MFJustin
Welcome to Thunderdome
Stay tuned I've got some pics of the camshaft and rocker box coming up in a few. Wanted some input on wear patterns on some of the stuff.
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New to this, bike cut off and now wont start.
- Thread starter MFJustin
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- bobber engine maintenance
I'm surprised at that. I've not done it myself but with the tensioner completely removed there ought to be some slack.
The cam bearings should slide horizontally so it shouldn't require much slack anyway because you're not lifting the camshaft at all.
I'm going to need to do the same thing in reverse soon as the PO stripped the engine without breaking the chain.
The cam bearings should slide horizontally so it shouldn't require much slack anyway because you're not lifting the camshaft at all.
I'm going to need to do the same thing in reverse soon as the PO stripped the engine without breaking the chain.
MFJustin
Welcome to Thunderdome
I'm surprised at that. I've not done it myself but with the tensioner completely removed there ought to be some slack.
The cam bearings should slide horizontally so it shouldn't require much slack anyway because you're not lifting the camshaft at all.
I'm going to need to do the same thing in reverse soon as the PO stripped the engine without breaking the chain.
Yeah I've done a lot of reading and watched the helpful videos on this forum of other members who have pulled their motors and as soon as the cam chain tensioner was removed that thing was super loose. Unfortunately mine still barely moves.
MFJustin
Welcome to Thunderdome
So heres the pics I took of the rocker box and camshaft.
First thing I noticed was that the rocker arms seem REALLY worn down. The pics may or may not show it properly but they are so worn down that there is kind of a lip on the outside of them. I tried to focus in on it as best I could but I'm not sure if I captured it properly. Also in between the cam lobes it looks as though something was rubbing a groove into it. I've compared pics of what I took to others who have posted pics of their internals and mine definitely look pretty worn.
First thing I noticed was that the rocker arms seem REALLY worn down. The pics may or may not show it properly but they are so worn down that there is kind of a lip on the outside of them. I tried to focus in on it as best I could but I'm not sure if I captured it properly. Also in between the cam lobes it looks as though something was rubbing a groove into it. I've compared pics of what I took to others who have posted pics of their internals and mine definitely look pretty worn.
MFJustin
Welcome to Thunderdome
Managed to get the cam out. I might catch some flack for this but I stuck a long screwdriver through the cam bearings and into the camshaft and just kind of pried up a bit. I guess the bearings just needed to be popped out of their groove, it was enough for me to pull the bearings off and therefore remove the cam.
well done. 
looks like you need to lever a little to get the slack needed.I was going to suggest turning the crank a little to loosen the camchain.
Those tappet faces are seriously worn
and will need replacing . They are bound to have worn the cam too but I can't see it from the excellent images.
mmmm one of the cam profiles looks seriously galled . I f they are all worn that badly that cam is probably scrap
Your best bet could be to buy a low mileage used head complete as I expect resurfacing your cam profiles would be very expensive .
looks like you need to lever a little to get the slack needed.I was going to suggest turning the crank a little to loosen the camchain.
Those tappet faces are seriously worn
and will need replacing . They are bound to have worn the cam too but I can't see it from the excellent images.mmmm one of the cam profiles looks seriously galled . I f they are all worn that badly that cam is probably scrap
Your best bet could be to buy a low mileage used head complete as I expect resurfacing your cam profiles would be very expensive .
MFJustin
Welcome to Thunderdome
So the head is halfway off. When I pulled it up it brought the piston sleeves up with it. I'm assuming that's not supposed to happen? Seems every video post I've seen showing engine tear down doesn't have that happening.
MFJustin
Welcome to Thunderdome
Haha oh wait....oops....looks like I didn't pull the head off but rather the head and jugs off as one.
MFJustin
Welcome to Thunderdome
MFJustin
Welcome to Thunderdome
As you can see from the pics, right side piston looks ok and was covered in oil. Left piston is absolutely SCORCHED. Do bad piston rings really cause that? Like I said this is my first motor rebuild endeavor.
I'd forgotten that this was the bike with the burnt piston. Ouch that looks expensive.
I'd seriously add up the cost of everything required to rebuild that engine and compare with buying a used low mileage running engine.
