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1978 honda cx500
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Discussion Starter · #301 ·
So the new cylinder head came in, and everything looks good. Looking underneath, the valves all look great, but are just quite dirty and coated with carbon deposits. Im going to clesn the surface of them, but should i also be trying to remove them to clean their edge too? Would there be any sealing problems if i don't take them out and give them a good cleaning?
 

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'84 CX650E that is evolving into a GL500
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You really should take the valves out, clean everything thoroughly and then lap the valves to the seats before you install the new head.
But if you don't feel that you have the skill set for that you could screw in an old spark plug, sit the head on something combustion chamber side up so it is close to level and fill the combustion chamber with something thinner than water (alcohol, mineral spirits &c - gasoline would work but is NOT recommended) and let it sit for several hours to see if anything gets past the valves.
If the valves don't leak you can probably get away with leaving them in but if they do you need to lap them.
 

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Discussion Starter · #303 ·
You really should take the valves out, clean everything thoroughly and then lap the valves to the seats before you install the new head.
But if you don't feel that you have the skill set for that you could screw in an old spark plug, sit the head on something combustion chamber side up so it is close to level and fill the combustion chamber with something thinner than water (alcohol, mineral spirits &c - gasoline would work but is NOT recommended) and let it sit for several hours to see if anything gets past the valves.
If the valves don't leak you can probably get away with leaving them in but if they do you need to lap them.
Hmm ok thank you, that's good to know. And im sure i could do it, i would just need a compression tool for the springs. And im not sure how quickly they go bad but new valves stem seals
 

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'84 CX650E that is evolving into a GL500
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New valve stem seals could be a good idea.

Here's a pic of my valve spring compressor, a 6" C clamp and an old bushing with one side removed
Brown Wood Gas Tints and shades Auto part


In use on a GL1100 head. The telescopic magnet is for fishing out the collets and putting them back in
Gas Wood Auto part Metal Nut
 

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1978 honda cx500
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Discussion Starter · #305 ·
New valve stem seals could be a good idea.

Here's a pic of my valve spring compressor, a 6" C clamp and an old bushing with one side removed
View attachment 210162

In use on a GL1100 head. The telescopic magnet is for fishing out the collets and putting them back in
View attachment 210163
Haha love the innovation. Im definitely such an overthinker, telling myself i need a special tool for the job. And im going to lay the head upside down first and see if there are any leaks first. Its riding season and im ready to take her out for a spin, especially once i install this raesan unit
 

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'84 CX650E that is evolving into a GL500
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A real valve spring compressor would be nice but I don't need one often enough to merit the expense or storage space (the last time I needed one was 3 years ago and the time before that so long ago I can't remember).
The modified bushing lives in a drawer with other homemade special tools and the clamp and magnet get used for other things.
 

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Discussion Starter · #307 ·
Ok it definitely leaks, not crazy fast but still the liquids getting through.
A real valve spring compressor would be nice but I don't need one often enough to merit the expense or storage space (the last time I needed one was 3 years ago and the time before that so long ago I can't remember).
The modified bushing lives in a drawer with other homemade special tools and the clamp and magnet get used for other things.
Very good point, id only need it for this job, but i have some c clamps that woukd work. And the head definitely leakes from the valves so looks like ill be taking it apart. Gonna order some valve stem seals
 

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Don’t we have a member on here advertising valve seals?
 

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Discussion Starter · #310 ·
Thank you for the link! Gonna order some. Ill be rebuilding the cylinder head tomorrow and lapping the valves.

Before i order one from david silver spares, does anyone happen to have an ignition cap for sale here? I can't gey the aluminum rod out of one of mine and have tried everything. Its stuck in there good
 

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Discussion Starter · #311 ·
Quick question, so i took apart the head i bought from eBay, and everything seems to be good, except one of the valve seats has a bit of pitting on it. Ill post a pic of it. I just want to know if its too far gone, since this is my first time doing a valve job, im not 100 percent on when to call it quits. This is how it looks without me doing anything to it
 

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That doesn't look very promising. By the time you get that cut or ground out the valve will be a bit low in its seat.

