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Discussion Starter · #1 ·
Just want to know what you guys think about removing just the head on the bike and nothing else? I have a 79 cx500 and the valves are not seating and need to be fixed but this is just on the left cylinder and not the right.



I have about 40-60 psi when doing a compression check on the left and around 120-130 on the right, when I added some compressed air to that cylinder I can hear air coming from the carb. so I really think it is the intake valves that need some work... what do you guys think before I pull the head?
 

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Before you pull the head, make sure the valves were closed all the way. Remove the valve cover and check that both sides of the rockers are loose when you do your compression test.



Do a wet test too, and a leak down test if you have the time and tool.



Double check your readings and conclusions before you start tearing into the engine, although you'll find that the CX is probably the easiest one you'll ever work on.
 

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Discussion Starter · #3 ·
I did h\the leak down test and that is when i was getting the air from the carb, what do you mean by a wet test? also I checked to make sure that the valves were closed with the cover off.
 

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Check the compression again after putting some engine oil (3 or so capfulls of a quart container) in the cylinder. If the compression numbers go up, then you've got stuck or worn rings. It's common for rings to sick if the bike has sat for a long time.
 

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Air coming out of the carbs is a sure sign the intake valve is either bent, bad or badly misadjusted.
 

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Air coming out of the carbs is a sure sign the intake valve is either bent, bad or badly misadjusted.


Air leaking out of the blowby tubes can sound like it's coming from the carbs.
 

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Discussion Starter · #7 ·
I know that it is coming from the valves because I filled the valves intake with carb cleaner and hooked up the air compressor and could see bubbles, now i did not feel any air coming from the blowby tubes. also about what Cobram had up there, I thought that it might have been stuck rings because the bike had not been used in 3+ years and I filled the cylinder up with penetrating lube and let it sit for a day then checked the compression again and still at 40-60 psi, at one time it did spike to 120 psi but I have not been able to get the pressure up again
 

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There's no problem removing a single head.I've done it several times over the years for varying reasons.Remember to use the coolant jacket drain bolt(10mm M6) on the front of the cylinder otherwise you get coolant into the cylinder and holes.



Head gasket re-fit video with tips,



http://www.youtube.com/watch?v=S1Bsc2zyihU
 

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Discussion Starter · #9 ·
Well I jumped the gun and removed the head, cylinder and walls look fantastic and some carbon build up on the valves so I think I will just replace the valves and call it good.



Also I was thinking of cleaning the intake ports to make it a little smoother (clean as is) but if I did that I would need to do both heads, what do you guys think, worth the time?
 

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In my humble opinion, soley based on removing the heads on my bike, I would do both. These have to be the easiest and best engines to ever work on I have seen in my life. All the work can be done without removing the engine, and takes no time at all.

My bike had sat in a bran for almost 30 years (only had 13K on it) and I stripped and cleaned it. I removed the heads BEFORE removing the engine just to look (looked really good) but did both just to make it perfect (cleaned valves and seats, although it didnt need much).



If the valves and seats on the other side are within spec, just clean them up. As for the bad side, I would replace them as a set.
 

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There's no problem removing a single head.I've done it several times over the years for varying reasons.Remember to use the coolant jacket drain bolt(10mm M6) on the front of the cylinder otherwise you get coolant into the cylinder and holes.



Head gasket re-fit video with tips,



http://www.youtube.com/watch?v=S1Bsc2zyihU


I just watched your head gasket video. Do you use that red stuff instead of a new gasket or in addition to a new gasket? How do you clean the surfaces? Is it okay to use a wire brush attachment on a drill? Just bought a non-running 1980 CX500 for $250 was told it needs a head gasket. I think this might be fun.
 

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I use Red High temp RTV,



http://cgi.ebay.com/ebaymotors/HIGH...Z200571309926QQptZMotorsQ5fAutomotiveQ5fTools



with 2nd hand head gaskets.



I use Blue Hylomar or the above with new ones,



http://cgi.ebay.com/ebaymotors/HYLO...ptZMotorsQ5fCarQ5fTruckQ5fPartsQ5fAccessories



I soften old crud on the surfaces with household paint stripper 1st(Use gloves).Then some WD40 and Scotchbrite/Pan scrub.You can use a Drill and wire brush attachment but never gouge,just a light and side angle with the Attachment.You can carefully use a scalpel/razor blade to get off stubborn bits but again only at a light angle so and to NEVER gouge the metal.I prefer the Wire brush attachment as I'm quite nimble with them and a small dremel is even better with wire brush attachment.



Then for good measure lay some 500 Wet and dry on a Glass flat surface and rub the heads to get a nice flat surface.You can use a Rubbing block with 500 Wet and dry for the Cylinders.



Paint stripper is also useful for softening carbon as is old brake fluid.Carb and Brake cleaner and some loo roll for degreasing/cleaning before application of any gasket sealant or gaskets.



As above ALL holes must be cleaned out before head bolts are put back in.Failure to do this will cause premature head gasket failure and head bolts torques re-checked after one thermostat opening heat cycle and the engine left to cool.



There are NO short-cuts on this job.Get it right and you may not have to touch the heads for years.Get it wrong and you could have to do it all again within days.
 
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