Weird plug readings**Updated W/ pics**

[Mike W]

Well I dialed in my carbs on my '06 RN today and got it pretty close. I'm having the same problem I had with my '98 RN though. I checked the plugs when I got home and the diode on the rear plug is washed clean. It is wet but the diode looks like a new plug. The front plug has a nice brown color. I have an ADA head w/35cc domes which came off my old 98 RN. Not sure if its the head but I removed the head last time I had it out and the O rings looked fine. The carbs are jetted/adjusted the same so I can not figure this one out.

 

[Boris]

2 motors, same head and same problem.
Are both domes the same and have you tried switching them around ?

I'm no expert but might be worth a shot ?

 

[Mike W]

2 motors, same head and same problem.
Are both domes the same and have you tried switching them around ?

I'm no expert but might be worth a shot ?

Yep... When I had the head off I took the domes out to inspect. Got them mixed up and just put them back in the head. I saw nothing at all wrong with them.

 

[Mike W]

I rechecked the L/S screws and the rear was set at 1 turn out and the front was at 3/4 turn out. Not sure how that happened but I'm sure I turned it the wrong way when setting the idle. Anyway, I'm Not sure if the screws being off like that will cause this though.

 

[750SX]

I think it is your head as well. Try switching the domes for sure, and est it again. If it continues to happen you may have to get the top of your cylinder decked a little because a sleeve may have dropped, which will cause a leak. I think Boris made a good point about, "same head, different motor, same problem.

 

[Mike W]

I think it is your head as well. Try switching the domes for sure, and est it again. If it continues to happen you may have to get the top of your cylinder decked a little because a sleeve may have dropped, which will cause a leak. I think Boris made a good point about, "same head, different motor, same problem.

I don't really see it being a sleeve. Its a '06 stock motor. It has to be something going on with the dome or O ring but I dont see ANYTHING wrong with either.

 

[felix5oh]

That has happened and turned out to be water injestion.


1 turn rear and 3/4 front sounds normal to me, Isn't the rear the hotter one?

 

[Idok]

I rechecked the L/S screws and the rear was set at 1 turn out and the front was at 3/4 turn out. Not sure how that happened but I'm sure I turned it the wrong way when setting the idle. Anyway, I'm Not sure if the screws being off like that will cause this though.

shouldnt the screws be more like 1.25 out on both?

 

[tipafew]

shouldnt the screws be more like 1.25 out on both?

I guess that would depend on his jetting.
I would do a leak down test.
I have also found head leaks by running my boat on a hose and just watching the water flow coming off the head when I blip the throttle. If you get bursts of air, you know you found your problem.

 

[Idok]

I guess that would depend on his jetting.
I would do a leak down test.
I have also found head leaks by running my boat on a hose and just watching the water flow coming off the head when I blip the throttle. If you get bursts of air, you know you found your problem.

I agree, but with std. dual 38's and a FPP on a non ported motor.......pretty sure they should be about 1.25 out on each one..

 

[Mike W]

I agree, but with std. dual 38's and a FPP on a non ported motor.......pretty sure they should be about 1.25 out on each one..

Your right. however I had 72.5 pilots and had to turn them in more. I rejetted the carbs this morning and put the 70 pilots back in. Now it's at 1.25 turns out and it idles good. i think it was a little rich on the L/S anyway.
I also replaced the BR9ES plugs with BR8ES and I will run it and see how it goes. I'm not going to rip this thing back apart and chase this problem. I'm just tired of wrenching. When it breaks I will know exactly what it was then fix it. :biggthumpup:

 

[Idok]

Your right. however I had 72.5 pilots and had to turn them in more. I rejetted the carbs this morning and put the 70 pilots back in. Now it's at 1.25 turns out and it idles good. i think it was a little rich on the L/S anyway.
I also replaced the BR9ES plugs with BR8ES and I will run it and see how it goes. I'm not going to rip this thing back apart and chase this problem. I'm just tired of wrenching. When it breaks I will know exactly what it was then fix it. :biggthumpup:

with 70 pilots, it should be sitting at 1.25 out (+ or - a little bit)

9's arent hot enough, you def need 8's

 

[Mike W]

with 70 pilots, it should be sitting at 1.25 out (+ or - a little bit)

9's arent hot enough, you def need 8's

I just found that out. :icon16: Not up on this spark plug thing.

 

[Mike W]

Took it out this morning for about 10 minutes and the same thing. Just off idle to about 1/4 throttle it just ran bad. Sounded like a person with a cold with a flemmy throut. Thats the only way I can describe it so sorry.
I rechecked the plugs and the rear plug was dry and washed clean. The front was nice and dark. I got it home and pulled the head. I inspected everything and I found ABSOLUTELLY nothing wrong with the domes and O rings. In the picture, the rear of the head is on the left. The top of the pistons looked fine as well. The front piston looked a little rich but I'm no expert. I'm really at a loss.

 

[Crab]

sounds to me like a popoff thing, perhaps your needle and seat is worn, time to check it. One cylinder may be going rich and blubbery if the popoff is too low, I had that trouble on my X2 when tuneing it this year.

 

[Mike W]

sounds to me like a popoff thing, perhaps your needle and seat is worn, time to check it. One cylinder may be going rich and blubbery if the popoff is too low, I had that trouble on my X2 when tuneing it this year.

I just switched around the domes. I'm going to reinstall the head and take it to the lake to see what happens.

 

[Big Kahuna]

well, look at the rear dome, it has a different burn pattern on it, like something was blowing by........... also, carbs are not ment to be exactly the same, 1 turn on one carb may not be the same on the other........ also, check to see if the butterflys on the carbs are sync'd, if one is open more than the other that could be causing problems also.

 

[madscientist]

how about using a carb balancer from a vw shop that is used to balance the carbs via vacume ?

 

[Superjet3]

fire the motor up on the trailer and look down the carbs.. You shouldent see gas dripping out the booster at idle. If you do you need to replace your needle and seat or adjust your popoff pressure a bit higher.

 

[Mike W]

well, look at the rear dome, it has a different burn pattern on it, like something was blowing by........... also, carbs are not ment to be exactly the same, 1 turn on one carb may not be the same on the other........ also, check to see if the butterflys on the carbs are sync'd, if one is open more than the other that could be causing problems also.

I don't have much experience reading domes but I see what you mean. My front carb is slightly open. I just thought thats the way they were supposed to be.

fire the motor up on the trailer and look down the carbs.. You shouldent see gas dripping out the booster at idle. If you do you need to replace your needle and seat or adjust your popoff pressure a bit higher.

No excess gas dripping out. That was the fist thing I checked. I have brand new needle and seats and I adjusted the popoff at 40 psi.

Well I switched the domes and its still doing the same thing. Rear plug being washed clean. I did notice that the rear part of the case just below the cylinder has some oil residue oozing out between the case and cylinder at the gasket. When I removed the head a week or so ago the cylinder rocked to the port (left) side seperating itself from the gasket. I didn't think too much of it until now but could that be a potential air leak?