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So like the title says, all of a sudden yesterday and today, the bike will not stay running unless I hold the throttle. As soon as I let go it sputters and dies.

I realize it's a carbed inline four but even after running for 15 min today it still would not stay running w/o the throttle. I've ridden it many colder mornings before today and it took maybe 5 minutes to warm up and run w/o choke and throttle.

Any ideas?

Check your electricals - make sure the bike is firing on all cylinders!

Have you been riding it lately or is it the first run of the season?
Check your idle screw.

I've been riding it daily since I got it.


[quote=TechBMW]Check your electricals - make sure the bike is firing on all cylinders![/quote]


Is there an easy way beside pulling the plugs and grounding them against the block?

Would a FUBARed choke do this? not saying mine, jsut guessing.

Well - when something just all of a sudden goes wrong, it's usually an electrical problem. Unless you ahve a spark tester the best way to check for spark is to pull the plugs (You could also touch the pipes QUICKLY and see if all four are hot.)

Could be a spark problem like mentioned, but I am not so sure that the choke would keep it firing on less cylinders. Mostly an engine will run withuot choke even if a cylinder is missing.

Be sure to check the fuel system properly as I think you will find your problem here.

One question, does she run well with the choke on?

If she does, its hardly going to be a FUBARed choke, as this would be more likely to run her rich than lean(as seems to be the problem)
Make sure the tap is flowing the correct amount of petrol, and that the tank cap breather hole is free.

Once you ascertain that this is not the problem, and the sparks are fine, im afraid you might need to clean the carbs.

Oh, and on a side note, make a quick check that the air intake system is not leaking, a perrished carb rubber with cracks could in theory cause too great an air-inflow, thus leaning the mixture to much

It runs poorly with or without the choke pulled, which made me think it's broken. could be stuck shut.

But the bike ran for 15 minutes in decent morning weather and it still ran poorly, and died every time I let off the throttle

The cylinders were as hot if not hotter that they usually are when I start to ride.

As for air leak and such, i don't see how. The bike was running good, parked it, and then it started to act up the next time I fired it up.

I haven't looked too hard but there is no breather that I can see. The gas cap is solid and there is a locking bar that fold on top of it.

I'll check when i get home to see what I can find, had no time this morning before work.

rapidblue wrote:It runs poorly with or without the choke pulled, which made me think it's broken. could be stuck shut.

But the bike ran for 15 minutes in decent morning weather and it still ran poorly, and died every time I let off the throttle

The cylinders were as hot if not hotter that they usually are when I start to ride.

If the choke was broken it could well cause something akin to what you describe, but probably not for that long. The cyls being hotter than usual often mean a bike running lean. So check the choke mechanism well.

Once you have the plugs out to test them for spark, let us know what colour they have please!

There must be a breather somewhere. But regardless, just to make sure of it, run the bike with the tank cap off for a few mnutes.

Cheers, and good luck!!

Ok so i got it running buy twisting the hell out the throttle adjsuter.

Still having problems though, The adjuster seems f'ed. When I finally get it to run it's at like 3000rpm idle, if I back it off a hair it drops to 1500rpm and threatens to die. This was in 20+ degree (celcius) weather.

Feels liek there is still tension in the adjsuter but it's like its not really doing anything most of the time unitl a certain point where it'll jump from ppor idle to a 3000rpm idle.

What rpm should this bike idle well at 1500-2000 right?

Still sort of sounds like the bike is pulsing a bit when it running, not exactly a smooth idle.

1500-2000rpm should defo be a good idle speed.

Pulsing sounds like either misfire or a missing cylinder.

We really can't say much more until you have tested all the plugs for spark, and dont forget to report on the colour of the plug tips, as this will give a good idea of the fuel/air situation.

At this point, dont try to get her running without doing a systematic check of everything that could be wrong.

Cheers

T