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Discussion in 'Thumpers' started by mtn500, Sep 29, 2008.
There's bolts under your valve inspection covers. DO NOT USE A CROWBAR!! Pull those covers and you'll see.
after the bolts from under the covers are out tap on the cylinder head cover in the solid spots with a rubber mallet to break the seal between the gasket and the head.
Please clean the motor off before taking it apart.
If by chance you get it doing again, you do not want all kinds of sand/dirt inside.
Maybe power wash it.
Now, if I am looking at this right, it took mtn500 2 years and 3 months to fix his, if it is even fixed by now.
I hope that this never happens to me.
Hope that you finally got her running, you certainly have stayed with it.
Well I took the advice and got the top cover off and it looked good. When I drained the oil out, I found that there wasnt much oil to drain. Now I know why it seized ... Also took the side cover off and I find a broke stud and a washer that goes below the half-circle weight. What is that mechanism called/for? Since there was no stud holding the small guide in place, it damaged the chain guide as you can see below.
That's your counterbalancer adjustment. You'll definately want to repair that.
Did you find any debris in the drained oil? You may have some pieces hanging out down in your sump.
I found the stud and washer in the oil pan. Stud is broke and intake threads are pretty mangled. I might have a to buy this used xl500r motor I have my eye on, but I'm hoping the head will be workable ( even though the kicker is stuck and it won't move ) :eek1
I will have to make my own timing chain marks since I'm having no luck getting the piston to move to TDC, or to move at all. Maybe a piece of wood hammered into the spark plug hole will do the job
I got the piston loose. Now I got to check out the condition of my cylinder. I also started my own thread, so I won't be jacking your thread anymore .
Did you order the Athena Complete gasket kit? Does it come with all the rubber seals as well?
Yes the Athena kit does come with several rubber seals; I don't know if all that are needed are there as I have only needed the right side crank case cover gasket thus far. It was the result of said gasket slipping during installation that has led to my multi-year engine rebuild adventure .
I'm still working on mine. I did manage to get the time to remove the cam and sprocket and all bolts holding the head on.
<a href="http://s136.photobucket.com/albums/q191/mtn500/?action=view&current=IMG00312-20120111-1908.jpg" target="_blank"><img src="http://i136.photobucket.com/albums/q191/mtn500/IMG00312-20120111-1908.jpg" border="0" alt="Photobucket"></a>
This piece looks toast as is. My next step is to dig deeper and see what else may be damaged. As for the head I will either try to acquire another one or send it off to be machined.
It has been 5 months since my last post but I have made progress on the motor just not the progress I would have like to have made. I have purchased a motor from a 79 model that is in good shape and plan on using that cylinder head and cover to replace the ruined parts.
My new/current question deals with the cylinder from the original motor. I plan on installing a new piston and rings but I do not want to bore out the cylinder and install an oversize piston. Based upon the condition of the cylinder from the below pics, can anyone with experience comment on if the cylinder needs work? I can only see one minor vertical mark, which I think would be OK, but I would like an experienced opinion
Its definitely glazed if its shiny enough to read the reflection of the bag... Nothing running a hone through it cant fix. General rule of thumb is to run your fingernail across the scratch. If it catches, you should bore it. If not, probably okay to just hone it. If you have access to a bore gauge, check it to see if it is in spec and ROUND.
Definately measure it to see if it's in spec.
Just recently I had my machinest measure a standard bore XR600 cylinder I've had kicking around for a number of years. It looked great. I figured I'd hone it and use the 10.8:1 compression Arias piston that came out of it (it looked great as well) and be good to go. Wrong! It was way out of spec in both size and roundness.
So the moral is, just because it looks good doesn't mean it is.
Thanks. I've located a local machinist and I am going to see if I can get honed and measured there.
I haven't been able to find a source for OEM size pistons, only larger sizes. Anyone know of a source for original size pistons? I don't want to go with a bored cylinder/larger piston if I don't have to. What are the downsides, mechanically, to running a bored out similar type motor?
Downsides? None that I can think of.
I have a 1980 xl500s that I am redoing. Took me a few months to get the engine back together and I still need to paint the side covers. My piston was toast but the cylinder looked ok so I was hopeful like you that all I needed was an OEM piston. No such luck. My cylinder was over the serviceable wear limit so I had to go 1st over. I went with a Weisco10.5:1.
My inner valve springs were shot and there was evidence of slight vlave floating ( cacrbon on the top of the piston was scuffed from the valves kissing the top of the piston, luckily the valves were undamaged) Might want to check your springs while you have it apart.
I was expecting my cam bearings to look like yours but I got lucky. Even so I debated about boring it for some needle bearings. I'm sure I'll regret not doing it while I had the valves striped out of the head.
I got lucky, my cam chain is in good shape, but if you have a line on where to get a cam chain guide and a new adjuster Id love to know.
It has been a little while since my last post and I do have a little progress to report; but again not as much as I would like to have done. I had a local machinist bore my original cylinder for a slightly larger aftermarket piston.
In looking at the cylinder head from my donor engine and comparing it with my original head, I noticed that oil channels are not present on the cam journal surfaces on the 1979 (donor) head but they are present on my original 1980 head.
The smoked 1980 head:
The donor 1979 head:
My Clymer manual references the oil channels but the manual is generic for all model years.
Did the 1979 model not have the oil channels? If not how was the cam bearing lubricated? The 79 head is not worn/damaged...
I'm looking into sending my smoked 1980 head off to MegaCycle Cams in Cali to have a needle bearing cam installed. I could use the repaired head and keep the motor mostly original or keep it as a spare part; though I'm leaning towards using the repaired head if I'm going to spend the money to repair it. Does anyone have any experience with MegaCycle Cams?
I have a few more questions but I won't list them all in this post.
Thanks in advance.
Bump per my last post.
Anyone familiar with the 79 XL500 head and if it has the oil channels like the 80 head?