Cleaning carbs

[hillsy]

You are best off not touching those mixture screws until you have the carbs off the bike. That way you can work on them on a bench (especially if you have to remove any plugs). With the carbs on their side, squirt a little bit of penetrating fluid on the screw to lube the threads (the threads are REALLY fine and the screws themselves are soft). Make sure you have a good fitting flat blade screwdriver to fit in the screw slot - again they are soft and you can easily damage the screw. Like Herb said - screw them in and count the turns paying close attention to the fractions of turns (IE: 2.25, 2.5, etc). The screws will have a dramatic change on the fueling within half a turn so you need to make sure you have that part right so you know where to reset them.

There is a spring, o-ring and washer under each screw:


They may not want to come out easily and if so you will need to pick them out.

[Acton67]

Removed the mixture screws today with a 1/8ths" drill bit successfully. Used a wood screw to assist.

The front carb seemed to turn in 4 full turns (1 turn meaning 360 degree rotation) starting 10 o'clock position until it was "lightly seated".

The rear carb was 2.1 turns starting from the 12oclock position, ending in the 1oclock position until it was "lightly seated".

I'm concerned for two reasons. One because I'm not confident in my ability to determine what "lightly seated" is and if I can accurately reproduce it when I reinstall the needles. I went until I met light resistance.

Secondly the difference between the first and second carbs in terms of seating position seems significant. There must be somewhere where it's documented how many turns the needles should be set at from a "lightly seated" position. I will check the manual(s) but does anyone have any info on this?

[navigator]

Lightly seated means just touching.
When it takes more resistance to continue...you are there.
No damage is done until you start applying force or torque, as in tightening a fastener.
When starting from scratch, after a carb rebuild, 2.5 turns out is a good starting point.
All carbs are different, so the difference between 4 and 2.1 can be affected by other variables.
If after you finish, 2.5 turns seems a little lean, you know you can go up to 4 on that carb if need be.

After your rebuild, start at 2.5 turns out. When the bike is warmed up and running, you can lower the idle some with the idle adjustment thumb screw on the rear carb. The lower idle allows you to hear changes in speed. Then one side at a time, you slowly turn the mixture screw CCW until the motor starts to stumble, then turn it CW past your initial setting (2.5) until the motor again starts to stumble. Return the screw to the center of the two stumble points to achieve the best possible idle. After this procedure on both carbs, Raise the idle to approx.1000 rpm with the thumbscrew.

[Acton67]

Lightly seated means just touching.
When it takes more resistance to continue...you are there.
No damage is done until you start applying force or torque, as in tightening a fastener.
When starting from scratch, after a carb rebuild, 2.5 turns out is a good starting point.
All carbs are different, so the difference between 4 and 2.1 can be affected by other variables.
If after you finish, 2.5 turns seems a little lean, you know you can go up to 4 on that carb if need be.

After your rebuild, start at 2.5 turns out. When the bike is warmed up and running, you can lower the idle some with the idle adjustment thumb screw on the rear carb. The lower idle allows you to hear changes in speed. Then one side at a time, you slowly turn the mixture screw CCW until the motor starts to stumble, then turn it CW past your initial setting (2.5) until the motor again starts to stumble. Return the screw to the center of the two stumble points to achieve the best possible idle. After this procedure on both carbs, Raise the idle to approx.1000 rpm with the thumbscrew.

So I installed new pilot jets today, cleaned out all the passages thoroughly with carb cleaner and then compressed air including where the idle mixture screw seats. Tomorrow I will test the carbs. Should I test one cylinder at a time by disconnecting the other cylinder from the spark plug boot or run both at the same time? Also looks like I will have to remove the carbs 2-3x just to adjust the idle mixture screws, I see no way to access them with the carbs on the bike. I did not touch the sync cables but should I put the carb sync I bought a while back on them to ensure they are both pulling the same amount of vacuum after I tune them as described above? Also should I invest in a tiny tachometer to ensure I'm running 1000 rpm with the thumbscrew adjustment?

