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Discussion Starter · #1 ·
Hi, I'm trying to restore a '72 CB450 and don't really have any experience with this. The bike was in storage for a couple years, but it ran fine before it was put into storage. Unfortunately, it was stored with the old gas partially filling the tank with no stabilizer in it. When I tried to start it after trailering it back to my garage I found it wouldn't start. It would start for a couple seconds if I used starter fluid...until the ether burned off. I'm assuming the carbs are clogged and need to be cleaned. I've removed them from the bike, and I can access the top of the carb. On the left carb the piston was stuck, but now that is moving freely. If I blow through a straw the piston rises without much effort. I'm unable to get the bottom off the carbs though. I moved the wire hook down and tried to remove what I think is the float bowl. I don't see any screws or bolts holding it in, but neither will come off. Are there any bolts holding that piece in place, or is it just stuck. I'm guessing it could be stuck by varnished gas, or perhaps the previous owner used some king of sealant on the gasket that is holding it in place. My question is should I try to force it, or is there something else that should be removed? I tapped it lightly with a hammer, but it seems to be on very solidly...I just haven't been able to find anything else that is holding it in place. I'm suspecting the jet may be clogged...but I won't know until I can get access to it.

Thanks,
Mike
 

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Do the carbs one at a time so no parts get mixed up in the process. You might have some luck by folding up a towel/rag on your workbench and rapping the bowl on different corners until it pops loose. You'll get it eventually.

Remove ALL JETS. Spray carb cleaner through all air passages and soak the jets before blowing them out. I pull a tiny bristle from a wire brush to help clear any obstructions in the smallest jets. Been doing it for years with no adverse affects. It wouldn't hurt to verify that your float height is set to factory specs, and also do a test of the float needle valves to see if they shut off fuel flow.

It's probably be a good idea to flush out the tank and remove the petcock for cleaning as well..


GB :mrgreen:
 

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Discussion Starter · #3 ·
Thanks for the advice. I'll try wrapping it in a towel and tapping it on the table until it comes free. So there should be nothing else holding it in place, I take it? I feel clueless asking such basic questions. I thought it would make sense once I got it apart after reading the carb setup thread here and many others. I've got to get it apart first though. So would you recommend using the spray carb cleaner, or the type that you soak the parts in?

Thanks again.
 

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The dip tank will require you to totally take it apart - there are felt and nylon washers on the choke and throttle shafts that will get destroyed.
Do not dip tank the "dome" or the slide needle either, more nylon stuff to destroy.
 

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No - there is nothing else (screws or otherwise) holding the float bowl onto the bottom of the carb. I would guess it's "glued" on by years of varnish and accumulation.

Joe
 

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If you can't see any gasket maker silicone around the bown to carb mating surface, then I'd agree with the other and say that they're just stuck on with varnish (old fuel).

I personally don't like soaking whole carbs or any major parts of them. I do soak all of the jets in carb cleaner though. Then spray through them with the carb cleaner straw and poke around VERY GENTLY with a brush bristle. Don't jam or force anything into the jets. If a bristle doesn't fit the holes then don't force it. Find one that's ultra thin, flexible and very very tiny. I always used the carb cleaner spray can cap to soak my jets in. A glass bowl or baby food jar would suffice..


GB :mrgreen:
 

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Discussion Starter · #7 ·
Thanks. That seems to have worked well. When I put the carbs back on the bike yesterday it was leaking gas from the left one quite badly. I reseated the o-ring on the drain screw last night and just put it back on the bike. It seems to be running very well now, after some slight adjustments of the idle screws. Now I just have to rebuild the front break caliper, replace the chain, do some other basic rust removal/cleanup and it should be in great condition...thanks again for the advice.
 
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