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Message started by Mekh on 05/15/17 at 23:46:54

Title: Runs a bit uneven when cold
Post by Mekh on 05/15/17 at 23:46:54

When the engine is cold 5-10°C / 41-50°F, then for the first kilometer or two it feels like it skips an ignition or two here and there... Almost feels like when you are about to run out of gas and the engine starts skipping a beat here and there.

It starts on first try within 2-3 rotations, so that is fine and I can run it for hours and have no issues whatsoever, except for the first minutes of running. If it's a bit warmer outside (+15°C / +60°F) when starting the engine from cold there is no or very little issue.

I use full choker when starting and for the first few minutes, which helps compared to if I push it in right after start...

Any ideas on what may be going on... Could running too lean result in symptoms like this?

Title: Re: Runs a bit uneven when cold
Post by Dave on 05/16/17 at 03:04:20

This is not a fuel injected engine. The carb does not have any ability to adjust the fuel mixture to changing engine conditions......so that weird place between cold/ warm is an area it just doesn't have the ability to provide a proper fuel mixture. All equipment used to be this way before the invention of electronic fuel injection.

Title: Re: Runs a bit uneven when cold
Post by Mekh on 05/16/17 at 03:55:58

All four bikes I have had, has been with carburetor so I am familiar with that.
However, this feels more like if there was no spark at all from the spark plug on some strokes while cold, but not sure if I somehow can check the power of the spark myself.
Prior to the renovation of the engine I cannot recall it doing this.

Title: Re: Runs a bit uneven when cold
Post by Gary_in_NJ on 05/16/17 at 05:15:29

You can jet your carb for a cold engine or a warm one. Obviously, that's not a real-world choice, but the engine is only cold for a few minutes. If your bike runs well the remaining 99% of the time, I wouldn't give it too much thought.

My bike has a slight lean surge on the lower part of the needle just before it warms up. I only notice it when accelerating through the 2-3 shift. It lasts about 50 feet as I pull away from my driveway and never reappears for the day. I know it's there, but it certainly doesn't bother me.

Title: Re: Runs a bit uneven when cold
Post by SALB on 05/16/17 at 10:36:33

This last winter, I had similar issues. Adjusting the idle mixture just a tad richer helped a little. I also found myself pulling the choke out at idle, and pushing it in above about a quarter throttle. This was an old technique I learned when cars still had choke knobs before the "automatic" choke. Your results may vary. ;)

Title: Re: Runs a bit uneven when cold
Post by Mekh on 05/16/17 at 10:59:23

I'll try adjusting the idle screw a bit and see if that helps.
Warmer weather seems to be on the way though, so that should help also.

Thanks all for the feedback... :)

Title: Re: Runs a bit uneven when cold
Post by justin_o_guy2 on 05/16/17 at 19:06:55

If you're not old enough to remember tires being flat on one side on cold mornings, you are excused for not understanding how a carbureted engine acts.

Title: Re: Runs a bit uneven when cold
Post by HAPPYDAN on 05/17/17 at 12:43:05

56494F4855526353635B49450E3C0 wrote:

If you're not old enough to remember tires being flat on one side on cold mornings, you are excused for not understanding how a carbureted engine acts.

Thump, thump, thump, thump - until you turn, then - Ba-dump, Ba-dump, Ba-dump, Ba-dump...etc. ;D Gnarley rhythms, man!

Title: Re: Runs a bit uneven when cold
Post by Dave on 05/17/17 at 18:51:36

352A2C2B3631003000382A266D5F0 wrote:

If you're not old enough to remember tires being flat on one side on cold mornings, you are excused for not understanding how a carbureted engine acts.

We used to have a van for the survey crew when I worked for the City of Fort Thomas - a work van with no interior or paneling in the back....just metal bodywork. The back tires were snow tires with nylon cords, and the van would sometimes sit for weeks and not be driven. When it did sit for a while - the next time we drove it the ride sure was a loud and bumpy for a while!

Title: Re: Runs a bit uneven when cold
Post by batman on 05/19/17 at 06:59:13

"runs a bit uneven when cold" Me too , sometimes I even limp just walking! ::)