Fast Idle and Cylinders 2 and 3 not firing

I've read a lot of posts before asking for help.

History:
I have a 82 XJ650 Maxim with 18,000 miles. I just bought it this year. I'm new to bikes. I had a guy clean the carbs for me. He put it all back together but was staling around and never got it tuned up so I took the bike back and now I'm trying to tune it myself.

Symptoms:
It idles fast and erratically (3- 4.5 k). I have the throttle stop unscrewed all the way. There is slack in the cable and it still runs fast. It will sometimes run slow enough were I can increase the throttle a little and it speeds up but then when I release the throttle the speed does not decrease. Also, the exhaust pipes on cylinders 2 and 3 stay cold when running. I unscrewed the plug and turned the engine over, there is spark.

What I've done so far:
I got 4 vacuum gauges and a blanking tool and tried to sync the carbs but I think I need to get the idle down and figure out why 2 and 3 are not firing before that will work. I have not checked the float level yet but I did loosen the drain plugs on each carb to make sure there was gas in each and there was. When attempting to sync the carbs, I had the gas tank off and the fuel lever set to PRI (I figured I needed to do this because the vacuum gauge is connected to the hose that normally goes to the fuel regulator). The guy who cleaned the carbs replaced the intake manifolds and I checked all the connections on the boots on both sides of the carbs.

I bought the blanking tool from chacal and he recommends adjusting the valves which I am willing to do but I though I would at least try to get it running half way decent first. Can I rig up the restrictor as described in Old School Method of One Vacuum Gauge Carb Sync? (one for each gauge)

Any help would be greatly appreciated.

 

I would bet he did not bench sync your carbs. If your butterlfys are open too much at idle it is just like opening the throttle. Not at all hard to do. You will need to pull the carbs.

Bench sync
http://www.xjbikes.com/Forums/viewtopic/t=6366.html


While you are at it I would look a this also. Look at the clunk test near the end of the cleaning process.

Clean carbs
http://www.xjbikes.com/Forums/viewtopic/t=2908.html

 

Thanks Bill - I was anticipating that I would need to pull the carbs. I'm wishing now I had found this site before taking it to this guy. Now I'm not sure what's been done and if it was done correctly. Well, live and learn. I'm ready to dive in.

Do I need to be concerned at this point about cylinders 2 and 3 not firing? Is this a separate problem from whatever is causing the fast idle? Do you think getting the carbs close and ensuring they pass the clunk test will solve that problem too.

I'll post after I complete the process and let you know the status. Thanks for the help!

 

The carbs have to deliver alomst perfect air fuel ratio for the cylinders to fire properly. I would guess there is still dried gas in some of the critical passages for the pilot circiuts. Reclean and run a tourch tip cleaner through all the passages. Do not enlarge your pilot jets or main jets. Pay close attention to the little orfices in the bottom of the wells in the float bowls. Also if the guy who cleaned the carbs mostlikley soaked them in carb dip and that may have damaged your throttle shaft seals. Carbs sucking air from the shaft seals can give you poor idle quality for sure. Good luck and if you need help PM me back since I am close to you.

Ron

 

Thanks Ron.

You are correct. I know he soaked them because he told me he did. He also told me he replaced some miscellaneous seals and O-rings. I really feel like I need to start from scratch so I can be sure everything has been checked. I think I'm going to do the entire process described in the link bill posted above .

I pulled the carbs and with out even taking anything apart, I'm seeing that carbs 2 and 4 don't pass the cluck test.

Thanks for the offer of help. I may just take you up on it.

 

Sounds like you have some work to do. Good luck and keep us posted. If you are unsure take Ron up on his offer. Most of us actually enjoy working on the bikes.

This is a great site I have met several folks local here and we help each other out.

 

I see that you are at the same point that I was on the bike. I had 2 and 3 with a weak spark. I pulled off the pickup coil cover and read between the pickup coils. They should read 700 ohms plus or minus 20%. I did switch the inputs on the coils and then the trouble was on 1 and 4. Make sure that the pilot jets are clean by squirting carb cleaner through them or you will be taking them off again.

 

Thanks for the tip chillywillie.

I will try that. I have no idea where the pickup coil is but I have a manual so I will be checking it out.

 

The pickup coil wires go into the bottom plug on the tci box mine are gray brown and orange black. IF you have a cheap meter they should both read the same resistence anyway. I have the 81 xj 650 h. The pickup coils are on the left side when you are sitting on the bike. I had to take off the engine guard on mine and use a vise grip to loosen the screws so I wouldn't strip them. You can also use a 1/4 inch scket and the proper bit and rap on the screws and it sometimes will loosen them up.

 

you can "bench sync" the carbs ON the bike, the term "bench sync" is used because it is a method of getting the carbs close to sync after being torn down & cleaned, before re-fitting them. you have to remove the boots between the carbs & the air box.

 

Ok- now that Christmas is over I'm back to this project. I've got the carbs off and apart on my workbench.

