Not a V-4 but Still an older Yamaha

[overdrive75]

So I have a question about my '91 Yamaha exciter. It has 9,800 miles on it and I have rebuilt the top end twice because of a melt down on the cylinder on the PTO side. So the engine has 2 O.E. bore Wiesco pistons in it, and a new jug on the PTO side. That is the only mod. Now I am blackening the plug on that side, while the other side gets dark but not black. I have gone though these carbs and they were supposedly synced when I had it to the dealer a few years ago. I have only riden it maybe 300 miles since then. It also has spark knock under some conditions, and boggs under others.

Help, I know this has to be carb problems, but I am not sure where to start.

Thanks. I know I have the v-max 4 but I do like riding this sled. Most of the times these problems aren't there, but when they are it's a really pain. To cure it I usually just put two new plugs in and then good to go, for a while.

Thanks for the help.

Patrick

:vmax4:

[AL P]

OMG..........Man...I just seen this thread, and noticed your from my area, and remembered that I was suppose to get back with ya on something, and completly forgot..SORRY overdrive..I`ve had soo much going on lately, I completly forgot..
anyway, as far as knocking, It sounds like its experiancing some SEVERE detonation, which is really really bad, especially on a two stroke, as I`m sure you already know..
anyway, what grade fuel do you run in it? what compression are you running, and are you positive the timming is spot on?
and lastly, when you rebuilt it, did you also replace the crank seals? if one were leaking, I`d think it`d cause it to run lean, but your plugs are telling a differant story, but still...

again, I`m really sorry for forgetting about ya..

AL P

[overdrive75]

Al P I run premium in this sled as far as fuel goes. I haven't check compression in a while, actually since the 2nd rebuild. I haven't replaced any of the crank seals, however when it was in the dealer to have the carbs matched, I did ask them to check that and they said the crank seals were good.

As far as the severe detonation, yeah I know that it is bad, thought I would have learned that on the first melt down, but I didn't, I learned the hard way, and had to burn it up twice, and take out the cylinder to boot.

Thanks for the reply, and no big deal on getting back to me.

Patrick

[AL P]

humm..weak ignition system? plugs could/would load up and look black if you were experiancing weak fire, may also contrubute to the detonation. maybe your plugs are`nt firing hot enough to cleanly burn all the fule in the combustion chamber, and its leading to the plug read, and detonation?

[fastmax]

If my ol memory serve me correctly, The exiter engines had a lot of burndown issues. I seem to remember they had some harmonic problems causing mysterious lean conditions and unexpained burndowns. I know PSI sold a fluid damper that was supposed to cure it. I dont remember what Yamaha did to correct the problem, maybe someone on here remembers. You may have to go to your local dealer and go thru the old service bulletins to figgure it out.

[overdrive75]

Fastmax,

Where would I find those old service bulletins. Also, this is the exciter II, this one has the Nicicyle (spelling) cylinders. My brother has an exciter and that one has the iron cylinder sleeves. He hasn't had a bit of problems and is harder on his than I was on this one.

Al I was wondering about the coil and maybe going to change it out.

Thanks,

Patrick