I'd seriously add up the cost of everything required to rebuild that engine and compare with buying a used low mileage running engine.
MFJustin
Welcome to Thunderdome
I've been online looking for motors for sale but haven't found much locally.
I'm making some money off of a project Jeep I'm selling, cost isn't necessarily a huge issue as I was planning on rebuilding the bike over the winter anyways.
I had already planned on new pistons, rings and other stuff. Obviously it needs bored out some so ill probably have to go with some oversized pistons, maybe even a big bore kit. I'm not too concerned with throwing some money at it as long as the whole thing isn't completely junk.
Problem with buying a motor online though is I don't know what condition it's in once I buy it unless I break it down too, even then I may find stuff needs replaced. Part of me just wants to rebuild my motor, I know it will cost me some.
I'm making some money off of a project Jeep I'm selling, cost isn't necessarily a huge issue as I was planning on rebuilding the bike over the winter anyways.
I had already planned on new pistons, rings and other stuff. Obviously it needs bored out some so ill probably have to go with some oversized pistons, maybe even a big bore kit. I'm not too concerned with throwing some money at it as long as the whole thing isn't completely junk.
Problem with buying a motor online though is I don't know what condition it's in once I buy it unless I break it down too, even then I may find stuff needs replaced. Part of me just wants to rebuild my motor, I know it will cost me some.
yeah I guess a used engine could be a bit of a lottery.
A big bore kit does sound fantastic I have to say. I've read lots about them. Apparently you can bore the XS out to nearly 900cc !
Have you read this article ?
http://www.biker.net/650/betterxs2.html
A big bore kit does sound fantastic I have to say. I've read lots about them. Apparently you can bore the XS out to nearly 900cc !
Have you read this article ?
http://www.biker.net/650/betterxs2.html
MFJustin
Welcome to Thunderdome
I'm actually pretty stoked about a motor rebuild, after being in Jeeps and offroad vehicles for so long it's exciting to get into new territory.
My biggest concern though was what all of us have discussed since the beginning of this thread, what was it that caused all of this to happen. Unfortunately I don't really know what I'm looking for other than obviously worn out parts. Does what I've shown so far indicate bad piston rings or is it more than that? I just don't want to throw parts at it and not fix the root cause.
My biggest concern though was what all of us have discussed since the beginning of this thread, what was it that caused all of this to happen. Unfortunately I don't really know what I'm looking for other than obviously worn out parts. Does what I've shown so far indicate bad piston rings or is it more than that? I just don't want to throw parts at it and not fix the root cause.
MFJustin
Welcome to Thunderdome
So another question for the masses, how exactly does the oil delivery system in these bikes work. I only ask because it seems like the entire left side cylinder is just dry. Underneath the burnt piston is bone dry, whereas the right side piston is just completely coated in oil. Is this the result of bad piston rings on the left side piston, being that the oil seeps by and thats why the left side is so dry because it burnt it all up?
MFJustin
Welcome to Thunderdome
Damn after doing a bit more reading around I'm worried the motor might be a total loss.
I don't want to hit the panic button just yet but it'd be great if someone who's done a lot of motor rebuilds on these things could offer some input based on pics
I don't want to hit the panic button just yet but it'd be great if someone who's done a lot of motor rebuilds on these things could offer some input based on pics
You have to remember the right side(of the motor not the picture) has a hole any air and fire was being pushed through the hole drying the bottom side?
The hole looks melted not broken?
The hole looks melted not broken?
no its simply due to the redhot compressed gases getting past the piston via the hole in the top !
MFJustin
Welcome to Thunderdome
Yeah you're right, I never based it on simple logic like that haha
it all depends on what you intend to do with the bike really.
If you want to end up with a sweet running bike to keep which has been carefully and completely restored to good order then I would say you might be better off buying a 750 kit . The bottom end is likely to be ok as they are apparently bomb proof.
If you want to just run the bike on a budget and have some fun for a year or two then buy a used engine and simply swop the top end (jugs ,pistons, cam etc )and other parts you need . Maybe put some new standard rings on ,lightly hone the bores rebuild the head and run it.
It won't be the fastest sweetest bike on the block and it might even smoke a bit but it will run fine and give you lots of fun.