Floats, needle vale assembly are out, no problems. Did not find the "Beanie-looking" filter screen on my needle valve assembly that are described here: http://www.xjbikes.com/Forums/viewtopic/t=2908.html Is that a problem?

Unscrewed the main jets no problems.

Unscrewed 3 of the small jets. Could not get one out, rounded the shoulders a bit. I think I'm just going to leave it in and clean through it as best I can unless someone thinks it absolutely needs to come out.

Next - the top side

 

Got the top half all apart and cleaned now. Saw some problems on two of the diaphragms. They were not seated in the channel all the way around. I can see light through all of the holes in the brass nozzles that attach to the main jets.

My tamper proof plugs are still in place for the mixture screws. RickCoMatic says it's absolutely necessary to remove these in order to tune the bike properly. I'm hesitant. He describes small parts in there that I don't want to risk losing.

I want to get the bike running well but I'm not going to race it or do any high performance riding or anything like that. Feedback on the mixture screws is welcomed / requested.

 

To get proper tune and balance for your cylinders you will need to sync the carbs. Part of that is to get at your mixture screws and aquire a color tune plug so you can get it right. I have found if it starts off lean, its lean all the way up in Rpm's. If your carbs are working right and your cylinders are all close as far as compression is concerned it should idle with all cylinders contributing about the same. I assume you are pulling plug wires with it at idle.
You could unscrew your plug wire boots and double check the connection in there. It could be corroded and not getting good connections in the boots and that could give trouble with weak spark.
Otherwise You will need to get the block off tool and sync the carbs. One of my 750's was so far off it was a completely different bike after sync job. Woke it right up and the power was incredible. Good luck

 

Need to check compression. If its not in spec then look at adjusting the valves(should check them anyway). Hopefully they are close. If so then figure out why only 2 cylinders are firing.

 

Everything is back on the bike now. Hooked up my home made temp. gas tank, turned it over and ZING!!!! right up to 6K and stayed there.

I did bench syncing before putting the carbs on and everything. Started tearing what little hair is left out until I saw this post from Bill on a different topic.

I pressed on all the sync screws with a screw driver. The far right one had a little play in it so I pressed it down and started the bike. Idled at about 2K. As soon as I released a little pressure on the sync screw the engine raced back up. I could control the idle speed somewhat by adjusting the pressure on the sync screw.

Looks like I'm taking the carbs off again but at least I have zeroed in on the problem.

Thanks Bill

 

That was on my third carb tear down that I found the problem. Hopefully yours is as simple. Make sure, with your idle adjust all the way out, that you can not see light around the butterflys. (you may see a slight bit but should be near zero light).

The butterflys seem to be a custom fit so I assume you kept track and reassembled in the same place. However on mine I think someone before me did not as I had 2 that did not fit right. Swapping them resolved that issue.

Also check that the sync screws are assembled properly. If not that can allow some strange results.

Good luck - like I said I think I had 3 iterations of tear downs before I was comfortable I had them right.

 

I took the carbs back off the bike and PM'ed Ron to ask for help. He said sure come on over and we'll check em out. Thanks so much Ron for spending your Sunday afternoon with me and my carbs.

Here is what we (mostly Ron) discovered.

1. The throttle shaft bolts were loose and we found what appeared to be an unnecessary washer on one. Tightening the bolt made it bind so we removed it, which cured the binding.

2. Two throttle shaft springs were not hooked in the correct spot.

3. Two of the butterflies had the beveled edge facing the wrong way causing them to not fully close.

4. While we were at it, Ron suggested we check the float levels. They were all very high. They are good now.

5. Also checked the passages where the mixture screws go. All clear.

He then benched synced them for me. Now there is minimal light shining through and the throttle stop now contacts the throttle screw with some room for adjustment where as before it did not. It seem like I should be in good shape now. I'm going to try to get them back on the bike some eventing this week.

I'll post back the results ASAP.

Thanks again Ron (MN-Maxims) for the personal carb clinic. I learned a great deal!

 

*******Up date on this problem********

You know you never can trust anything or anybody.The previous guy that worked on the carbs did not pay attention to detail.
J came over to my shop on Sunday. The first thing I noticed was that two butterflys were closed tight and the other two were open. Weird. The idle adjustment screw was all the way in the the butterflys were still closed. Really strange. We went back to my house and got my spare carb set that I know have never been seperated before. We got back to the shop and found that there was a spare spacer washer on the throttle shaft on carb #3. I tryed to tighten up the nut that holds the linkage and it was binding up pretty bad. We took the rack apart and removed the plastic washer. The throttle shafts freed up but still could not bench sync. Ahhhh. So looking carefully I found that two throttle blades were in backwards. The taper on the blades were causing the problem. So we went to the auto parts store and got some locktite and removed all the screws and locktited them in and flipped the blades over. Got a good bench sync now. Cool Man. Now we took the float bowls off and I made sure the enrichement jets were clean and set the float heights to 17.5 mm as per the thread on that. Then I blew it all out and put the bowls back on. It should be close for "J" to get his bike running. It just goes to show you need to double check everything.
Now we will have to wait to get the report back on how well it runs.

