How a modified frame handles

Posted: Fri May 04, 2018 7:52 pm

So some of you know that I have recently did the steering stem tuck like the Factory AHM bikes had. This means cutting out the steering neck, moving it back 1" and then steepening it up by 1 degree.

My rider Darrin couldn't believe how light it made the bike feel. We run 17" F2 wheels with stock triple clamps and slightly modified 900 forks. This was the only major change we made to the bike this year and Darrin went 4 seconds a lap faster at Willow Springs and it's not very twisty. Mainly big straight and a couple really long right hand corners. He felt so much more confident on the bike because it went where he wanted it to. Before he complained that the bike wouldn't finish the corner and would stand up as soon as he got on the gas really hard. Now it carves and he had no complaints of the bike being twitchy. Even at 3 digit speeds.

To do the conversion. I built a very strong frame jig and I use Captains Chrome Moly steering tube. The cost is $800.00 labor and $300.00 for the steering tube. I can also weld back in your steering neck but the labor goes up by $100.00 as it takes longer to prep the old steering neck.

If you are interested in this for your own bike? Please email me at jesawtellbuilt@gmail.com and I will send you some pictures.

Peace, Jim

Posted: Sat May 05, 2018 3:06 am

Jim,

You should set up shop somewhere on the East Coast towards the North,,, for a few months of the year!

Thanks for sharing your real life experience with us.

Peace
Vince

Posted: Sat May 05, 2018 9:12 am

good stuff Jim, can you expand on what you think is causing the benefit - there's a few things going on here - maybe its just a proven combo that works
Your trail is now 97mm ? - versus 115mm std ? - ok that's going to quicken things up - but you could have achieved this via yoke offset only
changing rake has also shortened the wheel base and this has shifted the weight bias fwd a bit - also generally a good thing on older bikes
dare say my question is - how much better is the rake change versus the simpler yoke offset to achieve the same trail reduction
cheers

Posted: Sat May 05, 2018 4:07 pm

Again, I’m no expert but if the easy way of just changing the offset were the best answer? AHM wouldn’t have bothered.
I just did what Brent told me to do and it worked out just like he said it would. I will be doing his same mod for another forum members Hot Rod street bike in the near future. I believe that this mod with 17” wheels makes these bike ride like modern bikes do.

When have you heard an F’r say that the bike feels light and nimble?? Ya me either until now.

That’s all I know

Posted: Sun May 06, 2018 2:02 am

Jim how do you go with the frame number and the compliance plate? Do you engrave the Captains Chrome Moly steering tube or is that not an issue in the States?

I could understand it not being a problem on a track day bike but for Registration and insurance in Australia it would have to have them in place.

Mark

Posted: Sun May 06, 2018 2:47 am

It can be in Oregon. I had to get a visual inspection that included the engraved VIN when I obtained a salvage titled for my 750. Also, if you try to register a bike from another state then the DMV will want to see the engraved VIN.

Posted: Sun May 06, 2018 9:53 am

Some states aren't as strict on visual. I registered my new frame in Michigan recently and it was from New York. It was not a salvage title.Just went to the DMV and applied for a new title. Got it in two weeks. Looks like Jim said he could put the old steering neck back in.

Posted: Sun May 06, 2018 10:47 am

The reason that these changes make so much difference is because it’s a comprehensive update that addresses everything and is not just a “band aid” which wheel sizes and frame pitch (jacking the rear end and or dropping the front) are. You do all this "after" you get the hard frame geometry correct because in OEM form it isn't.
The steering head change is at the heart of it all and improves rigidity (Cr Mo) is machined accurately (OEM isn’t). The angle change and rebate reduces wheel base and gives F/R 50/50 weight bias (minimum) OEM is 49/51 or worse and this change to 50/50 is a crucial change that cannot be achieved any other way and results in two things, quicker response (reduced wheelbase) faster turning (forward weight and trail reduction).
To amplify this further you can increase the triple clamp offset to reduce trail further and this reduces input effort. All of what I have just explained results in a major improvement that is better than the sum of the parts and results in characteristics more in common with the better modern bikes. This is a major transformation that really has to be experienced as to how much this improves these bikes.
Jim has now validated all this for himself as he has actually implemented these changes. and now knows how good it is which is why he is now offering this service to all. All of this did not come about overnight as it has all been tried and tested in our Superbike during many seasons of trial and error. The results now stand that I’m yet to now see any CB-F that can equal it in this area.
Once this is done you then can tweak and or finesse the performance further to your liking with fork and swing arm settings and of course suspension adjustments / settings
But getting the steering head geometry right as I have just described is the foundation and is first and formost for true performance gains.

