Exhaust popping on decel and dogging at higher speed... - Honda Shadow Forums : Shadow Motorcycle Forum
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post #1 of 6 (permalink) Old 06-08-2019, 02:31 PM Thread Starter
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Exhaust popping on decel and dogging at higher speed...

I have a few issues, not sure if they are related. I have moved to Ireland, where we only have 95 octane unleaded gas. My 2006 Honda Shadow 750(which was shipped from North Carolina) started running a little off...felt like the engine was working harder than it should and seemed to be losing power in the top end. The bike had sat in a shipping crate for 3 months, empty, so I thought I would clean the carb. Took it apart and found somone had put Dynojet kit in, #42 slow jets, mains are marked 100 and 102, adjustable needle(has the e-clip and 5 grooves). Everything was pretty clean, so I wiped it down and put it back on. Bike has 26,000 miles, so since I had it mostly apart I checked the valve clearances and reset them to .006 and .008 according to the Honda shop manual. Got it all back together and now I get a lot of popping on decel(which I think I just need to adjust the idle screws out some more), but my top end power issues are still there.

Any ideas? What else should I check?

I did have some issues with the hoses on the carbs. Got in a hurry and did not pay attention to the correct routing...and I believe I have what once was a California bike, but someone has removed the emission stuff, but left some hoses, like the 2 connections at the intakes...the hose goes nowhere...unless I missed something.

I bought it with Vance and Hines pipes on it and have already done the advance timing mod with clutch springs.

Last edited by stholt5233; 06-08-2019 at 02:59 PM.
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post #2 of 6 (permalink) Old 06-08-2019, 04:45 PM
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Model: Vt750
Year: 1983
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The vent hose with the T in between should go down to vent and have a open end.
Take it for a good had run and pull the spark plugs to see if they are too lean.

Did you sync the carbs so both are opening the same amount?
Try the idle screws out to 3 turns and see if that is better or not.

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1983 750 Shadow
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post #3 of 6 (permalink) Old 06-08-2019, 08:08 PM
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Model: VT500C
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Location: PG, BC, canada
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could be carb jetting issue due to altitude change. May have to rejet. high octane fuel should make it run better not worse

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post #4 of 6 (permalink) Old 06-09-2019, 05:01 PM
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Not sure if Ireland uses the same octane rating system as US/Canada ie ROM. You could do a little investigation and determine the equivalent ROM octane rating but likely OK.

Your popping on decal is quite common. I wrote a few posts about curing it. Search for decal popping and I go through the procedure.

Your top end loss needs more diagnostics and as swifty notes. If your altitude has changed significantly then there is a slightly different A/F setting.

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post #5 of 6 (permalink) Old Yesterday, 02:47 PM
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I would bet on altitude being the culprit. 50% of NC is at or below 500ft. elevation, and your new home in Ireland is roughly 3,500ft. elevation.

It shouldn't be the octane: more octane = more oxygen = more bang. Conversely, higher altitude = less oxygen = less bang.

My suggestion would be to check and see what the jetting is for that bike and altitude - there's a website somewhere (carbjetkits.com maybe?) that will calculate it out for you and make recommendations. From what I read, every 2k in elevation or so can make a difference.
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post #6 of 6 (permalink) Old Today, 06:21 AM
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Ireland and Europe use RON so 90 US octane is about equivalent to 93.5 RON. So the 95 octane you are using there would be about equivalent to 90/91 US non-ethanol fuel. If the popping is in your exhaust that would indicate to me unburned fuel, or too rich a mixture dropping the throttle to idle, ergo possibly too large of jets for your new altitude.

If it jams, force it. If it breaks it needed replacing anyway.
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