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In need of brain storming from everyone

  • Thread starter Thread starter Anonymous
  • Start date Start date
A

Anonymous

Guest
I am having a problem with a bike I am working on and I am in need of some trouble shooting from everyone.

Here is the situation.

1982 Yamaha Maxim XJ650J. Been stored for 9 years. Has Stabil added to gas each year by owner (not me).

Now here is what I have done so far.

Took apart and soaked in carb cleaner all carbs (after removing all rubber parts from carbs), cleaned out all passages with carb cleaner and compressed air. Replaced float bowl gaskets and two diaphragm/slide assembly's that were bad. Put carbs back together and on bike. Cleaned air filter with compressed air. Oil and filter change. New plugs.

Here is the problem.

Almost impossible to get running. Once running (barely) it dies after 5 sec. to 1 min. then wont start again (want's to but wont). After I had got it to run for a few min. I noticed the number 3 cylinder was not hot at all (ice cold still), number four was warm and numbers 1 & 2 were hot. Now, I pulled each plug and checked them and here is what I found. #1 was covered in black soot, #2, #3 & #4 was clean as new still. So I checked for good spark on each plug by lying the plug (connected to plug wire) on the motor and turned bike over. I have spark on all 4 wires (not as good as I think they should, but still a nice blue/white spark).

Here is what I am thinking. You tell me of I'm wrong and let me know what I should look at next.

I believe that the number 3 carb is either not getting gas or not suppling gas. However, I made sure I could see through the little hole in each and every jet in all four carbs. I also believe that the black soot on only the number 1 plug might indicate a stuck valve in that cylinder. What does everyone think?

Please help, I would like very much to get this headache out of my garage and get back to riding my bike.
 
What rpm will the bike run at? Did you check the float heights?
Do you have to start it with full choke. If so, do you have to keep the choke on to keep it running?

Earl
 
earlfor said:
What rpm will the bike run at? Did you check the float heights?
Do you have to start it with full choke. If so, do you have to keep the choke on to keep it running?

Earl
Click to expand...

When the bike does idle, it idles between 1000-1500 rpms. As far as the choke goes, sometimes it wont start unless it's choked all the way, other times half way and then others none at all. In otherwords, it does not seem to matter where the choke is. The choke does work though cuz when I do get it running, moving the choke around does increase/decrease the idle. I did not check float heights because I did not mess with them except remove the pin and removed them to clean the carbs. The bike owner said it ran just fine before storing it, so I figured they were ok.
 
When you removed the idle air screws and fuel pilot screws, did you write down the settings and reinstall them with the same adjustments?

Have you checked the aircleaner element to be sure it is not covered in grime and blocked?

Earl



JGonier said:
earlfor said:
What rpm will the bike run at? Did you check the float heights?
Do you have to start it with full choke. If so, do you have to keep the choke on to keep it running?

Earl
Click to expand...

When the bike does idle, it idles between 1000-1500 rpms. As far as the choke goes, sometimes it wont start unless it's choked all the way, other times half way and then others none at all. In otherwords, it does not seem to matter where the choke is. The choke does work though cuz when I do get it running, moving the choke around does increase/decrease the idle. I did not check float heights because I did not mess with them except remove the pin and removed them to clean the carbs. The bike owner said it ran just fine before storing it, so I figured they were ok.
Click to expand...
 
earlfor said:
When you removed the idle air screws and fuel pilot screws, did you write down the settings and reinstall them with the same adjustments?

Have you checked the aircleaner element to be sure it is not covered in grime and blocked?

Earl
Click to expand...


Roger that, put the air screws right back to where they were. As far as the air cleaner element, I am assuming you mean the air filter. If so, I blew it out with and air hose. The filter looked new, just had some storage dust on it.
 
