Fouling Plugs, too rich a mixture?

MrSled

MrSled

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Hey Guys,
I bought a 1998 Vmax SX 600 this year. It is an excellent machine when it has new plugs in it, but for some reason, it doesn't take long to foul them up. If Im not riding at 60+ mph, they foul within a few hours of using them. Usually not all in one ride, but if I go back out to use it again, then they will foul. Here are the things I have noticed so far: when my plugs start to go bad, the machine will idle really low, and then die. And can correct this with the idle screw, and sometimes it will fix my problem for a bit, but after running it on lower RPMs, it will foul the plugs again. Whenever I pull my plugs, they are black and oily. I am currently using the BR9ES plugs, i think thats the name. So, I think that the mixture is obviously too rich. Can anyone try and explain what to do to decrease the richness of my mixture? I see that there is a cable adjustment for the cable that goes to the oil pump from the throttle, but it looks like it is already adjusted as far as she goes. So, are there any ways to adjust an air or fuel screw on the carb itself? Would I need to pull the carb apart to adjust it, or is there another adjustment I can make that I haven't seen yet? Any help is appreciated. Thanks a Lot!

-Rudamin
 
Hey Rudamin,
I had the exact same problem last weekend on my brand new to me 97 SX700. Last week was the first time I had it out and put actual miles on it. I fouled 2 sets of plugs in 1 day. Same scenario as you and same looking plugs. I brought it in and come to find out that the previous owner had replaced the carbs on my sled and the new carbs must have come off a triple pipe and I have a single pipe. Bottom line, shop said that I was using the wrong jets. That's why it ran strong, fast and great until I shut it off. No way I could get it started after about 50 miles, until I replaced with new plugs. Then would fire on the first pull. The shop guy also suggested going to the BR9EYA plugs. I'll give them a try but they can get expensive.
 
Rudamin, I had problems with my vmax 600 twin as you described and I found out to make sure when I first started the sled was to keep the idle up, just under engagement. Let the engine warm up a little while. Don't be so anxious to get on the throttle. I also dropped the needle a half adjustment, so it would run cleaner in the midrange throttle position(most trail riding). My first year owning the sled I must have went through a dozen plugs. My next year when I would let it warm up my plugs lasted over 2000 miles. The tech. pages explain this very well on adjusting your carbs...good luck CP
 
You may also want to check your oil pump adjustment. Yamaha came out with a bulletin back then, it contained updated specs (leaner) for the oil pump.
 
Mtn viper, could you point me to where I can find that bulletin? I am very new to owning a sled and getting around this site and all, so if you could assist me with this, i'd appreciate it.

My dad and I are beginning to think that my floats might be sticking and that my carbs just need to be cleaned. The guy I bought the sled from bought it brand new and it is all stock. He has never had any service done on it. So, maybe it does just need a good carb cleaning.

I have another question: Does anyone here run carb cleaner through their gas once in a while to help cleanout the carbs without pulling them apart? If so, what kind do you recommend?
Thanks again,
-Rudamin
 
I just posted this on another message...

I had the same problem and I took it into a local shop. (Motorsports Plus
in W. St. Paul, mn - the guy was awesome and inexpensive).

The twins on yamaha's have a problem where they collect the dust off of the belts in the carb intakes. He took out the carbs and cleaned out the intakes (which he said were really bad). The sled is incredible now, I didn't know I was driving without all my power, and boy does it sound nice now.
 
Rudamin, I used to have a copy of it, but I gave it to the guy who bought my XTC. Your Yamaha dealer should have one, but I can tell you what it said for the 600 twins. If you look at your oil pump, you'll see linkage with a tang on it, there is a line stamped on this tang. There is also a line stamped on the oil pump housing. The original spec was, with the throttle held wide open, the lines on the tang and housing would be aligned with each other. The updated spec calls for the lines to be offset 1mm from each other at wide open throttle. To achive this you bend the cable mount at the pump, downwards (adding a little slack to the cable so it dosn't pull the pump open as far)
This bulletin was for complaints of high oil usage, but if its using to much oil, it can cause plug fouling problems also.
 
Rudamin + Assultr = the same dude, just so you know

Okay guys, heres the scoop. I pulled the carbs, thoroughly cleaned them, including the jets and floats. There was some belt dust at the inlets, but nothing too serious. I put it all back together, popped new plugs in, and they fouled on me again. So...I decided to try a hotter plug, BR8ES. They have lasted much longer (about 4 days instead of 1) than the BR9's, but they are finally beginning to foul. Now, I havent actually completely fouled any plugs, but what happens is my engine will start idling very low, and I can't get the sled above 20 mph. So, I dont know what the heck is going on now. I have checked the oil pump, and it is adjusted like mtnviper recommended.
Now, here is a bit of info to add...when these plugs first started fouling, I could let my sled sit for about an hour, go back out, and they would start running just fine...but eventually, they would foul again?! Anyways, I dont know what the heck is going on. I also cleaned my airbox because it was a bit gunked up when I pulled the carbs. I guess my next step is to adjust the pilot screw for a leaner mixture. Anyways, I appreciate any help. Thanks.
-Assultr
 
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