Topic: Help with stalling after warm up

[Johnny5]

I had this stalling issue and it ended up being a clogged petcock. I would let the bike sit a while and then it'd run fine, until the gas was empty in the float bowls and the clogged petcock wasnt letting in enough fuel to keep the bowls full. The reddish stuff in your float bowls makes me think it's a fuel delivery problem.

[cb750fbomb]

I had this stalling issue and it ended up being a clogged petcock. I would let the bike sit a while and then it'd run fine, until the gas was empty in the float bowls and the clogged petcock wasnt letting in enough fuel to keep the bowls full. The reddish stuff in your float bowls makes me think it's a fuel delivery problem.

I'll add that to my to-do list as well. I'll pull and check the petcock, check the line from the petcock to the carbs and change the in line fuel filter while I'm at it. Fast stuff like that can't hurt even if that isn't it.

Crap from the float bowl:

[Johnny5]

Looks like tiny rust deposits to me. Be sure to pull the petcock completely apart and clean the inside well. It's the passages you cant see that get clogged easily.

[cb750fbomb]

Looks like tiny rust deposits to me. Be sure to pull the petcock completely apart and clean the inside well. It's the passages you cant see that get clogged easily.

Thanks for the heads up. To clean that petcock, I've never had one apart, do I need to use pipe cleaners or something like that?

[Johnny5]

That would probably work. I've had good luck just soaking in some Sea Foam and then rinsing the holes with some brake cleaner. Keep the brake cleaner away from rubber parts.

[78whiteorbs]

Cleaning the petcock is not hard. After you drain the tank over  a five gallon bucket look and I'll bet you see the same "flakes" in there. While draining it switch back and forth from the reserve to the main . You should get a steady flow . Put some fresh gas in give it a slosh around and repeat a few times till less and less is coming out . Then remove petcock and take apart and clean any sediment or gunk that may be hiding there.

There is a trick using marbles that I read about but forget exactly how it goes ,maybe someone else can chime in . Afterwards get your tank coated or do it your self . Again not that tricky and you do not want all that crap clogging up you carbs . Good luck ~

[Duke McDukiedook]

+1 tank coating (and etch).
If you have rust in your bowls, odds are ya got rust in yer tank. 

[PJ]

Are all the accelerator pumps shooting fuel when you twist the throttle? Remove the pods and just look into the carbs as you twist the throttle, you should see a small stream from each carb. Have you pulled the pilot jets and cleaned them? They are a press in design but with some careful nudging they will come out, they are a very common problem with PD carbs. Being a K7 the carbs are a different design from the earlier bikes. They have extremely small passages and clog easily. When it stalls does it still have spark? Pull a wire and hold it while cranking after a stall. This will tell you if it is lack of spark or fuel, painfully but by now you may feel as though you deserve it Can you keep it running by adding fuel to the carbs with carb spray or? Did you add the pod air filters or where they already on the bike? What size main jets are in the carbs? If you remove the bowls you can remove one with a standard screwdriver from the bottom. It has a number on the side of it. Get a magnifying glass if your over 40.  The stock jet is a 105, should be much larger than that with the pods as these carbs were lean with that jet size. Maybe a 115-120?? Before you can even start on these test your battery has to be solid though..

[cb750fbomb]

Pulled the tank off and I'm soaking the petcock in Seafoam while i'm waiting for my spark plug tool. I didn't notice rust coming out of tank. No luck finding a 18 mm socket for the spark plugs unless it was sold in a huge $40 set of stuff I didn't need. I'm stopping on way home from work tomorrow morning to get new fuel filter. The one installed in the fuel line was ugly, but it seems to flow fine.

Are all the accelerator pumps shooting fuel when you twist the throttle? Remove the pods and just look into the carbs as you twist the throttle, you should see a small stream from each carb. Have you pulled the pilot jets and cleaned them? They are a press in design but with some careful nudging they will come out, they are a very common problem with PD carbs. Being a K7 the carbs are a different design from the earlier bikes. They have extremely small passages and clog easily. When it stalls does it still have spark? Pull a wire and hold it while cranking after a stall. This will tell you if it is lack of spark or fuel, painfully but by now you may feel as though you deserve it Can you keep it running by adding fuel to the carbs with carb spray or? Did you add the pod air filters or where they already on the bike? What size main jets are in the carbs? If you remove the bowls you can remove one with a standard screwdriver from the bottom. It has a number on the side of it. Get a magnifying glass if your over 40.  The stock jet is a 105, should be much larger than that with the pods as these carbs were lean with that jet size. Maybe a 115-120?? Before you can even start on these test your battery has to be solid though..

