-
Enjoy XS650.com? Consider making a donation to help support the site.
XS650.com receives a small share of sales from some links on this page, but direct donations have a much greater impact on keeping this site going.
Complete Bike Rebuild?? Worth it?
- Thread starter Skfork
- Start date
If you want a sleepy little town for kids... Newton, Pinckard, Midland City.... place is full of nice little towns to raise kids.
Skfork
XS650 Enthusiast
Ok, so i did the leak down test:
Right side - had some issues early, ran it quite a few times, it was reading like 30% leak, then there was a popping sound, around 70-80psi started leaking aggressively through the carb intakes. I freaked out, ran it again, and it showed 0% leak so… dont know what to make of that but it seems pretty good
Left side - 100% leak no matter what i did. well boys. Im a fool but one semi capable of learning, i took a light to my piston (for the first time. Theres a massive hole that i think might be the problem.
So… engine rebuild time? Hows this happen, seems like the intake valve may be hitting it so is timing just massively off?
Right side - had some issues early, ran it quite a few times, it was reading like 30% leak, then there was a popping sound, around 70-80psi started leaking aggressively through the carb intakes. I freaked out, ran it again, and it showed 0% leak so… dont know what to make of that but it seems pretty good
Left side - 100% leak no matter what i did. well boys. Im a fool but one semi capable of learning, i took a light to my piston (for the first time. Theres a massive hole that i think might be the problem.
So… engine rebuild time? Hows this happen, seems like the intake valve may be hitting it so is timing just massively off?
Attachments
Very unfortunate 
If you have a small shop it’s time to pull the engine and take it apart for decision making
If you have a small shop it’s time to pull the engine and take it apart for decision making
Well, that certainly accounts for low compression! Yes, engine out, rebuild time and yes you need to work out why collision has occurred.
On mine, the chain was a step or two out on the cam sprocket and PO had set the tappets to huge gaps, presumably to avoid chance of valves and pistons getting up close and personal. Investigation needed.
On mine, the chain was a step or two out on the cam sprocket and PO had set the tappets to huge gaps, presumably to avoid chance of valves and pistons getting up close and personal. Investigation needed.
Holed pistons can occur without mechanical interference but too advanced timing perhaps ?
Skfork
XS650 Enthusiast
I do not have a small shop but i have a garage, am a young single dude with a lot of free time due to my job, so the decisions been made, @Bushyeyed1 hope i can make you proud and bring her back to her former glory.
@Raymond , I’m still learning what all this stuff means but hey i bought the bike because id heard it was easy to work on, so i figure by the end of it i will
@XSTime , with the valve looking like that I’m assuming its mechanical interference but any advice how to check for nonmechanical interference causes?
@Raymond , I’m still learning what all this stuff means but hey i bought the bike because id heard it was easy to work on, so i figure by the end of it i will
@XSTime , with the valve looking like that I’m assuming its mechanical interference but any advice how to check for nonmechanical interference causes?
Skfork
XS650 Enthusiast
Also if anyone has any idea what could cause that popping sound on the right side? Im less worried and more curious, was something sticking and the pressure cause it to pop loose maybe?
You might be able to tell if valve & piston have been meeting up by turning the engine slowly and watching. As you dismantle, you can check the cam-chain position and valve timing. And once you take the valves out from that cylinder, you ought to find evidence - the valve will probably have bent and if not it will show damage from the collisions. Non-mechanical would usually be the piston has melted due to weak mixture or incorrect spark timing. You would be able to see the piston has melted, it will be eroded not bashed and there might be lots of small alloy particles.
Looks melted and not hammered on my phone.
Skfork what ya doin ?
Ya, is popping back through the carb ? (Timing advanced )
Skfork
XS650 Enthusiast
Popping only happened once but yea it was back through the carb
As far as what I’m doing, i changed the oil over to rotella, and rebuilt the carbs w a mikesxs carb rebuild kit (after the power loss problem arose, but it was still running). I didn’t adjust the jets as i wasn’t sure what size i would need (on account of the engine being bored out).
When i put it back on and started running it it kept stuttering and dying on me, so i adjusted the idle screw up from around 850 to 2k, to see if that would help provide power, it let me run for a second, but kept shutting off, and then on one of my kickstarts there was a jet of fire out the exhaust. I think i got it up one more time after that and then it shut down.
850 is quite slow. 1000 -1100 is about right.
A well tuned XS engine will idle quite slow and smooth with the timing slightly retarded.
Skfork
XS650 Enthusiast
Once i get her up and running I’ll keep that in mind, thanks xs, thread might be quiet for a few days but ill keep you guys posted.
As much work as this may be I’m pretty excited, i got an ultrasonic cleaner in the mail and plan on polishing everything up nice, might take me a while to get it all together, but at least ill know my bike pretty well
That is a really major plus point to doing a project or at least doing maintenance on your own bike. You get to know the bike better, how it works, appreciate how to get the most out of the bike, how to spot things before they become problems, the confidence knowing that if something fails or you hit a problem you got some idea how to deal with it or at least deal with the situation and not just breakdown in tears so to speak. Good on yer!
I believe you found your leak. Ouch but I would assume the guy that bought the bike from me to flip real quick didn’t tell the next guy about the documentation I did in my build thread. This guy has a lot of good videos I used for reference for the xs650 engine.
Hopefully it’s just a holed piston and you can use most of the other parts. The only thing I didn’t do while I was in there last was the bottom end.
Skfork
XS650 Enthusiast
Thanks for the recommendation
Skfork
XS650 Enthusiast
Thanks bushy
