QuestionChris,
My son's bike will run at idle, but only with the choke pulled out. When I hit the accelerator, even a little, it kills the engine or if it doesn't die it seems to be missing and sputtering. There is also some backfiring. If I pull the choke all the way out the engine runs at about 3,000rpm and it accelerates fine. I checked all four cylinders for firing by hooking the timing light up to each of them and watching the light flicker. The plugs have a covering of dry black soot, but no oil which I expect with the choke out.
is the timing off ? the bike has electronic ignition which may have been added after the bike was bought.
thanks for any help,
Dave
AnswerHi Dave.
If I recall correctly, the '78 was either the first or second year with an electronic ignition. Those are fairly bulletproof.
There are a few possibilities. One or more could be occuring;
1) What may be happening is the carbs may be out of synch. On the electronic ignitions, most of them anyway, when the carbs are out of synch, the timing changes and it corrects itself as the synch is adjusted correctly. If you don't have a set of mercury synchro guages (like Carbstyx, for example), then get them and synchro the carbs.
2) Another issue that could be happening is if the bike spends any time in seasonal or other long term (more than 2 weeks) storage without being started up run a bit. If this is the case, then pull and clean the carbs, replace the fuel line and drain and reseal the tank. If the bike has spent time in storage, then "varnish" may have built up in the fuel system and that would also cause the bike to run poorly.
3) A dirty or clogged air filter will cause the bike to run very much like you have described as well.
Start with those and let me know what you find.
Good luck and ride safe.
FALCON
