cold start problems

[jdog]

I have an '84 FJ1100 that won't start when the bike is cold. It sat outside for a few years with fuel in the tank and carbs.

First thing I did was flush the tank and petcock filter then pulled the carbs and cleaned them. The bike still wouldn't start. Next, I took the the carb set to a shop and had them sonic cleaned. Still would not start unless I sprayed starter fluid into air box (I know, not good). Once the bike is started and warmed up, it runs ok. While the bike is warming up, turning on/off the choke doesn't seem to have any effect. The chokes seems to be working mechanically and I thought I cleaned the circuits when I had them apart. I checked the compression (compression in all four averaged 118# +/- 5#) and spark looked weak (orange).

I'm kind of running out of ideas. 

Could the vacuum diaphragms have anything to do with the choke circuit?  They don't seem to leak but they are wrinkled.
Should I clean the terminals on the coils (and hope I get a better spark)?
Or take the advice that I saw in a similar thread and clean the carbs....again?

Many thanks!

[SlowOldGuy]

Take the carbs back off and remove the float bowls.  On the side of the bowl you'll see a small hole that leads to a cast-in tube that runs up the side of the bowl.  Inside this hole and tube is a tiny orifice that provides the choke circuit with fuel from the float bowl.  When it's plugged, the choke is worthless.   In fact, using the choke when this orifice is clogged just makes things worse on a cold motor since opening the choke circuit adds more air (and no fuel) which makes cold starting even harder.

Use a small piece of wire and spray carb cleaner to remove any crud from this orifice and your cold starting problems should be solved.

DavidR.

[Arnie]

Just saw DavidR's comments.  He's the carb guru.  Take his advise :-)

Arnie

It sounds to me that your choke (enrichment circuit) is not engaging.  Re-cleaning the carbs won't hurt or cost you anything except time.  Are all the passages in the choke (enrichment circuit) clean?

Compression is a bit low, but should still start.  Was that with the engine cold or warm?

And, cleaning the terminals and switch contacts can only help.

Arnie

[jdog]

Thanks guys, for guidance on this problem.

The comp test was done with a cold motor. Is it OK to pull the spark plugs with a warm motor? ( it wasn't advisable to pull plugs on my old air cooled VW)
Also, the bike has  17600 miles on the clock and the valves maybe out of spec.

I'll post again after I clean the carbs.

Thanks again,
Jason 

[andyb]

Wouldn't pull plugs from a hot engine, but that's because I dislike being burnt, and I'm generally too stupid to remember to wear gloves until it's too late.    I'd be more concerned about putting  them in hot, and tearing up the soft threaded head.

If the valves are all down to  zero lash (or negative lash, perish the thought!) it'd certainly kill your compression readings.  Compression tests have to be done at WOT, remember also.

If you have quite low valve lash (zero or nearing it), then it's possible that when the motor is fully warm and things have expanded, they're hanging open... and covered in carbon, so even with a correct lash they will fail to seal, and probably trash the valve seats.  A leakdown test would reveal this, as you'll hear the air blowing out places it shouldn't... if that's the case, unfortunately you're due to pull the head off and at minimum lap them back in, or get a valvejob done.

[RichBaker]

I wonder about the WOT part.... with CV carbs, at least.   Even with the butterflies open, the slides are still closed..... I can't see the cut away flowing much more air.  Has anybody compared open throttle to closed?

[SlowOldGuy]

Rich,
At cranking speed, the airflow throught he slide cutaway is plenty adequate for a compression test.  Against closed throttle plates, it's a problem, but the slide isn't.

I made this mistake on my old XS750 with CV carbs.  In trying to diagnose a missing cylinder, a compression test said I had big problems, way low on all cylinders.  I pulled the carbs off in anticipation of removing the head and cylinders for service.  A friend came over and ask what I was doing.  I demonstrated the compression test to show him my problem and the cylinders were suddenly pumping good numbers.   I realized it was the throttle plates on the carbs.

Dead cylinder wound up being a cracked plug.  Saved lots of money from my friend asking a simple question.

DavidR.

[jdog]

I got it running 
It was the enrichment circuit that was plugged up.
Based on a lot of other post that I've seen that start off like "I just got this bike and it hasn't ran in years....or I parked the bike for some reason a few years ago and now I can get it to start" this has got to be a common problem.
This isn't my first old bike nor is it my first FJ (I've had 2 others) and I thought I knew how to clean a carb and when I paid a shop $250 to clean the carbs I thought they were clean. Like DavidR said, coming up from the bottom of the bowl, there is a very tiny hole in that circuit. I had to strip the plastic off a twist tie from a loaf of bread to find a wire small enough.

Thanks for all your help.
Jason

[SlowOldGuy]

Isn't the internat a wonderful thing?

You're welcome and good job getting it fixed.

Thanks for reporting back, always appreciate positive feedback on a fix.

Enjoy the Kook.

DavidR.