Another fork question.

I have stripped down two of my XJ750 for rebuild projects.

I noted that both of the petrol tanks has dents on the top where a bolt that secures the top of the forks to the triple tree hits the tank when the steering is on full lock (either side). Upon closer inspection, I noticed that there was a cap that could be screwed off revealing an air valve...similar to that on your tyres.

Two questions:
what is the purpose of this air valve
How do you stop it from hitting the tank?

Thanks

 

The air valve is to add or release pressure in the forks for a firmer or softer ride. Some of the guys on here can tell you what they set their pressures at. As for the little tank dings from the bolts on the outside of the triple tree, those dents come from the front end flipping to that side too hard. This happens when the bike is flopped on its side or takes a hit to the front wheel. Releasing the bars and letting the front flop to the side can do it too. To keep it from happening as easy on my bike, I reversed the bolt so the acorn nut was facing away from the tank. Gave me a tiny bit more room.

 

Thanks for that answer. I was and still a little concerned that I may have a bent/damage front end. The bike is over on my property, so I can't take a picture of it,but it seems strange that they would have it that close to the tank. It hits the tanks well before the full lock stopper. i was thinking along the line that maybe the springs or front suspension my be lower that it should be... But I 'll take your advice and face the bolts the other way.

Thanks again.

 

be very careful when adding air. It's only rated for something like 35psi MAX and recommended is somewhere between 5-12psi. I like mine at around 15psi for a nice firm feeling when digging deep in the twisties.

To fill I pump it up with a small hand operated bicycle pump up to about 20psi then carefully gas them down with the gage in hand to the setting I want. Being sure that the last time I remove the gage I do so quickly and abruptly.

It is NOT like filling a tire. The volume is small (with a regular stand-up bicycle pump it takes less than one full stroke to get the pressure above max) and the walls aren't flexible like rubber, they're your forks so the pressure comes up and drops sharply.

On my to-mod list is plumbing both these together so it's easier to fill and even if I get a leak they will always stay matched.

As to the dents, I dunno, my tank has 'em too. I suspect it's a design error based on using trees designed for the maxim and adding both these different forks and the different tank. Just got overlooked in the design process.

 

Over inflation of the forks can also blow the seals prematurely, so be careful. 3 to 7 lbs. is plenty in most cases.

 

Worn steering bearings may be giving the front end a little extra play too. I noticed on one of my frames that where the steering stop comes into contact with the frame was dented in a small amount causing the triple tree to hit the frame. Maybe at some point the same happened to your bike.

 

Most common cause of the trees hitting the tank is bent (or sheared right off) steering lock stops.

On the 550s, the acorn nut is supposed to be on the side away from the tank.

 

Every 550 I have has always had them facing the tank, Fitz. And I thought I was just being smart by flipping them around. LOL

 

I learned some early lessons about my PO's mechanical abilities, so I started following the fiche/service manuals, and began not trusting things to be correctly assembled as I found them. Good thing, as virtually everything the guy had touched was reassembled wrong (like the rear axle, the oil filter, etc., etc.)

 

Thanks foe the input guys. The first thing to do then is to face the bolts away from the tank.
The stops are intact (so it appears) so might be worth looking a placing a new stop while the bike is apart. I ca'e see the value of having a fresly painted tank with new dents!!!.

I'll take some photos in a couple of days when I get to the bikes and post them up and make sure we are all on the same page.

Militant_Buddhist
In Australia, we never had Maxims to the best of my knowledge (although I would love to get my hands on one...just to be different), so I am not sure that the mix and match of trees and forks applies in this case. Mind you not being the initial owner ofthe bikes, everything and anything is possible.


Thanks again

 

gday pmjydnl, i have a 81 xj650 special and from what i can tell its more or less the same as the maxims. slightly raised bars , black,,just different badge on the side cover,could be wrong though but so far when i need new cables the normal ones i get here are short.

 

FRom what I have been told, the frames are slightly different, as well as the petrol tank, side covers and some internals...such as cam shaft profiles. But as I said, i am not aware that they were ever brought into Australia. I even thought of bringing a frame over, but it works out too expensavive. There is however a V twin chain driven variant that was sold here with reasonable success.

 

Hi I had a similar problem only the fork tops between the trees touched
my tank on full left lock right lock was ok. On investigation I found that
the stop on the bottom tree was ok but the stop on the frame that it bumps
on was very worn for some reason. This stop is only made of mild steel
and mine has about a 3-4mm depression worn into it. I did not want to
strip it all down at that time and so I very carefully drilled a hole
through the big stop on the bottom tree and run a 6mm thread tap through
and screwed a 6mm allan key screw right through the stop
so that now I can adjust where the forks stop on the full left lock. It works
very well and my new paint job is safe. The bottom fork tree is made of
some sort of cast iron so do not try to bend the stop on this part as it will
break off. One day when I have the bike front pulled right down I will put
some weld on the steering stop on the frame neck so that it works properly again.
My bike is a 1980 Seca and does not have any air assist valves for the forks.

 

I have managed to add some pictures to my last post to help show
what I am talking about. Bob

 

Thanks fot the pics Bob. That helps. For some reasons, all three of my 750's have the same problem. i have on with the front in pieces, so might be good time to get some welding done before it is powder coated.

 

Hi pmjydnl Yes my TX500 Yamaha also had the same problem. When I restored it I had to do the same fix by putting a screw in the left side
bottom fork tree exactly the same as the XJ. Again the right side was ok
it only touched the tank when on full left lock. With the screw in place I
have only to screw it in or out to vary the lock and make sure that the
trees or what ever never can touch the tank again.

 

Still grappling with this Air/fork issue.

I had a look at the forks and the clamps where these air nipples ar don'e seem to be connecte to anything. I read somewhere on another topic that there is supposed to be a hose of some sort attached (although that was for a 900). Where does this hose go to?

Are there any issue with reversing these clamps so that the air nipples faces the front?

Can these things be removed and disgarded? If so what are the consequences.

Many thanks

 

If you have stock unfiddled with forks..th air nipples should be at th front, maybe they got swapped around..left to right? at some time or just not located properly. They have a location tab on them that stops them from turning. Inside them are 2 Orings that seal to th fork, there is a corresponding hole..'bout th size of a match.. in th fork for th air to go through. Some of th other XJ models have th air hose, not th 750seca, it joins th 2 sides so you only put air to 1 side.

To do away with them you would have to seal th hole in th fork..bad idea I reckon. You might/maybe get away with dropping th forks down in th tree enough to get them off and swap them around, new Orings and air valve would be a good idea too..cheap.

 

Thanks Bushy.
Mine are definately facing the rear (explains why it hits the tank).
I definately would prefer to keep them on.
I noticed the stopper/locater, so obviously it belongs there. I will get some pics loaded tonight. The forks have definately been tempered with. On one fork, there seems to be a black spacer between the clamp for the air thingy and the triple tree and on the other side it is missing.
Cheers