cold starting

[p_s]

I've had my 1985 GS550ES since October. When I bought it, it'd start on full choke pretty much instantly. Over time it got harder to start, especially if it sat for a few days. It has a fairly new battery that goes on a deltran battery tender every night. Today after 40 minutes it just wouldn't start.

2 weeks ago I adjusted the valves. They were on the tight side. I set them midway and it definitely helped. The bike warmed up faster, too.

Last weekend I couldn't start the bike at all. Neither airbox boot was on the carbs all the way. I fixed that. They are quite old, though. After this it started nicely but the idle went from 1400 to 2000--then I adjusted it back down. This also seemed to help. (If the idle went up, does that mean there is an air leak?)

Today I put a timing light on all 4 HT leads and it flashed regularly. I put a spare plug in plug cap #1 and it sparked.

I don't know how old the plugs are but they look good.

My garage smelled like gas after 40 minutes of struggling.

I tried putting the petcock on prime for 2 minutes. Also tried blowing in the carb breathers.

The carb was rebuilt a few years ago by the PO, who is a far better mechanic than me. They were synced and the pilots adjusted.

Once the bike starts, it runs great.
Any suggestions? It was in the mid 20s when I was trying all this but the overnight low was 5 or 8.

[chiphead]

Once the bike is warmed up and running, at idle, take some BrakeKleen or WD 40 and spray it around the area where the intake boots meet the head. If the engine changes RPM or stumbles, you probably have an air leak there.

[Steve]

Last weekend I couldn't start the bike at all. Neither airbox boot was on the carbs all the way. I fixed that. They are quite old, though. After this it started nicely but the idle went from 1400 to 2000--then I adjusted it back down. This also seemed to help. (If the idle went up, does that mean there is an air leak?)

Most likely, yes.

If you adjusted the idle for the higher (incorrect due to air leak) idle speed, it is now probably too low. Try giving the master idle speed adjustment about half a turn in, then try again. Remember to NOT use any throttle when using the choke to start a cold engine.


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[Roostabunny]

Remember to NOT use any throttle when using the choke to start a cold engine.
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Why is that, Steve? Flooding?

[p_s]

If you adjusted the idle for the higher (incorrect due to air leak) idle speed, it is now probably too low. Try giving the master idle speed adjustment about half a turn in, then try again. Remember to NOT use any throttle when using the choke to start a cold engine.

I did turn it back in a bit. I was running out of battery by then. Actually the other day I had to turn it out several turns to get the idle to back off. I only turned it back in a little bit. There was slack in the throttle cable, so maybe it was my airbox boots that were leaking again after all.

I put in a GSXR rear monoshock and noone mentioned that you have to drop the shock now to get any wiggle room in the airbox. Grrr....

[Steve]

Why is that, Steve? Flooding?

No, it won't flood, it starves.

The "choke" circuit does not actually choke the intake like earlier carbs did. It actually enrichens the mixture by opening another port that allows gas to be sucked directly through a jet to the intake throat. It does this with engine vacuum. If you open the throttle, you don't allow the vacuum to build up while cranking, so there is not enough vacuum to pull the gas through the enrichener circuit.

In the following picture, you can see the enrichener (choke) plunger in the upper right. If you look on your carb, it is near the top, toward the engine, and pulls to the left.



You also say that the PO rebuilt and adjusted the carbs "a few years ago". Has the bike been in contant operation since then, or did it sit for a while? Yeah, you have been running it, but evidently it was not quite right or you would not be having problems now. It might be time to clean the carbs yourself and know what condition they are in. It would also be a good time to replace all the o-rings in the carbs and intake tubes (a modest cost from Cycle o-rings.com). Bad o-rings in the intake tubes might be what is causing your erratic idle problem, anyway.

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[Roostabunny]

No, it won't flood, it starves.

The "choke" circuit does not actually choke the intake like earlier carbs did. It actually enrichens the mixture by opening another port that allows gas to be sucked directly through a jet to the intake throat. It does this with engine vacuum. If you open the throttle, you don't allow the vacuum to build up while cranking, so there is not enough vacuum to pull the gas through the enrichener circuit.

Doh!

Thanks for this explanation, Steve! I've been wasting time every morning because I somehow couldn't lay off the throttle tweaking (but it's right there!). Like over-stirring pancake batter - the extra work doesn't make it better! :-D

This morning I gave it full choke and forced myself to be hands off on the throttle. Lo and behold she caught, stumbled, recovered, and kept on going without any "help" from me. Within about 30 seconds she was idling up around 3000 and I eased in on the choke to bring it to 2000 or so while I finished warming her up.

