Carburetor Cold Starts

10850 Views 16 Replies 10 Participants Last post by hogcowboy, Jun 22, 2019

CANTSiR

Discussion Starter · Jun 14, 2019

Got a new 2017 Honda XR650L. Bike runs great when it is warmed up, but cold starting the bike seems to be quite difficult. I followed the manuals advice, but it still struggles to run at first. This is what I do:

1. Choke 100% start bike no revving.

2. Half choke ASAP manual says, but the bike seems to need 10 seconds or so before I can half choke. No revving.

3. 0% choke after 60 seconds. The bike putters so i rev a lil or it stalls.

4. Bike seems like it's running alright. I go to pull out with good throttle and it stalls.

Any advice? Should I increase my idle speed? Just be patient and give it more time to warm up?

Also to note. When I park the cycle I just leave the fuel to ON position. Could this be contributing? Should I always turn the fuel to OFF position like the manual says?

1 - 17 of 17 Posts

Critter

· #2 · Jun 14, 2019

Some bikes are very cold nature. If there are no other problems, let it warm up.

Reactions: 3

Miss Mercedes

· #3 · Jun 14, 2019

Yup. I've found that even two bikes of the same model and year will react differently on cold starts. So long as it runs and rides fine and you aren't choked for power, I'd just let it warm up.

SemiFast

· #4 · Jun 14, 2019

There is a slow speed fuel mixture screw at the underside front of the carburetor. The parts diagram shows a cap covering it.
Most of those caps are NOT easily removable, don't know about this one.
Usually you have to drill the cap out to get to the fuel mixture screw. Probably not something a first time carb guy should do.
Anyway, if you could turn that fuel mixture screw OUT about 1/8 ~ 1/4 of a turn that would give it a little more fuel and make it less cold nature'd.
But be careful, turn it out too much and it'll rich (fuel) foul the spark plug.
-Or-
After about 60 seconds of running you could "feather" the choke a little while bumping the throttle a little to keep it running while you wait for it to warm up...

Leaving the petcock in the on position is not a factor here.
The manual is correct. Turning the fuel to the off position is a safety precaution and the right thing to do.

Reactions: 1

oldenslow

· #5 · Jun 14, 2019

Years back I had Kawasaki and Suzuki 250's that were, of course, carbureted. Full choke was absolutely mandatory for starting at anything below about 50 degrees, and warm-up was just about you described. No way to start 'em and ride right off -- you were lucky to get rolling in a minute and a half or two.

As for shutting off the fuel every time like the manual says -- come on! Why should you do it just because the manual says to? Manuals are strictly for entertainment, right?:wink2::grin:

ketchboy

· #6 · Jun 14, 2019

Miss Mercedes said:
Yup. I've found that even two bikes of the same model and year will react differently on cold starts. So long as it runs and rides fine and you aren't choked for power, I'd just let it warm up.

Exactly! All you really have to do is find out what the bike needs to start and warm up. If it takes 1,2, or 3 minutes, so what? Just 'listen' to the bike and give it what it wants.
Actually, you are quite lucky. Try figuring out the starting sequence on an old kick start Harley. LOL. :grin:

SemiFast

· #7 · Jun 15, 2019

ketchboy said:
Exactly! All you really have to do is find out what the bike needs to start and warm up. If it takes 1,2, or 3 minutes, so what? Just 'listen' to the bike and give it what it wants.
Actually, you are quite lucky. Try figuring out the starting sequence on an old kick start Harley. LOL. :grin:

Nah, those were easy.

All you had to do was set the timing with your left hand, give it the "right" amount of gas/throttle with your right hand and kick it while you adjust the timing with your left hand as you kick while also throttling it just the right amount, and at the right time, during the kick stroke.
Next you pick yourself up from the pavement and it's off to the doctor to get your broke leg set. :surprise:
Simple really... :icon_cool:

Reactions: 2

hogcowboy

· #8 · Jun 15, 2019

SemiFast said:
Nah, those were easy.

