Hard Cold Start

[Guest]

This is on a 77 GS750.

So my bike only wants to start on starting fluid when it is cold. It doesn't matter what I do, choke, throttle etc.

Symptom:

On the first try it sounds like it wants to start for a second, then the motor just turns over, you can hear compression (but no sound like it wants to fire). One little squirt of starter fluid and it starts right up.

When I turn my bike off it will randomly pop/snap, like an electrical pop/snap or something (hard to explain). I could never pinpoint where the sound was coming from until the other night, I was working on it after it was running and it poped/snapped, I sorta pinpointed the sound came from around my points.

Once I get it started and warmed up it will start & run great all day until it cools off. I had this same problem last year when I first got the bike.

I have done the following maintenance recently:
(with the same cold starting results):

1. Adjusted valves
2. Completely tore down & cleaned carbs - (all vacuum lines and everything seems fine, verified cleared passages, mechanical synch, Im awaiting a Morgan Carbtune.)
3. Checked voltage & did coil relay mod - (before/after = good voltage)
4. Petcock seems to be operating fine (using clear fuel line to verify)
5. Verified spark plugs ignite.
6. New battery with good voltage
7. All new o-rings

I plan to reset the points again and adjust the timing tonight, but i don't expect it will help much.

A little bike history:

The bike is not a barn find, it spent the last 10-15 years in a collectors "man-cave" basement and still looks relatively new, electrical connections and all.

I am sort of at a loss, any input, feedback or any similar experiences are welcome.

Thank You.

[Brendan W]

If she fires with lighter fluid the odds are spark and compression are ok which leaves fuel. Are the bowls priming, is the choke cable correctly adjusted ?

[tkent02]

It has no choke cable, the bowls don't need priming if it's just sat overnight.

Did you ensure the pilot jets and associated passages were clear? How about the holes in the choke feed pipe?

[tom203]

A man cave basement bike ! I thought they just had bar signs and wiiide screen TV's to impress each other.

"When I turn my bike off it will randomly pop/snap, like an electrical pop/snap or something (hard to explain). .... I was working on it after it was running and it poped/snapped, I sorta pinpointed the sound came from around my points"

Hmm, does this thing still have points ignition? maybe a PO upgraded to snappy ignition system.

[halz426]

It has no choke cable, the bowls don't need priming if it's just sat overnight.

Did you ensure the pilot jets and associated passages were clear? How about the holes in the choke feed pipe?

Wow fast replies, Thanks Guys

The pilots and passages are clean, I did a thorough overnight dip on each carb and dipped the jets etc. I sprayed out with compressed air, again upon carb assembly I sprayed carb cleaner in the
passages and blew out the passages with compressed air a second time, checked the other ends to make sure air was blowing through, i ran a guitar string through the pilot jet
and did a visual inspection checking for light through pilot jet.

It doesnt bog/sputter when I give it gas. 1/4 throttle

I may recheck "the choke hole" but the choke affects the engine rpm idle, so I assumed they were fine.

Thx

A man cave basement bike ! I thought they just had bar signs and wiiide screen TV's to impress each other.

"When I turn my bike off it will randomly pop/snap, like an electrical pop/snap or something (hard to explain). .... I was working on it after it was running and it poped/snapped, I sorta pinpointed the sound came from around my points"

Hmm, does this thing still have points ignition? maybe a PO upgraded to snappy ignition system.

Right, the PO actually was way into vintage dirt bikes, pretty cool set up.

Yes points ignition, I have no idea if they are upgraded or stock.

I like the idea of keeping points, The Dyna's seem to be problematic based on reviews I can find.

[Steve]

Sounds coming from the points could be bad condensors.


Please do yourself and your bike a favor, THROW THE STARTER FLUID AWAY.


Rather than continually apply a Band-Aid, why not just fix the problem?

What's the fix? Two items come to mind.
1. Clean the carbs PROPERLY and COMPLETELY.
2. Adjust the valves. Valves tighten up in general use, and the clearance is perilously small to start with, so any reduction in clearance quickly leads to damaged valves.

.

[BigD_83]

Hi Steve,

back in the original post, halz says he did a complete teardown of the carbs, and has adjusted the valves...so taking it at face value, what else could be going on?

Timing?

[halz426]

Thanks Steve,

I'm trying to diagnose the problem (and not just throw parts at it), I don't like using starter fluid either. : )

[Steve]

OK, I guess I missed that when I glanced through.

However, he does say this:

It doesn't matter what I do, choke, throttle etc.

Let's go for TECHNIQUE, then.
Set the "choke". Might need full application, might need less.
Set "kill" switch to RUN.
Turn key ON.
Pull clutch (unless "safety" switch has been bypassed, but it's still a good idea).
Push starter button.
Adjust engine speed with "choke" control.

Did you notice that NOWHERE was there an instruction to "move the throttle"?
That's because you don't touch it when using the "choke" to start the bike.

Even if the valves are correctly adjusted and the carbs perfectly set up, incorrect starting technique will make the bike a bear to start.

.

[halz426]

Steve,

I appreciate your K.I.S.S approach, I work IT Tech support so I understand starting with the basics.

I will admit that I had questioned the starting technique in narrowing down the process as well, I thought maybe the bike was extremely temperamental.

As for technique, I have tried the choke in every position from off to full, it does not make a difference. I only tried applying the throttle to see if it would make a difference in a one last attempt.

On another note, I have had other people try to cold start the bike who have more motorcycle experience than me (one was a mechanic/mechanical engineer) and the result was always the same, no start off the juice & same response/symptom.

[halz426]

Bump - anyone have any input/ideas/tech. . I am betting its in the ignition somewhere.

[tkent02]

What happens if you kick start it?

[halz426]

I havent tried kickstarting it cold yet, but once its warmed up it starts on first kick. Ill try when i get home. I actually never though about trying 2 kickstart it cold. Lol.

I appreciate the help/input fellas. Thx

[Steve]

I know you said you adjusted the valves recently, but cold starting problems are either due to tight valves or plugged "choke" passages in the carbs.

Even though the carbs might have "just been cleaned" that message doesn't always get to the crud that is waiting to wreak havoc.

.

[Big T]

Check for spark

Check you plugs -are they getting wet when the bike doesn't start?

Check your ignition-if you have points, replace the points and condensors

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