XT 600 Piston issues
 

Xt 600 Kick start

Bike died while driving, felt loss of compression when kicked over.
Pictures show piston/cylinder condition.

Any ideas how this happened? To prevent it happening again.
Oil level was fine.

Previously posted on top end noise. Which I thought was lifter. I replaced head and rocker box a few hundred miles ago but noise was still there.
Perhaps it was piston.

The cylinder is gouged up and piston is done.
What steps should I be looking to do, examine etc.

Greg

Looks like a lack of oil to me...

Are you 100% sure the oil level was OK? The dip stick measuring is kind of stupid on this bike.

shaise.... if it's oil related would expect to see also badly socred cam bearing and rocker surfaces. if cam journals look ok, might be serious dirt entering motor through broken rubber booths...

Always at the back of the piston on XT`s, less oil? hottest part of the barrel?

Mezo.

Cam looks to be fine and there is quite a lot of oil in journals as well as what snuck past piston after it burned up.

Oil level is at high mark of dip.
Oil had about 500 miles.

Figuring this had something to do with the breakdown.

elemental watson :)

didnt see the pics of the cam before, but dark color all around = overheated oil indeed. you're pretty lucky it dint do that much damage, but check also the rockers surface...

have you opened the pump?

it might have something jammed inside and that could break the plastic drive gear

Just opened the cover up
Still didn't take clutch out.

With clutch basket their is pushrod behind the the ball and manual says to remove with magnet. Is there another option?

Never had clutch out of the xt before

The ball should roll out by itself.

The cause is obvious. Your oil pump gear shattered.

The question is why ???

I'd be checking the gears it's meshed on. Those gears are notorious for coming loose on their shafts. Stripping woodruff keys etc. That could be the noise you were hearing.

Those oil pump gears don't just shatter like that. The meshing has to be incorrect. Is it also possible the oil pump is dead and jammed up. This could happen if it was running dry.

You said the bikes been stripped down. Whoever did it might have got something wrong.

Your cam is sitting in an oil bath. If the pump is dead it won't be filling the rocker box but it won't be emptying it either. It's hard to tell.


Your best best is to find a replacement sleeve for your cylinder. New piston, rings, piston pin. Hopefully your conrod survived the trauma.

Took bottom end and head to machine shop and they seem to think the damage was isolated to cylinder and piston.

Oil pump: From reading up on here i'm looking up for a later year xt 600.
Did the TT 600 come with a stronger flow oil pump? or was it the same as the years for XT?

Can i replace with cylinder from TT? I might be able to get a very good condition cylinder with piston (stock) from 1983 TT 600.

I'm quoted about $320 US, for a rebore and piston for the rebore size.
Wondering if its better to look at other options. Ex: find cylinder and piston together on Ebay? But then I run into a combo that would be 25+ years at best.

Zylinder Kolben 3AJ00 Cylinder Piston Yamaha XT 600 | eBay

Its possible to buy only the sleeve for the cylinder.

Stock piston and rings are very expensive, your quote might just represent that.

A new non-oem piston only costs a fraction of one labeled from Yamaha.

Wiseco Piston Kit Yamaha XT600 84 96 97mm | eBay

YAMAHA XT600 TT600 SRX600 XT TT SRX 600 WISECO CYLINDER LINER SLEEVE SIZE 95-98 | eBay

If the sleeve in yours dont have much damage you can rebore it at lower cost, find a cheaper place to rebore if they charge 200dollars.

Thanks for that

I can get a salvage cylinder with piston for a $100 but its from a TT 600 1983.
I'm waiting on pictures to see condition. Was told it was in good condition.

Looking for advise on that as well please.

If its in good condition as shown in several pictures perhaps its a better option.

Problems I'm thinking of:
Would it still need new rings
Would it need to be honed