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Mercury carb synching

  • Thread starter Thread starter J_C
  • Start date Start date
J

J_C

Guest
Hi GS friends,

My carbs are starting to finally get in order. I rejetted my pilot and air jets and that seemed to make a big difference. Using my morgan colortune I screwed out my idle jets until the flame turned yellow (rich) and then back in until it turned right to blue.

Two things at work here. I still have some popping on deceleration. I have NOT yet synched using mercury sticks. I'm wondering if having the carbs more closely synched might reduce the popping (In other words, what benefit does a closely synched set of carbs have over non-synched carbs).

The reason I ask is because, even after rejetting, it still took me 4 or 5 turns to reach the yellow flame on each carb. I'm wondering if I need to rejet AGAIN (+ another $30) in order to decrease the popping or if the synch might help accomplish this.

Note: I know that some popping is apparently inevitable with a 4-1 pipe.

Thanks!
 
Popping is not inevitable on a 4-1 at all. Usually means you are lean. A couple of questions. What's your set up besides the pipe? Pods? Stock air box?

What rpm did you do your tuning at? You'll need to do plug chops at 1/8, 1/3 (1/4), and full throttle to get what happening when different circuits are at work in your carb. If your doing the colortune only at idle that's good, but not telling you what's happening at greater throttle settings.

Have you done any needle work? Its the needle jets that control most of your throttle response. Pilot jets are just off idle, main jets are basically wide open. With my pipe I didn't get anywhere until I raised the needles on my carbs.

The carb synch is essential before you do the rest of your tuning.
 
Thanks Mark, that's great input. I'll do the synch before anything else.

I did only use the colortune/tuning at idle. The setup is K&N pods & a V&H 4-1 pipe. The popping seemed to mostly happen right after I let off the throttle and it began decelerating, mostly around the 5k rpm range probably. I guess I need to synch it and get it back out there to see if I can more closely identify what's happening and when. Then I can do my plug chops.
 
I've found that trying to completely eliminate decel' pop can cause bigger problems that are harder to live with. I put up with a certain amount. Hard to say in type what's acceptable and expected when you force more air/flow through these carbs. With the engine at 5K+ and the throttle plates at their tightest position, the engine is at its leanest conditions.
A good vacuum synch may help. Try it. It must be done anyway to get accurate plug reads and to best judge performance.
If you didn't replace the exhaust gaskets when you installed the new pipe, that will also cause decel' pop. About 10 ft/lb on those exhaust bolts, gradually/uniformly torqued, unless your manual states differently.
I always tune the mixture screws on your carbs to achieve best rpm. I wonder if that Colortune tool you're using is doing the same thing?
If your carbs have two floatbowl vent lines, removing them will help eliminate fuel starvation in many conditions due to poor float bowl venting. Leave the vent ports open.
Be sure you oiled those K&N's correctly. Very easy to under/over oil them.
Valve clearances and ignition timing must be correct before vacuum synching.
Besides what you've been doing to the pilot circuit, what have you done about the jet needle and main jet? What jet sizes did you use for the pilot jet and pilot air jet? What is/was your stock jetting set up? Are you using a stage 3 jet kit or separate jets? If a kit, what brand? Lots of past info around here on re-jetting your model.
 
I just wanted to follow up on this post to reiterate what the above said in response to my post. I ran the mercury synch, it was easy as cake to do using the instructions off Bwringer's site, and low and behold #4 (Source of most of my woes) was WAY off. After the synching was completed the popping has been virtually eliminated, even on decel. Thanks guys!
 
I still have a list of some things that need to get done, which have been greatly slowed by the fact that I live in MdR and the bike is in Burbank. But the status list of remaining items is as follows:

1. Change fork springs and oil (Will leave seals for now, will have it done at a shop eventually)
2. Test charging system to identify problem (most likely stator)
3. Fix master cylinder (Resevoir slightly leaking between resevoir and cup [wtf?]) and rebleed.


Cosmetically it's all back together
 
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