Depends how fussy you are.

Or you could source yet another head.
 

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Discussion Starter · #313 ·
That doesn't look very promising. By the time you get that cut or ground out the valve will be a bit low in its seat.

Depends how fussy you are.

Or you could source yet another head.
Hmm damn thats not what i wanted to hear. Well i do have my old head. Maybe the seats would be good, but id have to smooth out those rough surfaces most likely
 

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Discussion Starter · #314 ·
Ok so on the original head theres some damage from whatever was boucing around in there, but the valve seats all seem unaffected. So this head seems like the better option. If i was to grind down those jagges surfaces, would it affect anything?
 

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Discussion Starter · #315 ·
Ok, so i rebuilt the cylinder head, relapped the valves and all that good stuff. Installed it on the bike with a new gasket, torqued the head bolts down for the first time. And did a compression test real quick to see what progress i have made. So just a reminder the left cylinder was reading at around 165. The left one now reads about 125 instead of the dreaded 0. But its still a bit low. I saw an old post on here that said to put a little oil in the spark plug hole and try again, and when i did that the compression read 175 on that right side.


A couple things to add, i noticed the right cylinder isnt getting much oil at all when i crank the bike. The left rockers i can visiably see getting oil but the right is significantly lower. I checked my oil level and it was fine, it may be nothing but just wanted to add it in here in case it was an issue.

Also, these were cold readings, since im also going to be installing the raesan unit, i havnt started the bike since i know my pickups are bad, just to avoid any unnecessary damage.


I guess my question here is, is the right cylinder reading lower since i had just installed a new gasket? And havnt been able to warm the bike to really get everything seated? I checked valve clearances twice and guarantee they were adjusted correctly on the compression stroke.

Also. I have seen a few posts here where members have stated they are able to run their bikes fine at around 100-120 compression. However i know my case is different since one cylinder is much higher than the other.

I feel like im definitely learning a lot so thank you all for your input.
 

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The raise in compression with the addition of oil indicates that the rings are now the compression issue.

I would not concern myself as it is enough compression for the bike to run. The CX motor is fairly tolerant of this.

Likely though that with several hundred miles the compression will improve. I would expect that the rings are jammed into their grooves with a mix of gummed oil and rust. This will often sort itself out. Put some miles on it once it has an ignition and then check the compression again.

Wide open throttle top gear pulls from 40 to 60 or 70 miles an hour helps.
 

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Discussion Starter · #317 ·
The raise in compression with the addition of oil indicates that the rings are now the compression issue.

I would not concern myself as it is enough compression for the bike to run. The CX motor is fairly tolerant of this.

Likely though that with several hundred miles the compression will improve. I would expect that the rings are jammed into their grooves with a mix of gummed oil and rust. This will often sort itself out. Put some miles on it once it has an ignition and then check the compression again.

Wide open throttle top gear pulls from 40 to 60 or 70 miles an hour helps.
Ahh interesting, that makes sense, it was pretty rough in there when i took it apart. The gap the coolant usually circulates through was filled with rust. Quite a bit of it too. But perfect, since its good enough that works for me until i need to do a more in depth repair. Ok then tomorrow ill probably install the rae san unit and see how she runs.
 

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When you put water in it to run it it might be a good idea to add some cooling system flush to loosen the junk in it.
Servicing the cooling system after you run it a bit but before you use it a lot might be a good idea (and make sure you get real coolant into it before it gets too cold even if you store it for the winter)
 

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Discussion Starter · #320 ·
When you put water in it to run it it might be a good idea to add some cooling system flush to loosen the junk in it.
Servicing the cooling system after you run it a bit but before you use it a lot might be a good idea (and make sure you get real coolant into it before it gets too cold even if you store it for the winter)
Thank you for the link i will definitely do that. The amount of crud in there was quite surprising, i didnt think it was possible for that much to get stuck in there
 
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