[navigator]

So I installed new pilot jets today, cleaned out all the passages thoroughly with carb cleaner and then compressed air including where the idle mixture screw seats. Tomorrow I will test the carbs. Should I test one cylinder at a time by disconnecting the other cylinder from the spark plug boot or run both at the same time? Also looks like I will have to remove the carbs 2-3x just to adjust the idle mixture screws, I see no way to access them with the carbs on the bike. I did not touch the sync cables but should I put the carb sync I bought a while back on them to ensure they are both pulling the same amount of vacuum after I tune them as described above? Also should I invest in a tiny tachometer to ensure I'm running 1000 rpm with the thumbscrew adjustment?

You only need to install them once.
Set at 2.5 turns out, they should idle fine.
The procedure above is to fine tune them.

Should I test one cylinder at a time by disconnecting the other cylinder from the spark plug boot or run both at the same time?
No, run the bike normally, just drop the idle enough to hear subtle changes in speed as you turn the screws. You will hear the rpms drop as you go in or out, then find the best idle near the center.

Also looks like I will have to remove the carbs 2-3x just to adjust the idle mixture screws, I see no way to access them with the carbs on the bike.
You should be able to get to them, on a running bike.

I did not touch the sync cables but should I put the carb sync I bought a while back on them to ensure they are both pulling the same amount of vacuum after I tune them as described above?
After install, do your carb sync first. The fine tuning of the A/F screws should not change the sync.
Syncing can be tricky, you only need a small fraction of a turn on the sync cable to affect the sync. Even tightening the jam nut can affect it sometimes. Hold the cable end steady with one wrench, and tighten the jam nut while doing so.

Also should I invest in a tiny tachometer to ensure I'm running 1000 rpm with the thumbscrew adjustment?
You can set the idle by ear, set it so it sounds right, not so fast that the bike lurches forward while releasing the clutch without adding throttle.
And not so slow that it lopes like a Harley and stalls when releasing the clutch. If you rode the bike before, you can tell when it feels / sounds right.
A cheap tach set to measure 4 cylinder rpm will read half of your actual rpm with 2 cylinders.

[Herb]

What nav said is correct except that there are Tachs made to read the dual fire engines, like the suzukies.

I have one that has been on my 1400 for about 15 years and it is still working great. I have it mounted with double sided tape. I got mine for $4.95 from a dirt bike shop that was closing.

They are really easy to hook up, 1 wire that you wrap around a spark plug lead. Mine doesn't have a replaceable battery but still works well.

Here are some good examples, if you live near a large city there are probably small engine shops that sell them.

https://www.amazon.com/small-engine-tac ... e-asc-rank


Digital Engine Tachometer for for 2 Stroke & 4 Stroke Small Engine, Inductive Hour Meter,Replaceable Battery IP67 Waterproof Tachometer for Chainsaw Marine ATV Motorcycle UTV Engine Outboard Tractors
Brand: TOTMOX

$12.78

[hillsy]

Hard to tell from this pic but did you remove the washer and o-ring from the cavity? The o-ring and washer are pressed down inside the cavity by the spring - the o-ring tends to squash/ swell and sticks to the washer making them both difficult to remove at times - you often have to "hook" them out. You should have a replacement o-ring in your carb kits.

[Acton67]

Hard to tell from this pic but did you remove the washer and o-ring from the cavity? The o-ring and washer are pressed down inside the cavity by the spring - the o-ring tends to squash/ swell and sticks to the washer making them both difficult to remove at times - you often have to "hook" them out. You should have a replacement o-ring in your carb kits.

I did remove them.

Ran the bike today. Front cylinder idles high rpms, want to slow it down. Rear carb needs a little throttle to start but starts much easier now. Sounds like the front cylinder is running to lean and the back is to rich right? Or is it the opposite? Turning the idle mixture screws out makes the bike more lean or more rich?

[Designer]

I did remove them.

I kinda thought so.

Ran the bike today. Front cylinder idles high rpms, want to slow it down. Rear carb needs a little throttle to start but starts much easier now. Sounds like the front cylinder is running to lean and the back is to rich right? Or is it the opposite? Turning the idle mixture screws out makes the bike more lean or more rich?

Have you matched the "number of turns" on the the Idle Screws? I'd make sure they matched first. Sometimes,as has been said,...you might need to turn them In/Out a little to achieve a better burn, but after cleaning, this shouldn't be too far different. ( assuming you don't have worn jets, or a a vacuum leak, etc.) Also make sure you have an accurate Idle Carb Balance.