As for the issue (for street use) I cannot see any reason why cutting the serial number from the original head and welding or riveting it onto the replacement steering head wouldn't meetl the requirement. It is the original stamping and proof of title.

Captain

Posted: Sun May 06, 2018 1:38 pm

Thanks, Brent you might want to change your signature Wink

go for the power once you get the chassis sorted

Posted: Sun May 06, 2018 10:47 pm

nlovie wrote:

Thanks, Brent you might want to change your signature Wink

go for the power once you get the chassis sorted

You have a point and your comment is factually correct, but the world turns on power and this is what everyone wants to see first.

But to clarify our history, it is exactly what I did.... Messed around working out the frame issues in the early stages (a few years ago now) and once we had it "nailed" I moved on the engine. Has anyone noticed just how much of our frame etc is modified (it's more comprehensive than the engine IMO). It's just that I don't talk about it much as to be honest 99% of people don't really understand things like this well enough so until someone like Jim comes along who is prepared to put it into action it remains of vague interest to most...............Not everyone can be grouped like this of course and I don't wish to offend anyone but the reasons for this are because no one has explained to them or they cannot grasp the issue or are perhaps "gun shy" of changing a major component such as the steering head and further are sceptical that it could make such an improvement. Well maybe with Jim now advancing it in this way it will gain some traction. All I am trying to do is explain what this is about, how it changes for the better and hopefully in a way that those with less understanding until now can learn.
Everyone seem to be in love with power and talks about it endlessly but the truth is chassis and handling and brakes are first and foremost.

Captain

Posted: Mon May 07, 2018 1:01 am

I think its very important and relevant to the rideability of these bikes, and Jim is offering a great service. Something that most of us could not take on, because this needs a very precise hand and importantly a solid Jig. If your happy cruising and and loving the long sweepers, or simply restoring your bike to its Honda made showroom condition then I'd leave it alone. If you love the twisties and enjoy tinkering and improving these classic bikes then see Jim, he has the equipment and the know how to bring your F into the Fer Future.

Mark

Posted: Mon May 07, 2018 6:47 pm

i've done a lot of work on getting my bikes chassis and suspensions to my liking so have an appreciation of the work in both finding the right set up and just as importantly the investment in the hardware and skills ( as Jim has done) needed to achieve it - this does deserve the strongest of positive messages
I would bet you - even your std bike is twisted - if all Jim did for you was to straighten it out - you would be happy with your investment - but why fix what ain't best in the 1st place - go the whole hog and get the right no's

my next "toy" i'm looking for is a Yamaha SZR 660 - think they were only out in Europe ? - anyway - one ugly looking thing with a whopping 40 odd HP Laughing

but look at the frame / suspension / brake spec - this is going to be my track day toy

Posted: Tue May 08, 2018 7:58 pm

I figured I would echo some of the statements that have been made. Back in the 80's, I was one of those who was fortunate enough to know a few people who were indirectly involved with Honda. One of the first things I did to my frame beside the usual bracing, was the modification of moving the steering stem back 25mm. Unfortunately, at the time I did know all of the other details that were involved in getting the bike to handle as well as it could have. Fast forward 35 years, I have vowed to myself that I would get things right this time through. I have read countless post, written emails and asked questions in an effort to do my homework prior to starting any work on the frame.

For me, the process starts with sending my frame off to a shop to be straightened. Now I have a baseline to work with. Here lies the rube. Finding the talent with the experience, knowledge, tools and the time to complete the task in a timely fashion. The majority of those talents are stretched widely across many miles or are hidden like well-kept secrets. Even though it has taken longer then I would like it to be. I know the many benefits of having a chassis that is built based on a fair amount of time on research and development. Yeah, many of us may not fully benefit by having all of these mod's done to the frames.

