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82 CB 750K High idle/ Backfire from cyl 1 or 2

mattthebiker

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Hey guys,

I recently Purchased a 82 CB 750 with 18 thousand miles. It hadn't been used in the last two years or so. Got it home and got it going (no maint done) When it started to warm up and I revd the engine a little it would stay at a high idle (around 4000rpm) wouldn't come back down on its own, throttle was not sticking . We found a leak on the number 4 carb boot that goes from the carb to the engine. Maybe this was the problem?
So I tore the carbs off and ordered 4 new carb boots. New float bowl gaskets new rubber passage plugs that go over the slow speed jets. The carbs looked pretty clean when I took them apart very little varnish the bowls must have been drained when it was put away. I didn't split the carbs just took the bowls off and all the jets out. Sprayed cleaner all through out little bit very little if anything came out (again they were pretty clean. I soaked all the jets in carb cleaner for a couple days. Reassembled everything and got it back together. Bike started after the 3rd try with a bit of a high idle. Figured this may be because of hitting idle adjuster screw on over the course of cleaning and installing. The idle came down to normal. All exhaust pipes were hot. Everything seemed good. more vapor/steam was coming out of the number 3-4 exhaust pipe then number 1-2. When the bike warmed up a little more i gave it a couple of rev's and same thing happened was staying at a higher idle again with a little backfiring from the number 1-2 exhaust pipe. Again I adjust the idle screw and the idle dropped back down again. It was all back together and running enough I had to take it for a little spin, Even if it was snowing out.... Of course the roads were just wet, no snow. Took it up the road about 1 km or so and back. Gave it a couple good shots of gas. There was no hesitation she picked up real nice no bog. Of course it was revving higher again now.... idling around 3000 rpm.

Didn't have enough time to look at the plugs. Just put her up in the garage to dry off and pick it at some more another day.
Just wondering if anyone has any ideas what may be causing it to keep revving up like it is. I`m guessing the backfiring is caused by it being too lean on either carb 1 or two.

Any other things I should check?

Thanks
 
Need to check and sync the carbs. Backfiring and idle issues can also be a result of one or more air cut valves having bad diaphrams(under the little covers on the sides of the carbs). Also check the ignition advancer under the left cover and see if it is stuck or sticky, if it is sticking or have weak springs it can cause idle to hang also.
 
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