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hot pipes

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AndreRA3:
Nathan,
plug caps refer to the sparkplug wire boots, or connectors.  If the boots (or caps, or connectors) are toast, they will have higher resistance and as a result the spark will be weaker (if it sparks at all).  Same goes for wires and coils.  But if only certain cylinders are doing that, wires and boots are the best guesses (changing the wires might mean replacing the coils, though).

As for your problems, I would clean the carbs with Yamaha carb cleaner, with the carbs on the bike.  Just drain the bowls, fill them with a 3:1 ratio of gas and yamaha carb cleaner, kick twice with the ignition off, and wait 30 minutes.  Drain bowls, repeat until the liquid you drain comes out clear.  I did this on my bike and the bowls are shinny on the inside (I later opened them up to check the jets).  Kicking the bike will draw some cleaner up the jets, but DO NOT RUN THE BIKE, as the cleaner has a very low octane rating (I think).  One of the guys on the old forum (were I learned most of what I'm telling you) dipped his carbs in the yamaha cleaner and they came out shinny inside and out.  Inside only was good enough for me, though  ;) .

Checking your sparks might be a good idea, as upgrading my ignition helped a lot.

These are all guesses, by the way.  It's definately (probably? maybe?)  a combustion issue.  Wether it's fuel related or spark related, that's a different story...

Good luck

heffay:
you say you assume that it is in the carbs even tho you have them balanced to the best of your ability... i would still think it is in your carbs too.  what bob said about the idle circuit might be a good place to start.  BUT, i was unaware of the points being situated in that way too so they might also be onto something there. 

Sandcast 2356:
ah, now you're speaking my language. I have tested the spark and all seemed well, the carb cleaner thing sounds interesting, any particular reason I should use Yamaha carb cleaner? Can I rule out the points (being they are mechanically flawed, refer to open forum under "My Bike")

AndreRA3:
Nathan, Yamaha carb cleaner is good because it does not damage the seals and gaskets in the carb (which is why it can be used without dissasemblying the carb).  It's not too expensive, I paid 12 bucks for one at the local yamaha dealership, and it's used at a 25% concentration with gasoline.  Replacing your points (and setting a correct ignition timing)  sounds like the first step here anyway...

Good luck again, man.

eldar:
well I ran into something like this. I would not worry too much about points but a couple of quick tests you can do would be to check the wire coming from the coils. If there are cracks then it would be time for new wires and coils possibly. Next look at the plug CAP. measure its resistance with a ohm meter, you can get them for cheap about $15 or so. These are not the most accurate but work enough on a limited budget. The plug cap should be UNDER 10000 ohms around about 5000 is normal I think. Also change your plugs if you have not done that. If you have try moving them to different cylinders and see what happens. Otherwise I would have to say that your #4 is running too rich at idle and even at higher speeds. When do the rough sync, use a smooth wire and adjust all slides to that wire gap as a start. Also you may want to see about your pilot screws.

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