Topic: 1971 CB750 with GSXR Front End

[SOHC4 Cafe Racer Fan]

It's coming along nicely.  Devin's oil tank looks sharp, and I'm sure it will look good on your 750.

[GNGSXR]

Picked up another 07 GSXR 750 front end for my 1980 CB750.


My shocks arrived.

[Tews19]

Those are some fancy rear shocks!

[raymond182]

Seeing your problem with the fork hitting the tank and not having a good turning radius, it screams back if it was easy, you'd see a lot more custom bikes than you do.  If you're going to the trouble of having someone make a custom triple tree, have them make one that will actually work on your bike.  I've played around with various forks and found the 89-90 GSXR fork works best at getting the turning radius within reasonable bounds.  You may have to play with the fork stops but that fork is not as radical as the triple tree you now have.   Unfortunately, I've been where you are and learned from it the hard way too.  Good luck
Johnny

I didn't commission the top triple tree to be made specifically for my application. It's a piece meant for these type of "popular" front end conversions.
The turning radius is still in reasonable bounds. Not any worse than my race bike haha.

While the turning radius may still be workable, the trail is now well over 4 inches, thats the main reason triple clamps with a similar offset to the 750/4 should be used, less offset = more trail= slower steering... With the combination of more trail and a 17 inch front wheel the bike will be more stable in a straight line but will feel like it wants to "fall" into or "flop" into corners, this should be more prominent at lower speeds,  the 17 inch wheel is working against the slower steering geometry. The 17 inch wheel steers quicker than the stock 19 inch and now the trail is contradicting this, its trying to work against itself. I am having custom clamps made up for all 3 of my 750's and will run 18 and 19 inch front wheels  due to this problem. For the GSXR front end to work without modification,  the swingarm pivot to steering head measurement would have to be similar to the Gixxer and share its rake, it all gets a bit complicated but thats roughly how it works....

Could never quite understand all this esoteric talk about the trail  and rake bs...I have a USD front end on my '72 CB500 with a19" front wheel and 18" in the back. The bike handles beautifully and hugs the surface, as well as the corners, just right. And, of course, being actually able to stop is worth any potential sacrifice in handling if there indeed is one.

[Retro Rocket]

Seeing your problem with the fork hitting the tank and not having a good turning radius, it screams back if it was easy, you'd see a lot more custom bikes than you do.  If you're going to the trouble of having someone make a custom triple tree, have them make one that will actually work on your bike.  I've played around with various forks and found the 89-90 GSXR fork works best at getting the turning radius within reasonable bounds.  You may have to play with the fork stops but that fork is not as radical as the triple tree you now have.   Unfortunately, I've been where you are and learned from it the hard way too.  Good luck
Johnny

I didn't commission the top triple tree to be made specifically for my application. It's a piece meant for these type of "popular" front end conversions.
The turning radius is still in reasonable bounds. Not any worse than my race bike haha.

While the turning radius may still be workable, the trail is now well over 4 inches, thats the main reason triple clamps with a similar offset to the 750/4 should be used, less offset = more trail= slower steering... With the combination of more trail and a 17 inch front wheel the bike will be more stable in a straight line but will feel like it wants to "fall" into or "flop" into corners, this should be more prominent at lower speeds,  the 17 inch wheel is working against the slower steering geometry. The 17 inch wheel steers quicker than the stock 19 inch and now the trail is contradicting this, its trying to work against itself. I am having custom clamps made up for all 3 of my 750's and will run 18 and 19 inch front wheels  due to this problem. For the GSXR front end to work without modification,  the swingarm pivot to steering head measurement would have to be similar to the Gixxer and share its rake, it all gets a bit complicated but thats roughly how it works....

Could never quite understand all this esoteric talk about the trail  and rake bs...I have a USD front end on my '72 CB500 with a19" front wheel and 18" in the back. The bike handles beautifully and hugs the surface, as well as the corners, just right. And, of course, being actually able to stop is worth any potential sacrifice in handling if there indeed is one.

Well its nice you think your opinion trumps fact , maybe your time would be better spent researching the subject instead of just calling it BS, especially on a forum full of people that know better. Good brakes do NOT make up for handling problems and whoever told you that is an idiot. Your bike with the GSXR clamps will have more trail, now if you knew what that meant you would find that it slows the turn in response of the bike, making the steering a little slower but also making the bike a bit more stable in a straight line, the problem with the straight GSXR conversions is a lot use the 17inch wheels which want to turn in faster in a bike that now steers slower, this makes the bike want to fall into corners. if you "think" its all BS, why did you even bother commenting..? Posts like that just make me laugh....   Oh and most people that "think" a bike handles well wouldn't have a clue anyway....