[Acton67]

I did remove them.

I kinda thought so.

Ran the bike today. Front cylinder idles high rpms, want to slow it down. Rear carb needs a little throttle to start but starts much easier now. Sounds like the front cylinder is running to lean and the back is to rich right? Or is it the opposite? Turning the idle mixture screws out makes the bike more lean or more rich?

Have you matched the "number of turns" on the the Idle Screws? I'd make sure they matched first. Sometimes,as has been said,...you might need to turn them In/Out a little to achieve a better burn, but after cleaning, this shouldn't be too far different. ( assuming you don't have worn jets, or a a vacuum leak, etc.) Also make sure you have an accurate Idle Carb Balance.

I have them both set at 2.5 turns out. I also have new main and pilot jets in both. Same size as stock though.

When you say carb balance you mean carb sync?

[Designer]

I did remove them.

I kinda thought so.

Ran the bike today. Front cylinder idles high rpms, want to slow it down. Rear carb needs a little throttle to start but starts much easier now. Sounds like the front cylinder is running to lean and the back is to rich right? Or is it the opposite? Turning the idle mixture screws out makes the bike more lean or more rich?

Have you matched the "number of turns" on the the Idle Screws? I'd make sure they matched first. Sometimes,as has been said,...you might need to turn them In/Out a little to achieve a better burn, but after cleaning, this shouldn't be too far different. ( assuming you don't have worn jets, or a a vacuum leak, etc.) Also make sure you have an accurate Idle Carb Balance.

I have them both set at 2.5 turns out. I also have new main and pilot jets in both. Same size as stock though.

When you say carb balance you mean carb sync?

Yes Carb Sync. Since you have both New Jets and matched Idle screw turns, I'd go to the Carb Sync right away. and see if you can get a better match in speed.

[Acton67]

Made a lot of progress today on the carbs. Have both carbs synced at idle but the front carb seems to lose vacuum when I start to turn up the throttle. Any suggestions? When I reinsert the throttle cables into the splitter I made sure both cables where the same length, do I need to adjust the throttle cables on the carb more or does this make something to do with the idle mixture screws?

https://youtube.com/shorts/9jJO_k3ZIXc?feature=share

[Designer]

Okay,. we are making progress. the Idle speed issue seems to be corrected.

I'll wager what you are experiencing is that the Front Carb is not opening as soon as does the Rear, thus your diagnosis of ossing vaccum.

Time now to perform the Second Part of Carb Sync,....at about 2,000 RPM. I use the Adjusting Barrel at the Throttle to adjust the speed so as to hold it better that merely twisting the Grip. Yes, you might have to reset it while adjusting, but it sure beats the heck outta holding the grip!

[Acton67]

Time now to perform the Second Part of Carb Sync,....at about 2,000 RPM. I use the Adjusting Barrel at the Throttle to adjust the speed so as to hold it better that merely twisting the Grip. Yes, you might have to reset it while adjusting, but it sure beats the heck outta holding the grip!

The adjusting barrel at the throttle I'd this.



When you say, "adjust the speed so as to hold it better that merely twisting the Grip" you mean you use the barrel to keep the throttle open at 2000rpms to make further adjustments, correct?

Now I need to adjust the throttle cables so both carbs are synced at 2000rpms?

What I find confusing about all this is how that would work when the splitter/throttle cable linkage would allow the cable to move forward freely in the housing. It seems like all the adjusters do are to snug down the cable housing and shorten/lengthen the cables right? How could both carbs not be opening at the same time? Unless one cable is a little longer in the splitter and the other cable is shorter so the splitter pulls on one cable first before the other, thus opening one carb before the other? I know Im missing something here.

[Acton67]

Delete, repeat post

[Acton67]

Delete, repeat post

[Herb]

Actually, you are not changing the length of the cables, you are changing the distance of the housings from a specific point. Changing the housing position changes the way the cable itself pulls on the throttle.

Since the single cable, from the grip, is attached to the 2 carb cables it pulls on both the same amount.

[Designer]

The adjusting barrel at the throttle Is this.
When you say, "adjust the speed so as to hold it better that merely twisting the Grip" you mean you use the barrel to keep the throttle open at 2000rpms to make further adjustments, correct?

