Went out for a ride today with Mrs. Grilldemon on the back. It;s a fairly warm day (23 c). Just as we were getting home, it started chuffing/backfiring out the exhaust just as I was pulling up to the gargae. It's done it once before, but only when hot and only when deccelerating to stop. Carbs are synched within an inch of their lives, idle is good. IS this a heat issue? I ahven't put a manual fan switch in yet. I also have a new thermostat to put in along with some water wetter.
usualy id say your exhaust cam may be out a tooth or your valves are sticking, but you said the idle was good so heres a thought. This is only a thought, but if the throttle plates are fully closed and something is fouling the bypass air jet(if these carbs have one) then you would have more than enough vacuum at modest rpms to suck excess fuel through the engine. this fuel remains unburnt until it hits the mufflers causing a chuffing sound. I do not know how the carbs for a '85 vf1000 are setup, that is what extras they have built into them, maybe on of the other/older guys here can shed some light. I had a similar issue on a '87 hyundai ( yes i was a owner of a Hyundai) and found some varnish in a couple "balance" ports. after a long soak in some solevent (I had access to a hot tank) and a full reset to factory settings did it stop chuffing. This is just a thought and I may be way off base, but since everything works well cold Id look to your carbs for a cold engine/ hot engine change. may be as simple as a wax pellet on the bottom that closes/ opens a small valve. zen
Have you checked the valve clearances? A tight (or sticking) exhaust valve would do what you describe, and would be more likely to do it when hot. Heat can definitely affect ignition components, too. A good place to start might be checking the spark plug color. If one is very different in appearance than the other 3, that is likely the cylinder with the issue. I would not start it again until you have checked things out. If it is a valve that is tight enough to be problematic when hot, it could be potentially a motor killer. Hopefully that's not the case, but better safe than sorry.