I'll check the accelerator pumps when I get the fuel line back together. The pods came on the bike and I don't know if anyone every rejetted the carbs after installing them. Removing the bowls requires installing a new gasket afterword, correct? Or is that only if they're in bad shape?
I know I'll probably have to at some point, but I'm apprehensive about getting those carbs apart. Seems like there are lots of little pieces to loose. I'm sure they're not any more painful than a Quadrajet needles and springs nightmare.

[cb750fbomb]

Should I go ahead and buy a carb rebuild kit instead of ordering float bowl gaskets (if I need float bowl gaskets)? Sometimes you need gaskets and sometimes you don't and I don't know if float bowl gaskets go to crap easy.

[Tim in Ohio]

The stock tool kit includes a spark plug tool that can dodge the obstacles in the spark plug access tunnel.
Beware installation.   Cross threading spark plugs is a hang your head and cry affair.

Cheers,

+1 Amen Brother...  been there... hung my head and cried.   

[Tim in Ohio]

Should I go ahead and buy a carb rebuild kit instead of ordering float bowl gaskets?

Yes.  Working on these carbs is not hard.  Yes, there are little parts...  I would suggest taking lots of digital pics during disassembly so you can get it back together right.  If you don't have a digital camera, buy/borrow/steal one.  It will make it alot easier to get help on the forum here as well if your pics are clear.   

[PJ]

I have had my carbs apart at least 5 times and have never replaced a bowl gasket, it is more of an o-ring. My advice is pull the carbs, drain the fuel and take them inside and take them apart with good light. Keep each carbs parts with that carb. Don't do this in a messy garage with bad lighting. After you have taken them apart an air compressor is your best friend. Soak everything in carb cleaner then verify all the passages are open by blowing cleaner through all openings. You should see it come out somewhere. Take special care with the pilot jets, they are pressed in to the carb body from the bottom. They have *very* small passages and you will have to take them out and clean them. Now or later! Trust me.. Adjust float levels and idle mixture screws during reassembly and with luck you'll be good.

[cb750fbomb]

I was able to pull the #1 plug and the #4 plug and they are very carbon fouled. I will post pics when I get a chance. I couldn't get the #2 and #3 plugs out without buying an extension, so I'll wait on the spark plug tool delivery. Getting those plugs in is tricky. It seems like the angle in which the plugs screw in causes it to fall and not stay aligned. With a socket you have to lift it for it to go in correctly and not cross thread. I also discovored that I need new throttle cables.

[cb750fbomb]

Perhaps I'm making my ignorance very apparent here, but here it goes. I understand that it's possible to over oil your filter pods thanks to TwoTired. With this in mind is it is possible that I over oiled the pods, depriving the system of air which fouled the plugs making it run like crap? Making it get worse as the plugs get more crud on them?

[TwoTired]

Yes.  If the pores of the air filter are plugged with oil, it increases the carb throat vacuum similar to applying partial choke.  The fuel air mixture is thereby altered, providing more fuel molecules than there are oxygen molecules to pair off with.  The unburned hydrocarbons then deposit unto the chamber walls and the spark plug insulators as carbon deposits.  Carbon is conductive.  Coating the insulators with carbon basically shorts out the spark plug, preventing an arc from forming across the spark plug electrodes.

Or, the engine runs like crap with sooted up spark plugs.

But, there are certainly other causes for making the air/fuel mixture too rich, besides the air filter.

Cheers,

[cb750fbomb]

Yes.  If the pores of the air filter are plugged with oil, it increases the carb throat vacuum similar to applying partial choke.  The fuel air mixture is thereby altered, providing more fuel molecules than there are oxygen molecules to pair off with.  The unburned hydrocarbons then deposit unto the chamber walls and the spark plug insulators as carbon deposits.  Carbon is conductive.  Coating the insulators with carbon basically shorts out the spark plug, preventing an arc from forming across the spark plug electrodes.

