RGS front end

Yeah, he's a talker. If you accidentally start a conversation with him you'll be stuck there for half an hour minimum. Kinda the opposite to you, makes Rocket Rod look like a mute  :D :D

Nice guy though.

No worries, will pick it up sometime.
 
redax5 said:
no, is ours now, just bought the complete front end, little dearer then Fleabay but cheaper in the end as bought from Brisbane so no freight problems
Click to expand...

You probably got a better front end Red.
The one on ebay was a bit bashed around, which is probably why it was cheap. It's also another reason (apart from the freight) that I was a bit hesitant to hit the "buy it now" button.

Cheers,
Cam
 
redax5 said:
no, is ours now, just bought the complete front end, little dearer then Fleabay but cheaper in the end as bought from Brisbane so no freight problems
Click to expand...

Glad to be of help. Love helping other people spend money  :D :D
 
Just checked the regulations for P5 historic racing. Maximum allowable fork diameter is 41mm, which rules out K1100 forks (41.7mm).

Accordingly, I've shifted my search from K1100 to K75/K100. However, even that has it's complications. Those beemer models had two different fork manufacturers, Showa with 41mm forks, or Fichtel and Sachs with 41.3mm. So it needs to be the Showa version.

Question for BMW anoraks: Is there a way to spot the difference between the Showa forks, and the Fichtel and Sachs forks? I need to be able to sort out what's what on ebay.

Alternatively, I could go for something Japanese.
I found this handy reference table for fork tube diameters of Japanese bikes: http://www.caferace.com/forktubesizes.pdf
There's a whole bunch of them with 41mm forks - even some that fall within the P5 period (up to Dec 1982)

Cam
 
why don't we get Max to ask for a price and availability with Chris at the BM Shop for a 40.0mm front end
amount of time those two spent on the phone the other morning just sorting out the payment details for the 41.7mm front end, am sure Max could wrangle a better price by now
will find out



 
You might be able to get this one Cam:-

bad-crash.jpg
 
If I bend over, will someone please kick me up the arse?

I just remembered that I have a set of 41mm forks under the house. They're off my Kawasaki Z1300 which now has a sidecar and a leading link front end.

All I need now is some triple clamps, and perhaps some lighter springs (the big Kwak tips the scales ar almost 300kg)
 
Don't know whats worse,forgetting you have something or knowing you have something but not finding it
where it has lived for years.Might be a patten forming here.
 
I dragged the Kwak forks out from under the house. They're in good condition, but may not be suitable as they are leading axle type. The axle is about 30mm offset from the fork axis. I'd need triple clamps with a very small offset to make them work.

Back to the drawing board ...
 
laverdakeith said:
Fork action with Marzos or Cerrianis is always going to be compromised anyway due to the bushless design of the original fork which creates a bit of stiction, I use ActiV8 friction reducing additive in the fork oil which helps a bit. to      Keith
Click to expand...

you can convert these forks to bushings . i found a guy who can hone the fork lowers to 39 mm and machine the lower for a top bushing .

i had this done for a Swedish guy who races Ducati bevels ( Kent Jornevall  ) . he spend a fortune first a Maxton cartridge conversion . this was not up to par so later on he switched to a Ohlins cartridge .
still not happy with the fork action . i had the bushing conversion done for him and he said i really transformed the bike in a positive way


Eldert
 
Dellortoman said:
I dragged the Kwak forks out from under the house. They're in good condition, but may not be suitable as they are leading axle type. The axle is about 30mm offset from the fork axis. I'd need triple clamps with a very small offset to make them work.

Back to the drawing board ...
Click to expand...

i've got some big, longish marzos off something - no idea what - with a leading axle and the triple clamps do have quite a small offset. i'll have a better look tomorrow
 
Dellortoman said:
I dragged the Kwak forks out from under the house. They're in good condition, but may not be suitable as they are leading axle type. The axle is about 30mm offset from the fork axis. I'd need triple clamps with a very small offset to make them work.

Back to the drawing board ...
Click to expand...

they are 45s
offset 25 mm  how small do you want it????
total length more or less 94 cm
axle centre approx 77mm from bottom of leg

anyone know what they are off?
 
