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Discussion Starter · #1 ·
This seems to be a very informative site on the CB/CL450's. So, I thought I might ask for some help on getting my carbs dialed in. First, some info and history of my bike and what I have gotten myself into.

I have a CL 450 that I got from the original owner. It was a "barn find", literally. It hadn't ran for quite a few years. I have started a cafe project with the bike and first want to get it running properly. It has almost 14k miles on it. The bike was pretty much all there and the PO had stripped another CB450 years ago and had lots of spare parts to go with it.

I am using a CB500t tank. It is spotless inside. Good petcock. I set the valve lash, points, new plugs, adjusted cam chain tension and tore down the carbs and cleaned them as best I could. The carbs were actually not that bad inside. Jets are all clear and the piston/needles slide smoothly and easily. The carb boots seem good with a solid seal. I set the floats according to the "credit card" method on this site and adjusted the carb balance and air screws are at about 1 turn out on each carb. The float bowls are in need of new gaskets. They have hardened a little and leak pretty badly. Would this leak keep the fuel at too low of a level in the bowls? Should the float bowls even be full enough to leak around the gaskets?

I am using UNI foam filters and stock pipes. The bike fires on the first kick or as soon as you hit the magic button, but doesn't want to run smoothly or for very long. It will rev up fairly well with the choke on, but doesn't want to idle. Or it will idle pretty good with the choke off, but as soon as you turn the throttle it dies.

I'm just a shadetree mechanic and do not make any claims of mechanical genuis whatsoever. So, anybody got any tips? What am I not thinking of here? This is a really cool little bike and I would love to get it running reliably for the spring.

Thanks in advance for the help. If I think of anything else, I'll post it up.

Chris
 

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It's definitely lean Chris. Are you sure the slow/pilot jets are not plugged. The holes in them are very tiny. They are under the plug that is beside the main jet. Number 42 in the picture.

 

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The fact that it runs better if the choke is closed (even a little) indicates that it's a lean condition.
If your "air" screws actually have an effect if you manipulate them, then your low speed jet is probably ok.
You did not mention the size of your main jets - ??
Depending upon the year of the carb you are using, and the cams in use, 450's can run anywhere from 130 to 150 on the main jet.
I doubt that you will be able to get any sort of meaningful plug reading at this point.

I would also suggest doing a good critical static-time on it (using a little light bulb) before proceeding any further.
At this point you cannot rule out an electrical problem - it's very common for point/condensors/coils to glitch once they get hot, but act ok when they're cold. If the coils are original, remember that they're very old - and condensors have a limited life, even if they've just been sitting on the shelf and never been used.
Folks just tend to assume they need to mess with the carbs right away when things don't go right.
Remember, this is just about the simplest carb ever made - not a lot that can go wrong with them if they're kept clean.

You also did not mention your compression readings - ??? This should be the very first thing you do, very basic diagnostic info.

Give us a little more info.....
 
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Discussion Starter · #4 ·
I haven't done a compression check, but it seems to be fine. There is equal resistance on both cylinders when rotating the crank. I will check that. The timing definitely needs to be checked. Will do that too once I can get it to idle consistently.

I think I'm going to get a complete tune up kit for the bike as well as carb rebuild kits and do a super clean up job. The float bowl gaskets are shot anyway. The bike is a 73 CL450, so I would guess it has 145 mains and 38 slow jets? I don't remember what they were when I had the carbs apart before. I wouldn't think that using the Uni filters would require a rejet. But maybe. Possibly shimming hte needles? I have heard that these carbs are pretty tolerant of small changes in intake and exhaust.

Thanks for the input. Keep it coming.
 

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The carbs are very tolerant - usually rejetting is not indicated when switching to Unis.
The needles are not adjustable on a 450 - they do, however, need to be loose and wobbly in the end of the slides, not frozen in place.

If it starts quickly and easily, the compression is probably ok - but you should check it anyway - it's like how the doctor checks your blood pressure and heart rate first thing when you see him - basic diagnostic info. Engine warm, throttle wide open, NO CHOKE.

You do a static time with the engine off.....
 
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