single rotor conversion questions for '82 xj750 seca

hi all.

i have a '82 750 seca and the front vibrates under braking. i have not measured the rotors but i assume theyre crooked a bit. from what i have read the rotors are virtually impossible to get straight, so getting new ones is the only option.

well it came to my mind that i could use a radial master cylinder on the handlebar, and route braided lines down to a single caliper, forgetting the anti-dives (more on that later) and custom fitting a nice four piston superbike caliper.

then i found this:



from here: ABM

the chart says it fits xj750 year models 83 to 86.
now the big question is would there be any possibility of that fitting onto my seca? can i use a dual rotor wheel with only one rotor?

i dare believe this setup would have sufficient stopping power for a soon-to-be heavily lighteded xj.

the process also includes the rebuild of my air-assisted front forks. i'm hoping to get rid of the anti-dives and the air valves. on the board i have read a bit about fitting the stiffer progressive springs and disabling the anti-dive, but i cant seem to find any decent threads about that issue.
i want to know is it possible to loose the air valve?
also need info about disabling the anti-dive system. does it fully disable by removing the units and blocking the holes or will doing that leave something loose inside the fork? or what?




help anyone? insights? ideas? links perhaps?

 

Before you go buying all those parts and doing all those mods, try researching a GSXR 750 front end swap that, IIRC, takes a different (available) headset bearing, has larger fork tubes and better brakes.

All problems solved in one go.

 

A good machinest can true your rotors, mine cost me 30$ each. After machining they are still within specs for thickness. Maybe not the best route but it works for the budget minded. Installed new pads and no more vibration. Used rotors can be found on EBAY but they may also have the same problem.
Send Chacal a PM , he has replacement EBC rotors.
Have you tried cleaning the rotors real good with brake cleaner. The vibration may be from dirt/grease spots on the rotors.

 

timetoride, thats a nice idea, but i want to keep my old front wheel.

mlew, i have a machinist nearby, i phoned him and he said rightaway he wont do motorcycle rotors. said they vibrate and wont come out good. he said he would do car rotors, so i mentioned my rotors arent floaters and he told me to bring them over.

the question still remains

are the brake rotors different on the 83-86 xj750 than on my 82 750 seca?

 

Find a automotive preformance machine shop. The guys there said my rotors were similar to his race cars rotors and they would be no problem. The one near me used a flywheel cutting rig to do mine. I don't know if the rotors are interchangable. I have used BikeBandit.com to check part numbers to see if they are the same from year to year.

 

rrriiight. the fourth shop i took the rotors in was willing to give it a go. see what the results are when i get them back.


im still thinking about incorporating that abm rotor. see what comes out of that plan




nobody else is intriqued with this mod???
only few replies and both suggest i should do something else than what i asked about. feels like im on the wrong board because i dont want to keep my bike stock.




or what

 

ok. i'll just have a monologue here about the single.

the front wheel is the same part number for the '83 xj750 and '82 xj750 seca. so wouldnt the rotor for '83 model then fit to the '82 wheel but not necessarily to the caliper? when im going to change my caliper in the future this possible misalignmet wouldnt matter?

 

oh yes, forgot to mention my rotors were crooked by .5mm on the right and .2mm on the left. maybe thats because po left the bar clamp bolts a bit loose. damps the vibration from rotors ha ha

i guess my steering bearings are shot too

 

finally got my rotors machined. waiting for other parts now.... i still need a suitable handlebar/clipons and some braided lines.


has anyone put braided steel lines from the calipers to the anti-dive units?

 

venlis, I have made the whole braided steel line conversion on my SECA. Send Chacal a pm, he has all 4 lines that you will need. You will be amazed at the difference they will make

 

nice rob, glad to hear youre pleased with it.

i'll get them locally, shop near me does any size braided lines i want.

i will post pics later when i get my upgrade done. i need to get my bike on the road fast, its a great summer here, although very short.


about the original subject of this thread, i need to get the dimensions for the abm rotor from the factory and figure out how to fit things.

so the single rotor conversion plan is on ice at least until snow comes. (wont be long, soon the days will start being shorter again and there we go)

 

From what I know, the '81, '82, '83 front brakes, calipers, rim, spacing are all the same, so the rotor should work.

Tell us about the "heavily lightened" part of your plans.
I had some ideas about grinding away all unnessesary metal to bring down the 518 LB a little, but ideas like that don't get too much traction around here.