All you had to do was set the timing with your left hand, give it the "right" amount of gas/throttle with your right hand and kick it while you adjust the timing with your left hand as you kick while also throttling it just the right amount, and at the right time, during the kick stroke.
Next you pick yourself up from the pavement and it's off to the doctor to get your broke leg set. :surprise:
Simple really... :icon_cool:

Yeah, those things had a mind of their own. You even had to make them go where you wanted and couldn't text your buddy while riding. These new self-riding bikes are so much better. Wait...I maybe ahead of myself there. For the OP, leave it at half choke until it's warmed up well if you must immediately start riding. Just remember to open the choke all the way once you are underway. That may require doing two things at once though.

Reactions: 1

ketchboy

· #9 · Jun 15, 2019

Bottom line is this, CANT. The bike is fine, it's you that has to learn what the bike wants to start.

Self riding bikes, key fob starting, electric center stands, reverse 'assist' gear, fuel injection and more. I can't even imagine what is coming down the pike.

Never did break a leg, Semi. But my friends old Pan Head did kick me off to the side once. He couldn't start it, and I had one of those 'Hold my Beer' moments. lol. I'm very cautious these days when I kick over my '66 Shovel.

Unkle Krusty

· #10 · Jun 16, 2019

I have bikes that take minutes to warm up, not seconds. I fire them up, wait a couple of nano seconds, and head down the road.
If they gurgle I shut of the choke enrichener thing. If they die, then I did it too soon. They are all different, and I adjust, and that is why I get along with so many different engines.
The diesel engine in my boat takes about ten minutes before it will idle.

UK

Reactions: 1

GatorJoe

· #11 · Jun 16, 2019

Critter said:
Some bikes are very cold nature. If there are no other problems, let it warm up.

Best answer .. Cold Start my Carbed Dyna at Full Choke unless above 70 degrees and even then start at Half Choke and let it run 2-3 minutes before putting in gear and push the choke in when go into 2nd gear after running slowly in First for about 500 feet or so .. Once it has warmed up No Choke needed unless been parked over an hour and below 50 degrees F ..

Reactions: 1

450zuki

· #12 · Jun 21, 2019 (Edited)

ALWAYS....let ANY engine warm up!

A very high %%%% of total engine wear, over the engines life, occurs at startup.

The second most wear occurs between startup and until the engine reaches operating temperature.

Example: When metal gets cold, it shrinks. So, you have a cold crankshaft and cold connecting rods...the gap between them is much bigger than when the engine is hot...so, while cold, they're pounding against each other..and to add to the disaster, the oil is cold and stiff and doesn't ready flow into the gap...lots of wear occurring.

If you want to absolutely minimize engine wear, then let the bike reach operating temp before riding it.

~~~~~~~

Much of what is in an owners manual is a "starting point" for proper operation. Cold starts, the engineers worked out the procedure for a new bike in a test lab...is that your situation? Of course not, so you start with what they say and tune it to fit your situation.

Over 40 years of experience starting carbed bikes, here's a summary.

Below 50 degrees, especially with an "old" bike, use a quick dash of starting fluid. One of my bikes is 40 years old, starts instantly at ~70 degrees....impossible to freaking start at 50 degrees. I rigged/ran a small piece of fuel hose right to the carb intake behind the air filter, pull the cap off that hose, one puff of starting fluid, put the cap back on, hit start...she's running on the first revolution from the starter.

See less See more

Reactions: 1

Miss Mercedes

· #13 · Jun 21, 2019

450zuki said:
ALWAYS....let ANY engine warm up!

A very high %%%% of total engine wear, over the engines life, occurs at startup.

The second most wear occurs between startup and until the engine reaches operating temperature.

Example: When metal gets cold, it shrinks. So, you have a cold crankshaft and cold connecting rods...the gap between them is much bigger than when the engine is hot...so, while cold, they're pounding against each other..and to add to the disaster, the oil is cold and stiff and doesn't ready flow into the gap...lots of wear occurring.

If you want to absolutely minimize engine wear, then let the bike reach operating temp before riding it.

~~~~~~~

Much of what is in an owners manual is a "starting point" for proper operation. Cold starts, the engineers worked out the procedure for a new bike in a test lab...is that your situation? Of course not, so you start with what they say and tune it to fit your situation.

