ClassicIndy600

Let me start from the beginning. There are two plugs coming from the engine (one goes to the CDI box and the other goes to the main wiring harness). The plug from the main wiring harness also has two single wire plugs (one goes to the CDI box and the other goes to the plug from engine that the main wiring harness plug plugs into).

All three coils have good spark with the key and kill switch on. This is where it gets confusing to me. Only two cylinders will fire and not always the same two cylinders. When I started cylinder #2 and #3 where firing. When I pulled the plug wire from #2 the motor died a little (like it should if all cylinders are firing correctly), but when I pulled #3 the motor died completely.

I tried three different sets of coils and a different CDI box with no different results. I tried switching the plug wires and spark plugs around with no different results. This is when I pulled the carbs to look them over (I did not find any issues so I re-installed them). When I re-installed them I switched #1 carb with #3 carb. When I fired the engine #2 and #1 cylinders now fired.

This is where it gets mind boggling. I then switched #3 and #2 carbs and #3 fired, but #2 did not fire so I took #2 carb off and tore it apart. The only thing I found was the 0-ring for the fuel overflow on the bottom of the card was missing. I replaced it, re-installed the carb and fired the engine. Now #1 and #2 were firing (this is when I thought I finally had it figured out), but now #3 was not firing (keep in mind I made no changes to the #3 cylinder which was firing before).

So at this point I don’t have a clue. If anyone took the time to completely read this entire post I really appreciate it and look forward to your thoughts as I am completely baffled.

BC_Dan

Have you checked the spark using an in-line spark tester? Weak spark or a bad plug may be the problem that will only show up when the piston is working. If the problem is always on the same cylinder, I would consider the possibility that the crank is out of phase, but your problem moves to different cylinders, so that's probably not an issue. With clean carbs, good spark, and mechanical ok (compression fine, crank fine) the engine should run. Try unscrewing the plug boots from the plug wire and cutting back 1/4" or so of the wire to get a better connection. I would throw three new plugs in, just to rule out a marginal spark plug...

__________________
2007 Dragon RMK 700 155", 2008 RMK 600 155", 2006 RMK 600 144", 95 Prowler 550 2-up, 1990 Indy 650, Really OLD AC Cheetah

http://www.avalanche.org/accidents.php

ClassicIndy600

Thanks BC DAN. I really am puzzled on this. I actually did cut the plug wires already and the spark plugs are brand new. I have even tried switching the plug wires around to see if the problem follows and the same with the plugs them selves. It seems that no matter which wire I put where the non firing cylinder still does not fire. I tried once again this morning to switch the carbs around, right now #3 is not firing so I swapped #3 carb with #2 and it still will not fire. So far I have had it where all three cylinders will not fire of course only one at a time. I don't understand why sometimes when I move carbs around the non firing problem follows, but not always. I think I am going to try a completely different set of carbs. Would you suggest using the same main and pilot jets or putting a different set of both in? Thanks for any ideas because this makes no sense to me.

I have an 84' and (2) 85' 600's and they are wired exactly the same as I have this 83' wired. Is there anything that would only allow the engine to only fire two cylinders and not always the same two cylinders?

Polaris650freak

Could be bad Cdi box. Try another one off your other 600


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ClassicIndy600

I think I will pull one of my others and try it, atleast I know they work. The one I tried before was an extra one I had lying around and was not sure if it worked. I thought it was strange though when I did try it I had the same results as the original one. Really what else could it be. Doesnt the cdi box distribute spark to the coils? Maybe there is a short or something. At this point I am ready to try anything new. Thanks

Polaris650freak

Or it could be a stator taking a crap. Stator's act real weird when there going bad.


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BC_Dan

Check for good grounds, too...

__________________
2007 Dragon RMK 700 155", 2008 RMK 600 155", 2006 RMK 600 144", 95 Prowler 550 2-up, 1990 Indy 650, Really OLD AC Cheetah

http://www.avalanche.org/accidents.php

ClassicIndy600

Polaris650freak, I am going to try a cdi box from one of my other 600 later today. BC DAN If that does not work what grounds should I be looking for. The only ground I know og is the voltage regulator, are there others? Polaris650freak, I am going to hope its not the stator, but if it nothing else seems to work I guess that would be my last resort. If no luck I Am going to swap the complete engine with a stock 600 that I know runs and if there are no issues there I do have another good crankcase I could swap the rebuilt top end to that crankcaes and hope I don't have the same issue. If I have to do that it won't be until spring. I will let you know later about the other cdi box. Thanks guys for the help.

mrholmquist

your wasting your time if you think this problem is CDI. On this engine all three coils are connected in series to the CDI box. It uses the same pulse for all three cylinders. In other words all coils are connected together and fire simultaneously three times for each revolution of the engine. The engine will run with any spark plug wire connected to any cylinder as long as the wire will reach.
If you had a bad CDI you will lose spark to all three cylinders .

