Help Carb Sync

[Straka]

Hey, I just recently picked up a 2002 Yamaha Vmax, no when I picked it up I noticed some issues with the carbs, I assumed it was just a sync issue, so slowly I have been doing some much needed maintenance, now here comes my frustration, when going to sync it seems like it just doesn't want to behave and runs way to lean, my pressure gauges only really sync together after turning each of the a/f screws 8 turns each, I did remove the carbs and clean up with some carb cleaner and removed everything to remove any gunk which Im not opposed doing again although it wasn't particularly gunky, also the throttle cable seems to get kind of stuck even after lubricating it snaps back when I roll on the throttle but sometimes get stuck if I got from 3/4 throttle to 1/4 throttle but that isn't the main issue, I feel kind of lost when it comes to syncing and balancing my bike. If someone wouldn't mind helping me out here give me a good step-by-step. Also, I pretty much changed out everything maintenance-wise from spark plugs to oil.

 

[MaxMidnight]

I think you need to have a look in the Service Manual for the correct process, section 2-11 refers.
What you are synchronising is the relative position of the throttle butterflies to each other so the volume of air being drawn in is the same at all throttle openings.
This is achieved by the adjustment screws on the throttle linkage and NOT the idle mixture screws.

 

[Radioguylogs]

There are two throttle cables; a push-pull arrangement.

While you are in the service manual, you can find how to adjust the cables.

 

[Fire-medic]

We have the factory service manual on here available as a PDF I suggest you take a look at that and in the back in the appendix are diagrams for the circuits in the routing of your carburetor cables. From what you're describing it could be that you have a binding cable so check the routing

 

[gentsvmax]

Hey, I just recently picked up a 2002 Yamaha Vmax, no when I picked it up I noticed some issues with the carbs, I assumed it was just a sync issue, so slowly I have been doing some much needed maintenance, now here comes my frustration, when going to sync it seems like it just doesn't want to behave and runs way to lean, my pressure gauges only really sync together after turning each of the a/f screws 8 turns each, I did remove the carbs and clean up with some carb cleaner and removed everything to remove any gunk which Im not opposed doing again although it wasn't particularly gunky, also the throttle cable seems to get kind of stuck even after lubricating it snaps back when I roll on the throttle but sometimes get stuck if I got from 3/4 throttle to 1/4 throttle but that isn't the main issue, I feel kind of lost when it comes to syncing and balancing my bike. If someone wouldn't mind helping me out here give me a good step-by-step. Also, I pretty much changed out everything maintenance-wise from spark plugs to oil.

These carbs require a very thorough, complete disassembly and cleaning. I mean a carb clean soak minimum, ultrasonic bath being the best IMHO+ two cents.

 

[brian hicks]

Make sure that your meters are correct by switching lines when the engine is running to see if the correct pressures transfer to the meters that you swap over. Some of these gauge kits ( especially the blue ones from China) are not very accurate.

 

[Maxnewby]

This site has some real die hard want to help helpers, 5 replies with earnest suggestions to an obviously none mechanically inclined can be very complicated VMax owner. Sounds like F/A mix screws are being used to sync. Remember sync sequencing is L- screw both L - carbs R-rear both R-carbs, then touchingly front R-screw sync R-carbs to L-carbs. Sounds like the cables are not in the cable cups on carbs like mine were.

 

[Maxnewby]

And worst of all cheezy (blue kit) vacuum gages will drive U crazy! The black 68.00 buck ones on U know where are best.

 

[Radioguylogs]

Make sure that your meters are correct by switching lines when the engine is running to see if the correct pressures transfer to the meters that you swap over. Some of these gauge kits ( especially the blue ones from China) are not very accurate.

I have the blue gauges.

I bought some nylon T fittings and rubber hoses to make a fixture to connect all four gauges to one carb. I check them once-in-a-while. They don't drift from my original adjustment.

 

[Maxnewby]

I have the blue gauges.

