Warming The Bike Up From Cold Start

[IanDMacDonald]

So, how long does it take your bike to warm up to a smooth idle with choke off? I start mine with full choke, wait for the instant rise of rpm's to 3K or whatever it rises to, then half choke for another couple of minutes, then no choke. Keeping in-mind this is current temps of 70°+. I've found that my bike idles bad with choke off (sputters) until I take her for a ride. I thought maybe I had the idle set too low, but discounted that thought once I saw she idles at a little under 1100K while warm. I do believe this is all related to my timing though. Gotta save-up for that mechanical advance . . .

[MarkD]

Seems I have a different issue. My bike starts and warms up only with the choke off. When I pull it 1/2 way or all the way out, the bike stalls/ runs super rough. I feather the throttle while it warms, or ride it super slow for a few minutes.

[haywardguy929]

I use half choke for a 1/4 to1/2 a block and it's plenty warmed up by then.

[Prothec]

My XJ takes 1/4 to 1/2 choke at startup, let it idle for a couple minutes and usually let rpms rise and warm up around 2 to 2.5k rpm. With choke off, I idle at about 1.4k rpm, assuming the tach is accurate.

My valves need re-shimmed and carbs do need some work, but will wait until next year.

[jjz28]

I pull full choke and have to give just a tiny bit of throttle to start it. Let it run about 20 seconds and give it throttle a couple of times till its taking throttle good then go to 1/2 choke and take off then usually by the stop sign I take it off. That's just me but something isn't quite right cause it used to start without giving any throttle. Now I have to give it just a tiny bit to start.

[DGXSER]

So, how long does it take your bike to warm up to a smooth idle with choke off? I start mine with full choke, wait for the instant rise of rpm's to 3K or whatever it rises to, then half choke for another couple of minutes, then no choke. Keeping in-mind this is current temps of 70°+. I've found that my bike idles bad with choke off (sputters) until I take her for a ride. I thought maybe I had the idle set too low, but discounted that thought once I saw she idles at a little under 1100K while warm. I do believe this is all related to my timing though. Gotta save-up for that mechanical advance . . .

I think your looking for issues to blame on the timing. This is a big engine as bikes go, it takes a while to get good and warmed up. If it runs fine once it is warmed up, and it is not running well when you initially cut the choke off, then your removing the choke (enrichment) to soon.

How long it takes for the bike to get fully warmed up is dependent upon the outside air temps, what the air movement is around the bike, and I am sure we could go in depth into the other physics and spend pages going over it. But at the end of the day, you need to let it warm up more before you drop the choke out.

Personally, I also warm up on full choke, which may take a couple minutes in winter or half a minute or less in the summer. Then to half choke for a minute or two. I blip the throttle and see if it responds well or sputters with throttle. If it sputters, I wait another 30 seconds or so, try again. When it responds well, I take off with the half choke. After a mile or so when I get to a stop sign, typically the bike is idling high, and at that point I turn the choke off, and she runs great.

[IanDMacDonald]

I'm really surprised to hear how long it takes these bikes to warm-up. Another surprise was hearing that some ride with half choke. My warm-up procedure is about four seconds on full, three minutes on half, and maybe a minute on no choke before I ride off. While that's happening, I'm getting my jacket, gloves, earbuds, etc. going.

However Don, I still believe I need to break the carbs down over the winter and make sure they're all clean, then I want to pull the calipers apart to make sure they're good, clean and grease all electrical connections, and I'll replace my advance to get my gas mileage back up.

[skippy344]

Ditto, DG

I am just like DG. First start in the morning is full choke for about 30 sec, then 1/2 for about 30 sec to a minute, then the Scorpion is ready to go.

In the afternoon, I can do a 1/2 choke for about 15-20 sec, and then choke off, and she is ready.

But I spent a lot of time, getting my carbs right, and I use Star Tron Enzyme with every fill-up, so as to eliminate the ethanol in my gas. That has made a HUGE difference with starting and performance!

Shims have got to be spot on, air mixture has to be right; I colortune my carbs, carb synch is critical, and finally, good, clean plugs.

