Carb Sync Woes

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Forge
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My Bike: 99 Valkyrie Interstate- 05 S83
Location: Griffithville, Arkansas

Carb Sync Woes

Post by Forge »

First let me tell you my setup. I have an '05 S83 with K&N drop in replacement filters. I am running the stock airboxes with the rubber inlet boots removed (not the carb to box boots, but the outer atmosphere into the box boots have been removed). I have installed the Dynojet stage 1 kit with adjustable needles and I am running the stock jets. The exhaust is OEM headers with Vance & Hines Classic II Slip Ons. I am also running the Dynatek Dyna 3000 ignition.

I have been having trouble keeping my bike synced. I have replaced the worn idle sync and throttle cables with new ones. I have synced the carbs and had her running nice and smooth. My carbs have been cleaned and are spotless and an inline 5/16" fuel filter has been installed between the lower petcock and the fuel pump inlet. I verified that the low speed transition ports are flowing properly when I had the carbs off.

I sync my bike and sometime during my ride, the bike will start running a little rough and I find that the throttle sync is off when I get home. As soon as I pull into my driveway, I slowly rev up the RPM and the rear jug will start to stumble just above idle. I check the sync and the throttle sync is off. I adjust it and she is running smooth again.

This past Saturday, I took her to my brother's house across town and she was running smooth on the way over there. On the way home, I noticed she was starting to have more vibration on the highway. I got home and same thing. The rear jug is sputtering off idle and the sync is off. This has been my history with this bike and I am unsure where else to look. I know the cables are tight at the connectors. I also know that when the tank is replaced after syncing, it can shift the cables and cause things to go out of sync, but then I don't believe it would be running smooth and then become rough after some miles have been put on her. I am competent mechanically and do my own work when it is needed, but am by no means an expert at these things. I am open to any input. I love my bike and the Intruder was always my dream bike until I finally got one. Now I am getting frustrated and need advice. No, I don't want to trade her in on another bike. I love this one and want to make it run as right as I can. Help?
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WintrSol
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Re: Carb Sync Woes

Post by WintrSol »

Have you checked that the cables are properly seated in the splitter under the tank? Made all adjustments with the cable barrels at the front carb? Adjusted both the idle sync and the open throttle sync? Verified that the carbs are properly seated in the boots at both ends of the carbs?
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Forge
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Re: Carb Sync Woes

Post by Forge »

Yes to all of the above. As I said, it runs great for a short while (during the same tank) before needing to be resynced.
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Fred
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Re: Carb Sync Woes

Post by Fred »

First of all you are not alone. The crap carb set up was probably one of the reasons the intruder died off.

You sound like you know what you are doing so im going to skip baby stuff and explain about cables being biased when the tank goes on but it is a very important point --but if you are sure the cable run is free and you can turn the bars without stressing the cables we will move on.

( I dont use stock cables I make my own from low friction mountain bike cables)

Your throttle should snap shut with an audible click, these bikes dont have a return cable as do most other big bikes.

The only other thing is the cheap plastic splitter, allumium better ones are available.

It would seem if I get your post correctly all you need is the cables to stay where put.

When you adjust the synch cable pull the outer sheath out of its ferule and let it untwist. When adjusting you will be twisting this and it will untwist from vibration and alter its length later when you are riding.

The synch cable is critical and should not be too short or too long or it will distorted by the tank.

Lubricate the sync cable so the furules don't resist the sheath.

See how you go.

Forge
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Re: Carb Sync Woes

Post by Forge »

Fred wrote:First of all you are not alone. The crap carb set up was probably one of the reasons the intruder died off.

You sound like you know what you are doing so im going to skip baby stuff and explain about cables being biased when the tank goes on but it is a very important point --but if you are sure the cable run is free and you can turn the bars without stressing the cables we will move on.

( I dont use stock cables I make my own from low friction mountain bike cables)

Your throttle should snap shut with an audible click, these bikes dont have a return cable as do most other big bikes.

The only other thing is the cheap plastic splitter, allumium better ones are available.

It would seem if I get your post correctly all you need is the cables to stay where put.

When you adjust the synch cable pull the outer sheath out of its ferule and let it untwist. When adjusting you will be twisting this and it will untwist from vibration and alter its length later when you are riding.

The synch cable is critical and should not be too short or too long or it will distorted by the tank.

Lubricate the sync cable so the furules don't resist the sheath.

See how you go.
Fred, I consider myself mechanically inclined, but I am by no means a master mechanic. I never considered the sheath twisting. I will check this. I have always been amazed at how little adjustment is needed at say 2500 or 3k rpm to make a major difference in the sync at that rpm. 1/8 to 1/4 of a turn is major. I installed new cables, but I did not lube them. That was an oops on my part. I will lube them, re-sync. and report back.
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Forge
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Re: Carb Sync Woes

Post by Forge »

I lubed the cables and resynced my carbs on Monday. Fred, I don’t think it was the twisting of the cables because once I pulled the tank, I remembered that the throttle sync cable that is adjusted is the very short one from the front carb to the splitter. The throttle sync is where my problem was. As for the cable runs, I use a small inspection mirror as I lower the tank to make sure the cables don’t shift or bind.

One thing I had not done and did do this time was allow the throttle to snap shut several times. I have installed a throttle meister cruise control and the light tension did not allow me to snap it shut quickly and hard. I loosened it up and snapped it several times. I suppose this could have kept things from totally seating. I did this at my brother’s house across town and she felt great on the way home. I need to put some more miles on her to see if she stays synced, but unfortunately I am currently down with the flu.

Thanks for the tips Fred. I will post back in the future with another update after I put a few hundred miles on her.
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Lechy
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Re: Carb Sync Woes

Post by Lechy »

Did you re-fit the springs on the AF needle screws?

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Forge
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Re: Carb Sync Woes

Post by Forge »

Lechy wrote:Did you re-fit the springs on the AF needle screws?

[emoji41]
Lechy, do you mean slightly stretch the springs before reinstalling to give them more tension? No, I didn’t. The screws aren’t moving on me though.
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Re: Carb Sync Woes

Post by Lechy »

No, it was something I once forgot to do and the bike kept drifting out of tune on the rear. I got home from the run, found the spring still in the bits box, replaced it and she was back to normal.

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Forge
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Re: Carb Sync Woes

Post by Forge »

Lechy wrote:No, it was something I once forgot to do and the bike kept drifting out of tune on the rear. I got home from the run, found the spring still in the bits box, replaced it and she was back to normal.

[emoji41]
Oh. Lol. The springs are in place. Thanks for the heads up.
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Fred
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Re: Carb Sync Woes

Post by Fred »

Spring washer and o ring.

Forge
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Re: Carb Sync Woes

Post by Forge »

Fred wrote:Spring washer and o ring.
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