I am not someone that "cannot actually grasp the issue, are "gun shy" of changing a major component such as the steering head and further are skeptical that it could make such an improvement. " For me, the limiting factor is having easily accessible talent that can produce a quality product.

Thanks for your continued support.

Posted: Thu May 10, 2018 3:39 am

TCRacing wrote:

I figured I would echo some of the statements that have been made. Back in the 80's, I was one of those who was fortunate enough to know a few people who were indirectly involved with Honda. One of the first things I did to my frame beside the usual bracing, was the modification of moving the steering stem back 25mm. Unfortunately, at the time I did know all of the other details that were involved in getting the bike to handle as well as it could have. Fast forward 35 years, I have vowed to myself that I would get things right this time through. I have read countless post, written emails and asked questions in an effort to do my homework prior to starting any work on the frame.

For me, the process starts with sending my frame off to a shop to be straightened. Now I have a baseline to work with. Here lies the rube. Finding the talent with the experience, knowledge, tools and the time to complete the task in a timely fashion. The majority of those talents are stretched widely across many miles or are hidden like well-kept secrets. Even though it has taken longer then I would like it to be. I know the many benefits of having a chassis that is built based on a fair amount of time on research and development. Yeah, many of us may not fully benefit by having all of these mod's done to the frames.

I am not someone that "cannot actually grasp the issue, are "gun shy" of changing a major component such as the steering head and further are skeptical that it could make such an improvement. " For me, the limiting factor is having easily accessible talent that can produce a quality product.

Thanks for your continued support.

Well all of your concerns are answered if you send it to Jim...... His jig is the most comprehensive I've ever seen (better than mine) and he can correct the error that is in the OEM frames from manufacture (the steering head will not be at 90 deg to the swing arm (they never are)) has all the "correct" bracing pieces "AND" can change the steering head that that that has been described in my previous posts. No secrets, confidential withholding of set-up information as everything I know has been given to Jim as my policy is to help shed light on that that is usually dark.

Captain

Posted: Thu May 10, 2018 9:54 am

i'd suggest there is a "service" opportunity here -- going to do a back to frame restoration ? how does the average hobby workshop dude inspect their frame ?
Jim could make a simple set of equipment that could be sent out to do a pre repair inspection
1st check for swing arm twist - easy - two spindles for the swing arm pivot and wheel + x 4 matched V blocks - any corner to corner wobble when you lay the arm with spindles across the blocks and its twisted ( less than 1mm will give measurable rear wheel offset once its amplified by the wheel diameter )

Next the frame:
using the swing arm pivot spindle - make a bush with a plate welded to it - to replicate the swing arm bush that sleeves over the spindle - make plate maybe 18"+ high
make a dummy extended front yoke stem - +/- 24" extending below the lower bearing - best mill a key slot along the length of the extended stem
make a sliding block that runs on the key slot - fit a laser pen to this sliding block
ok - fit the dummy plate swing arm and point the lazer at it - run the block up / down the dummy stem and you will trace a line on the plate - if its perpendicular to the pivot - frame is good - if its not - send to Jim to do his thing

all the above works for me - added bonus is the line can also establish the centre line of the head stock relative to the swing arm - once you've got this - if your fitting a different back wheel - it gives you an easy datum for centring the wheel

Posted: Thu May 10, 2018 5:42 pm

Quote:

Everyone seem to be in love with power and talks about it endlessly but the truth is chassis and handling and brakes are first and foremost.

Every motorcycle I have ever raced or owned got the suspension sorted out first and then went after the power. The key is to get each to their potential with suspension edging the performance so the power can be taken advantage of.

Posted: Thu May 10, 2018 11:51 pm

Hp sells. I see it all the time in my line of work. Guys spend huge amounts of money on their engine and twice that on the paint job and wheels and have no money left for the chassis. They then wonder why the guy with less power is faster than they are.

It doesn’t matter if it’s a motorcycle or a car, there’s just not as much info out there on chassis design and tuning as hp development. I’m thankful that Brent and Jim are willing to share with those who are willing to listen!

