did you choose to use a 650 wheel?  I assume you are not keeping the dirt front tire??

[work9to5]

I choose the cb650 rear to keep the bike even stance wise. Shorter fork up front as well as a smaller diameter wheel I had to compensate without going to smaller rear shocks. I couldn’t use smaller rear shocks because I was worried the hooped rear end would bottom out on the tire. So I used the cb650 16” wheel and 1” larger than stock rear shocks. It retains the stock stance/rake/handling of the cb550 estenially, it’s just lower to the ground. Also I think it just looks better having the mag in the front and comstar in the back. It’s something I’ve done before. I’ll post a pic of my daily (which btw is for sale $4k and has some engine goodies hidden in there).

The front tire is tkc80. It’s the same tire that comes stock on gs1200. It’s awesome and I’m definitely/defiantly keeping it.

[calj737]

You will have much shorter trail with the GSXR swap. You might take a minute and measure the result. Stock CB trail is 4.1". Stock rake is 26*. The GSXR is about 23.8* of rake and 3.8". BUT, since your using the CB headstock, and the stock GSXR fork offsets, your trail will be very short. You have about 20mm less offset which translates into a MUCH shorter trail number.

The more rake coupled with less offset equates to a lot less trail. Less trail makes bikes "twitchy". So while you kept the riding geometry similar front-to-rear with a 1" smaller rear tire to compensate for the 2" smaller front, you have not balanced your front steering geometry at all. I'm not criticizing you at all, just making sure you accurately understand the aspects of your modification.

Have a look at the attached image to get a clear picture of what is involved in measuring these numbers for your bike. I'd be curious as to what it actually measures with the GSXR swap, as it is a very common modification.

[work9to5]

Guys, I understand what rake and trail are. I appreciate it Calj but neither of these bikes are twitchy. Now, the other build I have going on, she’s twitchy af.

Anyways...I got tuned to a point where I was excited and comfortable enough to put a chain on her and roll her down to the street. Gotta do some clutch adjustment. She started “baby stepping” with the clutch held in. Which I didn’t look at as a totally bad thing at least she wanted to go. But unfortunately when I shift from neutral to either 1st/2end she would die on me. So either I’ve got stuck clutch plates, the clutch is WAY out of adjustment or possibly the battery being so low from messing around all day tuning was throwing it off. Gonna get back in there today and see if I can get my first ride down the block! I may fab and stitch the seat as well. Wish me luck!

[calj737]

Do you mind sharing what your results were, or measuring for me? I have this swap planned, and am curious about having some offset built into my custom triples. Wasn’t suggesting you hadn’t done a proper job, was only providing information in case you hadn’t. 

[work9to5]

I measured everything on the first one. I’ll do measurements in this on this one today and post up the results. I expect them to be different between my two gsxr forked bikes. I’ll also do it on my bobber build just for sh&; and giggles.

I’ve had these type of rake/trail convos often in the past year. I became friends with a group of sport bike riders who track occasionally. They get so worked up about these suspension changes to their bikes (even though none of them probably own a wrench). Ive asked one of them recently after he raised the back of his bike “well does it feel better”, does it make you more comfortable on your bike so that you can corner with more confidence and enjoy it more. He responded “no, but it’s the correct rake and trail for a track bike. That kinda stuff drives me nutz

[work9to5]

Ok! Took around the block a dozen times! Tiny leaks from tapper covers and there a blank spot right at 1/4 throttle. One other thing is as soon as I turned the key after riding around the block the battery went from 12.7 to 10.4 immediately. Any idea what would cause that big of a drain? (Head light is not attached currently). It’s only a basic wire right now so I’ll find it when I do the final wire but a point in the right direction would help.

