Seca idle problems

Hey all. Newbie here. Looking for some help.
I have an 81 seca 750. Doing a full restore.
Here’s what I have done.
New fork seals
rebuilt calipers
New wheel bearings
Every fluid changed
Rebuilt rear brake drum
Stem bearings
Added air box back (came with pods)
Valves checked and reshimed
Except that 3 exhaust valves are still tight by .05. (2 are 2.65 need 2.60 1 is at 2.60 needs 2.55)I am waiting on 3 shims to correct
FULL CARB BREAKDOWN AND CLEAN
Ordered new throttle seals and fuel rail seals from Len ( awesome dude)
Wet set carbs twice
Bench synced 3 times at least
Full carb clean 3x
Polished slides and bore
New fuel bowl gaskets
All manifold boots have been inspected and Rtv’d.
Waiting on fresh manifold caps. Old ones are a little hard and suspect.
New fuel line
New vacuum line.
checked the petcock with vacuum method making sure fuel was pulling with vacuum on vac line
New plugs
New battery
All kinds of beautifying


ok
So this may be counter productive until ALL valves are within spec but I just have to know
I have finally got the bike to start. Killed one 1/2 dead battery in the process.
At first it was a run away idle. ( hang on to that thought)
Plugs where black sooty and dry
Did the throttle seals and rtv’d the boots
Adjustment screws 2.5 turns out
Will crank over eventually. Full choke will get it warmed up. Once warm the idle is funny and boggy, kinda of low (800 rpm) and twisting the throttle stalls it. If I turn up the idle screw the idle gets worse. Seems like it’s a mirror image of the throttle behavior. Gets boggy and wants to die. If I back out the idle screw the idle hunts or shoots up to 3k and stays there. No noticeable effect with adjusting the 4 mix screws. I’ve tried 2 turns out, 2.75,3 and 3.5. i am going to get the new valve shims in and then retry the process but it doesn’t seem that far off. ( like I said 3 intakes are out .05 shim measurement. ). Correct me if I’m wrong but The starter at times sounds like rocks in a blender and im wondering if the 3 tight exhaust valves have anything to do with that. Before I changed out the shims I couldn’t even rotate the engine with the timing head bolt(19mm square one). Could the out of spec valves be too tight still to crank consistently?
My next thought is to check for air leaks propane style. But I did rtv those suckers pretty good. I’m not giving up cause this bike seems like it will be fun. I really wanted a gs to work on but you can’t always get what you want. My wrenching has been limited to enduro thumpers thus far ( 90 dr350 ) and a vstrom that never needs anything. The Toyota Corolla of motorcycles. I’m excited for a sweet ol street bike.
Even though I checked vacuum with the petcock I’m suspicious that the petcock in the on position is not pulling fuel. It may have run out of fuel a few times and died after I switched from prime to on. At that point it wouldn’t start again until I switched back to prime position and refilled the bowls. ( I think) Then it would crank over with the same idle issues stated above. Weird huh? The vacuum test told me the petcock was ok but…. It’s hard to know for sure because the idle has been so erratic and the bike has died a lot while diagnosing but for sure at times I have switched back to prime position and then it would start.
If this isn’t worth getting into until all valves are within spec then just shame me and we will see what happens after the valves are 100% shimmed. I appreciate you all for the efforts you have made in helping so many others. It has been a wealth of knowledge in this process.
thanks
J

 

Can you believe I forgot to mention something.
At first go around before the throttle seals were replaced and full cathedral experience the rpms would surge bad and die back with a twist of throttle then die out. After the throttle seals etc replaced and boots rtv’d the idle just hangs around 3000 once warmed up and if I totally back out the idle screw it dies. The throttle now has no effect on the hanging idle
For anyone who has read all of this you must really love these bikes….

 

Love the yellow!! Here is what I would check you stated you put RTV on the boots , did you remove them or were they left on the engine? You may have a bad gasket between the engine and boot . I put new intake boots on my Seca and used new gaskets . Another item to check the vacuum caps are in good knick and are not a hillbilly piece of vacuum hose with a bolt pushed in . When you reassembled the carbs it is possible the butterfly plate on one carb is not fully centered. I have done several sets of these carbs and one set I did had this issue, loosened screws and moved the plate and solved issue. Cheers.

 

Nice yellow as well. I reused the gaskets so I’m guessing that’s another step. The vacuum caps are ordered and on the way. I’m pretty sure the butterfly plates are seated correctly. I loosened them and snapped the throttle open and closed and retightened. Carb 2’s crescent shaped bottom is ever so slightly askew but not by much. I can’t get that totally centered but it’s barely noticeable.

 

What exactly should I be looking for with the butterfly plates jetfixer? After bench sync they seem seated well and evenly spaced at the bottom. Snapping shut very well and to the same place every time-Edge of 1st hole up top.

