Gearbox Problems 280 '02

[bartje]

Hello all,

Since last Sunday I have this strange problem with my gearbox of my GasGas TXT280

[bartje]

Does anyone has time to have a look at my problem please?

Thank you in advance!

[laser1]

did somthing happen (like a crash) to precipitate the problem?

[jse]

Hello all,

Since last Sunday I have this strange problem with my gearbox of my GasGas TXT280

[peterb]

Hi Bartje,

All of Jon's advice is great, I'll just add my experience on these, assuming you have already tried the eccentric adjustment.

1) It may well be just the top hat shaped piece that is under the gear shift return spring has rotated it's two parts out of alignment, check to see the spring separator tab is in the same plane as the cross piece in the top of the top hat - you'll see what I mean when you strip it out. If not in alignment then the two parts that make up the top hat have rotated and need to be re-aligned then brazed up - or better still - fit a new top hat with spring attached.

2) If the top hat is looking good, then the problem is more sinister, most likely to be a bent selector fork or 3. If you do need to go this far, check the forks back to back to see if they are square, any bowing will then show up. New ones needed. Also, on the early 02 models, the selector drum was heavily machined out resulting in the material between the tracks to be too thin, these sometimes collapsed giving rise to the symptoms that you have. (sorry!) Newer drums were fine.

I just re-looked at the original post - it is a PRO 280 isn't it? Not the edition 280.

Ta ta, PeterB.

[bartje]

did somthing happen (like a crash) to precipitate the problem?

The day I suddenly had these gear box problems I had no crash at all.

[bartje]

It could be as serious as a bent shift fork, damaged roller assembly in

the shifting mechanism inside the shift drum or as simple as an adjustment

of the shift centering spring.

Always start with the simple and cheaper to fix things as a rule. The

centering mechanism is located underneath the clutch, so you'll need to take

off the clutch sidecover to get at it. You'll see a coiled spring with two

tangs that go on each side of a special bolt/bushing that has a 4mm Allen

capscrew and a 10mm hexhead eccentric bushing.

The process of centering it is a little tricky at first, so expect to make

several attempts to get it right. If someone who knows how to do it shows

you, it's a lot easier than describing it. Lay the bike on it's side to take

the sidecover off and you won't have to change the oil and the rear wheel

will be free. Loosen the 4mm capscrew up a little but not loose. Put the

shift lever down into first but do not release it (you may have to rotate

the rear wheel a little to get it to go into gear). SLOWLY allow the shift

lever to come back to center and just before it hits center you should hear

a light "click". If you don't, adjust the eccentric bushing (10mm open-end wrench) a

very small amount either way and try it again (it only takes a very small

amount of turning). Repeat this if necessary till you get the click. Then

try the same process with shifting up into second gear, slowly allowing the

lever to return to center to make sure you get the click. If you hear the

click in first (downshift) and second (upshift) the shift shaft mechanism is

centered, tighten the capscrew down and your problem should disappear,

hopefully.

It will take a few attempts to get it right, like adjusting four-stroke

valves, but once you get the hang of it, it should be a lot easier.

The brazed "top hat" bushing that holds the shift centering spring usually

snaps when a rock hits the shift lever in order to save damaging internals

but not always. Your problem does sound like a centering spring adjustment,

which hopefully is the case.

Jon

Hi Jon,

Thank your for this great advice, I was hoping on a non expensive solution and maybe this was just the one I needed!

I'll let you know if this fixes my problem!

Thanks!

[bartje]

Hi Bartje,

All of Jon's advice is great, I'll just add my experience on these, assuming you have already tried the eccentric adjustment.

1) It may well be just the top hat shaped piece that is under the gear shift return spring has rotated it's two parts out of alignment, check to see the spring separator tab is in the same plane as the cross piece in the top of the top hat - you'll see what I mean when you strip it out. If not in alignment then the two parts that make up the top hat have rotated and need to be re-aligned then brazed up - or better still - fit a new top hat with spring attached.

2) If the top hat is looking good, then the problem is more sinister, most likely to be a bent selector fork or 3. If you do need to go this far, check the forks back to back to see if they are square, any bowing will then show up. New ones needed. Also, on the early 02 models, the selector drum was heavily machined out resulting in the material between the tracks to be too thin, these sometimes collapsed giving rise to the symptoms that you have. (sorry!) Newer drums were fine.

I just re-looked at the original post - it is a PRO 280 isn't it? Not the edition 280.

Ta ta, PeterB.

Hi PeterB,

Thank you as well for your input, now I have three possible causes for my gear box problem, and really hope one of these is the solution!

(I've already heard several times that the '02 280 PRO isn't the most reliable GasGas on the planet)

[jse]

Hi PeterB,

(I've already heard several times that the '02 280 PRO isn't the most reliable GasGas on the planet)

Actually, I have an 02' 280 Pro as my personal bike and with a couple of updates, it's been great.

I like the 02' handling and lightness (the 02' has the Magnesium engine, like the Raga, 03' on up

are aluminum). The nice thing about the Pro is that just about all updated parts retrofit the

earlier models. I could probably have a new bike if I wanted (actually I have my order in for one

of the new 4T's when they get over to this side of the pond) but I tend to develop a close, personal

relationship with my bikes and hate to give them up.

A "quick and dirty" way to check the straightness of the shifting forks is to put them back-to-back

on a shaft and rotate them back and forth. The fingers should slide past each other closely and easily,

if they scrape or there is a gap between the fingers they are most likely bent. The usual way to

check forks is to look very carefully at the wear pattern on the tips, it should be even. If it's worn

on one side or other of the flat surface that contacts the collar, it's bent. The sure giveaway is that

if there are slight contact marks at the bottom of the "U", between the fingers, the collar has been

scraping there. The forks are a really tight fit, with little clearance, in the shifting collar ring, so any

misalignment usually shows up as contact marks.

Jon

ps. Thanks for all your posts, PeterB, I always learn something extra from them.

[bartje]

Hello again,

Yesterday we removed the clutch again and had a closer look at the shift shaft centre locator (Page 3 / part 11 / TXT-PRO 03 user manual).

When we remove the shift shaft centre locator I could pivot the gear pedal in a complete vertical position (upwards) and then I can shift into second gear without problems

[peterb]

Hi Bartje,

If your gear lever is in the usual 9 to 10 O'clock position at rest, then the travel upwards to select a gear should not be in the vertical position. Did you try adjusting the 10mm hex eccentric on the spring locator to obtain all of the gears as per Jon's info? It's never so easy to diagnose problems without actually "being there" but if it were me, I'd probably strip the motor at this stage and check out as detailed earlier.

Bye, PeterB.