Ok trail 3.9” on this one
On my daily it’s 3.75
On my ridiculous 70’s bobber build (standard forks) which is “twitchy as f”, looks super cool but is basically an advanced rider course all in its self is 2.9”
I don’t have an angle finder (someday 🙁) is cant accurately measure rake degree

[work9to5]

Pics of each in order of listing

[work9to5]

For some reason I can’t upload more than one photo at a time

[work9to5]

70’s bobber

[calj737]

...as soon as I turned the key after riding around the block the battery went from 12.7 to 10.4 immediately. Any idea what would cause that big of a drain? Bad battery. Charge it fully. Let it rest 2 hours, then measure voltage directly at terminals. Then with headlight fuse removed, and key ON, measure it again.

Ok trail 3.9” on this one With stock GSXR triples? Hmmm....
On my daily it’s 3.75
On my ridiculous 70’s bobber build (standard forks) which is “twitchy as f”, looks super cool but is basically an advanced rider course all in its self is 2.9”
I don’t have an angle finder (someday 🙁) is cant accurately measure rake degree If you haven't modified the stock neck, it's stock to the frame. Or are you referring to a different bike?

[work9to5]

That was my first thought (battery) as well. It’s brand new and I havnt cranked on it. I switched in a different batter, same result. It maybe that it’s a tiny battery...true gel MG4L-BS. I’m not worried about it so much as I’ve got leads hanging for the non-essentials and havnt covered and soldered every connection. I’m going to take most off it out and start from scratch anyways now that the engines up and tuned.

Does 3.9 sound off for some reason? This one does “sit” differently than my daily. It’s lower to the ground and seems easier to roll around the garage a bit lol. I should mention that they are different years forks/triples 97’/01’


Finished the seat pan just now and drilled it out for rivets and mounts. My next post I’ll do a step by step on sewing/making the seat. I’m going to try to get the tuck n roll pleating to match the cb200 tank pad so it’s a bit more “consistent” tank to tail.

[MetroRedneck]

Trail should be around 4.51” depending on your tire - that’s about what I have calculated with a 23.6” (120/70 17) tire and gixxer forks. The higher the number the twitchy-er it will be. As you bring the forks closer to the stem, the trail increases all other things the same.  The CB550 has about a 26 degree steering head angle.  To decrease you can play with tire sizes and fork length to adjust head angle to the road. 

[calj737]

Does 3.9 sound off for some reason? This one does “sit” differently than my daily. It’s lower to the ground and seems easier to roll around the garage a bit lol. I should mention that they are different years forks/triples 97’/01’

That's a better trail number than the stock CB, using less offset forks. That sounds odd to me. What is the offset on that year GSXR? From your pictures, it looks very small.

[MetroRedneck]

Does 3.9 sound off for some reason? This one does “sit” differently than my daily. It’s lower to the ground and seems easier to roll around the garage a bit lol. I should mention that they are different years forks/triples 97’/01’

That's a better trail number than the stock CB, using less offset forks. That sounds odd to me. What is the offset on that year GSXR? From your pictures, it looks very small.

It's probably around 1.125".  That's what my 06 is, and I doubt they moved much looking at pics of the earlier years.

[calj737]

It's probably around 1.125".  That's what my 06 is, and I doubt they moved much looking at pics of the earlier years.

That would make them 28mm. That would increase the trail quite a bit from stock. Since he posted a number lower than the stock CB, I'm dubious. I would expect the GSXR to be around 30mm offset, increasing trail, maybe not too much, but closer to 4.5-4.7". I may have to run up to Cognito and measure his 550 with his GSXR swap for true measurements.

[MetroRedneck]

Trail of a cb550K with a GSXR triple and fork length is 4.51".  That's mine using a calculator and running a 120/70 17 and stock gixxer fork length and my measured offset - which is not super accurate, but close enough.

[calj737]

I would expect the GSXR to be around 30mm offset, increasing trail, maybe not too much, but closer to 4.5-4.7".

Trail of a cb550K with a GSXR triple and fork length is 4.51".  That's mine using a calculator and running a 120/70 17 and stock gixxer fork length and my measured offset - which is not super accurate, but close enough.