Preferably not leading axle. I don't want the total offset of axle from steering head axis to be significantly greater than the original steering geometry (45mm) otherwise I'd end up with reduced trail and twitchy steering. I'd prefer to err on the side of stability rather than quickness in the steering, at least as a starting point. I also want it to look reasonably similar to original and no fatter than 41mm so the scrutineers don't give me a hard time.

I found a set of Beemer forks (showa 41mm) on ebay that should pass muster. They're on their way to me as I write this.

Thanks for looking Henry

Cam
 
Good idea of Red's to use a BMW front end on the RGS frame.

The BMW K75 forks and triple clamps that I bought on ebay arrived yesterday. This morning I put the lower triple clamp with steering stem into the RGS steering head, mainly just to check the the stem length. It still has the beemer's tapered roller bearing on it and lo and behold, the bearing sat perfectly into the outer bearing cup in the frame. That's a bit of a surprise I thought, so I put the top bearing in and it did the same. When I screwed the nut town to seat the bearings home, the internal locking bolt (that I hadn't moved) seated just as the bearing took up, indicating that the steering head bearing spacing is also identical to the Beemer's. The steering stops on the lower clamp also lined up with the stop lug on the frame, and worked perfectly. Even the RGS steering lock lines up with the locking hole in the beemer steering stem!! The bearings move smoothly so I reckon I'll simply re-grease them and use them as they are.

I had anticipated having to make a new stem, lengthen the headstock, find some different bearings, or some other alterations to make it fit together. I couldn't believe it was so simple. Basically a bolt on fit with no modifications whatsoever.

As for steering geometry, I haven't measured it precisely yet but it looks pretty damn close. The Beemer clamps have slightly greater forward offset than the Laverda ones, but the axle is behind the centreline of the forks by about the same amount, so the trail should end up pretty much the same.

The only alterations necessary will be to accommodate a different sized axle. The Beemer axle is 25mm diameter and the bearings in the RGS wheels have a 20mm ID. My bearing book doesn't list a 25 x 42 x 12 ball bearing so it might require some minor juggling to fit the larger axle to the wheel. The bearing book does list a 25 x 42 x 9, or a 25 x 47 x 12, so If I can't find a suitable bearing from another source, I'll either need to make up some spacers to fit the narrower bearings or machine the wheels out to 47mm diameter. I'm leaning towards the former option because the wheel diameter is more than I can swing on my lathe.

Now that I know I don't have to muck about with the steering head, I can get on with the job of frame stiffening.

Cheers,
Cam
 
Dellortoman said:
Good idea of Red's to use a BMW front end on the RGS frame.

I had anticipated having to make a new stem, lengthen the headstock, find some different bearings, or some other alterations to make it fit together. I couldn't believe it was so simple. Basically a bolt on fit with no modifications whatsoever.
Click to expand...

not my idea, as stated before, it came from Andre the Swift who will be at Spa this coming meeting with his new Laverda track bike complete with BMW front end

MarkQLD and I looked at the K1100 front end that I bought in Brisbane but that is about as far as we went with it, too many engines to get through
is a future project so am glad that it is going to be an easy fit up by the sound of it
we will be mounting a Suzuki front wheel to it so our bearing issues are different to yours and I also plan on getting some CNC machined top triple clamps made to replace the BMW unit that has the rubber mounted handle bar provision on it that we will not be using
plan to spend some time working on the triple clamp next break in August




 
Dellortoman said:
The only alterations necessary will be to accommodate a different sized axle. The Beemer axle is 25mm diameter and the bearings in the RGS wheels have a 20mm ID. My bearing book doesn't list a 25 x 42 x 12 ball bearing so it might require some minor juggling to fit the larger axle to the wheel. The bearing book does list a 25 x 42 x 9, or a 25 x 47 x 12, so If I can't find a suitable bearing from another source, I'll either need to make up some spacers to fit the narrower bearings or machine the wheels out to 47mm diameter. I'm leaning towards the former option because the wheel diameter is more than I can swing on my lathe.

Cheers,
Cam
Click to expand...

Somewhat confused here. If the RGS axle is 20mm, Beemer is 25mm why not just sleeve the Beemer fork clamps to suit the 20mm RGS axle? Then you can use the original RGS axle, wheel bearings & etc.
 
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