 

I seat them in till one hole at the top of the carb is showing there are two holes by the way . I use two number 20 drill bits put one under number three carb plate synch the rest till there is slight drag. Pulling bit slightly , once they feel good , I adjust the idle knoob till the number three carb drill bit as drag and carbs should be close ,i check the two holes at top of carb both should be visible.

 

i have 3 XJs .. none of the starters sound like rocks are in them .. so that's concerning. that's probably the first thing that should be fixed.

have you done a carb sync with gauges or a sync tool? a running sync while the bike is at operating temp is a must do

and have you gone over your ignition circuits to be sure you have the right ohms through coils and plug caps and have the right plugs?

 

Max
The starter sounds like that after trying to get the bike to start (10-15 cranks ) then a few times stalling out and restarting. A stressed battery does it every time. A fresh battery ( overnight charge) gets me a good crank. I will test the coils
The plugs I have are the same # but the “r” version ( I believe) Couldn’t get a hold of the original. I know there is a thread somewhere on here about switching over to the more updated version of these plugs but also the caps as well. I will look into that. The plugs are pretty sooty at this point so I just pull them and clean them up.

 

I use Autolite 63 plugs with resistor caps with no issues .

 

Yeah. I just spent some timing checking the coils (good 2.5 ohms)
Wires and caps ( unsure because they are some aftermarket hack job that came with the bike, couldn’t get the caps off).
There was no resistance between 1 and 4 wires ( should be right around 11k right?). What’s weird is that I did get fat spark with all 4 wires before the test by grounding the removed plug and cranking. I switched over to the 2 coils and wire sets from my parts bike that tested out ok. The caps are the original td133 and td134. The caps ohmed out at 7.5 and 8 k respectively. I thought they would be at 5.5 or so. Will try some new plugs once I get the valve shims installed and new manifold boot gaskets and caps.

 

Three things to consider: 1) check the throttle cable to make sure it's not binding anywhere and that it slides easily/quickly. (you may have already done the check but I thought I'd mention it just in case). 2) Check to make sure that you're not using an energy-conserving oil, I use Rotella 15W40. There's a recent posting about which oil to use. If it's still making the rating noises after changing the oil, there are forum posts about how to try to rejuvenate it with diesel or snake oil or something... 3) did you use a YICS blanking tool during your running synch?

 

Thanks for replying Andrew
1.I have a brand new cable lubed and it seems to snap closed pretty easily. I have routed it a few different ways and think I may have it. When I broke the carbs and reassembled I was just slightly out of wack so I re adjusted with 2 levels and that freed up the throttle snap a little.
2. I’m using 20-50 as recommended specifically for motorcycles. Im switching to a 10 40 cause I’m in mass and it’s getting cold. I don’t have a heated space until I crank the torpedo when I get there. 20-50 may be a little thick right now
I do have a starter rebuild kit I think I’m going to rebuild with. I have a brand new battery and it seems like there is just not enough current getting through. After a battery tend overnight it starts fine. After 10 or so restarts in a sync session it starts to act up.
3.I just started the sync process without a yics tool. Lots of opinions on that here so I’m going with the less expensive option for now since this has been a full rebuild and I have sunk a lot of resources into it so far.
My current issue:
Bike will start right up. New e-3 plugs and caps and correct ohmed coils
It will idle around 1k after enrichment. When I bill the throttle the idle then hangs around 2,500 and then slowly dies back down to stalling. I rejected main fuel jet to 122 since it has a 4 into 1 exhaust that came with it. Prior to that rejetting I had the pilot mix screws out almost 4.5 turns to get a decent idle. Now it’s around 3.25 turns and with a running sync it is idling as described. The idle is erratic hanging around 2,500 with a throttle blip then settling down and stalling or with a throttle blip it might settle to a 2k idle. Can quite get it to purr. I replaced the carb intake gaskets and the carb boots along with the usual suspects ( petcock vacuum test, throttle seals , fuel rail seals ). I’m a little stumped at this point and after spending a little too much time last night trying to sync I had to call poison control due to carbon monoxide. I’m fine but I’ll have to open the bay next time.

 

You have similar symptoms to me when I was running lean. Hanging idle, hard to rev. Get her warmed up with no choke, let it idle for a bit and check the plugs. Another thing that can help if it is real bad is with the bike cold, start it up, and keep a hand on each of the exhaust pipes. When I was running super lean, some of them would heat up quick and hot, and other ones took their sweet time. Plugs should look a little darker than tan.

 

On my UK 1980 XJ650 4K0 model, at idle, I could grab hold of #3 cylinder exhaust header pipe, is was cold. Can't remember which way the pilot air screw was turned but after some adjustment, the bike fired on all 4 cylinders. The bike was taken to a dyno centre for exhaust gas analysis on each individual cylinder. The guy said, "this bike is running so weak, it's a wonder it hasn't seized up". Following corrective action and then having the carbs balanced, I've never looked back and the bike runs and idles perfectly. IMO, without WG analysis it's just pure guess work.