 

Thats too funny we were both writing about this at the same time. Let us know how it runs' and thanks for coming over. Nice to meet you and hope to get that bike out on one of our rides. Good Luck

 

The first time I tried starting it I could not get it to catch and wore the battery down. I pm'd Ron and he told me to get the get the battery charged and clean the spark plugs with carb cleaner then dry them out with a torch. Did that and now...

We are cookin with GAS! I can't tell you how excited both my Son and I were to have it running with a controlled idle.

I think I have some more tuning to do and I'll probably have to pull the carbs off again. The throttle is a little stiff and doesn't snap shut when releasing. Some of it may be the cold weather but I think I need to figure out what's hanging it up.

Seems like all cylinders are firing now. All the pipes are hot / warm. I still need to check the plug wires as well.

See my carb installation technique here: http://xjbikes.com/Forums/viewtopic/p=1 ... tml#127652

Thanks again Ron!

 

was the throttle stiff before you redid the carbs? If so take take the cable off the perch and slide the cable into the bottom of a funnel, duct tape the cable to the funnel and put a zip tie around the tape around the cable. hang the funnel from the ceiling with a wire, bungy etc, and pour a light weight oil into the funnel (marvel mystery) and let it sit and soak down the cable for about 10 mins.

If it was fine until you put the carbs back on then you need to check to make sure your routing is clear and your not pinched any place along the cable.

 

Thanks,

Nope, It's not the cable, it's the throttle shaft that opens and closes the butterflies that's stiff. I got the carbs off now and just trying to figure out whats causing it.

 

UPDATE 2/14**********

Carbs were back on the bench. We split the rack again and found #3 carb binding. Remove throttle shaft and clean what looked like gasket adhesive off of inside bores. Put it all back togeather and it worked very free and nice. Waiting for report on how bike runs now with carb sync.

 

Got it back together again and after warming up the carbs with a hair drier, got it started. Trying to do the sync now. Either I'm not very good at this or there is something else wrong or I don't have the right equipment. My gauges really flutter. I did install restrictors.

Could not get any consistency and by the time I ran out of gas I noticed that the number one cylinder stopped firing. The other three pipes were hot. There is spark on all cylinders.

Going to get some fresh gas ad try again tomorrow.

It starts great now but still runs kind of rough.

I'll keep you posted. I'm determined to get it running correctly.

 

Are your restrictors adjustable? Send a pic of what you are using.

As far as #1 you must have closed the throttle blade all the way shut or you got something caught in the pilot jet.

 

Jeff why don't you come up and get my sync gauges. You have put so much time in on this you are going to go crazy. I'll put them in my truck so if you want you can pop over and get them. I'll be in the shop again today till noon.

Ron

 

Your gauges really worked well. I was able to get it synced with the yics tool in place. I need to find those restrictor valves that you have. I tried one aquarium shop and they did not have the same kind.

Still not firing on cylinder #1. Took out the carbs agian. No obvious obstruction in the idle jets or the main jets Blew air through them all just to be sure.

Before taking the carbs off, I took off the boot on the air box side of cylinder #1 and held the unlit but open propane torch in the intake. No change in the engine. That's telling me that maybe it IS getting gas and it's the spark I'm missing.

One thing I noticed is that when I took the spark plug wire off while it was running, I could feel the shock while holding the wire at the base. When I did this on the other cylinders, I could feel no shock. Maybe I have a bad plug wire.

 

Mm...you could be grounding out on that cylinder, but pull the plug first and make sure it's not fouled or anything from all the previous carb problems.

 

Well Swap plugs from another cylinder and see if the problem follows. That will tell you if the plug is bad. Turn the lights off in the shop and see if the wire is jumping to ground somewhere. Last but not least do a compression check to make sure something didn't happen with that cyclinder. Call me tomorrow and we will go over it again. Good Luck Ron

 

Put the carbs back on and fired it up. Still nothing on cylinder number 1. And now cylinder number 4 stopped firing.

Swapped plug 1 with 2 and 4 with 3. Guess what, now 2 and 3 don't fire. SPARK PLUGS! Good call Ron.

Went down to Checker and picked up another set of brand new plugs. (I got these only last October and they replaced them for nothing), put them in the bike, synced, color tuned.

Put the tank back on. My son and I took her for a ride. SWEET! It ran well and responded well on the throttle. I didn't even mind riding in 30 degree weather.

Many thanks to all of you who responded with helpful suggestions and especially to Ron (MN-Maxims) for helping me through this ordeal. I learned a lot and will be looking forward to riding with you and your pals. I'm ready

Consider this thread closed! Successful!

 

Good luck with that bike and I know its hard to do, but don't grin too much when you open that trottle in this cold weather you'll freeze your teeth. Have a good one and we will see you this summer.