choke problem

[wouter]

At coldstart, the choke has no effect. (rpm does not raise)
When the engine is hot and you pull the choke the rpm do rise.

The engine (cold) starts but stalls a when the throttle is closed.
When the enginge is warm it starts and idles like it should.

carbs are cleaned and rebuilt, intake boots and o-rings are rebuild.
valves are in spec, carbs are synced, engine runs good, idle is stable,...

what could be wrong?

[tom203]

At coldstart, the choke has no effect. (rpm does not raise)
When the engine is hot and you pull the choke the rpm do rise.

The engine (cold) starts but stalls a when the throttle is closed.
When the enginge is warm it starts and idles like it should.

carbs are cleaned and rebuilt, intake boots and o-rings are rebuild.
valves are in spec, carbs are synced, engine runs good, idle is stable,...

what could be wrong?

Since the "choke" (actually fuel enrichment) has noticeable effect when warm, but not enough when cold (stalls), I would guess the "choke" circuit is partially restricted, so the cold engine doesn't get all the extra fuel it needs.

[Charlie G]

Wouter,

I don't clearly understand your choke problem. I am not an expert, but I'll describe a few thing about starting my 650.


To start I put the choke on and hit starter button. Never any throttle. The bike starts and warms up as I put on my gear. I may have to adjust the choke a little as the bike warms to keep it ideling at 1000rpm by reducing the amount of choke. I do not twist the throttle at all while warming up.

Once my gear is on ( about 2-3 miniutes) I get on the bike and slightly twist the throttle to enter the street. As I reach the speed of normal traffic on my street I reduce the choke totally.

Once I have traveled 5 kilometers and stop the bike, I will not have to use the choke again to start.

This is how I think your bike should start and run.

If the carbs are clean, with no air leaks on the intake (air box side) or at the cylinder head and the air box is clompletely sealed at the openings, it should work like mine. The access door on your air box, for servicing the air filter should be sealed really good. The plastic door can warp over time and the gasketing become worn or missing.

When I start my GS450, the rpm will slowly rise to 3000rpm as I am putting on my gear and I have to adjust the choke constantly to keep it at 1000k. Once the engine is totally warm (20 kilometers) it runs fine at normal idel. I am pretty sure I have an air leak at the intake boots on the cylinder head and need to change the o-rings or boots. It is on my list of things to do.

Hope this helps....

cg

[hampshirehog]

Pretty common with the modern stuff they try and sell as petrol- the choke circuit is blocked.

Remove the float bowls and blow some carb cleaner through the float bowl holes and then through the carb tubes (take the plungers out first). Make sure that you can blow through everything in the circuit - it's either blocked or it isn't (no halfway measure in this circuit).

I bet it's those holes in the float bowl as that's where the fuel sits before it evaporates away leaving a clear crusty residue.

[wouter]

@John,

#1, correct
#2, correct
#3, correct but only with a cold motor. When the engine is hot it idles ok.q
I counted the position of the 'air screws' before i cleaned the carbs. (they were 2 turns1/4 and 2turns1/2 out) I started there and then adjusted them to highest idle. After that I adjusted the idle screw. (idle rpm)


@hampshirehog

I dismanteled and cleaned the carbs completely. I did that with an ultrasone machine. As you can see in this thread.

But i must consider every possible cause.

[hampshirehog]

Did you blow through the holes to check that they're clear? The float bowl holes can accumulate great big turds of gunk that might not get dislodged by ultrasonic cleaning.

[wouter]

Did you blow through the holes to check that they're clear? The float bowl holes can accumulate great big turds of gunk that might not get dislodged by ultrasonic cleaning.

I think I did. But maybe not good enough.

[hampshirehog]

The little extension pipe on a tin of WD40 fits those holes spot on. If you've got a tin, give it a squirt and see what comes out.

[wouter]

No, I did not poke it with the special tool. I tought ultrasonic cleaning would do the job. I've head excellent results with dirty lawnmower carbs.

I'll remove the bowls tomorrow and recheck the holes, pickup tube and choketube stuff.

[tom203]

The little extension pipe on a tin of WD40 fits those holes spot on. If you've got a tin, give it a squirt and see what comes out.

Yeah, or use the tube on a can of Gumout which is really pressurized- wear safety goggles!

[wouter]

I removed the cab and carbbowls.
On cyl 1 the small hole in the choke intake was blocked, the 3 other were clean.
Only in cyl 3 the kanal in the bowl was free, in bowl 1,2 and 4 it was blocked.
I gave them a WD40 shot after cleaning and it went right trough.

All choke plunjers go smooth. I removed them when i cleaned the carbs and changed the o-rings.

Mounted the carbs and tested with a cold motor.
The rpm's raise when i pull the choke. So for now it is OK.

I feel a bit stupid now. I read everywhere on the forum clean the carbs, clean them very good,.... I tought I did a good job with the ultrasone and see what happened. I did not clean the carbs goog enough.

Thanks for all the help!

@ tom, i don't know what gumout is.

[tom203]

I removed the cab and carbbowls.
On cyl 1 the small hole in the choke intake was blocked, the 3 other were clean.
Only in cyl 3 the kanal in the bowl was free, in bowl 1,2 and 4 it was blocked.
I gave them a WD40 shot after cleaning and it went right trough.

All choke plunjers go smooth. I removed them when i cleaned the carbs and changed the o-rings.

Mounted the carbs and tested with a cold motor.
The rpm's raise when i pull the choke. So for now it is OK.

I feel a bit stupid now. I read everywhere on the forum clean the carbs, clean them very good,.... I tought I did a good job with the ultrasone and see what happened. I did not clean the carbs goog enough.

Thanks for all the help!

@ tom, i don't know what gumout is.

It's a learning experience! I've heard many folks praising ultrasonic cleaning of carbs, but what GS1100GK said about solids and sticky stuff makes sense.
Gumout? A favorite among lazy carb cleaners forever. Spray it into carb throats and pray that those nasty clogs vanish! (but it is good for forcing junk out of liitle holes). Probably banned in Europe- Ingredients;
petroleum distillates
acetone
xylene
ketone- yummy stuff

[wouter]

Is it necessary to adjust the 'air screws' , adjust idle and to sync the carbs again?

[hampshirehog]

Is it necessary to adjust the 'air screws' , adjust idle and to sync the carbs again?

No, you should be good to go. All you have done is cleaned the choke circuit and this is standalone.

Now you have to ride that bike every day forever. If you don't, the junk they call petrol nowadays will foul up your carbs again if you leave it parked for a few days. That and it's a good reason to just go for a ride......