hi there

disassembling engine after the session of excessive smoking.
broken piston skirt and some vertical crack on cylinder wall for now
more details and photos bit later.

for now just curious to know, *IF* it's only about piston and cylinder, which years/codes to avoid as a replacement?
also, is cylinder sleeve (separately) could be a reliable solution (press fit etc.)?

considering mileage (reaching 170k) and overall amount of scars, used to think about new engine as well even before this issue. same question here, which years to avoid in terms of fitment?

Hi, yes best is to find a used low mileage, years from 90-02. The 96-02 best engine with, gearbox issue sortet 5th gear and top cover welded differently so it wont crack. You can change sleave, you have bits of piston all over engine so it must be teared apart.

thanks for info.
will try to go with 96-02 engine option, but so far not sure if current budget will allow this, so maybe will have to find cylinder-piston kit instead.
how about earlier years in such case? checking some stuff online and so far older cylinders visually look similar...

meanwhile, here's the main character of the dark story above -


yep, some archeology must took place in the engine. oil rings were also broken (partially), luckily, at least their remains were successfully captured by the magnets.

You dont know what was captured or not before entire engine is dismantled, dont take easy shortcut changing cylinder/piston and start up.. End up with new failure and heavy damage on cylinder walls/piston. Before 90 it was 2kf cylinder, after its 3tb up to 02, its expensive for piston wiseco is 190$ + cylinder. Total overhaul with gaskets and bearings + some workshop help is fast 1500$. I would think its easy to find a used old bike one for 2-3000$.

thanks again for infos.
guess after finishing the engine disassembly will have more clear idea as well as further plans.

If you doing rebuild buy new rod with bearing when you first have to dismantle everything, i would never reuse the rod bearing after this. And maybe a part of the reason piston failed is slack in that bearing. Anywaysits importan to do maintence before this happens, no piston last forever, pre change parts is alot cheaper than total rebuilds after all is crashed.

ok, will have a closer look after having crankshaft out. for now i don't feel any slack vertically, only slight lateral free play which i guess is normal.
as for maintenance you're right. sadly, this trouble happened just couple weeks before the winter's planned check-ups and service. more attention probably will bring more luck next time )

What is the concern is bits and damage in the bearing, it can feel ok now but fail later after rebuild and you are back to start again. Same goes for all bearings at this mileage, do all or nothing is my advice. A piston change around 100k km is a good solution, offc it depends on how bike have been used and oilservice. If people dont know its not a big cost and can save alot of problems with piston change, oversize and bore cylinder + gasket, i will do the valve seals when its open. These engines are so easy to work with vs a 4cyl so there is no excuse to ride untill it breaks and tear up everything. In worst case you will end up in a an accident with rear tire suddenly lock up in highway in heavy traffic...

Btw good luck removing rotor, if its stuck like mine was its worth buing a 6t cylinder hydraulic jack.

yep, right point.
somehow, rotor used to be not a big deal in my case. considering earlier experience, nut of the clutch basket seems more challenging for now )

As someone who builds a lot of engines and buys and sells a lot of bikes, I think it's generally a terrible idea to buy a twenty year old second-hand engine unless you've seen it running well in the bike it came out of. Or can verify it some other kind of way.

80% of the engines I've bought on the second hand market have needed expensive work. Or have been scrap. Or worse than the engine it was bought to replace. It's obviously not always that way, but its a huge lottery in time and money.

It's generally why they're for sale. It's a scammers market. A motor is impossible to test properly until it's been built back up. And then you have no come back anyway as you've worked on it yourself. MEH !!!!!!

Over the years I've learned to just rebuild what you've got. And do it properly. It can be expensive. But generally less expensive than pissing around with lottery engines or doing half repairs.

The XT600 engine is a simple motor. You've gone this far. It's now very easy to take it down further and replace the crank or have the crank rebuilt. £200-£300. You can also then clean everything out of the cases and check everything else.

Measure and inspect your connecting rod. Replace if necessary. It could have been rod knock that caused the failure. Not uncommon on a high mileage XT.

Then you build it up with a new piston and rings.

The XT has a cast-iron liner. You can remove it easily just by heating the barrel in your oven at about 120c. Suspending on some fire bricks or metal blocks. It will just fall out.

A liner is about £150.

Good luck

__________________
Did some trips.
Rode some bikes.
Fix them for a living.
Can't say anymore.

lot's of good and useful infos as well as experiences here.
thanks a lot sharing all these stuff.

indeed, engine disassembly is progressing and more facts will appear with time.

thanks again!

meanwhile, progressing with disassembly.
side covers, rotor, clutch, gears etc. are off.
already collecting piston pieces.
there's some fine debris in the oil filter, not attracted by magnet, seemingly aluminum.
oil pump seems alright, with slight dents on the edges and very few/slight circular marks (not even grooves) on the flat parts of internal gears. could be worse.
but outside gear (plastic one) has clear signs of wear.
not as much, but driving gear of the pump, located below the clutch basket (also plastic) is also not in the best condition.

(photo for reference)

now just making sure, if it's about the replacing this drive gear, seems i'm gonna need clutch basket as a whole, right? it doesn't look to be made to disassemble easily...

Yes its correct its a unit basket 400$, cant see from pict what is damaged.

Buy from Germany, good buy and use yours for spareparts or sell as is.

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