Author Topic: CR750 / Dick Mann replica - replica front forks from GL1000 forks ?  (Read 32484 times)

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Offline lordmoonpie

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Re: CR750 / Dick Mann replica - replica front forks from GL1000 forks ?
« Reply #100 on: November 09, 2010, 03:15:13 AM »
Sam, Mark - this 'dispute' is in itself a part of the history of CR750s, RC750s and CB750Rs - we really should break this out into a separate thread and let it run. Regardless of what you think of the different perspectives, the views are historically and first hand relevant to the overall subject.

Can you split it out so we can leave Sander's fork topic alone and still allow the sub-thread to be explored?
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Offline Sam Green Racing

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Re: CR750 / Dick Mann replica - replica front forks from GL1000 forks ?
« Reply #101 on: November 09, 2010, 04:54:15 AM »
Problems at work at the moment, I'll do it at home tonight, in the meantime It's locked.

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Offline lordmoonpie

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Re: CR750 / Dick Mann replica - replica front forks from GL1000 forks ?
« Reply #102 on: November 09, 2010, 11:56:36 PM »
all i did was make some pvc spacers and fit the forks to the bike.
:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
What were the pvc spacers for Patrick - extra preload or did they fit somewhere else? Seems an odd material to use for something other than preload so intrigued as to where you applied them?
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Offline lordmoonpie

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Re: CR750 / Dick Mann replica - replica front forks from GL1000 forks ?
« Reply #103 on: November 10, 2010, 01:23:06 AM »

you guessed correctly, simon -- the pvc spacers were for spring preload. i seem to recall they were about 20mm in length. again, al my notes, sketches, and drawings are back in alexandria; so, i don't have the specifics here. and, yes, pvc isn't normally a material one would want around a racebike. it was fine in this particular application, however -- expedient, easily sawed and finished, and disposable enough to not worry about trying various lengths... which i don't recall ever doing, actually.

regards,
patrick
Thanks Patrick - makes a lot of sense in that application. I suppose in these modern times the solution would be something like the aftermarket pre-load adjusters that Kevin sells (TTR400), however the pvc is a nice simple solution as you say.  ;)
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Offline CR750

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Re: CR750 / Dick Mann replica - replica front forks from GL1000 forks ?
« Reply #104 on: November 10, 2010, 03:14:55 AM »

Hi Patrick,

Setting up the forks changes from bike to bike anyway, I think I know the basic procedure he did then.
Was just inquiring if he had any 'magic' touches ( other then the common tips and tricks on forks ).
I'll get to that part after I have the welding done on the GL forks ( first need to find good donors ).
A quick test with some scrap f2 forks looked ok to the eye, but I want to have it x-rayed somewhere to see how good it actually is.

1) When you used the GL1000 forks which year did you use and which brake calipers did you use ?
2) Do you have any pics on the original cr750 bike of Dick Mann you would like to share in this thread/with us?

FYI:
I've seen the PVC spacers used many times.
For the exact reasons you both mention: cheap, light weight, easy to saw etc. which allows for easy swapping and testing.
Although the more 'fancy' pre-load adjusters like at ttr's are of course the quickest way as you don't have to open your forks every time you adjust.

I also use a bit of pvc pipe from the local hardware store for putting in fork seals for instance for the same reason. Usually you can find some with an internal diameter that fit's your fork, and otherwise;
Too large: cut it twice length wise to make it fit ( take out part you don't need and bend it close with 2 tywraps around it around it to the correct diameter.
Too small: cut it once length wise to make it fit and bend it open a bit.
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Offline Sam Green Racing

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Re: CR750 / Dick Mann replica - replica front forks from GL1000 forks ?
« Reply #105 on: November 10, 2010, 04:01:43 AM »
I really like PVC ::) ::) ::)









































it makes super cable ties. :D :D   not really a hyjack ;)
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Offline Bill/BentON Racing

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Re: CR750 / Dick Mann replica - replica front forks from GL1000 forks ?
« Reply #106 on: November 10, 2010, 06:02:25 AM »
Welcome aboard.Comunication is what we desire.Civility should be a given! We realize and respect your knowledge and insight and look forward to more posts....PVC was used a lot for fork spring spacers...and worked well.Thanks and get back over and dig out more info and get one of your projects going and post! ;) :D,Bill
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Offline CR750

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Re: CR750 / Dick Mann replica - replica front forks from GL1000 forks ?
« Reply #107 on: November 10, 2010, 06:06:02 AM »
Quote
jeez! we're actually communicating here -- well... you, moonpie, and i, anyway -- in civil tones.

We always did/do that over here 8); glad your contributing to the Forums and my thread. And although I share your enthusiasm about this fact, might I make a friendly request from my side; please think these things but not write them down, as they might be taken personal (even if you not intended them to) and start the whole off topic thingy again. Thank you.


Quote
why are you intent on welding on your forks?

