Bent Spark Plug Tops

[Routs1]

I am running a Yamaha 701, with a B pipe, stock carbs/intake and a ADA head with 185PSI in either jug. The issue i am running into is that spark plug in my front cylinder(closest to the nose), continues to bend after a few rides. The part that is bending is just the threadded metal at the top in which your plug wires connect to. Unfortunatly around my area I am unable to find solid top NGK plugs. Currently I am running BR8ES.

From reading on the internet, this bending is an effect of running too hot for the plug. Is this something that other people have had happen? I had this issue with my 650 as well.

My next step is to switch that cylinder to BR9ES in hopes to run a bit cooler.

Your thoughts are greatly appreciated.

 

[Magyar68]

thought you needed the short plugs on any 61x. BR9HS

 

[Scraggly]

not with a ada head, they use long reach. stock head is short plug

 

[JHD]

So BR8ES is the correct plug for the ADA head? Sorry for the thread jack..

 

[stagesrt4]

So BR8ES is the correct plug for the ADA head? Sorry for the thread jack..

thats what ive ran for 2 seasons

 

[Freakrider]

Never heard of this issue ? Is your coil wire short and pulling on it when motor moves around and tip gets loose to where it can bend it ?

 

[schicks]

i have seen this happen on my old 701 motor. I am not sure what causes the bent tips. It would not happen all the time, but every once in a while I would see that the tip bent...somehow. I also noticed when the tips were bent that they also unscrewed partially as well. I run the solid tips now, have not seen it happen since. I know the 701 was running a little lean from an air leak about that period, so heat causing the tips to bend seems plausible.

 

[OCD Solutions]

I would believe they were contacting the hood liner long before I would believe they were getting hot enough to bend.

All the references I found on the web refer to the electrode getting bent due to detonation or heat range, not the top where the wire connects.

 

[schicks]

hmmm....not sure that my hood liner is anywhere close to the plug tops. b-pipe head pipe towers the plugs as well i think.

could current jumping a bad contact in the boot cause this?

 

[OCD Solutions]

I agree but mechanical contact is about the only thing that makes sense to me. If not the liner then what about a breather tube not setting right when you put the head on?

 

[schicks]

that is logical, but i am with the OP; i don't think that contact with something was the root cause. I am ocd with my stuff, my friends make fun of me for it. I no longer experience bent tips...ever, and my stuff is tuned per builder specs now. Still no answer i know, but more info on the issue. I will talk to some gear heads about the problem and see what they say. Maybe it was poor water migration.

 

[Routs1]

On both my 650 and my current machine I am 100% confident that there is no physical interference. I do question the caliber of my plug wires and boots and have the intention to change them to some 8.5 mm MSD's. On a side note is pulling apart the black box, chanign these and resealing it a time consuming job?

One thing that I didnt mention is that I do have an audibal miss in my low speed circuit which goes away at about 1/2 - 3/4 power. I havent taken the time to determine which cylinder is causing this, or it may be both for that matter.

Does anyone know if it would be wrong for me to run the BR8ES in one cylinder and the BR9ES in the other?

Thanks for chiming in everyone.

 

[yamanube]

Does anyone know if it would be wrong for me to run the BR8ES in one cylinder and the BR9ES in the other?

Yes, are you running plugs with solid terminals or screw on terminals. I am with everybody else, in saying there is some sort of physical force on the plug that is causing the issues, either improper wire routing or hitting the hood/drain tubes. I'd have to think the terminals are coming unthreaded giving something more leverage on the terminal and bending it. The miss could be from something as simple as this terminal being loose and getting poor spark, test the spark on both plugs. You ski has a single coil so both plugs fire at the same time and being that you (likely) have a single carb your fuel should be delivered to both cylinders the same. If you are having issues with one cylinder only look into reeds or plug wires/boots.

*edit, just saw your comment regarding solid top plugs

 

[OCD Solutions]

Wrong would not be the correct term but unnecessary comes to mind. Nobody else needs to do this so neither should you. Sounds like you need to focus on solving a few of the known issues like the miss and not look for bandaids to put on the symptoms. A good rule of troubleshooting is to fix what you know is wrong and see what is left. In your case, solid top plugs and new coil wires might be all that is needed.

The ebox is pretty simple to pull apart and the seal is usually salvageable. If not, they are available for $15-18. A decent screwdriver that mates with the ebox screws is a huge advantage as well.

 

[Routs1]

So plan of action would be to continue running the same plugs, change my wires/boots and work out the miss.

I havent been able to locate solid terminal NGK's in my area (central Canada) so I am forced to run the screw on's. I do notice that even on my back cylinder which seems to be performing correctly, there is enough vibration to cause the tops to slowly thread themselves out.

 

[yamanube]

So plan of action would be to continue running the same plugs, change my wires/boots and work out the miss.

I havent been able to locate solid terminal NGK's in my area (central Canada) so I am forced to run the screw on's. I do notice that even on my back cylinder which seems to be performing correctly, there is enough vibration to cause the tops to slowly thread themselves out.

No, the plan would be to put new plugs in, the same on each cylinder, then figure out if you have an ignition or fuel related issue then work from there.

 

[OCD Solutions]

The threaded tops shouldn't be an issue either. That's all that is available to most these days, including myself. They don't come out of the box with the caps tight so I make sure the are all secure before I install.

I buy plugs in a 10 pack, gap and tighten the tops on all in advance so they are ready to go whenever I need them.

 

[Routs1]

There is obviously a larger issue than the type of tops that I am running. I will work out the miss and be let you guys know if that or the wires make a difference.

From my understanding the miss could potentially be caused by running lean, and in my case specifically in the low speed circut as it clears up as the carb opens further.

Thanks again for the insight.

 

[yamanube]

If it is just happening on one cylinder, it is less likely a low speed circuit issue (but still possible) I would check the reeds and test the spark before putting a new coil in. It is not as simple as just putting new wires on, the wires are epoxied into the coil and you will need a special tool (or makeshift tool) to dig the old ones out. There is no reason to throw new parts at untested issues.

 

[Quinc]

You should post a picture.