Carb Question - Rick is the heavy hitter, but any takers?

When starting out on any trip with the choke on and the bike having a running minute under its belt, if there is a need to stop quickly, the engine stalls. This could add up to be a real safety issue in the wrong situation. It sounds like it's drowning in fuel as it stalls. Once re-started, the smell of fuel is obvious and it takes a minute to run smoothly again. Once warmed and the choke is off the problem is non-existent. Is this a carb rebuild job that I have been putting off or is there something else?

I have tried locating carb kits locally but with the dealer going away, chances are slim. He also says that there is nothing in the Yamaha catalog except individual pieces or whole carb assemblies. Surely chacal has something in the way of kits, but is a complete rebuild necessary to fix this issue?

Any help appreciated guys.

 

Re: Carb Question - Rick is the heavy hitter, but any takers

check the clutch is fully disengaging & you might need to go to a thinner oil for the winter, also give your bike a bit more time to warm up before pulling away.

 

I'll give it a shot. This is my guess.

The enricher only really works correctly when the throttle is closed. The vaccum from the throttle being closed sucks gas through the enrichment circuit. On a carb with a true choke, you close the air off, in a carb with an enrichment circuit, you do the same by leaving the throttle closed and adding more fuel. My bike is really easy to flood, I never ride with the enrichment circuit open. I use it to start the bike, and push it in after about 30 seconds(or about the time it takes to get my helmet on). When you are riding with the enrichment circuit open, your throttle is also open, so the bike is running a little richer than normal, but when you close the throttle to slow down, the rpms are still up for a second with the throttle closed, and alot of vaccum is created, intern alot of fuel is quickly sucked into the cylinders.

That's my best guess. Doesn't sound like there is any problem in the carbs to me.

 

+1 from me.

Do not pull away until the bike can idle with the choke lever off. It only takes a short interlude to properly warm up the bike.

 

I agree that there is probably not a carb issue in this instance. SOME warm-up is necessary. One note though; I regularly ride off after a couple minutes warm-up with the "choke" still partially on and do not have problems. I wouldn't try to start off IMMEDIATELY but after 2-3 min the bike only wants about 1/3 choke and can be ridden away.

 

Of course it should be noted that Fitz rides in Antarctica. *wink*

 

My Bike will do the same thing, If I stop really hard with the bike cold and the choke open, It will either stall or seem to bog down.

 

Prime example of the "Cold Blooded" nature of the XJ-Engine.

It takes more than a minute for the Cylinder Head to absorb some heat from a Rich Mixture getting burned for a fraction of an instant in the Combustion Chambers at this time of year.

Bikes not tuned-up very well are almost impossible to start when the Head and Block are COLD. Real COLD.

But, with a fairly decent tune and a good-working Enrichment Circuit; the Bike will fire-up and run on the RICH Mixture.
It would rather not run when cold.

If you start the Bike on Full Enrichment and allow it to warm-up while tending to the Mixture ... it will warm-up faster.

Reduce the amount of Enrichment ... making the Mixture LESS Rich ... by using the Choke Lever as a Valve Lever and NOT and ON-OFF Switch.
Get a hotter Mixture working for you to warm-up the Head and Block.

Until the Engine come-up to something close to an Operating Temperature you run the risk of "Flaming Out' ... just as a Turbine Engine would if not run-up to temp before take-off.

Chilled Fuel and a Chilled Block will let the Intake Mixture "Snuff-out" the Spark rather than ignite.
You need to warm the Engine longer before taking-off to avoid stalling-out and possibly wet fouling the Plugs.

 

Thats exactly how mine runs now that the carbs are synched.

 

Re: Carb Question - Rick is the heavy hitter, but any takers

Mine acts in a similar manner. I posted a thread about it last year, but I don't think I described the problem as well. If I start out with the enrichment on the bike will die when I stop. If I stop quickly its like flipping a switch, If I stop slowly it will stumble sometimes before it dies. I don't ever smell gas when it happens though. I was planning on going back through my carbs with this as one of the reasons, but now its sounding pretty common. I guess I'll just give the beast some more warm up time.

Mike

 

MIne will do the same if it's not warmed up, I try to get it warmed and have the choke off before leaving for that reason....

 

Re: Carb Question - Rick is the heavy hitter, but any takers

My bike starts fine, from cold, with full "choke". As it warms up I have to keep turning down the amount of choke to keep the idle under control. I quite often leave the driveway with the choke still on about half way. As soon as I hit the street and catch second gear, I shut the choke off completely. The bike will not run worth snot if the choke is on while riding. My first stop sign is only a block away and if the revs drop too much as I sit there, a little blip on the throttle keeps it running nicely.

 

The fuel also surges forward in the float bowls when you stop and can cause a richer mixture or slight flooding. My Seca did this when new so don't worry about it.

 

Thanks guys for the responses and I appreciate your experience. Thankfully, it means I can spend time on items other than the carbs that need my attention more.

Cheers and Merry Christmas.

 

Re: Carb Question - Rick is the heavy hitter, but any takers

While everyone is talking about using the choke to start the bike and letting it warm up for a few minutes before riding, my XJ has apparently had some wanna-be working on the carbs before I got it a couple months ago. I don't need to choke the bike at all to start it. ever... In fact, using the choke lever seems to have no effect on how the bike runs. Moving the choke lever lifts all 4 plungers an equal amount, but seems to have no effect. Yet the bike doesn't act like it's being choked when warm. It seems to run fine with no hint of dying. I was thinking that the fuel-air may be set rich causing the choke to not be needed. Or maybe the floats are set too high causing a rich mixture. Yet, the spark plugs are a tan color as they should be.
Any Ideas

 

Re: Carb Question - Rick is the heavy hitter, but any takers

someone has put in bigger jets.