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So just when I think I know all there is to know about 450's.... We restored a 69 CL450 last year pretty much all stock except with 3mm oversize pistons which takes the displacement from 444CC up to about 483. There are no other mods except that the baffles are pretty much gone out of the muffler/s. The problem I have is that it fouls NGK B8ES spark-plugs in as little as 10 miles B6ES's, which are two ranges hotter take slightly longer. I am pretty sure it is fuel not oil as the deposits are black and fluffy and not brown and sticky. In most riding conditions, say on a flat road and 1/4 throttle the engine seems to surge as if you are suddenly slamming the throttle shut all the way and then going back to 1/4. I do not know how better to describe it other than feeling like throwing a light switch on and off. Oh, and I cannot get a good idle either, too fast or not at all.
I have checked everything multiple times, points and timing are dead-on, I have changed coils, condensers, plug wires, plug boots etc. I have checked and rechecked the float levels, checked the operation of the carb slides which are vacuum and they seem fine, even checked to see if they were reversed or on the wrong sides and they are both the same so that did not matter. Also checked to see that the choke butterflies are completely opening and that the air filters are not plugged. Swapped the main jets with others the same size from another set of carbs just in case the DPO (dreaded previous owner) drilled them. Checked for vacuum leaks, synced the carbs them rechecked everything again.
So, I contacted two of the bigger carb places on the net, Carb Parts Warehouse and Motorcycle Carbs Unlimited, Both told me those jets are no longer available (old large round button headed), but felt despite the two condition changes, larger displacement and less restrictive exhaust, that the jet size is not likely to be the problem anyway.
Any one run into this before? Any suggestions? Thanks for the replies. Kevin

KCampbellNH
 

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I don't know what I'm talking about, but it sounds like the vacuum isn't holding up the slides.
I have no idea how you check that, and I'm real interested in what you ultimately find out, 'cause I'm going to be putting my 450 together soon, and I've never worked with those "Constant Philosophy" carbs.

Somebody help him!


FR
 

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Yeah, there's a reason why I went with 32mm Mikuni roundslides.

Surging means rich. 1/4 throttle means needle and pilot jet. If the stock carbs have an air screw, open it up to let more air in. See if there's any adjustments on the needles, and if so, raise the clip one notch to lower the needle. At 1/4 throttle, you're not even on the main jet yet.

Do a compression check just to make sure the rings are sealing.

I believe you can make the whole carb richer or leaner by raising or lowering the float level a mm or so. If none of the above works, lower the float level by 2mm.

quote:but felt despite the two condition changes, larger displacement and less restrictive exhaust, that the jet size is not likely to be the problem anyway.
Ooooookay... that's a silly thing to say. Your engine is pumping more air with the less restrictive exhaust and larger displacement. The air flow through the carbs is most likely faster since more air is going through them in the same amount of time as before. So more fuel is being sucked out of them, making things richer.
 

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I am sure the jets are still available from any Honda dealer. The problem is that most parts guys dont know how to find them. The trick is to get the part number for the stock jet. For instance if it is a 120 theen the last 4 numbers in the part number will be 0120. If you want a leaner jet then use the same part number except the last 4 should be 0110. That would be for a 110. The parts clown may not believe you since Honda doesn't list alternate jetting on the parts fiches(which are computerized now anyway) like they used to. Have him look up the part number anyway and you will see that they exist. Make sure he is using the 3 part Honda part number, not the Honda code.
Give it a try.
Ken

AHRMA 412
Vintage racing - old guys on old bikes
 
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