Author Topic: Carb Adjustment (Read 2395 times)

gbal06 · « **on:** July 08, 2016, 12:47:15 PM »

I have seen on line two ways to sync the carbs using a vaccum. One is to take the top off of the carb and then adjust and two is to adjust the hex nuts next to the top of the carb. Which is correct? Also just to be 100% clear, the #1 carb is on the right as it sits in the bike and you sync 1,3,4 to 2. Thanks

Scott S · « **Reply #1 on:** July 08, 2016, 02:27:53 PM »

You use the slotted screws with the 8mm lock nut on it....not the brass caps. You do not take the tops of the carbs off.
On those carbs, there is no "master" carb. You just sync them until they're all the same. If a couple are close, then sync the others to them. And don't worry about the vaccum reading number. Just make them all match.
It can be a bit fiddly. When you go to tighten the lock nut you can disturb your setting.

Do it on a warm motor and run a fan on the engine while doing it. Try to do it on the center stand if possible.

flybox1 · « **Reply #2 on:** July 08, 2016, 02:36:57 PM »

^^^+1
Some carbs have the adjuster screws as Scott mentioned, under the top caps.
The only time you would take the top caps off is for a bench sync, but if your bike is running and you just want to dial it in, follow what Scott outlined.

Nice clean carbs btw

gbal06 · « **Reply #3 on:** July 08, 2016, 06:25:50 PM »

probably a stupid question and want to apologize right off the bat, but do you loosen the lock nut before adjusting the slotted screw and then re-tighten the lock nut once it is adjusted?

Also the number 1 carb is on the right as it sits in the bike correct? Thanks

scottly · « **Reply #4 on:** July 08, 2016, 06:58:46 PM »

Yes, loosen the lock first, and tighten after adjustment.
No, the number 1 carb is on the left side, and the number 4 is on the right.

gbal06 · « **Reply #5 on:** July 08, 2016, 07:05:35 PM »

Great thanks Scottly,

Is there any particular order I should go in? 1-4, 1/2 then 3/4?

HondaMan · « **Reply #6 on:** July 08, 2016, 07:10:31 PM »

#1 is on the left as you sit on the bike. Don't adjust #2: it is always considered the "baseline reference" carb, and many of them cannot be adjusted anyway. Start with #3 if it does not match #2, then do #1, if needed. #4 is last, if needed. Most of the time, just one is off a little bit. Don't try to be 'perfect', as the engine isn't. Just get them close, then blip the throttle to see if it 'pops' during decel or accel. If so, adjust the lowest one upward a bit and repeat. Put a fan on the engine to help keep it cool during all this, as you might be at it for 10 minutes or more.

Scott S · « **Reply #7 on:** July 08, 2016, 07:14:05 PM »

I answered that above. There is no particular order. On some of the later PD series carbs, #2 carb is not adjustable and it's the "master" carb and all others are synced to it.
But on your carbs there is no master carb. Just hook up the gauges and see what they say. Let's just say that two of them have ~5 inches of vacuum....just a random number I picked, there's no "right" reading.....ANY two carbs. It doesn't matter if it's 1 and 2, 1 and 3, 2 and 4.....it doesn't matter.
If those two are really close, make them match each other exactly. Then, one by one, make the others match those two.
Just pick the two that are closest first and go from there.

Scott S · « **Reply #8 on:** July 08, 2016, 07:18:26 PM »

Of course, Hondaman is the authority and has forgotten more than I know about them!

Follow his advice, but my way works, too.

It'll all make sense once you start. And bench sync them first. Gets you close right off the bat.

jonda500 · « **Reply #9 on:** July 08, 2016, 08:00:22 PM »

With those carbs I am fairly sure you do not take off the top caps to do a bench sync.
John

flybox1 · « **Reply #10 on:** July 08, 2016, 09:00:18 PM »

Quote from: jonda500 on July 08, 2016, 08:00:22 PM

With those carbs I am fairly sure you do not take off the top caps to do a bench sync.
John

ummm, yeah! Those adjustment screws are right there in the picture

mickvain · « **Reply #11 on:** July 08, 2016, 09:59:50 PM »

I am sure this has been covered before, but is there a certain throttle position or RPM we should be suing to sync the carvbs?

flatlander · « **Reply #12 on:** July 08, 2016, 11:44:16 PM »

idle or just a little above.

jonda500 · « **Reply #13 on:** July 09, 2016, 02:56:54 AM »

Quote from: flatlander on July 08, 2016, 11:44:16 PM

idle or just a little above.

+1 that's what I do
John

gbal06 · « **Reply #14 on:** July 10, 2016, 10:37:57 AM »

Great thanks for the help guys

gbal06 · « **Reply #15 on:** July 12, 2016, 01:52:31 PM »

Ok these are the readings I am getting on my vacuum. Any advice would be great! Thanks

flybox1 · « **Reply #16 on:** July 12, 2016, 01:58:04 PM »

when was the last time you calibrated your gauges?

fyi....unless you have your tubes crossing...they are labeled backwards

gbal06 · « **Reply #17 on:** July 12, 2016, 02:05:38 PM »

Never. First time using it

Scott S · « **Reply #18 on:** July 12, 2016, 02:05:42 PM »

Quote from: gbal06 on July 12, 2016, 01:52:31 PM

Ok these are the readings I am getting on my vacuum. Any advice would be great! Thanks

You've got the cylinders numbered opposite. #1 is on the left as you sit on the bike and #4 is on the right.

That said, your "1 and 2" are close, so leave them alone. Pull down the one on the far left to match them, then the next one. See how close you can get them that way. Report back, please.

And be advised: Your idle may change as you do this. Occasionally blip the throttle to clear it out and adjust idle to ~1,000-1,100 RPM. It's not unusual to see the readings change as you go through the procedure of syncing them.
And run a fan on the engine.

flybox1 · « **Reply #19 on:** July 12, 2016, 02:13:18 PM »

OK. First....change all the tape #s on your gauge.
time to calibrate the gauges.
you can use any carb for this. Lets use #1....note the needle position of #1 gauge(up there between 2 &3 lbs) and put the screws back in vacuum holes on 2,3,4.
plug your #2 gauge tube into the #1 carb.....turn the calibration screw (brass screw, in bottom center of gauge) to get the needle to the same 2-3lbs.
Repeat for this for #3&4

now...plug them each in their respective vacuum sync screw holes...then proceed with getting them all to read the same value using the sync screws between the carb top caps.

flybox1 · « **Reply #20 on:** July 12, 2016, 02:15:09 PM »

With each vacuum adjustment your idle will change.... blip your throttle, and allow the idle to rest, and adjust to maintain an even, comfortable idle. Adjust it up or down as needed.

gbal06 · « **Reply #21 on:** July 12, 2016, 02:34:18 PM »

I adjusted the #1 carb and it started to "pop" from the exhaust. I tried posting a video, but the site would not upload it

Scott S · « **Reply #22 on:** July 12, 2016, 02:36:35 PM »

You're getting there. Now adjust 3 and 4 to match 1 and 2. Keep going.

What are your mixture screws set at?

Scott S · « **Reply #23 on:** July 12, 2016, 02:42:24 PM »

And, unfortunately, you have pods and an open exhaust....you're probably going to get some popping until you spend a lot of time jetting and changing needle position.

gbal06 · « **Reply #24 on:** July 12, 2016, 03:13:31 PM »

Should I bring #1 down a little bit more or would it matter? Also the popping is something new and kinda freaks me out a bit

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Author Topic: Carb Adjustment (Read 2395 times)