Air/Fuel Mixture Incorrect - Could this be my problem?

Hello everyone. New guy to the forum here. Pardon the long write up, but I figure more info the better? Anyway, I'm left scratching my head on something and looking to get your professional advice. So I have an 81' Yamaha Seca 650 race bike that I'm trying to get going for the track this year. I just bought it and I've been in the process of getting it back to life after sitting in a garage for 10 years. I've cleaned the carbs thoroughly 3 times now, not skipping corners - bringing it to the church of clean. My tank was pretty rusty so small bits of rust were getting swallowed up in the carbs (hence why I took them out and cleaned them 3 times). I eliminated that issue recently however by properly cleaning out the tank. So now my tank is clear of any debris and the carbs are practically spotless.

After the first carb cleaning, the bike ran, although it was very resistant. As much as I hated to do it, I peppered a little bit of starting fluid in it and it did fire and run after that. I let it run for a short amount of time and then shut it off ( by that time it was clearly running on it's own - not on the starting fluid). 15-20 minutes later I tried it again and it started right up and idled with no problems. I thought my issues were resolved. The next morning I went to fire it up and it was right back to square one - it wouldn't start. It would sound like it wanted to catch - or right on the verge of starting but no such luck. I cleaned the carbs for the second time thinking that more junk had gotten sucked inside. At this time (by the request of someone online) I bottomed the fuel/air screws out gently on each carb and reset it to the "factory setting" (2-1/2 turns). I still had the same problem with the bike not wanting to start. Cleaned the carbs for the third time yesterday and put them in - and again, still having the same problem. I'm wondering if maybe my carbs were getting clogged by all of the junk in the tank on the first two cleanings and now on the third cleaning (after resetting the fuel/air screws) it has become a matter of getting the right mixture. Could this be? Would an offset fuel/air mixture on each carb cause the bike to not start?

I'll also post a pic of the spark plugs below so you can see what they look like. As you can tell, they are all over the place, making me question the fuel/air mix and thus coming to you guys to see if this is my problem or if I should troubleshoot other areas. Much thanks for all of your help! I greatly appreciate it!

 

Hmm you said carbs have been to church did you fully read down carbs and soak carb bodies and replace butterfly seals? Did you bench synch carbs first and then sych by either manometer or vacuum gauge set up? Carbs that are off will cause starting problems and no adjustment of mixture screws will help. I assume you running the dreaded PODS This creates more issues yes it will run but takes playing with jets. One more thing if you run pods make some type of bracket to support carbs do not rely on the carb boots alone it will end up cracking at some point from the weight of carbs.

 

I would be looking at ultrasonically cleaning the carbs if it's been stood for 10 years.
The internal passageways will be totally caked in varnish and gum and it will only run on the choke and idle circuit.
I could be wrong but.....

 

but you're not.

 

Jetfixer's questions are all "right on." Replacing the throttle shaft seals (aka butterfly seals) is a must-do at this point. While you're at it, replace fuel o-rings, float needles and seats. I suspect you've got problems with the enrichment circuit. With bowls off and flashlight beaming into it, can you see the tiny glimmer of light coming from that passage?

Your restarts while the engine is still warm may not need the (non working) enrichment passages. That's why I suspect your next day non start problem rears it's ugly head.

 

Next time try to jump it with a car battery. You may have a weak battery--I did. That's why I keep mine on a tender.

 

Hey guys, thanks for jumping on to help. Here's an update: I have the carburetors off again. This morning I bench synced them. The butterfly valves should be somewhat synced now (I'll be syncing them completely once I get a gauge). I also took apart and cleaned the enrichment circuit completely, although the ports didn't appear to be that dirty. I attempted to contain the carb cleaner that I pumped through it and I didn't see anything that looked like it could have been causing an issue. Anyway, I am now fairly confident that the carbs are cleaned thoroughly so there should not be a problem there. You guys mentioned to clean the carbs ultrasonically. I don't have a machine at the moment but I am looking to buy one next time I'm at Harbor Freight.

If this time around doesn't work and it's still pointing towards a carburetor issue, I will order the new o-rings, float needles, seats, etc. but I think it should be good to try again in the bike.

So is there anything else I should do before putting the carbs back in the bike? I'm assuming the fuel/air mixture will still be an issue once I do put the carbs back in, but who knows, maybe I will actually be able to adjust the mixture screws with a running bike. Haha

 

So you didn't break apart the carbs yet?

I feel like you'll be chasing your tail trying to fix the problems that are actually hidden deep, DEEP inside your (probably never previously cared for properly) 36 year old carbs.

Just cleaning isn't enough. Those rubber parts in there (especially the shaft seals) have gone from pliable to petrified. Replace and rebuild!

Good luck man!

 

And make sure the enrichment well jet is clear.

If you haven't taken them at least this far apart, they, aren't clean yet

 

You do not need any special equipment , a 1 gallon container of Berrymans carb cleaner (Auto zone /Oreilly etc) do FULL tear down soak carb body( 1 at a time) for about 1 hr , remove wash with hot water and a little Dawn dish washing soap , Dry and reassemble with all NEW rubber seals /gaskets . THIS is church of clean !!!!

 

Do this and also the little passage in float bowls are always an issue

 

I have disassembled the carbs entirely 4 times now. Everything seems to be in check and clean. I am leaning towards rebuilding the carbs anyways while I have them off, to absolutely eliminate that worry. Where can I purchase a good rebuild kit? Should I replaced everything or just the seals/gaskets?

 

XJ4Ever - upper right hand corner of this web page.

You should have rebuilt/ refurbished them the first time, just doing a 'clean' (even a Church Clean) without replacing worn parts is just an exercise in disassembly/ reassembly.

So now order the Deluxe Rebuild Kit from Len - and go through those carbs for the 5th time - you should be able to do it in no time flat with your eyes closed because of all the practice.