Troubleshooting Assistance with Starting

[Emshri]

Ok, I now need smarter people looking into my troubleshooting. I have a 1983 GS750T in excellent shape. I'm having trouble getting it started from cold.

It won't start on it's own. So far the only way I can get it started from cold is squirt a little gas into the airbox. When I do this, it starts right up with some choke. It only takes about 20 seconds with choke, then it is running good. This started after I removed the carbs for a cleaning. Here is a list of actions:

• I orignally removed the carbs and cleaned them. I had a gunked up carb, so I cleaned it and reinstalled.
• I adjusted the valves.
• I inspected the spark plugs and they are good.
• The petcock vacuum is working good.
• I put the petcock on prime for a little while, but this still didn't allow it to start.
• I put the petcock on reserve, but this too did not allow it to start.
• It has a new battery and cranks hard.

Once I get it started, it runs perfect. Once the engine is warm, it starts perfectly with a single push of the starter. The mixture screws are set to the recommended level.

Any suggestions?

[Killer2600]

Did you break down and dip the carbs or just go at it with spray cleaner?

Could have a clog in the enrichment circuit, could have an air leak, could have weak spark, could have bad/crap gas, or it could be user error.

[spyug]

Welcome.

The GS series are notorious for being cold blooded and hard to start almost always needing choke (enricher) to start. Once warmed up as you note, they start fine.

You seem to have done all the things necessary to make for good starting but like Killer said, I wonder if your carb cleaning was thorough enough. If you didn't dissassemble and dip them for 18 to 24 hours, they are unlikely to be clean. Spray will just not do it.

The other big issue that could be causing hard starting is the airleak problem. Usually through the o-rings sealing the carb intake boots to the head or even cracks in the boots themselves.

I wouldn't discount a weak spark either so you should check voltage at your coils if it is more than 1 volt ( lower than battery voltage) then coil voltage can be down 10,000 v or more at the plug. You want a nice fat blue spark. If you do have a substantial drop in voltage, the coil relay mod, detailed on Bass Cliff's site ( he'll be along shortly to give you the mega welcome and details) will sort you out.

So tell us more about your carb cleaning.

Good luck, its not a huge problem and we'll help you get sorted.
Spyug

[Emshri]

It was my first carb job. I pulled the carbs out and disassembled them. I did not seperate them. I soaked the entire assemble and all parts overnight. I did further scrubbing and cleaned all the passages, to incude needles, etc.

I'm new to this, so maybe it needs to be done again. Can the choke plunger be my culprit? The thing that throws me is it runs perfectly, even when it is cold. It is just the actual starting that is causing be problems.

I have extensively looked for any signs of an air leak around the boots, but all are solid.

[Seana23]

Hi babes.
Hmmm, this is a quandry...
What air filters are you using? Have you oiled them recently?
What spark plugs? Are they new and set right?
Have you checked the valve clearances recently?

Keep posting. We'll get to the bottom ov it.

Xxx

[tom203]

The enrichment circuit (aka the choke ) is fed by a tiny line that runs from bottom of fuel bowl up to choke plunger- easy for this to get clogged and cause no fuel at cold startup. Drop a bowl, you'll see the little hole.

[Emshri]

Plugs are in good shape and gapped right. Running stock carb settings, air box, and OEM paper filter, which is new.

As for the enrichment circuit, and it's "hole", can I drop all the bowls and clean out the hole, or are we talking an entire carb breakdown again?

[Emshri]

I should also add- this problem was happening prior to adjusting the valves. I opened it up and adjusted them, but the bike's start problem continued after the adjustment (no change).

[BassCliff]

Greetings and Salutations!!

Hi Mr. Emshri,

If you dipped the carbs without completely disassembling them then you may have melted O-ring goo in the idle circuit. There is an O-ring under the idle mixture screw on each carb. This screw is usually covered with a cap that must be removed in order to completely disassemble the carbs. It's all well-documented in the carb cleaning tutorials you will find on my little website. Everything starts with properly cleaned carbs.

Have a look at the links here... New Members, CLICK HERE!! The "mega-welcome" and my little website contain much of the accumulated knowledge necessary to get your bike back in reliable and safe condition. Go through the maintenance lists and make sure each item is properly addressed. Welcome to the forum.