When you're right, you're right  That extra .4" will make these bikes prone to tank slappers if everything goes wrong. did you use a steering damper on your build? I know many of the newer GSXRs do is why I ask.

[work9to5]

Ok guys, even though this convo is boring as hell to me I’m going to indulge you. There can not be a standard “set in stone” number for trail. Even sitting on a bike can change its trail. I’ve done more than just sit on them. I changed rear rim size, changed rear shock size, changed swingarms. Even between these two bikes there’s a difference in ground height clearance (I’ll try to get a picture before I leave for work of them sitting next to each other to show the difference. I didn’t measure super accurately, I just used a steel rod and a 90 but I did not manipulate the numbers.

[MetroRedneck]

I am re-purposing the factory damper.  Waiting on a tube clamp to come in.  With the way I am doing my headlight, there is not enough room to use the factory mounting location.

I don't think it's going to matter much for me though - At 6'2" and 200 pounds, I don't plan on going hard through any twisties in the bayou flat lands with the anemic 550 that might put down 35 horse with a tail wind - that's what my 848 streetfighter is for.  My stature is also a big factor in probably not ever getting a tank slapper.  I now also have a 900F swing arm which increases the length of the bike and should slow the turns.  Running a taller tire in the rear too, which should decrease the stem angle to the road and bring down the trail a bit more.  From sheer volume of these swaps done without altering the offset, I don't believe it will be much of an issue unless you're planning on running it on track days.

Will see how she does once I put it on the road.

Ok guys, even though this convo is boring as hell to me I’m going to indulge you. There can not be a standard “set in stone” number for trail. Even sitting on a bike can change its trail. I’ve done more than just sit on them. I changed rear rim size, changed rear shock size, changed swingarms. Even between these two bikes there’s a difference in ground height clearance (I’ll try to get a picture before I leave for work of them sitting next to each other to show the difference. I didn’t measure super accurately, I just used a steel rod and a 90 but I did not manipulate the numbers.

I think cal is just making sure you are aware of the adverse effects of the swap.  I think his concern grew when the answer did not line up with an expected trail number.  Cal is looking out for us!  BTW sitting on the bike is going to adversely impact your trail, too

[calj737]

Ok guys, even though this convo is boring as hell to me I’m going to indulge you. There can not be a standard “set in stone” number for trail. Even sitting on a bike can change its trail. I’ve done more than just sit on them. I changed rear rim size, changed rear shock size, changed swingarms. Even between these two bikes there’s a difference in ground height clearance (I’ll try to get a picture before I leave for work of them sitting next to each other to show the difference. I didn’t measure super accurately, I just used a steel rod and a 90 but I did not manipulate the numbers.

Odd to me, you post a build thread in a public forum, but wince at questions and input. My original input was based upon reading your post, which made no mention of certain facts or details, and conveyed to a reader a lack of accurate understanding. You need to realize that your thread and posts/replies within it are not solely for your benefit. There are numerous others who read these threads silently and extract information from them. With that in mind, its important that information be accurate.

You are right; there is no "set in stone" trail number that makes a bike handle properly. But there are ratios and ranges that effect it greatly. Since you did not "measure super accurately" it calls into question your results. That's my point. Whether you change the rear wheel diameter and shock height matters little if you move the geometry into a bad handling "window". Lowering a bike's ride height has little effect on these measurements either. Since there are many who perform these swaps, and others who plan to do so, getting some actual measurements from someone who has the bike in front of them is communal help. If you are burdened by that, then why seek help for other matters if you are unwilling to offer it back in return?

Perhaps too many perform these swaps thinking it will improve their bike; which by default is NOT the case. It may help in some areas, but it can have grossly negative effect. Understanding the causes and remedies is critical for a safe riding bike. And since it is highly unlikely that people will own these bikes for the rest of their lives, a well-built, safe bike is everyone's obligation.

As boring as that is.

[work9to5]

What?