This was a much less nerve wracking experience than I've had every day for the past several weeks. Will I get it started before I use up the battery? What's wrong with her? Well, apparently an ignorant owner was the problem.

Thanks again!

[Steve]

This morning I gave it full choke and forced myself to be hands off on the throttle. ... Within about 30 seconds she was idling up around 3000 and I eased in on the choke to bring it to 2000 or so while I finished warming her up.

Eventually you will find the 'sweet spot' in the choke travel (might be around 2/3 or so) that allows the engine to start, but keeps the revs down around 2000 or even lower when it first starts. Then you can gradually lower it to 1500. If you do this just before you put your helmet on, the bike will be ready to roll by the time your helmet is fastened, and the choke can be turned off by the time you are in third gear.

Well, apparently an ignorant owner was the problem.
Thanks again!

Nice that you recognize that, but don't feel bad. We are all ignorant, but hopefully in different areas.
Albert Einstein and I had an agreement...I would not mess with his theories and he wouldn't touch my carburetors. 8-[


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[nabrams]

Every bike is different with regards to the "sweet" choke setting for initial startup.
I have two Honda CB750 bikes. One will start only with a maximum of 2/3 choke (more than that is too rich for it). The other has no chance of starting with anything less than full choke. Now, these have the exact same engine design and carbs. The only difference I note between the two is that one has border-line compression (in the 120's) and the other has near-spec compression (in the 150's) - which, of course, makes all the difference in the world. Now, add in factors like minor air leaks, somewhat weak spark, slightly plugged-up jets - and now you can have wildly different startup choke settings (and startup ease/difficulty) for two exact same model bikes.

[waterman]

I've had my 1985 GS550ES since October. When I bought it, it'd start on full choke pretty much instantly..

My garage smelled like gas after 40 minutes of struggling.

I tried putting the petcock on prime for 2 minutes. Also tried blowing in the carb breathers.


Once the bike starts, it runs great.
Any suggestions? It was in the mid 20s when I was trying all this but the overnight low was 5 or 8.

I have to agree with others about each bike has its preference on starting procedures. My oil burning 650, 2/3 choke max, fires up down to 25 degrees, my newer replacement 650 with repaired transmission, full choke down to who know what temp. My 550 full choke always, but will die after starting unless I blip throttle to help it from loading up. (It still needs a little carb fine tuning, most likely reset floats to better level.)

My concern would be too cold to start reliably. If I depended on riding it, I would place a heat source (small heater, incandescent light bulb) near motor and get it warmed up if possible before starting. When you drop below freezing, battery performance drops, fuel doesn't evaporate as well and more heat is required to light mixture in combustion chamber. All in all, I doubt too many of our bikes will reliably start below 10 degrees. I am sure mine won't at least.

[trippivot]

full choke no throttle -- standard starting procedure all bikes w/o accelerator pump. keeps the vacuum up for the enrichener circuit

I use tiny bit of quick start it really saves the starter and battery in frigid cold.

[p_s]

You also say that the PO rebuilt and adjusted the carbs "a few years ago". Has the bike been in contant operation since then, or did it sit for a while?

It's been in almost daily operation for four months. Before that it was in regular operation at least. The intake o-rings are new but the boots are not. I moved the airbox boots around and it started right up afterwards (this was Wed night). Yesterday was too cold to ride and I thought I'd be posting a victory message today but the starter made a light show and let out some magic smoke so not today. I guess I need to replace a wire or two. I'll let you know how it turns out. I REALLY want to get it sorted out by Sunday, since it's supposed to be 42 degrees warm.

[Roostabunny]

full choke no throttle -- standard starting procedure all bikes w/o accelerator pump. keeps the vacuum up for the enrichener circuit

I use tiny bit of quick start it really saves the starter and battery in frigid cold.

How do you use it? I've never tried anything like that.

Don't think I need it at present, I'm just curious about the procedure.

[Steve]

How do you use it? I've never tried anything like that.

The best way to use starter fluid is ... NOT. :shock:

Especially if you have never used it before.

Some people have the knack for how much to use and when, but, for the most part, it is far too easy to get carried away with the theory "if some is good, then more must be better". Not so in this case. Too much starting fluid usually has very unpleasant (and possibly expensive) results.


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[TheCafeKid]

The best way to use starter fluid is ... NOT. :shock:

Especially if you have never used it before.

Some people have the knack for how much to use and when, but, for the most part, it is far too easy to get carried away with the theory "if some is good, then more must be better". Not so in this case. Too much starting fluid usually has very unpleasant (and possibly expensive) results.


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Not to mention possibly PAINFULL results as well.