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600-mile carb sync of doom

Old 05-24-2005, 07:08 PM
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600-mile carb sync of doom

So I take my bike to get its 600-mile service to the dealership as I figure, "Well, at least they sync the carbs and tighten things from when they assembled it." After which I noticed the bike was lacking in power a tiny bit, particularly at 3-5k rpms.
When I rode from Denver to Pike's Peak International Raceway to watch the AMA Racing near Pueblo (way to go Jake #98 Team HONDA Hai Domo!) I noticed it started to bog. WOT produced NO power at 4k rpms, and I had a huge flat spot between 3k and 5k rpms. I noticed it was way more noticable at 6500 ft altitude than Denver's 5800 ft altitude. Upon returning back (annoyed that wide-open-throttle produced almost no results anymore) the bogging lessened.
I suspect perhaps they -did- sync the carbs up nice but a bit too rich as my gas milage went from 147 miles to reserve-blinky-light (exactly the same for all 4 fill-ups) to 113 miles to reserve-blinky.
So I call them and am bringing the bike in Thursday to have them take a look at the carbs again as I suspect it was a tad rich and told them so. They said a vacuum line might be loose or off (though I didn't notice any).

Suggestions?

I'm actually very angry with them because when I brought my bike in, the carb-sync (which ultimately I shouldn't have let them do) was included in the price of $104 (very reasonable with oil change, etc.) but they didn't do it, nor the chain-clean/lube. I went back and complained about both, and they did both (supposedly) but one of the things they checked-off was to tighten bolts. I left one purposely loose to see if they'd tighten it and it was loose when I got it out of the shop so they obviously didn't do that either. I suspect they just gave me the $104 oil-change in YO FACE treatment, "Cradle-Rock-Style, BAM!" Sigh.

This is Sun Honda/Kawasaki in Denver.
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Old 05-24-2005, 07:53 PM
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Look for the plug that connects to the back side of the front intake manifold. Its basically a screw. Betting its off and there is just a hole there or there is a fitting sticking out of it with nothing connected to it. If the back one was disconnected, gas wouldn't flow.

Syncing doesn't do this and doesn't change the fuel air mixture. It merely balances the carbs which (unless they are really far off) only affects idle smoothness.
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Old 05-25-2005, 08:26 AM
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Re: 600-mile carb sync of doom

I would bet they didn't sync the carbs for you either since it requires installing a fitting for the front cyl to hook up a vacuum line. Just installing the fitting ( and then removing it) is a true PIA - just making it more likely they skipped that part of your service checkup also.
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Old 05-26-2005, 10:02 AM
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Re: 600-mile carb sync of doom

Well, I took it in today and they rode it around and found nothing wrong. Sigh. They did zero diagnostics. They suggested gas quality might be not good. I always use 91 octane and I doubt it changes much from station to station.

The change is very subtle but Sun Honda admited they didn't actually do the carb sync (even though I took it to them twice) because it was perfect. I suspect they just examined the idle and were content and skipped it as you suggest.

I suppose I could be getting used to the power of the bike such that I don't notice it any more, or they used a poor-grade motorcycle oil, though they told me they used Honda GN4 10W-40 which is satisfactory.

The flat spot is very mild and hesitation is minimal but I notice it. I'm pretty tune to those things and can tell when something's a little off...

Without taking off the tank, can I get at this screw near the intake that you speak? Can you describe it's location? I thought that carb adjustments affected richness/leanness of the mixture but I guess not? Wow, I feel like a total squid newbie now.
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Old 05-26-2005, 10:20 AM
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Just below the rubber boot that connects the front carb, directly in the back. Usually this hole is filled with a screw. During syncing, it is removed and replaced with a fitting for a hose. Afterwards, the screw is replaced.
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Old 05-26-2005, 10:30 AM
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Re: 600-mile carb sync of doom

Owner's manual doesn't show this part. Can I see it from under the tank without removing it? I'm only slightly tech-savvy. I can change my own oil, lube my chain, and sometimes spark-plugs, wires and bulbs and that's about it. Oh, and adjust the idle rpms and tire air-pressure and some cosmetics (like windscreen, etc.)

(Still, this knowlege usually saves me several hundred a year from evil dealer charges).
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Old 05-26-2005, 10:39 AM
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Old 05-26-2005, 01:35 PM
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Re: 600-mile carb sync of doom

Mike,
yes, go to jschmidts link above on the RonAyers site and you'll see there are items #14 and next to it item #7. You want to purchase item #7 which is Honda part #16214-MB0-000 ( JOINT, BOOSTER ) and replace the stock bolt on the front cyl. It's about $4. This is exactly the same part on the rear cyl where the vac line it tapped off.

Here is a photo of my front cyl where the vacuum line is permanently hooked up to the above part.

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Old 05-26-2005, 01:38 PM
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The oil change and the type of oil wouldn't cause the problem you are describing.

Also, a carb synch would only be changing your idling characteristics. Once you open the throttle, the carb synch/out of synch effects are negligible.

I have had issues with bad gas before, so that is a possiblity. I say ride it for a few more days and see if you still notice a difference. Sometimes, when we leave our cars/bikes to be repaired, and go back to pick them up, we pay extra attention and pick up things that probably were there before, we just didn't pay any attention to it.
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Old 05-26-2005, 08:10 PM
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Re: 600-mile carb sync of doom

Wow! I've never been to a better forum ever! All of you are amazing! I checked for part #7 and the photo helped TONS. The bolt is actually still in place, thankfully!

The bike started rough this morning at 55 degrees (though not entirely uncommon for a V-Twin when it's cooler) and took about 30 seconds before it'd turn over which made me cranky.

I put a new tank of gas in and it seem to be a bit better than before. I put in 91 instead of 87 (of which the 87 I think was an ethanolled 85) and it idles about average for the V-Twins I've owned, plus or minus dance of about 200 rpms each way. Throttle response is improved and gas milage I still have 2 bars left at 113 miles. I suspect I can get to my 147 miles before reserve blinky comes on.

I really appreciate the extreme help everyone's given me. Thanks everybody!
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