Possible fuel line issue?

[oldyam80sg]

I used the bread tie sync before I got a set of gauges. I use the Morgan Carbtune gauges as they are nice and compact.

[Radioguylogs]

Seems like the A/F mixture is off whenever you try to rev it.

Wonder if the vacuum pistons are operating properly.

Maybe you could remove the air pods and look into the carb air inlets to see what the pistons are doing?

Spark timing advance might another suspect.

[cajun31]

OK, I got an update. I bought and installed the Dynatek coils. I left the resistor unplugged/looped the two wires together. Still running the same. Tried to ride it around the block with choke on/off/mid still not good. Here is what it sounds like after it had run for a bit and me trying to ride it around the block. I also did the velocity stack to pod filter trick so that shouldn't be an issue anymore. Where should I go from here guys?
https://youtu.be/_YQW4WclJRc?si=34se5LGhH8NtL_k5

That sounds like a bike that needs to synched. From all you have said so far the carbs should be clean. Can't say much about the jets you have installed because I have no experience with them. I had a bike run just like yours after it had sat a while and it ended up being crud buildup from old gas. Removed the carbs and did a thorough clean of the jets and basically everything, put them back together and all was well. I also synched them and tuned them in with a color tune. What kind of gas are you using? Ethanol or non? Pete made a good suggestion about doing a bench synch of the carbs if you don't have gauges. That gets you very close but truly they need to be synched with gauges. They don't have to be very far off to run just like your bike sounds.

[shopteach]

OK, I got an update. I bought and installed the Dynatek coils. I left the resistor unplugged/looped the two wires together. Still running the same. Tried to ride it around the block with choke on/off/mid still not good. Here is what it sounds like after it had run for a bit and me trying to ride it around the block. I also did the velocity stack to pod filter trick so that shouldn't be an issue anymore. Where should I go from here guys?

https://youtu.be/_YQW4WclJRc?si=34se5LGhH8NtL_k5

[oldyam80sg]

Good eye Ray! I looked at pics of my carbs and had a brain lapse and couldn't see what was different.

[DiverRay]

Looking at the photos I see one thing no one has mentioned. The fuel lines are connected to the bottom "T" fittings between the carb 1,2 and 3,4. The top "T" fittings WERE connected to the airbox, as vents for the carbs. If something crawled in and died, no vent, no happy carb. You need to make sure the vents are clear, and then put a small filter on each one. A paper "fuel" filter will work.

[oldyam80sg]

Shopteach- use the search button on here and do the bread tie sync-that will get you close-I have used it on older bikes others than ours and had success. Yes vacuum cap in your 1st pic is the one-You should see some more -they become cracked and dry rotted and need to be replaced. The bike will pop if they are bad and not run good.

[Larrym]

No wurries or hurries on this side of the interweb... (^_^)

The foist pic showing the Vac port on the intake boot between the carb(s) and the engine covered wit' a female black plug lookey just fine. (´ ᴗ｀)

Iffin theres a plug missing or even slightly cracked (and a vacuum leak...) at any of the 4 (four) caps then you'd be surprized at how crappy these engines will run. (◕_ゝ ◕)

[DEEBS11]

But to NOT buy this Chinese garbage copy.

https://www.ebay.com/itm/31429544383...KX7TY9EMP7SA9X

[DEEBS11]

This is a good start. There are forum topics on how to install in the search function.

https://www.ebay.com/itm/36538606027...Bk9SR6LK7JDiZQ

[shopteach]

Sorry guys, I've been really busy. I finally got some time to work on it and I ran the bike as best I could by myself (one hand on half throttle, and the other playing with the wires) and I couldn't get anything to change. So I thought I would try and check the system from the ignition coils to the P/U coils. I tested the ignition coil as per manual and I got resistance between the primary side (little wires), but none on the secondary side (plug wire side). The coils wires are very hard and seem brittle. My thought is that the coils wires aren't good and made contact at certain times and not most of the time. Thoughts there? Does anyone have suggestions on where to get a coil? Places to stay away from on getting a coil?

oldyam80sg asked about the vacuum cap. My thought was it was this or is it this? Or am I completely off base? If it is different than these could you send a pic so I can address it?

You also asked about the carb being clean and yes they are. Synced, I haven't because I am trying to limit adjustments until I get it running better. I figure it should be at least close and don't want to throw one more variable into the equation, I already have too many at this point. And I haven't been able to run it enough to check the plugs.

[oldyam80sg]

Heard very little from Sigma.

[Larrym]

I do have a Dynojet recalibration kit installed in 1986 by a Yamaha mechanic and the jets are Genuine Mikuni.

I do have a Dynojet recalibration kit installed in 1986 by a Yamaha mechanic and the jets are Genuine Mikuni.

Yup! That's wut I wuz remembering from years ago...Alls I had to do was read it in yur signature. (｡•́︿•̀｡)

DYNO-jet...and Genuine Mikuni Jets installed at the same time? Wowzers! ┐(°ヮ°)┌

Might explain how's come you can just turn the choke completely off after 30 seconds of idling in the driveway and ride away all normal like. (O_o)

Comparision of Apple and oranges here as I've only had direct experience wit' wut happens when someone (me....) with a stock bike/carbs buys and installs the Taiwan Kits offered on Fleabay.... THEN swaps back to genuine Mikuni in order to get the bike to run like it did beFoAr the kit wuz installed cuz it ran so badly.... ¯\_(シ)_/¯

IIRC, the OP don't got jets/needles like EITHER of us. Some kinda kit frum SIGMA? ¯\_(°╭╮°)_/¯

I gots absolutely NO experience or knowlwdge 'bout THEM or how's they's s'posed to wurky.... (ノ_<。)

[DEEBS11]

Just a note on Dynojet kits. They are a proprietary jet kit. In other words, the Dynojet company makes it's own (quality) jets. They have a proprietary jet number that does not correspond to Mikuni or Keihin carb. This makes it very difficult for the future mechanic to figure out years down the road when they are trying to figure out what jets they have if they don't know what they are looking at. The tell tale sign is in the adjustable needle but even then some bikes made before 79 have adjustable needles stock from the factory. This causes many problems and many new owners of bikes end up here or some other forum looking for help that will never come because of the unknown modification. This is also true with Chinese junk jets that are apparently drilled with masonry bits. Too many modifications. Too much complication. Many, many opportunities for problems.

[oldyam80sg]

Shopteach-are the carbs cleaned? Are they synced? What do your spark plugs look like after a ride?