Please read this thread from the start as that is probably quicker then me typing the whole thing ;D I short.... I want to make an replica of the Dick Mann bike and the Gl1000 forks are a pretty close match to the very unobtainable titanium version (my pockets are not that deep). My goal is to make it look correct as far as the outside is considered to the original. So this would require welding on the proper caliper stays as the cb750 calipers with fins are of course not liking the gl 1000 orientation.

Quote
1. if memory serves, the forks were '78 goldwing parts. i do definitely recaall that they were the model year (or years) where the tubes and sliders had a lot of overlap -- i.e., long sliders. i used a larger diameter axle, the small end being the same diameter as he large end of a cb750 front axle. the large end of the larger diameter axle required me to make a stouter axle cap from solid using the stock cap as both a template and drill guide. the slider and cap had to be bored, which required just nipping into the cap studs (just into the threads, i think; so, no loss of strength, really). that will give you an idea of how large the axle was. i made aluminum spacers as required and, again if memory serves, the wheel bearings were vfr 750 parts with the larger required i.d. (same o.d.). the calipers were the newer versions of the classic old style lockheed caliper (CP2696) with pads provided by jeff gehrs (sp?). i fabricated 2024 aluminum brackets that adapted the lockheed hole centers to the lugs on the gl forks and the 296mm disk. i have the cad drawings for the brackets on my computer, if that's of interest (i can convert the dwg file to a jpg). everything was bolted up using 10mm countersink bolts inserted from the inside of the forks through appropriate aluminum spacers positioned between plate and caliper in order to center the throat of the latter on the disk. i might be able to provide a reasonable close up of the arrangement, if you can tell me how to insert an image in a post.

Brilliant detailed information, thank you for that.

Quote
i also have a couple of shots of the bike that was on display at the paris show in the fall of '70 (right after the bol d'or). i was there at the time (touring europe with my first wife on a cb350 sent over in a crate!), but i wasn't a journalist and had to limit myself to whatever shots i could get through the acrylic display case enclosing the bike. if i had only known! i could certainly have arranged access to the bike after the show and could have taken shots that would answer many questions now. there's a tremendous amount of history surrounding the daytona bikes that went to france; a longer history, in fact, than in the u.s., as they were raced repeatedly. i've interviewed practically everyone involved and learned a great deal by cross checking, but there remains a lot of mystery... which is just fine, really!

Any of that info and shots is very interesting to me as I am compiling a database of knowledge on the bike. You can Pm me if you want to share those, or post them on here ( but you have to resize big images)

Quote
3. pvc. i made a set of 4 really swell ring compressors for my 750 from apprpriately sized pvc pipe. the material is nice and gentle on the rings and allows things to slide easily, which is useful in starting all 4 pistons into their bores at the same time. i seem to recall them being about 3/4'' in length with a single slot hacksawed lengthwise, so as to spring them open around the connecting rods. minimally tightened hose clamps closed everything up just right. i may have had to modify the i.d. on my lathe... i'm  not sure. again -- cheap and expedient.

We should start a PVC fanclub  ;D. I frequent some bike forums on the internet and always like to check the homemade tools sections. Brilliant time and money savers are to be found in those.


Sander

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Offline lordmoonpie

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Re: CR750 / Dick Mann replica - replica front forks from GL1000 forks ?
« Reply #108 on: November 10, 2010, 09:54:05 AM »
i don't think cable ties are made out of pvc, sam. i think, mostly, they're made out of nylon...

maybe you just like plastics. i do. i hate it when someone proclaims: ''that's no good; it's plastic!''.

i guess we'll have to talk about the honda works-daytona-rc-cr-replica-kit-counterfeit-franco-nippo-american pvc forks to steer this back on topic!


You'll get used to Sam, Patrick - he's very special to us, almost a cultural relic all by himself so you learn to smile at his proclivities! However, I would caution against mentioning nylon to him....Sam and nylons are not something to start conjuring images up with ;D

I did see some plastic toothed wheels used as camchain tensioners on smaller SOHCs, a 350 in particular I think. It wasn't teflon and would break down over a period of a couple of years but the guy who used them swore that it lengthened camchain life. I couldn't see the logic myself - buy a new camchain and replace every two years whetehr it needed it or not OR, open the cases to replace the camchain tensioner wheels after having machined new ones yourself. Would have loved to know what the material was though as it seemed to withstand a lot of engine abuse and could be useful as slipper tensioner blade material in a 750...

Out of interest Sander - what are you using/planning for your camchain tensioning arrangements? (Please don't mention nylon though, Sam is lurking... ;))
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Offline CR750

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Re: CR750 / Dick Mann replica - replica front forks from GL1000 forks ?
« Reply #109 on: November 12, 2010, 01:14:05 AM »

Hi Patrick,

brilliant info !
And thank you for the time travel pictures !
This thread is about the forks, but in the end I need as much info as I can get to be able to work over the entire bike.

What I find very interesting is some other detail:

If I look closely on the image of he Paris show I notice there is a transparent cover over the white nose area where the number is ? I have never seen that before/ been able to make that out on any of the other low res pictures... Maybe you can shed some light on that ?
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Offline voxonda

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Re: CR750 / Dick Mann replica - replica front forks from GL1000 forks ?
« Reply #110 on: November 12, 2010, 01:37:45 AM »
Here a well known pic of the bike at the Bol d'or, ridden by famous Morio Sumiya: See the headlight?

