T8's 750 Cafe Racer Project

[Chuck78]

Awesome man! Really glad to hear that you are finally nearing the moment when you can get that thing on the road!

 

[T8erbug]

Seat Plug

Seat Plug

I have been dreading this moment for a while now.. But with the last warm streak we had here I couldn't help but think about how this bike was already supposed to be "ready to ride". Anyways, the challenge with the plug is making it symmetrical. Since it's all been built from scratch there are minor imperfections everywhere.. as you shape it and reshape it some things get close while others seem to drift out of shape. Looks fine but I want it to look great and don't want nitpicky people to have anything catch their eyes. It's a tough deal but anyways hopefully I can get this done in the next week or so and finally experiment with laying some fiberglass.

 

[GregT]

What caliper are you using ? Number of pistons ?
Bore of the M/c you have now - usually cast into the underside.

tell me that and i'll give you a close figure for what size M/c to look for.

 

[Triam]

I have been dreading this moment for a while now.. But with the last warm streak we had here I couldn't help but think about how this bike was already supposed to be "ready to ride". Anyways, the challenge with the plug is making it symmetrical. Since it's all been built from scratch there are minor imperfections everywhere.. as you shape it and reshape it some things get close while others seem to drift out of shape. Looks fine but I want it to look great and don't want nitpicky people to have anything catch their eyes. It's a tough deal but anyways hopefully I can get this done in the next week or so and finally experiment with laying some fiberglass.

Maybe you could design what you want the seat to look like in solidworks, and then have your friend stick it in the mill and surface mill it until it looks like you want it. It'd be symmetrical if you did that.

 

[T8erbug]

What caliper are you using ? Number of pistons ?
Bore of the M/c you have now - usually cast into the underside.

tell me that and i'll give you a close figure for what size M/c to look for.

Awesome, thanks! I looked under the MC and didn't see a casting but I know it's not the stock unit for the donor forks/brakes (2001 GSXR600). It's a nissin unit, however the caliper is stock for the model and runs on four pistons.

Maybe you could design what you want the seat to look like in solidworks, and then have your friend stick it in the mill and surface mill it until it looks like you want it. It'd be symmetrical if you did that.

We do have a new mill that will do this kind of stuff in high density foam but at this point it's almost more work to stop where I'm at, design the part in solidworks, figure out a clamping situation, and try to mill it all straight in one try with my current plug.. If we'd have had the ability to do it this way from the start I would have done it no doubt because you're right about it being totally symetrical. I will be taking full advantage of the new mill when doing the underbelly pan plug. It should make things much easier.

 

[T8erbug]

Here is the rear brake situation now. All installed and ready to go!

 

[steve murdoch]

Any mechanical advantages to your brake stay?
I love the cool factor.

 

[GregT]

Awesome, thanks! I looked under the MC and didn't see a casting but I know it's not the stock unit for the donor forks/brakes (2001 GSXR600). It's a nissin unit, however the caliper is stock for the model and runs on four pistons.

Late 4 piston Nissin caliper - you'll find a surprisingly small M/c will work very well - 12mm or 1/2inch bore will give you a good feel and plenty of power. Look at dirt bike M/c for a start.

Your rear brake setup looks good. On my wire wheels I got discs with them very like yours but can't use either front or rear...wave discs are banned in the class I'm building the bike for...
How does your chain line work out ? I'm having to move mine inboard on the hub which isn't easy. Pics will come on my build thread soon.

 

[boontonmike]

T8,

Every time I see an update on your bike I get a little more jealous. I haven't touched mine in months and every update you post there is some new cool machined bit. Keep it up.

 

[Morrison]

Mad props! Subscribed!

 

[Chuck78]

Your brake stay's short reach and abrupt angle leave me wonderimg if an excessive amount of force at awkward side loaded angles would be generated, since the caluper will wat to push horizontally. It makes we wonder if the slightest amount of wear or slop would allow radial slippage movement if rge caliper/habger, sbd then more side loading if the stay's spherical heim jointsabd threaded connections.
Have other production bike used a similar setup?

 

[GregT]

Your brake stay's short reach and abrupt angle leave me wonderimg if an excessive amount of force at awkward side loaded angles would be generated, since the caluper will wat to push horizontally. It makes we wonder if the slightest amount of wear or slop would allow radial slippage movement if rge caliper/habger, sbd then more side loading if the stay's spherical heim jointsabd threaded connections.
Have other production bike used a similar setup?

Have another look - the caliper thrust is actually tangential to the disc and the arm angle follows this quite well. The arm itself is IMO well up to the loads involved. Can't see the point where it picks up on the swingarm but everything else is well enough done to give me confidence it's good too.
You may be surprised at some factory setups...look at some Ducati ones to see what you can get away with.