 

ive tried to look into the abm rotors and they fit the xj750 41y model only which on chacals year model thread is

1984 XJ750 MODELS:
COUNTRY: EUROPE

MODEL NAME: XJ750
STREET NAME: 1984 XJ750
MODEL ID CODE: 41Y
FRAME ID: 41Y
SERIAL NUMBER STARTS AT: 000101

i think i got overexcited of the pretty picture of the rotor that looks to fit our bikes..

timetoride, i have plans to strip everything off the bike i dont need. minimal electrics too. i like to plan as i go and now is the time for the brakes..
ive also had thoughts about getting rid of all the useless bits of metal off the frame.

i too have noticed that my stuff would perhaps get more appreciation at customfighters.com or ratbike.org after im done

 

Unless your before pic is of a bike that looks like it just rolled out of the factory (i.e. is in impecable stock condition)...I think you will find lots of appreciation here .

But the Seca 750 has a lot of "extras" including in the front end. The anti-dive units are also a part of the forks, and complicates the dampening in them. Perhaps you should consider a whole front end swap with something that has the look you want?

 

nice to hear manbot. my bike is not in an out of the factory condition but for a bike almost as old as me it looks to be in a great shape. i dont think i will change the whole front since i really like how the wheel looks and i want them to look alike rear and front. guess i will just make the best out of what i have.

as i asked earlier would it be possible to loose the anti-dive system? i hear some of us has done it. is it possible to remove the air valves from the top of the fork?

 

There is no such thing as a "83-86 XJ750 model".....the manufacturer may have some specifications mixed up, which the retailer just copies and pastes into their catalog. ABM list the same part numbers for all of the components of the XJ750 '84-86 aa they do for the XJ900 models, which means I believe they are considering the 750RL Seca (1984)----which did use the 900 components----as the '84-86 models. Those rotors will not fit the standard Seca/Maxim 1981-84 wheels/forks/calipers.........

 

sidenote
if it would have been in a great shape i would have made it look exactly like out of the factory, polish it good and have it registered as a museum bike (when its 30 years old), and sell it for loads of €

 

No one would buy it...because it's just not that rare. That's good tho if you want to keep it...there's lots of spare parts to be had.

You can get rid of the anti-dive by blocking it off...there have been some threads on that in the past. I don't think you can get rid of the air valve without plugging up the hole in the fork. Again...might I suggest a different front end...from another XJ bike with a different air valve setup (or no air valve set up - were there any models like that?) and no anti-dive? The front wheels will be the same with the 650/750 Maxims/Seca (of course you don't want to go for a 750 seca )

 

He's not going to find a Maxim front end in Finland.

Venlis, if you want a single caliper look, and no anti-dive, you may have to buy the aluminium fork "legs" from a USA maxim, rebuild them with stiffer springs, or spring spacers, all new seals from Chacal, and a single Maxim rotor- - maybe the caliper too, and grind off the other caliper mount.

There's your clean, light, new front end.

 

My 1985 XJ750 has a 900 frame with a bikini fairing.. They were 83 or 84 weren't they? And it looks like the engine is off the last 750 run too.. The Model Number is 42M but that's not documented anywhere on the net that I could find, it seems there were 100 of the 42M's produced only for the Swiss market.. If the frame and engine didn't have the same number stamped on them I'd suspect that it was a chop job.

Don't know if that answers your question, but certainly XJ750's were being produced in small numbers in Europe in 1985.

 

manbot, in finland you can get your bike registered as a museum vehicle if it is at least 30 years old and in original condition. it can be restored to meet the original condition but there are loads (meaning LOADS) of strict regulations on how you have to do it. after you think you have the vehicle in an acceptable condition, a certified inspector will inspect it. if you dont happen to have a vehicle garaged for 30 years, i think it takes a true enthusiast to even start thinking about these things.
insurance is reasonable (compared to hyper-expensive for modern superbikes) for a museum vehicle, but i think there may be regulations also how much you are allowed to ride/drive it.
so yes, doing this kind of makes it a rare piece, and the price is greater.


about the topic:
i thank you for all the nice ideas and solutions. for now, i dont want to buy parts that i already have. i try to make the best of what i have.

the idea with single rotor conversion was that the bike would look nicer, be lighter, and i wouldnt have to buy more than one rotor

 

Hey, if you change your mind I have a '92 gsxr 750 USD front end that I'm not using at the moment. I don't know how crazy shipping to finland would be though. Still thought I'd offer. Good luck with all of this and post up some pics of the bike.

 

koolaid the shipping for the entire front would propably be more than you are asking for the front itself thanks for the offer anyway, pics later

 

yeah, that's what I figured. Let us know what you end up doing?