Over 40 years of experience starting carbed bikes, here's a summary.

Below 50 degrees, especially with an "old" bike, use a quick dash of starting fluid. One of my bikes is 40 years old, starts instantly at ~70 degrees....impossible to freaking start at 50 degrees. I rigged/ran a small piece of fuel hose right to the carb intake, pull the cap off that hose, one puff of starting fluid, put the cap back on, hit start...she's run on the first revolution from the starter.

YES!!! :grin: And if you have a rotary, you DO NOT want to run that engine unless you plan on actually driving/riding it. None of this starting it to move it then shutting it down. Rotaries hate cold starts with a cold shutdown.

Also, don't be afraid to wring out your engine. A lot of small displacement engines really love flirting with the redline and will last longer if you let them stretch their legs. There's a somewhat common issue that happens with my model of car and it's that the valves get burned and the engine basically kills out. A common finding about all these dead engines? Their owners were too afraid to let the engine do what it was designed to do. Poor things never stood a chance to carbon buildup.

Unkle Krusty

· #14 · Jun 21, 2019

My XS1100 fires right away at 28 F. How come? I often go a couple of miles with the choke / enrichener thing on.
At the tracks, most fire and go. How come?

Starting fluid can cause damage.

Most have no problem with riding off after the engine fires, with one caution, take it easy for a while.
Would be interesting to see some real measurements of a crank journal shrinking. And I would think that even IF they shrink, it would be well within tolerance. Used to be the oil would not flow, but modern oils fix that problem.

The hydraulics on my tractor were slow around 5 F, but again, modern oil fixed that problem. How come my 41 Ford tractor would fire below freezing without starter fluid?

Older bikes may have a week spark, due to poor E connections. Easily fixed.

UK

See less See more

450zuki

· #15 · Jun 21, 2019 (Edited)

Unkle Krusty said:
Starting fluid can cause damage.

And I would think that even IF they shrink, it would be well within tolerance.

UK

Well, yeah; you don't want to spray half the can in one shot. If a bike is hard to start cold, for whatever reason, a puff of starting fluid won't hurt anything. It comes out of the can as a vapor, burns right now, and gives the engine that first big breath needed to pull gas vapor in and get it running. Starting fluid is much better than cranking the daylights out of it. Sure, maybe there is a problem..it could just be weak gas, or the carbs are worn/damaged, ton o reasons, maybe no reason...don't drive yourself nuts or spend a fortune throwing parts at it...just a puff will do ya!

They do shrink, and it is within tolerances...the outer limit tolerances for a NEW engine.

Edit; Great info at PhysicsForums: https://www.physicsforums.com/threads/why-most-engine-wear-occurs-during-cold-start-up.929237/

As temps fall below 60F, wear increases dramatically...totally believable.

See less See more

SemiFast

· #16 · Jun 21, 2019 (Edited)

I believe a warm up is important, even with today's close tolerance engine designs.
One thing 450zuki did not mention is cold pistons. A simple explanation of the the piston is that it does not fit the cylinder until the engine is warmed up to running temp.
Is it enough to make any real difference? Maybe not but I'm all particular, so there is that.
I even give a warm engine a little run time after start up to allow the oil to circulate.

My wife's Toyota has a cold engine light that goes off when the car is ready to go.
When you drive away with the "cold" light on that 97 HP engine ain't happy till the light goes off. Could be an electronic thing for all I know.

"At the tracks, most fire and go. How come?"
I never gave my race bikes very much of a warm up because they would try to overheat during the race if I started with the engine totally warmed up.

Edit: I'm slow, 450zuki made mention of pistons/cylinder wall after all... Lol

See less See more

hogcowboy

· #17 · Jun 22, 2019

I use carburator cleaner rather than starting fluid for that one shot help on gasoline engines. Starting fluid gets used in my diesel engines. Over use of starting fluid can cause real problems even on diesel engines so be careful. Over use of carb cleaner not nearly as bad but still be cautious.

1 - 17 of 17 Posts

This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.