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Discussion Starter #1
Hey im looking into rebuilding my old cb450sc. Its been a couple years since ive had her running. Rebuilt the carbs before it sat so they should be fine. It only likes to start when its warm. Seems to idle a little low. Anyone have any suggestions or links on compression testing and general rebuild information?
 

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Carbs that have sat for two years most likely need to be cleaned. Seriously I doubt ther is anything going on that requires a compleat rebuild.
TOOLS
 

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Discussion Starter #3
Right on that may be true... however i might just do the rebuild as an excuse to stay busy in the garage. Just finished my turbo IDI swap into my dump truck... im getting bored. Anybody have a rebuild or gasket kit they recommend? Piston and Rings from honda? Any parts suggestions or general recommendations?
 

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Spec is 185 PSI per cylinder +/-15 PSI, giving a minimum of 170 PSI. Compression test should be done with the engine hot, the air filter removed and the throttle wide open. That being said I reliably ran an '82 CB450SC engine down past 145 PSI, and while burning a lot of oil, ran fine everyday for months. TOOLS1 is right, It's probably in the carbs. In my experience one of these engines with low compression will start easier cold than it will hot. When it is hot, the clearances expand and it will turn over longer before catching.

There is a sticky on how to rebuild and synchronize these VB carbs.

If you are lazy try using Seafoam or Berrymans B12 Chemtool. The hard parts in these carbs don't tend to wear out, while the rubber bits are easily degraded by the ethanol in modern fuels. If that doesn't work, start by rebuilding the carbs.

What was your storage procedure? IE, what did you do before parking it.

While rebuilding one of these engines is fairly straight forward there are some hard to find parts and oversize pistons are unobtanium. Before ripping into the engine, I would suggest checking around for the availability of wear parts.If you are talking about a full top and bottom rebuild you could easily spend $800 before you have any machine work done (valve seats ect).

This is just some food for thought as I am actively working on collecting parts for an '82 CB450SC engine rebuild.
 

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As above plus I would get it running properly then ride it a few hundred miles to get everything loosened up again before taking the compression test. Were I really hard up for something to do I'd find a project bike to work on when it rains and ride the Nighthawk when the sun is shining.
 

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I'm guessing you're in Canada, if you use the US dealer fiche system look at the 1983 or 85 since 1984's didn't exist here
 

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Discussion Starter #8
Oh sorry about that jim its actually a 1985 or so it says on the plaque on the fork. Looks like ill go ahead and rebuild them. I had them synced a couple years ago you think ill need to resync if i dont mess with the linkage? Where do yall get your gasket kits for the vb carbs?
 

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In theory the sync will stay the same if the adjuster screw isn't messed with. In practice that pretty much holds, it'll be close if nothing else.
I use the Honda OEM carb kits
 

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