Thank you for your indulgence,

BassCliff

[Steve]

I pulled the carbs out and disassembled them. I did not seperate them. I soaked the entire assemble and all parts overnight. I did further scrubbing and cleaned all the passages, to incude needles, etc.

When you soaked the assembly, what parts were off the carbs?
Were the tops removed?
Were the slides removed?
Were the bowls removed?
Were any of the jets removed?

To clean the carbs properly, they have to be taken down to virtually NOTHING left in the carb body, except for the throttle shaft and butterfly. ALL of the jets need to be removed. ALL of the o-rings need to be removed, this includes the Tees between the carbs for vents and fuel.

Now that you have likely gummed up the carbs worse than they were before, you might have to soak the carbs a bit more than the suggested 24 hours EACH, just to get the melted o-rings out.

You say the "mixture screws are set to the recommended level". Whose "recommended level"? Factory settings were set on a special meter, then sealed. Manuals only said "preset, do not touch". Opinions here will range a bit on where to set them as a starting point, but they will probably end up around 2 to 2 1/2 turns out from lightly-seated, after you are done tweaking them for best idle.

One last thing: are you using the proper procedure to start a cold engine.
1. Verify carbs are filled. If you have ridden within the last week, no problem, otherwise, use PRIme to fill them.
2. Set "choke" control to somewhere between half and full (experience will tell you how little you really need to apply).
3. Verify "kill" switch is ON.
4. Ignition key ON.
5. Pull clutch lever (unless you have defeated that "safety" feature).
6. Push starter button.
7. Modulate engine speed (2000 to 2500 RPM is good) by using the "choke" control.

Did you notice that NOWHERE did I say "use the throttle"?
That is because you DON'T use the throttle until the "choke" is about off, and the throttle will respond crisply to input.

.

[Emshri]

I should explain my carb cleaning further. I followed the following tutorial: http://www.mtsac.edu/~cliff/storage/...d_Tutorial.pdf
The only step I did not do it seperating the carb bodies.

Although this was my first time, I did it with someone who has decades of motorcycle carb cleaning. Yes, it was fully disassembled, but I did not use the conventional carb dip. This was a suprise to me: I used Pynsol. It was scrubbed, then soaked over night, then scrubbed again, and soaked again. We then did the detail work of cleaning out all orifices. I took two days to accomplish this. I first thought this was crazy, but it worked incredibly well. I don't know if this is normal, but this technique worked exceptionally well. Pynsol thourougly cleans the carbs without the cons associated with dip. It did clean the entire setup clean as a whistle. The Pynsol dip re****ed in stripping everything out of it. I was very pleased with the outcome, so I don't think I have any melted o rings.

Another couple of points:

I got it to start on its own last night and this morning. It took some cranking, but last night is started on half choke, and this morning it started on no choke.

Also, previous posts mentioned it may be a voltage problem. I forgot to mention I did install a high power headlamp. I plan on disconnecting the headlamp, do a cold start up, and then see the result.

[Emshri]

A question about using the prime. How long should I set it on prime prior to starting it? Are we talking 20 seconds, or 5 minutes?

[Emshri]

If I need to redue the carb rebuild and choose to dip it, what is the recommendation for carb dip, and where can I get some (i.e. brand, vendors, etc.)?

[Emshri]

Sorry, I continue to add tidbits, but I beleive they are all important. The inside of the tank is in good shape, and it has new gas.

[MisterCinders]

A question about using the prime. How long should I set it on prime prior to starting it? Are we talking 20 seconds, or 5 minutes?

You can leave in on PRI until it starts if you like. Just don't let it sit with the engine off and in PRI for a long time. Just like gravity petcocks, you don't want to rely on the needle valves to keep your engine from flooding. Otherwise, you can ride the bike with the petcock in PRI or ON, so don't sweat the timing of being in PRI if you are priming the carbs to start it up.

If I need to redue the carb rebuild and choose to dip it, what is the recommendation for carb dip, and where can I get some (i.e. brand, vendors, etc.)?

Berryman's is the go to brand of dip. Get the 1-gallon can and you can dip two carbs at a time. Get two cans and you can dip all four.