I'm at a loss and need spark plug help, REAL BAD!

[jsimonh]

I'm sure most people are aware of the Champion Plug thread. I have had the plug that the guy gave me in my Z for awhile. I tried the N3C with no luck. So I bought some plugs from O'Reilys, they were the NGK BR8ES. So on Wenesday I went riding and I changed the plug that the guy gave me (The old plug, I was going to do some plug chops because of my new jetting). When I took it out I noticed it was a BR8EG I thought no big deal. I put in one plug after another and could not get my Z to start. I could kick it and kick it and it would backfire, but not start. I went through 5 plugs and none would work. Every once in awhile I would stick the BR8EG in and it would start right up. I went to the local Yamaha place and the parts guy told me that the R would ruin my CDI? I have seen on here that many of you run the R plugs, so I didn't take him to serious. I asked if it would help to run B7ES and he said it would mess the piston up and I would have to stop and constantly make sure it wasn't overheating. I ended up leaving with 3 B8ES and his assurance that they would work. I just tried one of them and it would backfire, but not start. I stuck the BR8EG back in and it started right up. My Z has run on B8ES and BR8ES before, but isn't wanting to run now.

Any Ideas? I really need some help with this.

Sorry for the long post, but I wanted to provide as much info for you guys as I could.

[Howdy]

What does the plug look like when you pull it out ( the one when it ran for a minute )? Black? Silver? Tan? White? Wet, Dry, ect. The condition of the plug will help other determine the problem.
Howdy

[TeamGeek6]

. I went to the local Yamaha place and the parts guy told me that the R would ruin my CDI? . I asked if it would help to run B7ES and he said it would mess the piston up

Absolute, total, complete BS. Been there, done that, no kaboom. Ive run every range of spark plug from stone cold to the longest thread and resistor/non-resistor I can find with no problems. If a plug was too long and hit a piston or valve that would be bad, but going from an 8 to a 7? Not likely.

Heres the key:

"I ended up leaving with 3 B8ES and his assurance that they would work. I just tried one of them and it would backfire, but not start. I stuck the BR8EG back in and it started right up."

If I put a non- resistor plug in my 250R, even with the hopped ignition system, it wont start. Put a resistor plug in, it fires right up. If I connect the evil twin sister ignition, itll fire anything, resistor or non-resistor at an 0.100" gap, but its meaner than a pit bull with aids and quite dangerous to work with.

The ignition coil to the spark plug circuit must have some resistance or the coil is effectively shorted out when the CDI fires and no spark is generated. The resistor does electrical things I wont bore you with, but just say there needs to be some resistance there.

I use a non resistor cap and wire, with a resistor plug. The goal is to have the total resistance of the spark plug, cap and wire (added together) equal to the resistance of the secondary of the ignition coil. The world is at peace then.

The other part of your message, about running on a non-resistor plug in the past, thats hard to sort out, the ignition could be getting weak, fuel system or weather changes can goof it up. The place to start is putting whatever plug in makes it run, then go from there (obviously).

[freewheel3]

This might be a stupid question but, are you gapping these new plugs?

[grundlegrabber]

Just out of curiosity, which plug was stock original equipment on the Z?

[jsimonh]

Howdy
The old one that is working (BR8EG) is a creamy brown color. The ones that are not working (BR8ES and B8ES) are brand new and never been put into the Z. I have used other B8ES and BR8ES in the past, but these are not working now for some reason. When I put the plugs in the boot and ground it to the cylinder and kick it over I can get slight spark. But when I install them it's a no-go.

With the BR8EG in it, it will run fine and I can ride all day. But if I put something different in it won't even start.

TeamGeek6
What?

freewheel3
Yes to what the manual says.

grundlegrabber
B8ES

[brapp]

ok factory specs on it are a b8es plug gaped at 0.7-0.8mm(0.028-0.031) of an inch, that woudl be stock and that is where i woudl start from presonal experiance and then build from there.

[jsimonh]

Alright, this morning I took out the BR8EG and put in a new B8ES gapped under spec. When I did this it would act like it wanted to start but wouldn't. I removed the new plug several times and tried different gaps. The Z never would start, but once again I could put the BR8EG in and it would start right up. I'm becomeing very concerned that something else is wrong. Wold the EG plug have a hotter spark than the ES plug? Could this be a timing problem? I was thinking maybe the EG was creating a longer or hotter spark and was overcoming the timing?

I'm really having trouble with this.

[OldSchoolin86]

B = 14mm thread size

R = as you know resistor and who ever told you it's going to ruin your CDI is nuts

8 = heat range

E = 19mm thread reach (never changes by different heat ranges as someone else thinks so)

G = Fine wire nickle alloy center elctrode

I've never seen a G before, I had to look that one up. http://www.ngk.com/images/NGKsparkplugNum.gif

The "s" means it's thier basic 19mm reach plug with a center electrode type plug. Now just as a guess I wonder if you have a bad plug wire, cap or coil that only allows enough juice threw for the "g" to fire correctly. IDK but I'd check out those parts before you buy any more plugs.

[jsimonh]

I have checked the boot, but not much other than that. What would I check and what am I looking for?

Thanks

[OldSchoolin86]

I have checked the boot, but not much other than that. What would I check and what am I looking for?

Thanks

I don't have a book on the Z so I can't offer any specs for ya, hopefully someone that knows will chime in.

[jsimonh]

I don't have any electrical measuring equipment, but I did just check all the wires and connections and everything looks good. There was a ground wire that didn't look to grounded, so I grounded it better and put the new B8ES in. It was still a no go . I did stick the BR8EG back in just to make sure it would still work and it started right up.

[bigredhead]

Also a potential stupid question here.. but the plug that works good.. does it have the thread type tip or is it the screw on ball type thing ?

When you look inside the plug boot.. does it have 2 wires that grab the threads on the plug tip or is it a rounded shape for the screw on ball thing ?

Hey.. weirder things have happened lol...

[jsimonh]

They all have the screw on ball thing. I don't think that was stupid at all, because that is one thing I thought to (loose head thing on plug).

If my CDI was weak would that cause this problem?

It's frustrating to have problems and not know the answers .

[brapp]

well the only other question i ahve is what year is it and was any of the stator or timing parts replaced, the ytz 250n is set up to fitre at 16 degrees btdc at 2000 rpm and the ytz250s fires at 18 degrees btdc at 2000 rpm, not sure if this coudl be a possible problem, but her eis a bit of other info that may help, to check the pick up coil disconect the red/white wire and the ground wire between stator and cdi connect ohm meter lead to the red/ white whire and the other to the ground whire, the ohm meter readign shoudl be 9.6-11.8 ohms, to check the source coil, disconect brown wire and black wire(ground) between source coil and cdi unit and conect them seperatly and the readign should be between 284-346 ohms.

to check ignition coil resistance readings should be between 0.66-0.92 ohms for primary windings and 5015-6785 for secondary windings,and if the ignition system checks out try replacing the cdi unit with a new or known good unit and recheck ignition system.