[classicjeb]

I am having a problem with compression on the right cylinder of my 1979 CX500. I removed the Pistons and just can't figure out what is wrong. If anyone can help please shoot me any ideas. Thanks



Was a member on the old site, just haven't posted recently!! Eric B









[media]http://picasaweb.google.com/classicjeb/AppraisalPhotos?authkey=Gv1sRgCKmxr-mQmb7xCA#5511340001384424370[/media]

 

[Blindstitch]

Something doesn't look right with this picture?

 

[MotorcycleCommuter]

Low compression can be caused by worn or cracked rings, worn or scored cylinder walls, burnt valves or valve seats, bent valves, sticky valves or a head gasket problem. If you can't find any problem with the pistons or rings then I would examine the heads.

 

[MotorcycleCommuter]

Crap! You got me! I responded before I saw a picture of the rods. I never thought of that as an issue.

 

[cxlover]

The connecting rod on the right isn't bent and that's why it seems low. Light up the torch and give it a bend. That should drop the commpression so its even

 

[lucky]

Something doesn't look right with this picture?

is that the new mod to make your bike run like crap?? lol all i can say is damn thats bad

 

[Spring Brook Rider]

So what would cause a rod to bend like that? Too hot? Bad metal? Combination of both? Not enough Wheaties???

 

[lucky]

only time i have seen that is when the valves are to spec (to tight) i only saw that tho on small engines

 

[Toehead]

Hydrolock,





or hitting the valves. If it hit the valves you should be able to see the imprints on the top of the piston.

 

[kingston73]

I've seen pictures of broken or cracked rods, but not bent like that, crazy.

 

[cxlover]

That is weird, any marks on the engine were the rod was knocking?



It could also have been due to pre-ignition forcing the piston down while it was coming up

 

[Allan]

It looks as if it shortened the rod enough that the skirt of the piston was hitting the crank.

 

[Bryan]

You're the luckiest guy on the forum, Classicjeb. I've never seen any rod bent to that extreme. I can't believe that it didn't just break and throw it's way through the wall. Unbelievable.

 

[Billrod]

I think he should be nominated for the HAND GRENADE of the month award.

 

[CXSarnia]

You're the luckiest guy on the forum, Classicjeb. I've never seen any rod bent to that extreme. I can't believe that it didn't just break and throw it's way through the wall. Unbelievable.

I don't see much in the picture(s) to give a scale, but to me - those don't look like they came from a CX and Jeb is just pulling our collective leg. If a CX engine was still running with one connecting rod in that condition, we truely do have the most reliable bikes on the planet.

 

[Blindstitch]

Remember Dick had the one lung GL250.

 

[LRCXed]

I've been waiting for him to come back in and respond to you guys. These ARE from a 79 CX500. I have been working with him via email and phone for a few months now. I rebuilt his carbs for him. He sent them back with black carbon build up inside the venturi. SO he pulled the heads and found a slightly bent valve. So I did a valve job on a set of heads and sent those to him. Still only 70 psi on the right side. After several emails he was convinced to pull the motor down to see what's going on with the right piston. I told him the rings may be stuck and to look for that as a possible issue. So today he sends me an email and says the rings look fine but the piston has marks on each side of it. Also he asked if I had any other ideas of what else it might be. LOL He was sooo focused on what I told him to look for that he didn't see the rod. After we talked and laughed at the missed issue on the phone, I told him we were on a new site and to get registered again and put this post up. I LMAO when I saw how many jumped on this. It just goes to show how many of us are out there willing to help a newbie.



Anyway, he is in need of a block, crank, pistons and rods. His block ended up having rust pits on the R. cylinder anyway. If your close to Mississippi and can help him out cheep I'm sure he would appreciate it. He's worked on this bike for a long time on and off and only has this to show for it. I have parts to build him a short block but it might be cheaper if your closer. He already has the new rings for it.



And due to the large amount of bend in the rod, and there was only a slight bent valve, all I can figure is that the cylinder got flooded with fluid, gas or water, and it hydrolocked that piston when the engine started. That's what happens when the piston can't go up any further but the other piston makes it do it anyway.

Yes I would say these engines are quit resilient. The project I'm working on for myself started out much the same. I started it up before I tore the bike down. Of coarse it ran a bit sluggish, but it ran too!

 

[lucky]

damn so i was kinda right about the valves i didnt think about the hydro lock though on top of it all this just makes me love my bike even more now.....

 

[totaldoughnut]

I would say hydrolock to bend it that severe. Or maybe its possible that the engine was severly oversped and got some major valve float?

 

[BikerMike]

LOL the only thing that would do that to a rod is to be hydraliced..... u cant conpress a liquid