I bought some nylon T fittings and rubber hoses to make a fixture to connect all four gauges to one carb. I check them once-in-a-while. They don't drift from my original adjustment.

The insides of the blue case set from ama screwed up almost immediately for me I got the black set with the adj by the fitting and they are as quality as any can be.

 

[Straka]

This site has some real die hard want to help helpers, 5 replies with earnest suggestions to an obviously none mechanically inclined can be very complicated VMax owner. Sounds like F/A mix screws are being used to sync. Remember sync sequencing is L- screw both L - carbs R-rear both R-carbs, then touchingly front R-screw sync R-carbs to L-carbs. Sounds like the cables are not in the cable cups on carbs like mine were.

Hey Thanks for the advice, for the cables I was able to resolve the issue it looks like the throttle body springs were a little gunked and not moving freely, it took me a second to figure it out, before my thread, I inspected every aspect and thought the same as you suggested, but that was not the issue. as for the syncing I didn't buy the blue gauges but I will take your advice and check the accuracy of my gauges.

 

[Straka]

Also thanks to everyone's advice I appreciate it.

 

[Fire-medic]

OK, let's hope this fixes his issues.

I am curious as to where the "throttle body springs" are located?

You need the factory service manual, it has what you need to work on your bike, and to trouble-shoot it.

https://dn790009.ca.archive.org/0/i...ice-manual/yamahavmaxvmx12-service-manual.pdf

Please I.D. by one or two-digit part # what you call the throttle body springs.


The link containing this fiche: https://www.ronayers.com/oemparts/a/yam/50045c0ef8700209bc7942f3/carburetor

You can use the link and blow it up to whatever resolution you need, to find the part #



These are the synch screws.

My EMGO 'blue case' set have served me for more-than 40 years and I have a set of Motion Pro 'wet' sticks that is no-more accurate if I swap them out. I also have a third set which appears to be nearly-identical to sets on Amazon in a red blow-molded case. They all do what you're supposed to do, which is accurately balance the carburetors between and among themselves.

Sounds like the set Vmaxnewby got which gave him trouble was defective, a shame that they didn't perform properly and for a long life. Do they have a manufacturer's place of origin on them? I'd be interested to hear where they were made. Thanks.

The Old Guard used carb sticks with mercury in them. Like the glass thermometers with mercury in them 'no-longer available.' Place the Haz Mat sticker here.

​

 

[Straka]

OK, let's hope this fixes his issues.

I am curious as to where the "throttle body springs" are located?

You need the factory service manual, it has what you need to work on your bike, and to trouble-shoot it.

https://dn790009.ca.archive.org/0/i...ice-manual/yamahavmaxvmx12-service-manual.pdf

Please I.D. by one or two-digit part # what you call the throttle body springs.

View attachment 93050
The link containing this fiche: https://www.ronayers.com/oemparts/a/yam/50045c0ef8700209bc7942f3/carburetor

You can use the link and blow it up to whatever resolution you need, to find the part #

I couldn't find the specific part on that diagram but attached to this reply is a diagram found in the service manual, I was under the impression there were that these were referred to as Throttle Body pull/return springs, If not then I hope someone can correct me. They appeared a little gunked up and after carefully examining them wiping off any gunk and ensuring they were not broken or affected in any negative capacity the cables began to work perfectly.

 

[Fire-medic]

Just as a point of information, study the path your finger would take, if you were sitting in the seat, and looking down at the carburetors/cylinders below the airbox. On the faux gas tank cover, without lifting your finger, draw the path from #1 to #2, then #3, and finally, #4. That's how to remember the arrangement of the bike's cylinders and carburetors. What's that letter?