Or, the engine runs like crap with sooted up spark plugs.

But, there are certainly other causes for making the air/fuel mixture too rich, besides the air filter.

Cheers,

HAHAHA!!! I see you appreciate my newbie, neanderthal like way with words.
I know there are other causes, but if I see to it that the air filter issue is no longer an issue then I can scratch it off the list. Maybe I could try hotter plugs too, just for giggles since running pods makes is run rich. Is it a good idea to make a change like this? It couldn't cause any harm could it? 

[TwoTired]

Pods normally make the fuel mixtures lean.  If the filter hasn't been over-oiled, you are likely looking at some carb repair/cleaning work.  It IS possible to soot up the plugs, simply by operating too much with choke applied, and the engine never getting to run long enough at full operating temperature.

I don't think changing plugs to compensate for a mixture problem is a wise approach.

Cheers,

[cb750fbomb]

I don't think changing plugs to compensate for a mixture problem is a wise approach.

The rest was helpful, but the above that I quoted was exactly what I was looking for, thanks. Also, I think I did over oil the pods.  When I pulled them off I got a little of the oil on my hands from at least one. I'll rinse them lightly with cold water to get excess oil off before I put them back on. I've been thinking that this is something I did to myself. I sure am learning a lot though. I wish i had a garage so i could get another CB750 as a lab rat for my learning process. An old Yamaha and/or a Triumph would be nice too.

[cb750fbomb]

here are pictures of the plugs. Plug 2 is moist and the other 3 are dry:

[TwoTired]

I don't think changing plugs to compensate for a mixture problem is a wise approach.

The rest was helpful, but the above that I quoted was exactly what I was looking for, thanks. Also, I think I did over oil the pods.  When I pulled them off I got a little of the oil on my hands from at least one. I'll rinse them lightly with cold water to get excess oil off before I put them back on. I've been thinking that this is something I did to myself. I sure am learning a lot though.

Let me rephrase the statement.


I don't think changing the heat range of the plugs to compensate for a mixture problem is a wise approach.
On the other hand, new, clean plugs ought to verify there aren't other problems besides mixture concerns.

I'm afraid the spark plug pictures aren't really detailed enough for a good "reading".

You might compare them to these:

http://www.dansmc.com/Spark_Plugs/Spark_Plugs_catalog.html

I question rinsing off oil with water.  The two aren't supposed to mix.  I think I would prefer a blotting approach with paper towels or clean rags.  But, I haven't seen your pods.  (And, honestly, I haven't found any yet that I thought belonged on a street bike, with a stock engine.  I'm a form follows function kinda guy, not a fashion or fad maven.)

Cheers,

[cb750fbomb]

I don't think changing plugs to compensate for a mixture problem is a wise approach.

The rest was helpful, but the above that I quoted was exactly what I was looking for, thanks. Also, I think I did over oil the pods.  When I pulled them off I got a little of the oil on my hands from at least one. I'll rinse them lightly with cold water to get excess oil off before I put them back on. I've been thinking that this is something I did to myself. I sure am learning a lot though.

Let me rephrase the statement.


I don't think changing the heat range of the plugs to compensate for a mixture problem is a wise approach.
On the other hand, new, clean plugs ought to verify there aren't other problems besides mixture concerns.

I'm afraid the spark plug pictures aren't really detailed enough for a good "reading".

You might compare them to these:

http://www.dansmc.com/Spark_Plugs/Spark_Plugs_catalog.html

I question rinsing off oil with water.  The two aren't supposed to mix.  I think I would prefer a blotting approach with paper towels or clean rags.  But, I haven't seen your pods.  (And, honestly, I haven't found any yet that I thought belonged on a street bike, with a stock engine.  I'm a form follows function kinda guy, not a fashion or fad maven.)

Cheers,

I follow you on the plugs. I was planning on getting a new set of the plugs that were in it, D8EA.

Sorry those pictures suck. I'm not so good with a camera yet

I mentioned water because the K&N instructions say to rinse them with cold water while cleaning. I'm wondering if I should hunt down a standard airbox.

[PJ]

Did you discover that you had ignition spark or no??

[cb750fbomb]

Did you discover that you had ignition spark or no??

Only on the 2 outside plugs. I didn't even think of it when I pulled them yesterday. I'll try to check tomorrow.