Forks go down but don't bounce back!

[BigyellowGS]

Evenin' All..

Well the bitza is booked in for an mot next week.. BUT.. I've hit a snag!

I took her for a little bimble along a private lane and found that the forks dont seem to have any bounce.. They compress fine but just dont seem to bounce back! There is also quite the slurping noise when you sit on the bike and push them down!
They are not leaking and were fine when I first rebuilt the bike in its first guise.. but this time they dont seem right... My only thoughts are:

The bikes heavier with the big tank (unlikely as it's only half full).

I've put too much/wrong grade of oil in the forks? I think I got it right.. but you never know... would this cause them not too rebound?

Your thoughts ladies and gents please.. I've gotta get this worted over the weekend or I'll have a real issue getting the bike Mot'd and on the road in time for the wee-kend..

J

 

[DrFarkoff]

Try slackening bolts off and gently depressing the front end

I had a similar problem on my Mono RT

I had to add some polyprylene slugs above the springs to beef them up and then had to slacken all the nuts and go for a wee gentle ride about 300metres till everything aligned and tighten and ride and tighten and ride till I got the values right and it stopped with the stiction

 

[VAL. H.]

Evenin' All..

Well the bitza is booked in for an mot next week.. BUT.. I've hit a snag!

I took her for a little bimble along a private lane and found that the forks dont seem to have any bounce.. They compress fine but just dont seem to bounce back! There is also quite the slurping noise when you sit on the bike and push them down!
They are not leaking and were fine when I first rebuilt the bike in its first guise.. but this time they dont seem right... My only thoughts are:

The bikes heavier with the big tank (unlikely as it's only half full).

I've put too much/wrong grade of oil in the forks? I think I got it right.. but you never know... would this cause them not too rebound?

Your thoughts ladies and gents please.. I've gotta get this worted over the weekend or I'll have a real issue getting the bike Mot'd and on the road in time for the wee-kend..

J

There are a few reasons why the forks wont spring back.

Firstly, are the stanchions straight? Even if the look ok they might have enough of a bend to cause them to jam.

Weak or broken springs.

Wrong oil: Too thick and it can cause 'packing'. This is when the oil is compressed through the damper holes into the upper part of the leg, with the heavy oil preventing the fork re-extending. This is extremely rare in conventional damper systems (but can be more likely in forks fitted with Emulators) as you would need to have put in something like 20/50.

Worn bushes: If the bushes are badly worn or damaged they can grab or become stuck.

Sticktion: This is when the seal is either dry, swollen (contaminated with petrol or other spirit etc).

Kinked fork leg: This is when the stanchion has a small kink type of damage due to being bent and probably re-straightened incorrectly, causing the stanchion to stick in the lower leg.


HTH Val.

 

[Rob Farmer]

Either too much oil or the wrong grade. They were meant to have 5 or 10w. They had 7.5w in them when I sold them to you and worked a treat on the 90/6 they came off.

 

[Kenny]

All good advice... 5w ( maybe mix to 7.5 grade with that bigger tank )..and as Jaythro says, loosen top and bottom yokes fork brace etc ( just a tad ) and bounce the bugger up and down...amazing what this does as it aligns everything up nicely

... oh and then tighten up the bolts again ( usually ( 15 ft/lb on most bikes )

 

[BigyellowGS]

Thanks for the answers..
I've been out in the garage already this morning.. tried loosening things off, bouncing the front end but to no avail.
I then stripped the forks out, drained the oil (I refilled them with 7.5w a while back) and found they now bounce fine! So I guess I made an error with either the volume or the grade last time.
So.. I'm off to the shop to buy some more oil.

Cheers again!

See you at the wee-keed!