Start from the beginning you say there is spark so.....

compression test

check the fuel pump is supplying fuel to all three carbs adequately

make sure fuel quality is good and no sign of contamination

Check pistons skirts for damage .... because this is a piston ported engine (no reeds) a broken skirt will cause a misfire

Do a visual check for cracked carb boots , fuel pump pulse line split or sucking air. While you are at it check to be sure the fuel pump pulse line is dry inside. If it has fuel inside it is a sign that the fuel pump diaphragm is ruptured which will allow fuel to be drawn into the crankcase and this will flood the nearest cylinder.

As for the carbs make sure the choke cables all have frree play in them. If you have a tight cable it will hold that choke plunger off its seat causing that cylinder to flood and misfire.
as you were switching the carbs around did you always make sure the choke cables stayed with their original cylinders. If you weren't paying attention to that and one of the cables is too tight it would explain the random nature of your misfire

Polaris650freak

He is losing spark. Not compression/ firing. Broken skirt or fuel pump or compression have nothing to do with spark


Also I have ran into this problem before using a tuned Cdi box. So yes it is possible for it to be Cdi it if intermittently loses spark and comes back on.

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mrholmquist

nope not on one cylinder . As I stated all three coils are wired in series.

And where does he state he is losing spark, maybe I missed that?
All I get from his post is a random misfire and when he checks he has spark to all three cyls?

Polaris650freak

He says only 2 cylinders will fire and not always the same 2 and he switches wires than it change to the other cylinders.


I think I know how these sleds are wired as I make drag cut harnesses for them. If it was the same cylinder all the time not firing I would agree with you it being a fuel or compression problem. But it's not the same cylinder all the time.


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mrholmquist

go back and read his first post again . I think you may have misinterpreted it the first time
. He said when he switched the wires he got the same results. The problem didn't switch to the other cylinders like you stated. When he switched carbs around that is when the misfire changed.

I agree that the misfire should not change if you have low comp etc... in one cyl . I was trying to get an overall impression of general engine condition. I was considering the possibility of marginal compression or other problems in more than one cylinder at the same time. In that case the problem could possibly be percieved as random.

ClassicIndy600

Ya guys, all carbs are getting fuel and when motor is not running all plugs have good spark. Like I said in the begging when I swiched plug wires or spark plugs from a firing cylinder to a non-firing cylinder nothing changed. The only time the firing of the cylinders changed was when I switched carbs around, but not always. #2 and #1 where firing and then I switched #2 carb with #3 carb then #3 was firing. So now #1 and 3# were firing. I took #2 carb apart and noticed the 0-ring for the fuel line bolt on the bottom of the carb was missing, so I replaced it and put the carb back on. Then when I fired the engine #1 and #2 fired, but now #3 did not (keep in mind I made no changes to # cylinder, carb, or wires). When running the cylinder not firing is not heating up like the other two. I tried a cdi box from one of my other good running 600's and only a slight difference. The #3 cylinder (which is the one currently not firing) did not make much noticeable difference when I pulled the plug wire compared to the other two cylinders. There should be a noticeable difference when each plug wire is pulled. I am afraid it might be something with the stator, but I really don't know anything about the stator. Can the stator not supply enough spark to the cdi box? If not why?

mrholmquist

What about those choke cables.

Again for the record

take the time and do a comp test and check the other things I mentioned

ClassicIndy600

I have adjusted the cables a few times. They now open with ease from half to full choke, before I had them adjusted and was real tight when flipping to full choke. No difference. The cylinders have right around 115 in each.

mrholmquist

The adjustment procedure is that you ensure there is approximately 1/8" free play in all three cables NOT how easily the lever flips from half to full choke. If you are unclear on the adjustment procedure I can walk you through it.

ClassicIndy600

I think I got it, but thanks. When I cleaned the cables and put them back together, I simply did not allow enough cable for the spring to fully compress. Sorry I guess I didin't explain that very well. I did not just adjust the plungers with out pulling the cables out of the carbs. They are all about 1/8" looking by eye when lever is in full choke position.

mrholmquist

You cant adjust the cables with them out of the carbs. And you dont measure the 1/8" in full choke position. You have to do the adjustment in the choke "full off" position (lever down). You should have the free play at the flip lever. Again if you need the procedure I can walk you through it.

ClassicIndy600

How do you know when the plunger starts to move for the 1/8 free play if it is inside of the carb? Maybe I do need the procedure, why don't you let me know. Thanks