 

[Guest]

Question. What foam are you using for the old seat base? Is it compatible with the polyester resin? Normal fiberglass resin? Where to get foam that is compatible. I.E., won't melt once you apply the resin?
No epoxy, please.
Tnx
G

 

[T8erbug]

Late 4 piston Nissin caliper - you'll find a surprisingly small M/c will work very well - 12mm or 1/2inch bore will give you a good feel and plenty of power. Look at dirt bike M/c for a start.

Your rear brake setup looks good. On my wire wheels I got discs with them very like yours but can't use either front or rear...wave discs are banned in the class I'm building the bike for...
How does your chain line work out ? I'm having to move mine inboard on the hub which isn't easy. Pics will come on my build thread soon.

Hey Greg! Yeah, that goes right in line with what I was thinking as well as what I was told by one of the guys at Warp9. I'm going to use a dirt bike MC as soon as I can find the one I want for a good price!
As far as chain alignment, everything looks fine and has passed a visual inspection (as well as using a chain alignment tool, which is basically just a better way of eyeballing it). We'll see how it all works out when I get it rolling. I'll start by getting the wheels aligned and then go from there with the chain. Luckily it's relatively adjustable through the front sprocket as of now and I have some clearance to work with. The more I think about it the more daunting it seems but I'll just take it one bite at a time like I have throughout the rest of the build. Thanks for the info!

 

[T8erbug]

Any mechanical advantages to your brake stay?
I love the cool factor.

The biggest mechanical advantage to it is that I can adjust the alignment on the bike aka move the rear wheel side to side by adjusting wheel spacers without having to machine, weld, and/or tweak the stationary mating parts of the standard rear disc setup as well. The rod ends can each pivot so that is what makes the side to side movement possible where the standard modern set-up is totally stationary. The adjustability is a huge asset to me right now as I am still in the process of chain and wheel alignment. As for strength I can't say just yet. Set-ups like this have been used on custom springer front ends pretty regularly so it should hold up on the rear end without too many issues. I'll be sure to let everyone know if I do have any though!

PS It's also WAY easier to machine and install on a custom job

 

[T8erbug]

Question. What foam are you using for the old seat base? Is it compatible with the polyester resin? Normal fiberglass resin? Where to get foam that is compatible. I.E., won't melt once you apply the resin?
No epoxy, please.
Tnx
G

I'm just using good old fashioned blue foam available at the Home Depooohh. I put body putty over it to finish it off and there is some very slight meltage from the bondo but I think it's mostly just from the heat given off during the curing process. It's not enough to do damage to the plug. Paint, however, on the foam will eat it right away. And as you know just about anything can be put on the bondo afterwards without a worry

 

[T8erbug]

Your brake stay's short reach and abrupt angle leave me wonderimg if an excessive amount of force at awkward side loaded angles would be generated, since the caluper will wat to push horizontally. It makes we wonder if the slightest amount of wear or slop would allow radial slippage movement if rge caliper/habger, sbd then more side loading if the stay's spherical heim jointsabd threaded connections.
Have other production bike used a similar setup?

Have another look - the caliper thrust is actually tangential to the disc and the arm angle follows this quite well. The arm itself is IMO well up to the loads involved. Can't see the point where it picks up on the swingarm but everything else is well enough done to give me confidence it's good too.
You may be surprised at some factory setups...look at some Ducati ones to see what you can get away with.

Greg is pretty much right on point with what I was thinking. I made sure the angle of the arm was not acute or obtuse or in other words in line with the force of the disc under braking. I can also adjust the length of the arm to change these angles but settled on where it is pictured. I have not seen any production bikes with a set up like this but have seen many aftermarket kits for springers similar to my design. I actually thought I came up with the idea when I later found out it's actually been around for a while haha. I won't flatter myself next time. Just "google" Springer Front Brake Kit and you'll see plenty of examples. In most of them you'll see the force is the same as mine just flipped so that the force the arm undergoes is a pull rather than a push. The principal is the same though and I'll be sure to report any binding or negative feedback if it happens. If it does and as long as I survive I think I know a guy who can come up with something

 

[T8erbug]

