Choke/Warmup question

Well, after a long winters rest, I rolled the bike out today, not for a ride though, just a quick warm up to get the juices flowing through the system... man I cant wait to get it on the road!!

To start the bike, I have to use the choke. (It is only 2 degrees here in Toronto) Once started, I let the choke in from 100 to 50 % and had to leave it there while the bike warmed up for 15 minutes or else it would bog down and die. Once warmed up though, it idled around 800 really smoothly.

I know that it takes longer to warm up when its this cold outside, but when I started it up for the last time in November, it was about 12 degrees outside and it took about as long to get warm.

My question is this. Should it take this long to warm up? I had a single cylinder 125 (that I swear was like a mid 80's xj, looked EXACTLY like my 82 Seca, but smaller) in Asia, and that little bastard kicked over with one kick every time (or a quick hit of the starter button) I never needed the choke, even on the coldest, wettest mornings.

 

In my experience, it depends on the bike. My Xj's not too bad - sounds about the same as yours. But my fathers cb750 - Its unrideable, even in the summer unless you choke it and let it warm up for at least 5 minutes. And yes his carbs/valves are done and tuned/synched. The bike is just cold blooded. On the other side of the coin:

I had an old XS400 that would kick over when it was -15 out, turn the choke off as soon as it fired up and you could drive away.

 

They can be cold natured. Mine take full choke on real cold mornings then off too half. Ride it on half for several miles then she's fine. Real cold to be is upper 30s too so sounds like it's just a bit cold natured...

 

jhicks

Your enrichment circuits may be plugged.
Try just removing and checking the enrichment circuit of one or two bowls.

 

I plan on pulling the carbs apart and giving them a thorough cleaning anyways so I'll make sure to clean the enrichment circuit while I'm at it. I hear its rather easy to do with a guitar string which I have in spades.

The PO did all of his own work on the bike and he seemed to know what he was doing, but I wonder if he's ever pulled the rack and cleaned the fuel system. I figure after 27 years (It's weird owning anything older than I am, even if its only 3 years) and 43000 klicks, its due

 

Once warmed up though, it idled around 800 really smoothly.


idle should be 1050, perhaps turning the idling up a bit might help

 

This might help. I'm on the other side of the coin though. I managed to get my carbs spotless-clean, I had it idling at about 900, and I prefer to let her warm up a bit rather than crank the idle up, personally. Just my two cents though. Raising the idle may resolve this issue.

I know on my seca, while I have it on enrichment, it'll stumble and stutter if I hit the throttle other than a slow-roll-on. But once she's idled for 5 minutes or so, I can just kill the choke and take off.

Sounds like you've just got a slightly cold-natured one, in my opinion, but I wouldn't want to be waiting 15+ minutes to warm up, myself.

 

IF it only runs well when it HOT then that would indicate that the idle circuit is plugged.

I have ridden recently in 15 deg F weather. The bike only warms up for 2-3 minutes while I put on the helmet and gloves and sunglasses.

The bike runs BETTER in the cold. The air is denser and the bike has MORE horsepower. Thats why drag racers pack ice bags on their engine between runs.

While riding this weekend I was thinking "Where did all the ponies go?" The temp was near 70 deg F.

The only other reason I can think of for it to bog down is if the carbs are badly in need of synchronization.

 

My '83 550 Seca has a similar issue but it never "warms up." It simply won't take throttle below about 3 grand without the "choke" being at least halfway on. GIBIF (Guy I Bought It From, NOT the actual PO) said he "went through" the carbs. Yeah. Did a MARVY job, there is no float drain screw visible on the #4 carb, so at the very least, he mixed the float bowls up.

Bike seemingly runs fine above 3 grand, with the choke off. (Remember, "choke" is just the name of the lever, it's an enrichening circuit.)

MY GAME PLAN: Pull the rack and drop the float bowls, make sure all the parts are in the right spots and check the float levels dry. Reassemble correctly.

Bench-sync the rack.

Reinstall; check float levels with gas; vacuum sync.

TWEAK (colortune, plug readings, idle mixture adjust, ride, repeat) until it SCREAMS like my '81.

You could have a plugged jet or passage, or the carbs could be HORRIBLY out of synch. In my own case, they ARE spotlessly clean but the guy was an idiot so I suspect the latter.

You might consider following the same basic plan of attack. One caveat though, I plan to wait for a BIT warmer weather so I'm not chasing my tail fighting a cold-related lean condition.

 

I dont think the carbs are out of sync, as I said, after 15, I could turn the choke right down with no problems at all. And when I give it some revs, she still sounds great. I guess I wont really know until I either rip apart the carbs or get it out on the road and give'r a real run.

Thanks for the plan of attack Fitz! I think after I give it a run (I haven't had it on the road yet, save for a few laps around the block) I'll pull the rack apart and clean/rebuild the carbs

 

You may just have a plugged idle or enrichment circuit, if it runs fine after 'warming up.' Worth a check at least.

 

once the engine is hot, set the idle to 1050 revs, after inital warm up you should be able to ride on 1/2 choke for about a km.