While waiting for the new top end I dug around a bit more in the bottom end. The reed cage is still intact with 4 screws holding in the reeds. I tried to clean the crankcase through the crank opening with a microfiber cloth and long screwdriver, there were some tiny metal shavings but nothing significant. I used some compressed air to try to uncover any particles but nothing could be detected.
The wristpins were there and intact. Perhaps it was a piece of broken piston ring.
Does anyone know of instructions or a video on disassembling the bottom end? I'm unsure of the process or what tools I'd need to replace crank bearings & seals. Might be better left to professionals
Looking forward to getting the new top end on there.
- The fan has been working well, it's nearly on all the time but it's been hot over here (northern california). No boiling over or smell coming from burning coolant.
- Plenty of coolant came out when drained thankfully.
- The gear oil looks good, not milky nor any unusual particulates.
- I took another look at the piston/head and it looks like something was banging around up there, so looks like I'll need a new cylinder head. I'm assuming you can't replace the insert in these stock ones? Perhaps it was a piece of the broken ring, I didn't see anything fall out when I disassembled.
- There's very slight vertical play on the crank, it was hard to measure but less than 1mm.
I'm leaning towards a "core exchange" swap with Jim at http://trialspartsusa.com, should be around $500 USD all said and done, including the piston kit.
Thanks @suzuki250 & @Goudrons2 for the advice! I think you're right, it'll probably just cook another piston without correcting the cylinder first.
It's hard to say what the culprit was here. The bike is new to me and I don't have any history on it unfortunately. It appeared to have good compression and it ran well, I was running 60:1 motorex crosspower 2t.
Looking at the crank there is a bit of play vertically, does anyone know the recommended tolerance? I'm sure it would benefit from new bearings & seals.
I'm looking forward to getting the bike running again, I've never had so much fun riding so slow
Hi all, newbie here. I recently purchased a very used 2003 TXT Pro and quickly proceeded to torpedo the top end. Valuable lesson learned not to pin a 18 year old trials bike too hard up a long hill in the heat
After pulling it apart it seems the cylinder is still smooth, only one thin vertical scratch. However you can see where the nikasil coating has worn through.
General question: I only use this bike for practice and enduro skills development, as such I have a limited budget and would like to keep repairs as affordable as possible. Do you think a new piston & rings could be sufficient for low & slow riding?
Any advice or vendors (US based here) appreciated! Piston kit, base gaskets, etc.
GASGAS TXT PRO 250 2003 FORKS
in Gas Gas
Posted
Thanks so much @anthonysawrey!