Choke and Idle

Bike wont idle very well when I first start it cold and takes a while to warm up.

After I start it I give it a tiny rev to bring it to about 3k rpm, it sits there momentarily before returning to about 1k rpm where it stays for about 30 seconds before stalling out. Choke is on, full blast. I've tried it with different amounts of choke with the same results. With no choke it stalls immediately.

Other fun facts:

This is a 82 750 Seca

Bike does start up, instantly, always.

I've cleaned the carbs multiple times this winter and spring. I am confident that they are clean.

Bike showed the same symptoms last fall before I tore apart the carbs. I did find the enrichment tubes in the bowls to be clogged. They are now clear.

When the bike is warm turning the choke on ( just a little) instantly stalls the bike.

Its been color tuned, synced, floats set, checked valve clearance and ridden for hundreds of miles.

I want to be able to start my bike and let it warm up. right now I have to babysit it till it warms up by blipping the throttle. I feel like a weirdo sitting at traffic lights in the morning blipping my throttle.

runs excellent when warmed up.


Any suggestions? Ideas?

 

how do your choke plunger seals look? Wondering if maybe it's suckin air through there?

 

Are those the pieces of rubber around the plunger on the outside of the carb bodies?

 

Was it jetted for pods?

 

Have you done a colortune? It sounds like a rich mixture at idle.

 

it has a stock airbox, stock jets stock everything

I did a colortune. It was running VERY lean before the color tune. Had to back the mixture screws out to about 5 turns. Warms up the same before and after the colortune.

 

5 turns out is quite a bit. how do your plugs look now?

to answer your question - the "pieces of rubber around the plunger on the outside of the carb bodies" are the "choke plunger seals"

an unlit propane torch held around the carburetor will help you find any air leaks.

 

My plugs were white before, haven't checked them since the adjustment.

I sprayed insta start around the carb bodies and found no leaks but Ill try some propane and see if I get any different results with that.

 

I'm noticing a trend when it comes to the 1982 SECAs.

I've read this board for hours at a time, and a question I see consistently is "why is my SECA running lean?"

I have the same problem!!!!



Why is this particular model such a lean beast?
Did they use a different type of rubber for the boots and seals?
Am I sucking air from someplace else? What's the deal?

 

Dez's 82 seca 70 runs pretty nice mixture wise, it does have #43 pilots in it tho, 120 mains. all pilots at 2.5 out, plugs are a nice brown, on the side of rich.

 

Hmmm.... just rebuilt my carbs and am also running lean. Plug chopped 4 times still to lean and am almost 5 turns out. Just a touch of brown on 2&3, 1&4 are still white.

 

I have had to resolve a "Severe Lean" condition on several early Seca's.

I found:
Incisions through the Manifold "Necks" by improperly placed or incorrectly sized Manifold Neck Clamps.
(If the Clamp is NOT within the reinforced area, ... look for a split.

The Intake Manifolds Lead ----> ""Under LOAD""
The Bike will Idle like a Sewing Machine ... But, as soon as the Throttle is Opened the Engine loses tune.

Findings:
Hooked up to Carb Sticks ...
The Carbs will perform well enough to Idle
Upon raising the rpm's ... the Vacuum on one or more Manifolds does not respond to the change in rpm's.

Manifold Leak.
Back-side of Manifold to Head.
Dry Gasket and Worn-out O-ring FAILS under LOAD.

Replace O-ring???
Risky.
Solution:
Remove Carbs ... Seal Manifolds EXTERNALLY.
"Wipe" some RTV around the EDGE of the Manifold like CAULKING a Bathtub to a Tiled Wall.

Close-off the Mating Surface.'
Make completely AIR TIGHT.

REMOVE - MANIFOLDS - AT - YOUR - OWN - RISK.
Get Fancy and Break a warm-butter-soft Manifold Bolt and you will be up Sh1T Creek. No Boat!

 

Well let me jump into this boat too! The only thing not stock on my bike right now is the 4-2 MAC? exhaust with a perforated baffles (PO trashed the one that went with the exhaust and it's the best I could find), and the now 41 pilot and 122 main jets in my 1982 750 seca. Compression is good, valves are in spec, carbs cleaned thoroughly, just got new airbox boots, even got the intake boots off no problem and replaced the gasket (didn't "dress" it tho but I did put anti-seize on the *sigh* original bolts). I started blaming my fuel filter, and have replaced it with one that doesn't collect air bubbles, but I still need to plug chop.

However, my pilot screws are probably 4-5 turns out (with the original jets, the last time I said that, they were ALL 5.5 turns out). Hey Rick, you're right around the corner from me HINT HINT :twisted:

 

Ya got that right, Rick. Those manifold bolts will snap-off in a New York minute.

 

I put the propane to it today and found no leaks. Lots of propane around all the throttle seals, sync ports, intake boots, etc.

It doesn't idle like a sewing machine.

My other bike, the 550 has very different choke characteristics. That one will make the idle raise with the choke lever. that one starts hard, but will will idle till its warm.

 

filled it up today...

88 miles since last fill up.

Took 3.2 gallons of gas.

Not good. Makes no sense.

Its running lean, pops on deceleration and even sometimes constant throttle cruising.

 

What does?