Alright, the good news is since my last update a lot has happened. The bad news is that not a lot has happened to the 750. In fact what has happened is negative growth. Progress reversal. I cut the rear part of the frame off.. again. I have since had Ben lathe me up another shock mount and tweaked the design of the rear end again. It will all be the same except lower profile. It will give me more shock cap clearance so the heads of my shocks don't ever come in contact with the frame, lower the rear end 1/2", and change the shock angle ever so slightly. This all came about because I rushed the job the first time and one shock mount was slightly higher than the other aka slightly askew. Not something I wanted to sign my name on so I started over with revisions. This time it should be lighter and closer to perfect, however, I have finally come to accept that this bike (as much as I want it to be) will not be perfect. No bike is. It's impossible. With the aid of modern tools, jigs, shops, etc, it can be close but not perfect. I have come to terms that I will build this thing as well as I absolutely can and that it will fall short of perfect BUT if it rides down the road in a straight line and can take me through the twisties I will be happy because that's what this is all about. I lost sight of that for a while and it's made this project take twice as long as it should. I want to RIDE! She's close and I can feel it. I'm finishing this frame, throwing some temporary paint on it, making the seat, throwing the motor in and I'm riding it. Not everything will be in it's final place but that's the point. It will be done enough for now. Done enough to take out on a ride and know what I need to adjust and tweak. This upcoming winter I'll take it all apart again, powdercoat the frame, paint the bodywork, and shine it up. I may even rebuild the motor. But for now, I ride.

I also picked up a YZ490 the other day because I got it for $290. It runs like a champ and is fast enough to scare me ha so I had to buy it. I went to my local powersports store to pick up some 2-stroke oil and when my buddy who works there asked me what the oil was for I told him I picked up an old 490. He asked me if I wanted a spare motor and as I thought about it I figured it's always nice to have a spare of just about anything so I said yes. Did I mention the spare is a runner? O and I also got that spare motor for free. When I asked him how much he wanted for it he just said, "mehh.. You can have it." ANNND as if it couldn't get better .. it does. That spare YZ490 engine came with a 98' YZ125 wrapped around it almost fully built . Lucky lucky lucky. Anyways so I added a few more ponies to the corral over that last little while and that's one of the reasons I've been less busy on the GS750 as well as the fact fishing tournament season has started and I am gone almost every weekend.

No promises on when she'll be done but I am back to work on it and I'll post some new progress pics when the welding begins.

 

[posplayr]

If you are interested in frame bracing, which I did to my 1000 then this is a good read. You will find out that the only, or recommended , bracing is C, D(in red) and E.

http://www.thegsresources.com/_forum/showthread.php?t=142286&highlight="Frame+bracing"

That is about the cleanest frame bracing I have seen.

 

[posplayr]

Alright, the good news is since my last update a lot has happened. The bad news is that not a lot has happened to the 750. In fact what has happened is negative growth. Progress reversal. I cut the rear part of the frame off.. again. I have since had Ben lathe me up another shock mount and tweaked the design of the rear end again. It will all be the same except lower profile. It will give me more shock cap clearance so the heads of my shocks don't ever come in contact with the frame, lower the rear end 1/2", and change the shock angle ever so slightly. This all came about because I rushed the job the first time and one shock mount was slightly higher than the other aka slightly askew. Not something I wanted to sign my name on so I started over with revisions. This time it should be lighter and closer to perfect, however, I have finally come to accept that this bike (as much as I want it to be) will not be perfect. No bike is. It's impossible. With the aid of modern tools, jigs, shops, etc, it can be close but not perfect. I have come to terms that I will build this thing as well as I absolutely can and that it will fall short of perfect BUT if it rides down the road in a straight line and can take me through the twisties I will be happy because that's what this is all about. I lost sight of that for a while and it's made this project take twice as long as it should. I want to RIDE! She's close and I can feel it. I'm finishing this frame, throwing some temporary paint on it, making the seat, throwing the motor in and I'm riding it. Not everything will be in it's final place but that's the point. It will be done enough for now. Done enough to take out on a ride and know what I need to adjust and tweak. This upcoming winter I'll take it all apart again, powdercoat the frame, paint the bodywork, and shine it up. I may even rebuild the motor. But for now, I ride.

I also picked up a YZ490 the other day because I got it for $290. It runs like a champ and is fast enough to scare me ha so I had to buy it. I went to my local powersports store to pick up some 2-stroke oil and when my buddy who works there asked me what the oil was for I told him I picked up an old 490. He asked me if I wanted a spare motor and as I thought about it I figured it's always nice to have a spare of just about anything so I said yes. Did I mention the spare is a runner? O and I also got that spare motor for free. When I asked him how much he wanted for it he just said, "mehh.. You can have it." ANNND as if it couldn't get better .. it does. That spare YZ490 engine came with a 98' YZ125 wrapped around it almost fully built . Lucky lucky lucky. Anyways so I added a few more ponies to the corral over that last little while and that's one of the reasons I've been less busy on the GS750 as well as the fact fishing tournament season has started and I am gone almost every weekend.

No promises on when she'll be done but I am back to work on it and I'll post some new progress pics when the welding begins.

http://s1178.photobucket.com/user/t83rbug/media/temporary_zps6ef6b2a6.jpg.html

Good Luck you have made a lot of progress even if some of it was backwards but you arr close and I'm sure you will be ridding soon.