how long should it take to warm up?

[branson]

I have a 1980 xs400sg with 650 carbs? I was wondering how long should it take my machine to warm up? Yesterday I let it run for a half an hour. Got a mile an a half down the road and when I took a corner it decided to die and highside me. I'm displeased but ill live. Anyways I'm trying to get it tuned and any help would be great. Fyi I'm fine and learned why the front tire is the steering wheel. Promise not to ride it backwards again anytime soon

 

[branson]

Cleaned carbs till I could shave in them. Blew out all the holes. Choke circuit too. Diaphrams look good. Feel good. New plugs. Cigarette butt brown. Its been idling for 13 minutes at full choke (enrichment valve) any ideas / tips?

 

[DanMach]

I do not understand your question at all.

1. If its warmed up enough to go straight at all it shouldn't stall out during a turn. (AKA warming up enough is not your issue.)

2. Warming it up for 30 minutes is absurd.

 

[FUBAR]

im sure the cleaning will help your issue, probably 10 minute warm up max on a spring day

 

[branson]

Fifteen minute warm up today and she rode like a champ. Just wish I could find a rear turn signal rubber. Oh well. And I don't understand it either. My best guess is the insides of my cylinders are nasty. Bike hasn't really been run properly in god knows how long. Since it wasn't fully warmed up yet figure the throttling out of the corner was what snuffed it. I think ill try the ol italion service jobbie on my way in to work tommorrow. Hopefully no more falling down for a while.

 

[branson]

Thanks fubar. Ten minutes seems attainable. Anyone think 650 carbs may be a factor in this equation?

 

[bentwrench]

Warm up in the winter in Canada usually only takes like 5 minutes. I think your jetting is off. Might explain the stall, if you hit the gas to power out of the turn.

Too cold means too rich. Check the plugs to get a feel for how she's running.

 

[xs400neophite]

Wait...you highsided? Thats pretty crazy.

 

[ThePsuedoMonkey]

Sorry to hear about the high-side, here's hoping that's your last one. In the summer I only warm up for 10-30 seconds at full enrichment, when It's colder I may go up to a minute. I don't think more warm-up time than that is really necessary (unless you like to ride in the winter, at least).

 

[bcware]

The bike dying won't cause a high-side. Inertia my friend; it will keep the motor running regardless of temperature or turning over even if it dies.

If the rear locked up it was rear brake or some kind of mechanical failure. An xs400 can't power-slide to my knowledge unless the ground was slippery!

I am glad you're ok!

 

[dO-bOy]

Maybe crappy wiring that joggles around when you turn cutting the engine off?

I agree with monkey, I don't even warm it up, 5 seconds to make sure oil is circulating and I'm off because my bike doesn't like to idle and fouls plugs if I let it idle too long when cold

 

[branson]

Well the wiring thing is definitely worth looking into. It just felt like the rpms dropped very suddenly. Kinda like if u slammmed the throttle shut. The bike prefers the rear tire stay in the rear lol. Once I let it warm up she runs like a champ. The plugs looked good. I'm just lost as to why it would take any motorcycle fifteen minutes to become operably warm? (I don't think operably is a word but I've got other things to think about atm)

 

[branson]

Jetting being off seems like a very likely culprit. Idle speed seems doble what it should be.

 

[branson]

Maybe my xs is trying to tell me she wants pods?

 

[branson]

I suppose maybe its just the most cold blooded machine I've ever owned and I tend to let it warm till there's no lack of power

 

[OliverB]

As others have said, you shouldn't need anywhere that long to warm up and be able to ride away w/o any hesitation or cutout. In mild weather, I only use the first notch of the choke. Only need the second notch if it's cold outside. If the engine starts loping then you have too much choke. As others have said, jetting from the 650 carbs may be your issue, I don't know. Have you turned the idle mix screw on top of each carb to 3 - 3.5 full turns out? If there is a plug on top of the idle mix screws you will have to carefully drill it out to get to the screw.

 

[branson]

Yes. It seems to have little to no affect on my idle speed though and that puzzles me a great deal. It doesn't like to start if I twist them a turn either way but other than that it doesn't make much difference.

 

[OliverB]

Yeah, I think your problem lies in those carbs and how they are set up.

 

[bcware]

I know you're probably looking for some sort of solution because you think your crash was caused by this, but it wasn't.

If the bike runs fine otherwise, just turn the idle screw up slightly when you start the bike. As you ride down the road and it warms up, just turn it down slightly; I do this every time I ride. The xs400 is cold blooded.

You've posted that the bike has suffered no internal engine damage and runs fine; so an engine or transmission lock-up due to catastrophic failure did not cause the crash.

The only options left are locking up the rear brake or slipping on a road hazard; there is no other possibility. The engine dying mid turn will only cause you to slowly coast to a stop.

Inspect your brakes or practice braking; forget about how long it takes to warm up; this is not your problem.

I am not trying to be a jerk, but crashing is serious. You need to look at the real cause so it doesn't happen again.

 

[HoughMade]

This is going to become my mantra- sounds like it is lean. If the rpm drops when you open the throttle quickly, it's lean. These bikes need to be set up to runner richer than you think is right to have throttle response. There is no accelerator pump and no fuel injection to shoot fuel in. This means that when you are transitioning from a small throttle opening to a large one, it will lean out very quickly until the slide/needle has a chance to react and allow more fuel. How is this solved? Set it to run richer than it theoretically should so that when you crack the throttle open, the fuel is already there.

This will harm your mileage and you will smell plenty of unburned hydrocarbons, but it will run better. This could be the issue with warm up. What you perceive as a long warm up could be due to lean idle characteristics. What are the idle mixture screws set at?

On my bike, set up like I described, on a cool to cold day, it will start up immediately on full choke (enrichener), the revs start to rise after no more than about a minute, then I go to half choke, and about a minute or so later, it's to no choke. I sometimes take off on half choke, sometimes not. If I do, the first time the rpm exceeds about 4500, there is no need for choke and it runs perfectly. If I wait and take off with no choke, the throttle response is a little flat on the first run up the rpm before I shift to 2nd, but after that, everything is warm and perfect.