[raymond182]

My "opinion," mate, is based on a fact--I actually ride one unlike most, if not all, of the people who supposedly "know better." But let's not highjack the thread, it is not polite.
Cheers.

[Retro Rocket]

Seeing your problem with the fork hitting the tank and not having a good turning radius, it screams back if it was easy, you'd see a lot more custom bikes than you do.  If you're going to the trouble of having someone make a custom triple tree, have them make one that will actually work on your bike.  I've played around with various forks and found the 89-90 GSXR fork works best at getting the turning radius within reasonable bounds.  You may have to play with the fork stops but that fork is not as radical as the triple tree you now have.   Unfortunately, I've been where you are and learned from it the hard way too.  Good luck
Johnny

I didn't commission the top triple tree to be made specifically for my application. It's a piece meant for these type of "popular" front end conversions.
The turning radius is still in reasonable bounds. Not any worse than my race bike haha.

While the turning radius may still be workable, the trail is now well over 4 inches, thats the main reason triple clamps with a similar offset to the 750/4 should be used, less offset = more trail= slower steering... With the combination of more trail and a 17 inch front wheel the bike will be more stable in a straight line but will feel like it wants to "fall" into or "flop" into corners, this should be more prominent at lower speeds,  the 17 inch wheel is working against the slower steering geometry. The 17 inch wheel steers quicker than the stock 19 inch and now the trail is contradicting this, its trying to work against itself. I am having custom clamps made up for all 3 of my 750's and will run 18 and 19 inch front wheels  due to this problem. For the GSXR front end to work without modification,  the swingarm pivot to steering head measurement would have to be similar to the Gixxer and share its rake, it all gets a bit complicated but thats roughly how it works....

Could never quite understand all this esoteric talk about the trail  and rake bs...I have a USD front end on my '72 CB500 with a19" front wheel and 18" in the back. The bike handles beautifully and hugs the surface, as well as the corners, just right. And, of course, being actually able to stop is worth any potential sacrifice in handling if there indeed is one.

Well its nice you think your opinion trumps fact , maybe your time would be better spent researching the subject instead of just calling it BS, especially on a forum full of people that know better. Good brakes do NOT make up for handling problems and whoever told you that is an idiot. Your bike with the GSXR clamps will have more trail, now if you knew what that meant you would find that it slows the turn in response of the bike, making the steering a little slower but also making the bike a bit more stable in a straight line, the problem with the straight GSXR conversions is a lot use the 17inch wheels which want to turn in faster in a bike that now steers slower, this makes the bike want to fall into corners. if you "think" its all BS, why did you even bother commenting..? Posts like that just make me laugh....   Oh and most people that "think" a bike handles well wouldn't have a clue anyway....

I dont know what the argument is about but a GSXr front end with the 17" rim definitely reduces trail. Not increase.

Thats a common misconception GNG, reducing offset, as in the GSXR clamps have a reduced offset, 30mm as opposed to 60mm for a cb750k ,When the forks are moved closer to the frame as in with a GSXR set of triple clamps, the trail is actually bigger, not smaller, i was discussing this very thing in another thread yesterday with bwaller, he races a 550, ask any of the racers on the forum mate, actually, I have a rake and trail converter if you are interested, you can find out how much trail you have by putting in rake, and offset, giving you the trail any combination of rake and offset you have... I can absolutely garantee you that smaller offset gives you MORE trail...

[Retro Rocket]

Here you go, in this link go to the last post from Ewan, click on the trail calculator at the bottom of his post, when it opens up, go to where it says "offset" it is 45mm , double click on the 45mm, backspace it out and type in 30mm and hit enter ,  the trail goes from 90.93mm to 107.29mm, which is quite a large jump up in trail....

http://forums.sohc4.net/index.php?topic=138100.msg1559172#msg1559172

Don't worry, a lot of people think less offset = less trail, its the exact opposite...

[GNGSXR]

Here you go, in this link go to the last post from Ewan, click on the trail calculator at the bottom of his post, when it opens up, go to where it says "offset" it is 45mm , double click on the 45mm, backspace it out and type in 30mm and hit enter ,  the trail goes from 90.93mm to 107.29mm, which is quite a large jump up in trail....

http://forums.sohc4.net/index.php?topic=138100.msg1559172#msg1559172

Don't worry, a lot of people think less offset = less trail, its the exact opposite...