Yessir!

.....Now I need to adjust the throttle cables so both carbs are synced at 2000rpms?

Yessir!

.....What I find confusing about all this is how that would work when the splitter/throttle cable linkage would allow the cable to move forward freely in the housing. It seems like all the adjusters do are to snug down the cable housing and shorten/lengthen the cables right? How could both carbs not be opening at the same time? Unless one cable is a little longer in the splitter and the other cable is shorter so the splitter pulls on one cable first before the other, thus opening one carb before the other? I know Im missing something here.

The Splitter pulls both cables at the same time,...sorta.
You need to Equalize the movements of both Front and Rear Carbs so both are opening with the same amount of effect. (Balanced )

To do that, you adjust the Throttle Cable Adjusting Barrel at the Front Carb to match the Non-adjustable Throttle Cable at the Rear Carb that is being held at 2000 RPM (plus-or minus) by the Adjusting Barrel at the Grip. When done, you "loosen' the Adjusting barrel at the Grip back down to Idle Speed ( which you already have synced ) and so there is just a slight amount of play in the Throttle Grip.

And,,,GO For Some Riding!

[Acton67]

The adjusting barrel at the throttle Is this.
When you say, "adjust the speed so as to hold it better that merely twisting the Grip" you mean you use the barrel to keep the throttle open at 2000rpms to make further adjustments, correct?

Yessir!

.....Now I need to adjust the throttle cables so both carbs are synced at 2000rpms?

Yessir!

.....What I find confusing about all this is how that would work when the splitter/throttle cable linkage would allow the cable to move forward freely in the housing. It seems like all the adjusters do are to snug down the cable housing and shorten/lengthen the cables right? How could both carbs not be opening at the same time? Unless one cable is a little longer in the splitter and the other cable is shorter so the splitter pulls on one cable first before the other, thus opening one carb before the other? I know Im missing something here.

The Splitter pulls both cables at the same time,...sorta.
You need to Equalize the movements of both Front and Rear Carbs so both are opening with the same amount of effect. (Balanced )

To do that, you adjust the Throttle Cable Adjusting Barrel at the Front Carb to match the Non-adjustable Throttle Cable at the Rear Carb that is being held at 2000 RPM (plus-or minus) by the Adjusting Barrel at the Grip. When done, you "loosen' the Adjusting barrel at the Grip back down to Idle Speed ( which you already have synced ) and so there is just a slight amount of play in the Throttle Grip.

And,,,GO For Some Riding!

I already had to adjust the throttle cable once on the front carb because the throttle body wasn't completely closed at idle, so I had to back out the Adjusting Barrel so the cable in the splitter housing would be long enough to allow the throttle to close completely. Based on the results in the video the front carb is opening after the rear carb right? So I must have gone to far in the other direction so I need to tighten the Adjusting Barrel right? The idle sync also effects how much slack the throttle cables have at idle, there's probable more slack in the front cable for that reason too I guess.

Should I also check for vacuum leaks? The boots are on there tight and the "bump" on the carb bodies is in the notch on both boots. From what I've heard I can spray starting fluid on the joining surfaces of the carbs and boots and see if there's a change in RPMs that would indicate a leak, right?

[Designer]

I already had to adjust the throttle cable once on the front carb because the throttle body wasn't completely closed at idle, so I had to back out the Adjusting Barrel so the cable in the splitter housing would be long enough to allow the throttle to close completely. Based on the results in the video the front carb is opening after the rear carb right? So I must have gone to far in the other direction so I need to tighten the Adjusting Barrel right? The idle sync also effects how much slack the throttle cables have at idle, there's probable more slack in the front cable for that reason too I guess.

Yes, you pretty much have it figured out.

Now you need to "Fine Tune" the Front cable so it is in perfect Synchronization with the Rear.....at 2000RPM, of course.

Should I also check for vacuum leaks? The boots are on there tight and the "bump" on the carb bodies is in the notch on both boots. From what I've heard I can spray starting fluid on the joining surfaces of the carbs and boots and see if there's a change in RPMs that would indicate a leak, right?

Yes, that will do it for Vacuum Leak checking.