Why did the previous guy put in such large jets?

Could the jet set up be the reason for a bad idle?
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Should i jet it back to stock settings?
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Author Topic: 1980 CB750k Weird Jetting & Idle issue  (Read 254 times)

Offline piczker08

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1980 CB750k Weird Jetting & Idle issue
« on: Jun 18, 2017, 12:12:25 »
Hello fellow 750 lovers!

As a background story, I purchased a 1980 cb750k back in march and ever since it's had some problems with idling. It'll start and idle for a minute and slowly die off. If i give it throttle it'll stay alive as long as i keep throttle on. Recently though, it's gotten even worse and started to die on me at red lights/stop signs. Once i get going it has no problems, just that darn idle. I finally got angry though and took my carburator off thinking its a gunked up pilot jet/screw issue.

Here's where i start getting to the point :D . When i took the carb off everything was nice and clean, however my jets were wayyy off factory norms.

My first three carbs had a main jet 201 & Pilot Jet 89. The last carb had main jet 102 & pilot jet 89. WEIRD. The pilot screws were also wayyyyy screwed out compared to stock settings.

The bike has a stock airbox, but a 4-2 honda exhaust. (which i don't think would call for such large jetting changes; if any).

I read online that stock main jet should be 68, pilot jet 35 and pilot screws 1.5 turns out. So why on earth would the previous owner change them so much, and would changing them back to stock jettings possible fit my idle issues?

Thanks guys, looking forward to getting some help.