sx700 cdi help

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pinboy122

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Feb 9, 2006
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northern ill
I started the thread red head help. its gone from a "carb problem" to a possible cdi problem. can anyone tell me if a bad cdi can cause inconsistent or mis-timed spark? im not having any luck searching for info.
what is happening is the sled is not running on all cylinders at idle or low speed. At first it was the clutch side,then it jumped to the mag side. It moves around and sometimes only runs on 1. I still get spark on the cylinders that arnt running and theres plenty of fuel. I hate to just buy parts and throw them in without a good idea of the problem. is there a way to test the cdi? I don't know anyone close to switch with.
 

I say you still have a possible carb problem. The coils all fire at the same time, two are just wasted.
 
From what I understand is the only way to test a CDI box is to switch it with a good know one from another sled. It is cheap enough to try changing the coils. Did you take any reading with an Ohms meter ? I would try that first.
 
Have you moved your coils around? How about plug caps? They are cheap to replace. Essentially, the way to test a CDI is to test everything else one at a time and rule it out, until all you have left is the CDI. I would start looking also at your stator, maybe you have a weak spark. Clean the flywheel.
 
Thanks for the replys guys. I found a guy that has an extra cdi to try tomorrow. In the mean time I found a little crud in the fuel tank so I pulled it off,cleaned it up and will put a new filter in tomorrow. I'm going to add a clear in-line filter as well.i just have to be sure nothing is plugging the pilots.
As for changing the coils and plug caps, no I havnt changed them around. I may be wrong but it seems like I get good spark on all 3 even on which ever cylinder happens to not be running at the time.
I know it's not the same thing but this reminds me of a 289 ford race engine I built a few years ago. I tried everything to get it right but in end it was the new msd al7 box that was bad even though msd tech said it wasn't possible...
It's a good thing I don't have to pay myself by the hour!!!
 
If one coil is firing, then 3 are firing, and they all fire at the same time. Only one cylinder is at tdc though. If you're hitting and missing on all three, you have either got messed up carbs, messed up plug caps, or maybe the throttle switch is acting up. It is not the cdi
 
Just because you have spark at the plug, while it's laying on the cylinder head, does not mean you have spark inside the cylinder.
 
you can move the spark plug wires to any order to see if 1 paticular coil moves the problem to another cylinder. Have you removed the spark plug caps and used a ohm meter on them, those go bad often with age and they will cause you all kinds of goofy running problems, i would start right there, they need to ohm out at 5oooK
 
Ok, dwarf and mr.viper, I'm catchin on to how this works. I'll test the plug caps if I get time to work on it tomorrow. I didn't realise you could switch the wires all around but the problem moves from cylinder to cylinder so I can't isolate it. I think I shoulve started workin in this thing in October!!!
 
If you still have the factory plug caps on that sled, ohm them. Those things are known for goofy running problems. When putting the leads back on the plugs, close your eyes, and plug away. Any wire can go to any plug, and make no diference
 
This is so frustrating. So today I bought new caps,the old ones were green and crusty.i really thought that was it. Nope. I also cleaned the fuel tank with new filters. This time it was the mag cylinder that wouldn't run. It did at first but after it would idle down for a minute it would noticeably run rougher and drop rpm. I switched the plug wires all around with no difference. While running rough if I put the choke on half it would get a little better for a few seconds.It still runs awesome on the top end but every time you let it idle down the 1 cylinder drops out. So I was back to thinking fuel/carb problem and pulled them off again.i took the mag carb all apart and couldn't find anything wrong. It seems the problem happens most at idle to 1/4 throttle then you have to crack it wide open to get it back on all 3. The only thing I have not done is gone into the needles. It's been years since I've done it(different sled) and I'm not so great with tiny parts... Also I swapped the cdi,no change,dwarf was right. Also the flywheel looks ok.... Gettin ready to drive it into the bonfire
 
I am going to say it again. Your carbs are dirty!!! Clean the pilot jets, and physically look through them to make sure they are clear. Blow the pilot circuit clean. Remove the fuel screws, and clean that circuit. Make sure the tiny washer, and O ring are still there, and inspect the O rings for any damage!!! If you are not using an air compressor to clean the carbs, you are wasting your time
 
I hear ya dwarf. I've cleaned these things an blew out all passages at least 6 times. Pilots are brand new and I can see right through them. I think I'll order new orings for the fuel screws and inlet needle seats. I don't know what I could be missing. I'm going to add a inline filter coming out of the tank and run a bunch of fuel through the lines to be sure all the fuel is double filtered before I put the carbs back on.
 
What rpm do you have the idle set at? If they idle too low, I know that they drop cylinders. Idle should be in the 1600 rpm range. If the belt isn't adjusted properly, and is too tight, that also will drag the idle down, and cause it to drop cylinders. Your statement that you flip the choke, and it clears up for a bit tells me you have a carb problem. Without touching anything, try pulling the belt off, and fire it up. If the belt is too tight, and dragging the motor down, doing this will confirm that. DO NOT REV THE MOTOR WITH THE BELT OFF!!!!!!!!!
 
i know this is not the likely cause of the problem.... but have you ruled out a rub through?

ohm out the plug caps----> ohm out the coils----> ohm out stator and pu coil-----> look for rub throughs------> change plugs------> then go back to the carbs-----> pulse line okay?

other than that... i would have to guess a pu coil could be on its way out. thats almost every thing on that sled!
 
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roudyroy1 said:
i know this is not the likely cause of the problem.... but have you ruled out a rub through?

ohm out the plug caps----> ohm out the coils----> ohm out stator and pu coil-----> look for rub throughs------> change plugs------> then go back to the carbs-----> pulse line okay?

other than that... i would have to guess a pu coil could be on its way out. thats almost every thing on that sled!
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Pinboy... I really have no way to say this politely, so I'll just say it....Don't listen to this advice..especially the p/u coil part
 
it doesn't cost you anything to take a multi meter and check this stuff out so why not... Make sure you post the problem when you find it, I'm interested because now this got personal.
 
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dwarf717 said:
Pinboy... I really have no way to say this politely, so I'll just say it....Don't listen to this advice..especially the p/u coil part
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Maybe you should try a bit harder to find a way of being polite.

While I agree with most of your advice for pinboy - according to you I've waisted my time fixing hundereds of sled and many more other carborators without compressed air. Some visitors here may not tackle thier carb cleaning given this advice if they don't have shop air which kind of defeats the whole purpose of this forum.

Personally - blowing air through passages that move fluid doesn't always tell me they're completely clear but gauging backflow with carb cleaner does and has spit out stuff compressed air did not.

Anyhow - I'd agree that the pickup coil, or the ignition system in general is unlikely but no more so than an unmetered air leak which you haven't mentioned.

Most just want to help so lighten up, would ya?
 
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