Next to ride it was french star driver Christian Bougeouis:

Look closely at the numberplate, you can see the rivets(?) which keep the cover in place.


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Offline cbrfunk

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Re: CR750 / Dick Mann replica - replica front forks from GL1000 forks ?
« Reply #111 on: January 10, 2011, 08:29:53 AM »
hello,
First time poster from Winnipeg Canada...Trying to set up my own set of CR750 replica(ish) front end.
Have the dual front disc and fork set up (with cb750K forks). I have been trying to find the original length of the CR750 forks, I have been assuming that the tubes are shorter than the standard 23" for the race set up but maybe I am wrong? Can anyone enlighten me with the actual length of the CR750 front forks and tubes so I can attempt to modify/replace my current forks/tubes?

Thanks,
Chris

Offline H2Eric

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Re: CR750 / Dick Mann replica - replica front forks from GL1000 forks ?
« Reply #112 on: January 11, 2011, 01:45:26 AM »
hello,
First time poster from Winnipeg Canada...Trying to set up my own set of CR750 replica(ish) front end.
Have the dual front disc and fork set up (with cb750K forks). I have been trying to find the original length of the CR750 forks, I have been assuming that the tubes are shorter than the standard 23" for the race set up but maybe I am wrong? Can anyone enlighten me with the actual length of the CR750 front forks and tubes so I can attempt to modify/replace my current forks/tubes?

Thanks,
Chris

Hi Chris and welcome to the forum
I believe that the headstock on the works CR750 was lower (by about an inch) with respect to rest of the frame when compared with a standard frame. This allows the ground clearance to remain the same, but the forks were shorter (saves weight). Chopping your fork tubes will lead to less ground clearance, perchance this is not a good idea, unles you are the lucky ower of a works frame.
There is some pics of what was believed to be a works frame on page 20 of The 1970 Daytona CR750's thread.

Regards
Eric
« Last Edit: January 11, 2011, 01:57:48 AM by H2Eric »
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Offline Sam Green Racing

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Re: CR750 / Dick Mann replica - replica front forks from GL1000 forks ?
« Reply #113 on: January 11, 2011, 02:01:12 AM »
Hi Eric and welcome Chris, you can see the difference in the two head stocks half way down this page.

http://forums.sohc4.net/index.php?topic=27902.475

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Offline cbrfunk

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Re: CR750 / Dick Mann replica - replica front forks from GL1000 forks ?
« Reply #114 on: January 11, 2011, 05:35:05 PM »
thanks guys,
Still took me a while to actually figure out the differences. My tubes are in K forks and a full 1.5" shorter than stock and I am fitting them to an F2 frame so i will have to do some measurements to see what clearance I will have. I just fitted a billet aluminum triple tree from CycleX to the frame but not sure if that is going to change the measurements at all.

thanks again for the input.

Chris

Offline ttr400

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Re: CR750 / Dick Mann replica - replica front forks from GL1000 forks ?
« Reply #115 on: July 03, 2011, 09:52:52 AM »
A couple of pics of my replica 4 bolt cap fork lowers. this was my first go at this, not perfect but I am happy with the end result. Might do another set with the 35/37mm tubes.

This is a mock up to test etc and the testing of the fender, unfortunatly I will have to make new fender brackets as these touch the tyre.

Kevin



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Offline CR750

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Re: CR750 / Dick Mann replica - replica front forks from GL1000 forks ?
« Reply #116 on: July 04, 2011, 02:54:31 AM »
Hey Kevin,

looks nice, did you use the xl350 forks like you intended, or the GL1000 legs like I was after ?
You did weld the parts to the lower legs anyway  - so  no issues with distortion ?

I still have this conversion on my to do list; so would be interested to hear about what went like planned and what did not.
My firstborn got in the way of progress after I did initial welding tests, and progress on the CR has been very slow since this thread.
In the meantime I did acquire some other much looked after parts, amongst others the correct 160 psi oil pressure gauge, and I just visited Bikers Classics this weekend for some motivation to start squeezing in some workshop hours in my very busy days..

« Last Edit: July 04, 2011, 02:59:27 AM by cr750 »
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Offline CR750

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Re: CR750 / Dick Mann replica - replica front forks from GL1000 forks ?
« Reply #117 on: July 24, 2011, 10:49:35 AM »
PM-ed reply by Kevin ( published with his permission ) to keep info alive for the SOHC community:



Hi, Sorry for the delay, been a bit hectic here.

Yes I did use the XL350 forks. shortened the tubes and welded the lugs to the legs. no real issues and no distortion, small amount on the inside which was cleaned up without issues.
I am going to be doing another set shortly for a customer in Italy, this time I will CNC the lugs etc. I might look into having them cast in magnesium later. will also be turning up the tubes 35/37 like the CR, but not in Titanium..!!

Still waiting for my 160psi oil gauge from the UK.

Regards Kevin
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