Many told me I don't need to, but I only use premium fuel in the Scorpion.

Hope this helps.

[clcorbin]

Depends on the temperature and the tune.

In the summer, with the current "leaner" (still nice tan on plugs, but not as rich as it was because I dropped the float level 0.5mm), I start it up on full choke. After about 15 seconds, I move it to half choke and usually have to a couple of twists of the throttle to get it to settle down and idle at half choke. After putting on helmet and gloves, I ride off. As soon as I go around the corner and start accelerating down the block, I push the chock off completely and all is good. It will have a bit lower idle at stop lights for the first couple of blocks.

Winter requires full chock for a couple of minutes. This works out, as I have more gear to put on in winter and it takes longer. It is usually on half choke for 30 seconds to a minute before I drive off. After the first stop light (2 blocks away), the choke goes off and we are done.

I am definitely not in the "let it idle for 30 minutes to make sure it is GOOD AND WARM before riding" club. There is no point. Once the engine is warm enough to idle correctly at half choke, it is warm enough for easy riding. And, the engine will warm up quicker under a light load than it will idling.

[MarkD]

Wondering why my xs really does not like any choke at all upon cold start.....maybe in November it will want some? Only stalls out every time I try to give it even 1/2 after I have started it.

[motoman]

Wondering why my xs really does not like any choke at all upon cold start.....maybe in November it will want some? Only stalls out every time I try to give it even 1/2 after I have started it.

For whatever reason, you've got a really rich idle circuit, or enrichment circuit is leaking alot of fuel by........

[donebysunday]

Seems I have a different issue. My bike starts and warms up only with the choke off. When I pull it 1/2 way or all the way out, the bike stalls/ runs super rough. I feather the throttle while it warms, or ride it super slow for a few minutes.

+1 and my plugs are near white

[DGXSER]

So your bikes start from cold with no choke at all. And after warming up, and sitting at idle for a minute or two...or ten...your plugs are white, not black looking. This is definitely an interesting thought.

Just as a refresher, the cold metal in the carbs and the engine causes the atomized fuel to condense out of the mixture at start up, so your mixture to the engine is lean, and therefore it needs more fuel to run properly. Enter the enrichment circuit, adding fuel to the mixture temporarily. Once the metals get warmed up, the fuel stops condensing out, and no need for the enrichment.

So your mixture is already rich enough to lose the condensation and still start and run well. So with no changes, after the engine warms up, it would get a much richer mixture than when cold. And yet your engine seems to work well and efficiently burn the fuel up across that fuel richness range.

[KA1J]

From my experience with my bikes I've come to see that easy starting with no enrichment (choke) means my carbs are running rich at idle. If they run well at the initial cold start and the engine hiccups when I add enrichment, then that assures me I am running too rich at idle. Doesn't tell me why, just that the mixture is rich.

My XJ650 Maxim has always had a fantastic carb setup and I need to add enrichment to get it to start without blurbling until it warms up. It takes me maybe a minute of riding before I can shut the enrichment off without issue. If I shut it off before the engine is warm it will stumble and run roughly. Once warmed and I add enrichment, the engine stumbles badly and can even shut off; can't stand the richness. This is a proper expectation from well set carbs.

With the carbs on the XS11 being currently as-new, I have the same experience as with the 650; I need to give it say 1/2 enrichment to start instantly and it will idle around 1.5K If I give it more enrichment then it idles at a higher RPM. a minute of riding and I can shut off the enrichment. If I don't the bike idles roughly at idle. If I don't use enrichment at a cold start, I have to keep blipping the throttle for a minute or so to keep the engine running.

Your timing is probably fine, it sounds like your start up sequence is right. You do have your valve clearances set properly and your carns synced properly & colortuned, don't you?

Gary

[IanDMacDonald]

Hey Gary- Timing was set by the machine shop that did my cylinder head work (I guess I should check that soon). Timing (in my opinion) is off. I have plans of buying an unaltered advance from a '78 and re-attaching the vacuum pod.