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Discussion Starter · #1 ·
firstly a big hello to all found this forum while trying to find the answer to my problem and hope someone on here can help have searched the forum already and athough the topic has been mentioned I still cannot figure out what to do afriad I am a bit of a mechanical nupty when it comes to Hondas as I have spent most of my time working with old British Bikes and cars

anyway my 1984 GL 400 custom just failed its MOT on the front forks bottoming out and was told I may need to change/check oil level noticed when I got it home it also has a schrader valve on the top of the forks I presume needs to be pressurised with air?? so could this be the problem?? any body know how to do this the manual I have is a bit vague to say the least. Have never had any oil leak out of the seals so assume these are ok

Cheers Eddie
 

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As your bike is a misfit we need pictures. Any cx500/400 over 82 could have been made from any cx/gl parts that they had sitting around.



So we need pictures of your bike to figure out what it actually is.

Putting your location in your profile wouldn't hurt.





If the valve isn't holding air then that's also a problem. Some forks have drain bolts on them which would make chainging the oil easier.



A preload spacer on top of the springs will also help if the springs themselves are that bad.
 

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Discussion Starter · #3 ·
Blindstich thanks for the fast reply I have updated my profile I was informed that My GL400 is almost identical to the CX500 Custom but was sleeved down to 400cc for the Japenese market I believe it was imported into the UK in 1991 here are a couple of pictures



 

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I would use a hand pump to air up the forks and then check to see how long it takes for them to leak down(if they do). It doesn't take much air and a compressor usually

put too much air(very quickly; the reason for the hand pump). You may have to replace the seals and fork oil. AGB-1
 

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hi Eddie,

while i dont do mot or tests etc.i think im allergic to control


if i was in your shoes,id do what the tester wants.stop the bottming out.

let the air go,drain the forks,,,[you will need to undo the tops caps,with care]i can see by your picture you have drain screws.when you think its all out,it istnt.pump the forks,to get the last bit out.

refil with a 20cwt fork oil[whatever make you can get locally]



take the small top spring ouy,place the caps on top of the forks and mark the thread starting point...replace the spring

introduce a 3/4 inch piece of plastic water pipe over the top spring....marking up your thread starting point,replace the caps
 

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Seems like they're similar to 78-80 forks in the manual. Didn't know they were air. Since they are probably the same I would drain the oil, put in a preload spacer and fill the air to 10 pounds and see where that gets you.
 

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I think they also insist on a hand pump to keep from having an air-compressor blow water in the forks.
 

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Using something other than a hand pump you have the possibility of blowing out the seal...



I would measure the length of the front springs to determine if they are in/out of spec..if out of spec by being shorter - adjust the length by an appropriate length spacer back to required length. Then after emptying the forks of oil would fill with the correct volume of your desired weight oil.....

I would replace the valves with new ones - pretty simple and cheap to do, Make sure your bottom drain bolts are not leaking, caps are torqued properly, and valves done up as well.



That will probably get you over the MOT as long as they are not obviously leaking.



Note:

You may need to replace the seals - have they ever been replaced or leaked?

 

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If you, like 81Custom said, have to replace the seals, beware that your forks have slide bushings inside. A slightly different technique is needed to get the fork legs apart, compared to when there are no bushings.



Not difficult! It´s good to have a drawing, either from a workshop manual or a spare parts "fiche", to check that everything gets off, and later on, on again in the right sequence.



Sture
 

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Discussion Starter · #15 ·
Well have just spent a couple of hours in the garage and apart from the tight access (helped by removing clocks) and the struggle getting the spring caps back in (decided to try without preloading the springs) I have replaced the fork oil and pressurized the air assist and think I have sorted it. the springs looked ok but the left leg seemed to be a bit low on oil (decided to measure it as I drained it out of curiosity) air assist had no air when I started either unfortunately have to wait to Tuesday to get it retested

Thanks for all the advice

Cheers Eddie
 

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Well have just spent a couple of hours in the garage and apart from the tight access (helped by removing clocks) and the struggle getting the spring caps back in (decided to try without preloading the springs) I have replaced the fork oil and pressurized the air assist and think I have sorted it. the springs looked ok but the left leg seemed to be a bit low on oil (decided to measure it as I drained it out of curiosity) air assist had no air when I started either unfortunately have to wait to Tuesday to get it retested

Thanks for all the advice

Cheers Eddie
good luck for Tuesday.

i take it that they are not bottoming out now.

 

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Discussion Starter · #17 ·
well got the forks and the other couple of little problems sorted at the weekend and had it retested this afternoon and she passed
just need the weather to hold out and I can start racking up a few miles

Cheers for all the advice

Eddie
 

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great news Eddie.
 
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