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miner

TXT Pro 250 07 - Teardown Time

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Revised to account for developing scope....

Went out for a run this morning and noticed what looked like a leak, wasn’t sure if it was from the cylinder or the bike had boiled over. Checking it out when I got back in, looks very much like a leak... thought it was idling high. Backfire on one of the kickstarts a tell tale. Pics on this link:

Gasket Leak & Plugs

It’s run a little lean... think the gasket has been on its way the last few rides.  Is this a common failure on these bikes? Or sign of something else failing? Google indicates it may be a common issue.... got a gasket kit there.  Only recent changes have been a few rides on 60:1 premix (motorex same as used in the KTM 300... did add 10mm to the tank this morning though).  

Any suggestions on other works to be carried out whilst the barrel is off?  What are the ring gap and squish settings for these bikes (which don’t have workshop manuals unlike the KTMs!)?  Will get more pics when its stripped... got a pool pump to rebuild first. :)

Edited by miner
Revised topic

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Still needing feedback regarding the crank seals... engine out and cases split?

Stripping the bike going well... stripped half the bike just to get at the barrel... only the barrel to remove now, its a little stuck... try again tomorrow when less tired.  Had enough excitement for one day.  Cylinder looks good inside, no lipping, strong cross hatching... bolts not very tight, assume that’s how the leak developed.

Now... do we go for a water pump refurb and a new piston?  After all that striping I think so... :rolleyes:

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14 hours ago, miner said:

Still needing feedback regarding the crank seals... engine out and cases split?

Stripping the bike going well... stripped half the bike just to get at the barrel... only the barrel to remove now, its a little stuck... try again tomorrow when less tired.  Had enough excitement for one day.  Cylinder looks good inside, no lipping, strong cross hatching... bolts not very tight, assume that’s how the leak developed.

 

 

 

 

              

Quote

Now... do we go for a water pump refurb and a new piston?  After all that striping I think so... :rolleyes:

Only if your water pump has leaked coolant into the gear oil  or it has problems with overheating that suggest the impeller may have disintegrated [unlikely]  .........If your piston is audibly slapping due to wear then change it if not why waste  £200 ish to do both those jobs if they do not need doing.Taking off the cylinder is not really major work on a GasGas pro or stripping down the water pump.

Edited by oni nou
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You will need to split the casings and remove the crank so you can change seals.

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Ouinon - thanks... water pump is easy to do anytime... in enduro land, piston is cheaper than a disaster... guess trials bike engine is more like a lawnmower? :D Piston looks sound, will get the barrel off and have a proper look though.  

richt - thanks for that, thanks a lot... :D only joking, thanks... a wee bit grimey in the magneto side last time, can check again... other side, it’s not smoking like its leaking... can suck it and see...

Good time to inspect and measure at least....

Edited by miner
Added a bit

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Ah the one behind the magneto you might be able to change in situ. If the exhaust is smoking or if oil is coming out the breather pipe then you'll need to split the motor to change the crank main seals.

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Got the barrel off there... late home but not cabbaged which always helps...

Rate my piston here... 

https://imgur.com/gallery/frqRYdZ

Looks ok, tight in the bore, maybe a little blow by? Bottom end is solid. Barrel in good condition, strong cross hatching, no lipping/scuffing  

Ring gap 0.4mm... what’s the limit on them? That’s the limit on my old old KTM 200 enduro... trials 250 more?

looking like a new gasket and ride... ?

That and an o-ring for the mixture screw on the 26mm Dellorto, it’s weeping. 

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3 hours ago, miner said:

Got the barrel off there... late home but not cabbaged which always helps...

Rate my piston here... 

https://imgur.com/gallery/frqRYdZ

Looks ok, tight in the bore, maybe a little blow by? Bottom end is solid. Barrel in good condition, strong cross hatching, no lipping/scuffing  

Ring gap 0.4mm... what’s the limit on them? That’s the limit on my old old KTM 200 enduro... trials 250 more?

looking like a new gasket and ride... ?

