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well, I've read a lot about carb theory and how to adjust needles and whatnot, so I think I could guess my way through it mechanicly but how do I know where to stop. My cl 360's running rich currently (black dirty spark plugs) and I would like to lean it out properly, but I'd much rather have a too rich bike fouling spark plugs than a too lean bike fouling engines. So how do I adjust it properly and how do I know when it's right?

thanks
Kit

af

Hey, Kit. Are the plugs oily, or are you getting white smoke out the pipes? Well, you may already know these symptoms might indicate another issue besides fuel mix.
\Anyway, rich mixes don't make much power. You'll be surprised how quick your bike is when you get the mix leaned out a bit.
First of all, I'd make sure the float levels are set correctly and that the float valves are indeed seating. If they don't close off the fuel flow tightly you'll get raw fuel dumping into the carb bores... not good. Also make sure the air filter is clean and there is absolutely no obstruction to air flow. If there are problems with either of these, nothing else you do will matter much.
BTW,you'll know you're there when you get a tan or light brown color on your plugs.

you might also have plugs that are in the wrong heat range. ie. too cool etc. You could try a set one heat range higher. But. There can be many reasons for fouling plugs. You're jusy going to have to bite the bullet and try various things.. Could be jets too large. Adjusting the needles is a good place to start if they are easily done. That usually will be the least costly place to start. If you get the needles to the leanest position and it's still rich then you may have to look a one size smaller jet.

This is where the "fun" comes in to motorcycle ownership.

well the plugs are definiately the exact ones called for in the factory service manual, I've got no smoke and I don't think there's an oil leak. As far as I can remember, the main needle didn't have a clip on it for adjustment (although when I had it apart I didn't know to look) the float level could be off, but I don't get any fuel spilling out of the overflows (even when I forget to turn off the petcock) so I'm pretty sure thier seating the valve. Given the age of the various parts involved I think that I may have an air leak between the carbs and the head, or the diaphams might not be seated completely (She's developed a stumble, and is now unstartable without being fully choked and at WOT, and won't run worth a damn) also the filters are probably pretty bad, half the time I run it without them, I have some re-engeneering ahead of me to fit a K&N between the carbs and the battery.

where do I go to get different jets? it was hard enough just tracking down a rebuild kit.

so pulling the plugs is really the only way you can tell it's right?

thanks for the replies

could not having mufflers cause it to stumble and die? (I know these bikes are pretty backpressure sensitive... but that seems a bit extreme)

No Mufflers? Definately could be part of your problem. The bike is jetted for a given amount of back pessure caused by the factory mufflers. You start messing with that then you are rejetting if you want performance.

First you want to pull the carbs and find out what the jet sizes are that are in there. Then you go to any bike dealer (they all should stock jets and the jets are not brand specific as a rule)

Only thing is I can't remember if you need to go leaner or richer if you pulled the muflers. Pull the plug, that should tell you. NOw you are in for some trial and error . I would move up (or down) by two jet sizes at a time. You can also drill a set of the old jets if you have good equipment and numbered drill bits however at best that will only get you into the ballpark to the point where you buy the proper size jet to do the job.

Most likely you will have to change the high and idle jets for certain.

My suggestion would be to find a set of stock or near to stock mufflers and put them on. Better for the bike in the long run most likely.

are you saying your not running mufflers and no air box/filter!!!!!!!!!!!!!!!

i hope i read that wrong

if that's true you need to go back to engine basics 101


good lord its gotta make more hp without the air filter and mufflers,but i just cant figure out why its running bad

I wasn't sure how it would run, but when I first started it up and ran it around the neigbrohood it ran beautifully... I have the airboxes and mufflers (the mufflers are full of holes and the air boxes are a dirty mess)

I know that how I've got it now would need retuning (that's what I'm trying to do now) but I didn't think that it would be enough to seriously upset the idle to a point that it wouldn't run.

I've got a lot of experiance with fuel injected car motors, but as far as carbureted motorcycle motors I definiately need an engine basics class... that's what I'm here for.

hehe, you've made me all defensive

mysta2 wrote:I wasn't sure how it would run, but when I first started it up and ran it around the neigbrohood it ran beautifully... I have the airboxes and mufflers (the mufflers are full of holes and the air boxes are a dirty mess)

I know that how I've got it now would need retuning (that's what I'm trying to do now) but I didn't think that it would be enough to seriously upset the idle to a point that it wouldn't run.

I've got a lot of experiance with fuel injected car motors, but as far as carbureted motorcycle motors I definiately need an engine basics class... that's what I'm here for.

hehe, you've made me all defensive

ok you severly upset the flow of air in and out of the engine. you need air filters and perferably the air box to restrict the amount of air to keep a strong vacum through the intake track to help draw and mix the air and fuel together. what you did was kill that. same with the exhaust. backpressure is a idiots term. the last thing you want in any engine is exhaust backing up into the cylinders.


what you mean is a vacum pluse. the exhaust has to be of proper length and size to keep that. after each cylinder fires and the exhaust valve opens and the spent gases are forced out this devlopes a vacum behind that flow. which helps draw out the burn gas out of the cylinders. the more gas that comes out in the time the valve is opened the more fuel charge can enter the cylinder.


volumetric efficiency is what were dealing with here.. the more air you can stuff into the cylinders the better. but if there is exhaust still in there (there is always some) thats taking up vaulable space in the cylinder. most engines are around 85% that means in the time that the intake valve is opened the cylinder fills to 85% capacity. this is why a supercharger/turbo makes so much more power because its blowing air in and can fill well past 100%.


you narrowed the operating band of which the engine is efficient. with the proper tune of that combo the engine will probally have a very high idle and only make power at a high rpm in a very narrow band. less then ideal for a street bike.

you probally of seen race set ups without mufflers and such. but those work in a very narrow rpm band and are very unhappy anywere else.

so you need and exhaust and intake of proper size and length. plus the correct air/fuel ratio to match.

hope this helps. there is alot more to an engine then bolts and bigger is not always better.

good luck