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Author Topic: 1982 CB750F... The resto-not  (Read 33462 times)

Offline irk miller

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Re: 1982 CB750F... The resto-not
« Reply #130 on: Dec 12, 2018, 12:28:02 »
Honestly, just oil, plugs, timing, valve lash.  If it runs well, and you have good compression, no smoking, etc.  I wouldn't do much else.  If riding shows your clutch checks out fine, then ride it til is goes.  If the carbs need work, then clean them and replace any rubber.  Otherwise, I'd let them go too, if it's running well.  I'm all about fixing things when broken, but just because it's old doesn't mean it needs fixed.  This DR370 I have is a solid runner.  I'm doing some performance mods, like going to a VM carb, and changing the exhaust.  But I have no intention on cracking open the motor because it's a good runner.

Offline Jimbonaut

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Re: 1982 CB750F... The resto-not
« Reply #131 on: Dec 12, 2018, 12:43:26 »
Nice one, thanks mate.  This for sure helps, and you guys are right - no sense in fixing stuff that ain't busted. 

Once I pull the valve cover I'll check the valve clearances, and I'll also check the tension on the two cam chains.  Offline, I've been told conflicting things about replacing the valve seals.  On the one hand I've been told replacing the seals is a good idea, but on the other I've been cautioned that replacing the seals will alter the compression in the top half of the engine which would then mean replacing the piston rings as well.  Or something like that (it was all in French - my French is iffy at best).

First off, before doing anything, I'm going to shine a light into the exhaust ports and see if I can see any oil on the valve stems.  If I can't I think I'll leave well enough alone.  If I can I'll probably replace the valve seals.  What's the common consensus on doing this - would I also need to replace the piston rings as well?  Again, with such good compression in the engine I'd rather not.
"I'm telling you Donnie, nuthin' but nuthin' but right"

Offline irk miller

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Re: 1982 CB750F... The resto-not
« Reply #132 on: Dec 12, 2018, 13:00:57 »
I don't understand how valve seals have anything to do with your compression.  They keep oil from entering the combustion chamber.  They're on the cam side of the motor, not the combustion chamber side.  If they don't leak, keep running them until they do.  With your compression numbers, it appears the valves don't leak either.

Offline advCo

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Re: 1982 CB750F... The resto-not
« Reply #133 on: Dec 12, 2018, 13:05:25 »
Nice one, thanks mate.  This for sure helps, and you guys are right - no sense in fixing stuff that ain't busted. 

Once I pull the valve cover I'll check the valve clearances, and I'll also check the tension on the two cam chains.  Offline, I've been told conflicting things about replacing the valve seals.  On the one hand I've been told replacing the seals is a good idea, but on the other I've been cautioned that replacing the seals will alter the compression in the top half of the engine which would then mean replacing the piston rings as well.  Or something like that (it was all in French - my French is iffy at best).

First off, before doing anything, I'm going to shine a light into the exhaust ports and see if I can see any oil on the valve stems.  If I can't I think I'll leave well enough alone.  If I can I'll probably replace the valve seals.  What's the common consensus on doing this - would I also need to replace the piston rings as well?  Again, with such good compression in the engine I'd rather not.

I don't think whoever gave you that advice knows what they're talking about. Bad valve seals, as irk said, only allow oil to enter the combustion chamber resulting in some smoke in the exhaust. They have nothing to do with the rings and can be replaced completely independent of each other.

Honestly, I would just leave the engine alone other than the routine stuff. Get it running and ride it, and fix necessary things as you go.

Offline Jimbonaut

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Re: 1982 CB750F... The resto-not
« Reply #134 on: Dec 12, 2018, 13:09:08 »
Yeah, now it makes sense.  Of course - I figured something was getting lost in translation.  It's not the first time.  I spent the first two years in Montreal asking for a Russian beer instead of a red one.  French, merde.
"I'm telling you Donnie, nuthin' but nuthin' but right"

Offline Maritime

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Re: 1982 CB750F... The resto-not
« Reply #135 on: Dec 12, 2018, 13:26:23 »
Yeah, now it makes sense.  Of course - I figured something was getting lost in translation.  It's not the first time.  I spent the first two years in Montreal asking for a Russian beer instead of a red one.  French, merde.

they were probably talking valve "seats" the part the valve seals against in the combustion chamber, not "seals" which keeps oil from leaking into the intake or exhaust when running.  with 165 cold compression your valve seats are fine, don't even lap them. And your seals are probably fine too if you don't get smoke on start up or while running.
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Offline Jimbonaut

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Re: 1982 CB750F... The resto-not
« Reply #136 on: Dec 12, 2018, 13:32:29 »
they were probably talking valve "seats" the part the valve seals against in the combustion chamber, not "seals" which keeps oil from leaking into the intake or exhaust when running.  with 165 cold compression your valve seats are fine, don't even lap them. And your seals are probably fine too if you don't get smoke on start up or while running.
Yes!  That was it - valve seats. 

Language barriers + dicky hearing in my left ear = room for misinterpretation.
"I'm telling you Donnie, nuthin' but nuthin' but right"


Offline Jimbonaut

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Re: 1982 CB750F... The resto-not
« Reply #138 on: Dec 12, 2018, 13:54:46 »
Fan-fucking-tastic.  I think.  Like most beer here - even if I pronounce it all fucked up and order something totally wrong, whatever they bring me is generally excellent.

Unless it's white beer, wheat beer, whatever.  Undeniably and unwaveringly awful, always.  Gose is truly unforgivable too.  Had a few porters last night in a local brew pub.  Damn they're good.  Recently got into porters and milk stouts.  Had a peanut milk stout the other week which sounds weird to say and looks weird to write but tastes amazing.

Russian beer huh.  The world really opens up fast when you have no idea what the hell you're saying in a foreign language.
"I'm telling you Donnie, nuthin' but nuthin' but right"

Offline irk miller

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Re: 1982 CB750F... The resto-not
« Reply #139 on: Dec 12, 2018, 14:17:11 »
haha I bet it does.  My last drunk was off of oatmeal porter.  Stouts and porters are where i live in the cold months.