First of all YES you are correct. If You use the 19" rim and toss the GSXR front end with the 30mm offset onto the bike you will increase trail by a large margin. I have no intentions of ever using such a behemoth of a rim on any of my bikes though.

The exact procedure you are describing with the use of this lovely excel program is describing all things being equal except for the GSXR fork swap. Same 19" rim and no other modifications which is why your numbers are drastically different stock 90.93mm to gsxr dummy swap(w/ 19"rim) of 107.29mm. You have to consider that I am changing more variables than what you are describing.

Measured in the real world the stock trail on my particular CB750 is ~94mm. This is stock 19" rim with whatever is left for tread on the tire, 60mm fork offset, 27 degree headstock rake angle, 63 degree caster angle.
All stock but swap the GSXR front end 30mm offset would give you a ~130mm trail. stupid unless you are building a chopper.

I am using a 17" rim, 30mm gsxr fork offset, 23 degree headstock rake angle, 67 degree caster angle (due to my back end being raised). This gives me a trail of about ~94.5mm. yes i've increased trail slightly but not to the extent that you are describing. My trail length is in a perfect area to create a well performing bike but that is still up for debate until I actually get to ride the bike.
 

[calj737]

No disrespect GNG, but it sounds as though you're actually arguing for the same point as Retro. He is correct, and you've verified that. He did not state (at least where I've read) that your changes (the sum of them) would in any way reduce handling. On the contrary, his point on this matter is often exactly to perform the array of changes you are to restore the bikes original steering geometry.

I believe his comments were more directed at another poster who using anecdotal opinion over math to state their position about the handling of a bike. I think anyone would agree that your bike is definitely heading in a very desirable direction with respect to all the changes.

I will say this: the perception of a rider's comfort does matter as despite the math, most riders never use a motorcycle on the streets in a way that would uncover the true limits and foibles of geometry limits. Some will, definitely. But many spend way too much time going straight on a road-race inspired rocket and little time dragging their knee. It's quite an anathema as to why then they buy/build this style of bike.

Apologies for a thread-jack

[GNGSXR]

No disrespect GNG, but it sounds as though you're actually arguing for the same point as Retro. He is correct, and you've verified that. He did not state (at least where I've read) that your changes (the sum of them) would in any way reduce handling. On the contrary, his point on this matter is often exactly to perform the array of changes you are to restore the bikes original steering geometry.

I believe his comments were more directed at another poster who using anecdotal opinion over math to state their position about the handling of a bike. I think anyone would agree that your bike is definitely heading in a very desirable direction with respect to all the changes.

I will say this: the perception of a rider's comfort does matter as despite the math, most riders never use a motorcycle on the streets in a way that would uncover the true limits and foibles of geometry limits. Some will, definitely. But many spend way too much time going straight on a road-race inspired rocket and little time dragging their knee. It's quite an anathema as to why then they buy/build this style of bike.

Apologies for a thread-jack

Yeah I was initially wrong. Retro was right to a certain degree. Trail does increase but not as drastic as Retro was describing in my swap. I just wanted to make it clear for anyone else coming across this that there is a correct way to do this swap and make the bike handle "better".

[Retro Rocket]

No disrespect GNG, but it sounds as though you're actually arguing for the same point as Retro. He is correct, and you've verified that. He did not state (at least where I've read) that your changes (the sum of them) would in any way reduce handling. On the contrary, his point on this matter is often exactly to perform the array of changes you are to restore the bikes original steering geometry.

I believe his comments were more directed at another poster who using anecdotal opinion over math to state their position about the handling of a bike. I think anyone would agree that your bike is definitely heading in a very desirable direction with respect to all the changes.

I will say this: the perception of a rider's comfort does matter as despite the math, most riders never use a motorcycle on the streets in a way that would uncover the true limits and foibles of geometry limits. Some will, definitely. But many spend way too much time going straight on a road-race inspired rocket and little time dragging their knee. It's quite an anathema as to why then they buy/build this style of bike.

Apologies for a thread-jack

Yeah I was initially wrong. Retro was right to a certain degree. Trail does increase but not as drastic as Retro was describing in my swap. I just wanted to make it clear for anyone else coming across this that there is a correct way to do this swap and make the bike handle "better".

You misread what i was saying, I was only using what the calculator already had on it as an example of what offset did, I never used your numbers.. , you also need to take into consideration the 17 inch wheel , smaller wheels have different handling characteristics to the 18 or 19, so while the rake trail and offset are very important, so is the effect a 17 inch wheel adds to the equation as does swingarm length and swingarm pivot to steering head position. You race don't you..? I will be curious to see what you think when its all up and going....

