Help with carborator?

[martechy]

First let me thank all of you who have posted your problems and what you found to be the cause. I have learned a lot and hope I can aid others with my post.

The problem
My 1998 ST1100 is backfiring up through the carb's.

At first I thought it was the road I was feeling but soon found that the noise and knock was the bike itself. Just around 2000 RPMs it starts knocking.

Shop said it was most likely the carborators, but I didn't have the money so I took it home and took it apart...I am good at that but not so good at the putting back together part. :

I found the # 2 carb jet was totally blocked. Cleaned all four carbs. I did not remove the pilot screws. Installed new air filter/fuel filter/and spark plugs.

Put it all together again and started it up. Still backfiring. I removed the spark plugs and all four were coated in gas. See picture.

Help! I may have not seated the carborator well enough on the boots but sprayed some starter fluid around and got no response. Could I have both fouled jets and a faulty ignition timing? What would you suggest?

Monica

 

[BuddingGeezer]

Backfiring through the carb is usually an ignition or valve timing problem. The plug is firing while the exhaust valve is still open allowing the fire to come back through the carb. Causes can be untimed valves, wrong ignition timing and wrong firing order. I'm guessing wrong valve timing is not the problem in this case.

Fuel on the plugs is caused by the plug not firing and can't burn the fuel off, or a rich carb setting. Stuck needle valves or worn needle seats, improperly set float levels or a float that won't float. Don't know how ethanol affects the ST carb (hasn't affected mine) but will cause some to absorb the fuel and not float right.

If you didn't remove the pilot screws, you didn't properly clean the carbs. I believe your first step is to clean the carbs so you KNOW they aren't the problem. Also it's been my experience that once a sparkplug is covered in fuel, throw them away and buy new ones. They never fire right.

Hopefully someone will read this that's had the exact problem and will advise.

 

[martechy]

That makes sense to me. Well, I guess I am going to get better at this if I have to go pull it apart again.

After looking at it with better light I found that while trying to seat the carborator in the boots I managed to pull one boot up so that it isn't all the way on. I think it took me an hour to get that bugger in. Later I read that lube is the key and warming the boot up with a hair dry helps. Some one posted that they put a board on top of the carb, then put a latter next to the bike and than stood on the board to seat the carborator. I thought that was odd till I tried to seat my carborator.

I didn't pull the pilot screw out because I didn't have the D shaped tool but through reading some more post I learned that I may be able to fit something else over the D and get it out. That said I will be pulling the carb again. Do you guys soak the float needle in carb cleaner too? If I pull the jets, pilot screws, and the flout needles have I got it all? Also I pulled the flouts/needle and housing out but could not get the little mesh screen out. Any tips for this part? This is the first time I have ever done a carborator so any tips are welcome big time. :

What a bummer. I just pulled those plugs out of the box and now their toast. From now on I will keep an old set around for just this sort of thing. The shop synchronized my carborator before I did all this or so they told me, and my old plugs looked okay so the wet plugs have to be something I did to the carbs or the fact that I need to reset the pilot screw after I clean it. Is 2-5/8 the magic setting?

My poor bike! After I do the carbs again it is onto the ignition timing and I pray that I will find my problem easily.

 

[EE_BOTA]

"martechy," if you are still around, I'm curious how you are making out with your bike.

On mine, the little strainers above the float needle seat did not come out on two carbs, so I fished them out with a pick set. "Pick set" might not be the correct name, but they look similar to what a dentist scrapes my teeth with. The are cheap and handy as all get out.

I would not toss a new plug just because I got them wet with gas. It is something to keep in the back of your mind until your bike is sorted, and should be suspect. But after the bike is running right, and those plugs are the ONLY variable, substitute them back in and you may find they are just fine. If so, maybe clean up the ones you took out and carry one or so somewhere in a cubby in case of unforeseen problems on the road.

In roadside checking, sometimes we just want to know if we have a spark, so rather than jamming something in the wire, or risking getting shocked, or having to unscrew an installed plug, we could use a spare plug. If we learn which coil powers which cylinders, we'd have to do at most two different wires to know the state of both coils. If in a hurry, just check one plug wire, and if you see spark, go on to fuel.


What could we do about fuel. Many bikes are setup pretty well since they have an individual drain hose per carb. It we do that with the ST, instead of the ganged approach Honda used, then we can use them for diagnostics.

For example, if while they are on the bench, you attach clear hose to find out where the fuel "water levels" out to relative to some know landmark on the carb body. We can make sure all four carbs agree quite precisely before we ever put them on the bike.

If the replace the ganged arrangement with individual black hoses, but make them long enough for access under the bike, we can attach long pieces of clear hose with a connector, bring it up top, and compare the levels anytime we wish. Draining the individual carbs into a container capable of measuring things can accomplish the same thing. If one wanted to know if fuel is the problem during a *breakdown,* getting adequate amounts drained from at least one carb should tell you that bike ought to have been able to fire on at least one cylinder. One can do all four, if needed, depending on how desperate you are to see how many SHOULD be able to fire.

So we can tell compression by listening, fire with a spare plug. In the ganged arrangement, if we make sure the ONE big hose is long enough that we can capture the gas in to a measuring vessel, we can know if the bike had enough fuel in each bowl to run. If we un-gang them and bring out individual hoses, we can add extensions for severe troubleshooting circumstances, and even watch our fuel levels as we drive down the road if need be.

We can understand the precise level of all the bowl as a precise place on our concrete floor, while on center stand and running too.

A apologize that this is so long. Maybe someone will be helped, though.