That and an o-ring for the mixture screw on the 26mm Dellorto, it’s weeping. 

The  only way to know if you need a new piston is by mearuring the bore and the piston in the place and at the temperature as recommended by the manufacturer. ....but if you piston was not making a knocking noise before  you stripped it then just put it back together and ride it ....you are looking at this motor in the same way as your enduro motors and they are not the same ...trials motors are low stressed and motors can go for ages before needing to be rebuilt if the owner pays attention to the air filter and sealing of the hoses to stop dirt entering the motor.

Edited by oni nou

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Cylinder back on and doing the dry fit up... got an S3 top end gasket kit a while back to do an exploratory inspection at some point.... the inner ring is the wrong size (too big) but the outside one is ok but not impressed with it... considering the two 10yr old rings back in.  Better looking than the ones in the kit. 

Either that or another trip to the oilfield suppliers when I got to get a tyre for my trailer tomorrow... 250 inner gasket is 79mm x 1.78mm... got half a dozen 78 x 2mm viton ones from my 300 KTM there, outer ones are bigger though (105mm).  Found the sizes on splat shop at least since they're not in the manual or on the S3 kit. 

https://www.splatshop.co.uk/gasgas-cylinder-head-o-ring-inner-250-280.html

https://www.splatshop.co.uk/gasgas-cylinder-head-o-ring-outer.html

Just saw that the water pump kit is £60+vat and £120 inc vat for a piston... no thanks. :( 

Not 100% certain the clutch side crank seal isn’t leaking... but its not smoking like there’s a new pope, will suck it and see. 

Edited by miner
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Catching up with this one... new gasket in, S3 kit o-rings didn’t fit, couldn’t get a viton 78x1.76 locally, ordered from splatshop... still no joy. Put old o-rings back in. ??‍♂️

Rebuilt the carb, so many small pieces missing... all rest hard and perished... starts and runs better than it ever has. 

No leaks... clutch out it sounds like a bag of spanners but all good, it was like that anyway. Running a treat. 

Got new grips and levers... fit them through the week. (Mrs was working - had to take the dogs to the beach and debrief 5 loads of washing ?). 

Took it for a spin... happy days, missed it so much. Wasn’t too rusty as been out at the track twice and off-road twice in as many weeks... but forgot how much it can fly... didn’t loop it but survived a few surprise take offs!??

Can’t wait for next weekend now... ?

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Forgot I’d started this thread... after a couple of rides the thing is smoking like buggery and getting some oil on the pipe... time to strip it.

Asides front thinking like an enduro engine... what would you advise to do/replace whilst the cases were split?

Bike is solid but for me if you are going in deep to do the crank seals on a 12yr old bike, its time to replace bearings and do the top end at the same time. Thoughts? 

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Guess I'm just cheap and lazy ... so I like to rule out the easy things first; could the smoke you're experiencing just be a result of burning oil residue which has accumulated in the silencer packing? Why not pop the top off the silencer and inspect the packing first? Or is there something you're experiencing which makes you think that it's an engine internal issue?

I'm not questioning what you're doing or your approach, rather I'm just trying to learn (as I have two 2008 GGs).

Dale

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Is the gearbox oil level dropping?If its burning gear oil it really stinks.Does it perform ok apart from the smoke,I wouldn't be in a rush to strip it yet without checking the carb and premix ratio

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Silencer re-packed not so long ago.. oil level going down, stinks, smoking heavy, oils coming out when revved hard to check it was revving clean, responded to a little more on the fuel screw, was smoking after it was stopped, deffo oil.  

When I stripped it there was black gloop in the cylinder head, put it down to re-using the o-rings as it wasn’t right afterwards. New o-rings, base gasket and water pump seal, now smoking... will give it a couple of rides and see how it goes but going to start ordering stuff in parallel. 

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