Vmax running on 1.5 cylinders

E

EagleJason

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Joined
Jan 17, 2014
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30
Location
Alaska
hi, I'm new. I have an 01 SXR and a 98 Vmax500XT. the Vmax is not consistently running on both cylinders. I have changed the plugs, it does not seem to be overly fouling plugs. What could be the problem?
 

have you taken a look at the resistance on the plug caps? There is a 5k ohm resistor in the plug cap. They do go bad, and that can cause running problems. The plug wire is a stranded core, and the plug has a sheet metal screw inside it, you unscrew it counter clockwise off the wire. If the sled is that old and high mileage, they could be bad. Make sure you are running the BR9ES plugs, and if you have an inline spark checker you can test the plugs with it running make sure it is spark not fuel. Could be your idle circuits if you can get it back onto 2 cylinders at higher throttle settings.
 
I have the BR9ES plugs in, i put a brand new set in today... but first... I started it and drove it to haul water (I live in bush Alaska) from a creek. I ran up to dad's house and the machine was doing 'ok', but when i went to restart it, it backfired sharply and quit. after that it would start, but not rev over 3000 rpm. One plug was wet and clean still. I noticed that the exhaust had come off, wether from the backfire or was that way previously I don't know, but I put it back on. the machine would start, but still not rev up. I went in and called the 'local' Yamaha dealer (382 miles away by road, when the road's open) and they gave me some suggestions, including one that must have applied to a newer machine. I went out, looked at the the things the dealer had suggested, could find nothing and the machine started and ran ok. I drove it up to a local gas station, bought brand new plugs, put red Heet in the gas and it's run ok for the rest of the day... any ideas?
 
not revving over 3000 rpm is a tors issue. Follow the harness from the carbs back to the connectors. Pull the 2 bullet plugs apart from the harness, plug the 2 together from the engine harness. This bypass is to TEST if it is a tors issue, not fix it. Too little slack in the carb cable is what normally causes the problem, but if it just pops up like that it could be the carb switch shit the bed. If it backfired when you started it, there was fuel in the pipe so going back to the running on 1.5 cylinders again I would say it is a spark problem that is being intermittent. Down the line you can get into the stator, cdi, rusty flywheel but checking the plug caps and using an inline spark tester would be a quick start to check it out. You could also Ohm the coils and see if they are the same, could be a coil going bad.
 
a couple mechanics here local i am friends with also suggested the coil. 1 said 'try heet, it may just be ice in the line/carb'
i am going to try to get a line tester and find out, but i am in a bush community in alaska 100 miles from the closest city, in a straight line, with only snowmobile or airplane access during the winter as the roads are not kept plowed (10' drifts, glaciers, et al eat the road)
we don't have too many people living here, so it's sort of trial and error and any part i have to pay to get shipped in.
 
Also, what is tors? the tech at Yamaha said the same thing, but said that i should find 2 wires, 1 brown and 1 black w/yellow or white under the carbs. he said to unplug them from the sensor in the carbs and plug them into each other. they are not there. i did find 2 wires of said color but they were not under the carbs nor were they plugged into it. They were a part of a 6 wire plug head. Does the 98 have this? will i be able to find the right wires?
 
It's about time for some pics so that we can see what your looking at. As far as using dry gas in a 2-stroke: DON'T! Dry gas effects the way 2 stroke oil mixes with the gasoline. It will cause problems with lubricaton and damage the engine. If it speculative that there is water in your gas, drain the tank and pull and clean the carbs. Pull over the engine with the carbs off to clear the gas out of the fuel pump and start over. 2 stroke engines are NOT able to pass water through them like a 4 stroke, if there is water suspect it has to come out.
 
Sorry i've been away, I haven't had a chance to take any pics, helped fight a house fire, chaperoned a school lock in, then a birthday party and was asked to preach since it was the pastor's house that was on fire... all since you asked for pics. I did notice that the seals on the exhaust are different and not self-aligning on the Vmax as they are on the SX. I put the exhaust back together correctly (the machine was being used during the firefighting and so i noticed that problem more and more) and it is running much quieter and smoother now. I'll update more as I have time.
Thank you.
 
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