Nich

Posted: Fri May 11, 2018 1:38 am

Nunzio wrote:

Quote:

Everyone seem to be in love with power and talks about it endlessly but the truth is chassis and handling and brakes are first and foremost.

Every motorcycle I have ever raced or owned got the suspension sorted out first and then went after the power. The key is to get each to their potential with suspension edging the performance so the power can be taken advantage of.

Simple fact of the matter is, power is the enemy of handling.

Posted: Fri May 11, 2018 3:27 pm

I’m pretty excited because both Hondo57/Greg and Headless/Cary are sending me frames to completely brace and do the steering stem tuck. Both frame are also single shock. These will be some really cool Hot Rod street bikes.

I love my job

Posted: Fri May 11, 2018 5:07 pm

JJam, i'm envious of you in that regard. I wrench in my spare time after my day job and wish that the wrenching could be my day job. You make some pretty nice fabrications as well, so being good at what you love says something too!

Posted: Fri May 11, 2018 9:02 pm

Jim, are you doing the single shock conversion also?

Posted: Fri May 11, 2018 9:54 pm

n8n8n8 wrote:

Jim, are you doing the single shock conversion also?

Only the 07 to now CBR600RR single shock conversions. Just like TomK's two I did.

Posted: Sat May 19, 2018 6:40 pm

What's the stock steering head angle? Are all the dohc steering head angles the same?

Posted: Sat May 19, 2018 6:54 pm

JJam wrote:

n8n8n8 wrote:

Jim, are you doing the single shock conversion also?

Only the 07 to now CBR600RR single shock conversions. Just like TomK's two I did.

This is a tried and true mod that performs even better than I could have ever expected. Several others have ridden RMI and agree. My son also agrees and rather than fight with him over who gets to ride it, I had no choice but to build RMII, which is now underway.

nathanhouse wrote:

What's the stock steering head angle? Are all the dohc steering head angles the same?

Jim should be able to answer that. I wouldn't mess with it if you're planning on going with the present version of the CBR600RR swingarm. Bore out the stock triples, use 41mm forks, and you're good to go.

Posted: Sat May 19, 2018 8:03 pm

nathanhouse wrote:

What's the stock steering head angle? Are all the dohc steering head angles the same?

No they are all different Nathan. the 1100 is the worst at 29 degrees, 900 is 28 and 750's can be as steep as 26 going by a Honda frame print but the ones I have put in my jig were at 27.5 to 28 degrees.

I can tell you that all frames from one to the next are all different.

Thanks for the prop Tom. Once Greg and Headless get their frames done it will make your frames seem slow turning in comparison. Basically they will have a modern bike with old school cool mixed in. I can't wait.

Peace, Jim

Posted: Sun May 20, 2018 12:31 am

JJam wrote:

nathanhouse wrote:

What's the stock steering head angle? Are all the dohc steering head angles the same?

No they are all different Nathan. the 1100 is the worst at 29 degrees, 900 is 28 and 750's can be as steep as 26 going by a Honda frame print but the ones I have put in my jig were at 27.5 to 28 degrees.

I can tell you that all frames from one to the next are all different.

Thanks for the prop Tom. Once Greg and Headless get their frames done it will make your frames seem slow turning in comparison. Basically they will have a modern bike with old school cool mixed in. I can't wait.

Peace, Jim

Thanks Jim,
I'm going to be running 43mm forks and a mono shock rear, your frame braces and I'm thinking I might do the steering neck myself but I wasn't sure what to expect from the stock neck before I start cutting and welding.
So you would steepen the 900 neck to a 750 (27?) or take it all the way to 26 degree?

Posted: Sun May 20, 2018 12:42 am

If you want it the same as Brents or AHM Nathan? then 26.5 to 26 degrees and go back with it 1" on the bottom. If you plan to use yokes with less offset?? Then you might want to go steeper to keep the trail in the 95 to 100mm zone.

Theres all kinds of rake and trail info on the web. I was lucky and Brent explained all this to me. Once Darrin came in off the track and his voice sounded like an excited kid. I knew what I was told works. And this was with the shocks with too much sag. After I got him the proper suspension sag he really liked it. Completely different bike. I can't wait to ride one.

Posted: Sun May 20, 2018 2:48 am

That's awesome! Thanks Jim!