[GNGSXR]

Today was my previously set deadline for finishing this build. I've failed. oh well. Im still going at it just at a snails pace.

I received cognito moto's oil can. It is a great piece that is built extremely well. It'll also hold a bit more oil over stock. I wish it was aluminum but then again I probably wouldn't of wanted to pay the cost difference for aluminum over steel. I welded permanent tabs to the frame instead of using the provided clamps. The clamps make this tank a complete bolt on kit assuming you are relocating your electronics. It will even fit with the stock air box in place.



I was in the process of doing a pre-final assembly to mark remaining tabs that need to be cut off, make sure everything fits, works properly before powder coat and paint. Glad I did cause I need to do some modifications to the left side. I don't have clearance with the fox shocks and the huge nighthawk hub assembly. I knew this would be an issue but forgot to correct it before. A quick pass on a mill with the hub or a small modification to the bottom clevis mount should fix it. 

[reedrunner23]

Any measurements on the rear axle spacers? I have a DOHC model but just wanted to get an idea. I have the same CBR rim with a 160 tire.

[SOHC4 Cafe Racer Fan]

It looks like you are getting pretty close to PC and paint.  Are you going to detab the frame?  I noticed that you still have the mounts for the side covers and centerstand.

[Tews19]

Looks good!

Reed welcome fellow Wisconsinite! I'm just north of you and have a 550 gsxr build going on right now.

[GNGSXR]

Any measurements on the rear axle spacers? I have a DOHC model but just wanted to get an idea. I have the same CBR rim with a 160 tire.

I'll try and get measurements this weekend. The right side spacer is larger than the left if that helps any haha

[GNGSXR]

It looks like you are getting pretty close to PC and paint.  Are you going to detab the frame?  I noticed that you still have the mounts for the side covers and centerstand.

I am close to stripping it down for powder coat and paint but I am still sort of clueless on what colors I will do.
Most of the tabs have been removed. I've left a few such as the tabs above the air filters for maybe mounting some stuff and the stock rear fender "slots" for maybe making a custom fender. The seat pan bolts will get trimmed down as well.


I also got my seat custom made and picked it up a while ago.   

[GNGSXR]

I may splurge and get an m-unit V.2 for the this bike. I spent way more than I wanted to on rear shocks so why not blow more money on what seems to be an awesome backbone for the wiring system!?!?!?!

Some info on it if no one is familiar
https://www.youtube.com/watch?v=zdIeh2c6O5c
More details on it
https://www.youtube.com/watch?v=HNF-h6oBczg

I was also looking at my big chunky plastic GSXR hand controls and would much rather have smaller simpler button housings like this
http://cognitomoto.com/collections/motogadget/products/m-switch-3-push-button-housing-7-8-black-silver

Thoughts, opinions, or should I go back to buying good quality groceries instead of buying bike parts?

[SOHC4 Cafe Racer Fan]

It's only money.

The upholstery looks great.  How is the pan secured to the seat? 

Color choice is such a subjective thing but a great way to put your stamp on the bike.  Are you thinking of a colored PC for the frame or leaving the color to the body work?

[calj737]

Definitely use the MotoGadget products anywhere you can. You'll never regret it.

[SOHC4 Cafe Racer Fan]

Definitely use the MotoGadget products anywhere you can. You'll never regret it.

I am excited about incorporating them into my next builds.  It's like the Sham Wow commercial: "It's made in Germany.  You know the Germans always make good stuff!"

http://youtu.be/dYvP_bCnS2I

[GNGSXR]

Definitely use the MotoGadget products anywhere you can. You'll never regret it.

I am excited about incorporating them into my next builds.  It's like the Sham Wow commercial: "It's made in Germany.  You know the Germans always make good stuff!"

http://youtu.be/dYvP_bCnS2I

I'd love to get these turn signals but then I realized they were sold individually. Maybe I'll get drunk one night and accidentally order them.
http://cognitomoto.com/collections/lighting/products/motogadget-turn-signal-m-blaze-disc

[SOHC4 Cafe Racer Fan]

Those DO look pretty cool.  I'm not completely sold on their effectiveness.  I'm wondering how much they might get covered/obscured with your hands and forearms, BUT they sure look awesome.

[calj737]

I've got a pair waiting to go my BMW and my 572 build, and maybe the 500. As for their effectiveness, they're at the end of the bar, so I don't see the interference, except, maybe from the rear.