There are four throttle cables:
two are 'pull' (upper & lower)
two are 'push' (upper & lower)

Cables, especially in a bike which is at-best 17 years old, which were probably last lubricated at the factory in Japan, are probably not going to be at their best as a bike goes through six owners, for example. Check the throttle cylinder on the right handlebar for drag, cracking (due to an accident, I've removed the hand throttle cylinder before and had asphalt particles fall-out, and also found a cracked/broken throttle cylinder). Checking cable for fraying, checking the case for crimping, causing a 'dragging' inner cable, or itself also being crimped; a lack of lubrication, improper routing, causing drag and failure to retract as-designed, times four. That's what the used-bike buyer is up-against.



Motion Pro cable lubricator, $11, https://www.motosport.com/product/?...VMi7UAR1aKAT2EAQYBSABEgI0AfD_BwE&gclsrc=aw.ds

I have one of these which is probably more-than 45 years old, older than my EMGO carburetor balance gauges, and it has touched every one of the dozens of bikes I've owned/ridden since I got it. Use your aerosol red wand on the lube of choice, I like PB Blaster to clean things and then WD-40 for the final spritz. Do the injection at the cable top, and watch the lower end for the flushed-out residue, grit, & etc. Don't forget that the VMax has that nylon case for the connection of the upper cables to the lower cables at that point.

 

[Straka]

There are four throttle cables:
two are 'pull'
two are 'push'

Cables, especially in a bike which is at-best 17 years old, which were probably last lubricated at the factory in Japan, are probably not going to be at their best as a bike goes through six owners, for example. Check the throttle cylinder on the right handlebar for drag, cracking (due to an accident, I've removed them before and had asphalt particles fall-out, and also found a cracked/broken throttle cylinder. Checking cable for fraying, checking the case for crimping, causing a 'dragging' inner cable, or itself also being crimped, a lack of lubrication, improper routing, causing drag and failure to retract as-designed, times four. That's what the buyer is up-against.

View attachment 93055

Motion Pro cable lubricator, $11, https://www.motosport.com/product/?...VMi7UAR1aKAT2EAQYBSABEgI0AfD_BwE&gclsrc=aw.ds

I have one of these which is probably more-than 45 years old, older than my EMGO carburetor balance gauges, and it has touched every one of the dozens of bikes I've owned/ridden since I got it. Use your aerosol red wand on the lube of choice, I like PB Blaster to clean things and then WD-40 for the final spritz. Do the injection at the cable top, and watch the lower end for the flushed-out residue, grit, & etc. Don't forget that the VMax has that nylon case for the connection of the upper cables to the lower cables at that point.

Yeah, I removed them inspected them, cleaned, and lubed them, it was moving freely, snapping back and everything. but only got a little stuck when rolling down and up a little after looking at the aforementioned throttle body springs or what I was referring to in the early diagram and just cleaning that area a bit it began to move just as intended. and said the screws in the prior message have been the ones I have been using to sync as stated in the service manual, but thanks for all the advice I did clear a few small things up for me

 

[Fire-medic]

Take a look in the Appendix of the factory service manual, and match exactly the cable routing shown there. Sometimes just pulling the slack in the cable routing upwards from where it snakes into the bodywork will noticeably lessen the drag, Sometimes going the opposite way will ease the action. It's one of those things on a bike which needs a bit of experimentation to see which way is better, which way 'works.'

I once bought a VMax, not running, missing parts, but the engine was together, it wasn't a 'basket case.' As I got it home and began examining things, I found the rigid pipe to the slave cyl of the clutch was twisted like Granny from The Beverly Hillbillies was 'selecting' a chicken from the yard, and sending it to its greater reward by ringing its neck using one hand, in a circular motion. They were careless in seeing the way the rigid pipe ran to the slave cyl connection, and when it didn't line-up properly, they just forced the rigid pipe into a pretzel, permanently damaging it. I have a friend whose shop fabricates hydraulic lines, and he made me a replacement. The moral is sometimes prior owners bollox things which need to be found, to be fixed, and to find all the owner-caused problems. In that vein, checking the clutch and the brakes seem to be two important systems you need to closely-examine in a new-to-you (but used) motorcycle.