Did you clean out the choke tube pickups in the float bowls, or is the 650J model the one with the accelerator pumps instead?
(trying to put the bits n pieces of the situation together here) :-)

Earl

JGonier said:
Roger that, put the air screws right back to where they were. As far as the air cleaner element, I am assuming you mean the air filter. If so, I blew it out with and air hose. The filter looked new, just had some storage dust on it.
Click to expand...
 
earlfor said:
Did you clean out the choke tube pickups in the float bowls, or is the 650J model the one with the accelerator pumps instead?
(trying to put the bits n pieces of the situation together here) :-)

Earl
Click to expand...


Well, Not to sure what you mean but here is the rundown on the carbs. If it unscrewed out of the carb., it was removed and cleaned. If it had one or more holes I was supposed to see through, it was clean with carb cleaner and blown out with air hose til I could see through all these parts. After I took off everything I could off all the carbs., I then soaked all four carbs in a tub of carb cleaner that came in a one gallon can from Napa Auto for 24 hours. After I soaked the carbs, I used a spray can of carb cleaner to clean out anything left in any of the passages, then blow all them out with air hose. I then put everything back together along with the new parts.

Hope that helps put the pieces together for ya.
 
Replace the fuel filter if it has one. Check to make sure that the fuel lines are not kinked or blocked and that the petcock filter screen is not blocked with crud. Check the float heights just to be on the safe side. Just because it had stabil in there doesnt mean that some crud is not blocking something in the fuel lines.
 
If the bike's been lying up for 9 years, I'd do a compression check to start with. You should get over 120 psi in each cylinder. If any of them are low you might have gummed up rings or a stuck valve. The rubber inlet stubs on the XJ's are prone to splitting and perishing over time, messing up the fuel air mix, and it's not always easy to spot. I had a similar problem on an XJ 750 a couple of years ago. Having a spark with the plugs out doesn't mean you'll get one under compression. The insulation in the ignition coils can break down if the bike's been stored in damp conditions. A friend of mine put a pair of coils in the oven at 75 degrees centigrade for 2 hours to drive out the moisture and it did the trick, big fat blue spark! He's a television engineer and used to have the same problem with damp line outputs in stored tv's. Hope that's some help.
 
Good thought about checking the compression Guy. I think thats the next thing we need to confirm. I'm inclined to disagree about the possibility of moisture in the coils causing the problem because #1 is hot and #4 is warm.
#2 is hot and #3 is cold. 1 and 4 is a pair running off of one coil and 2 and 3 run off of the other coil. One plug off each coil is running hot.

If the carbs are squeaky clean, we need to know for sure we have comression and if we do, its looking like leaking induction boots because the induction system cannot be working.

Earl

Guy said:
The insulation in the ignition coils can break down if the bike's been stored in damp conditions. A friend of mine put a pair of coils in the oven at 75 degrees centigrade for 2 hours to drive out the moisture and it did the trick, big fat blue spark! He's a television engineer and used to have the same problem with damp line outputs in stored tv's. Hope that's some help.
Click to expand...
 
I'll see if I can get my compression tester to work and check the compression on it. I think I'm missing pieces to it though, might have to buy new one. Will get back at you with the results.

Thanks
 
I think I found some of my problem. I decided to try starting the bike with the petcock turned to prime. The bike then started and idled ok. Then it backfired real bad through the number 3 cylinder. This is the cylinder that has the hose running from the petcock prime right to the intake induction tube. I'm guessing the backfire was caused by leaving it run on prime, it was dumping too much gas directly into the induction tube.

I am going to remove the petcock and clean this before I run the comb. test on all cylinders. This might just be my problem.
 
All the prime setting on the petcock does is fill the float bowls without the need of vacuum to allow fuel flow. Prime is nothing more than a gravity feed bypass to fill the float bowls. There is no line dumping fuel directly into the induction tubes.

Earl

JGonier said:
I think I found some of my problem. I decided to try starting the bike with the petcock turned to prime. The bike then started and idled ok. Then it backfired real bad through the number 3 cylinder. This is the cylinder that has the hose running from the petcock prime right to the intake induction tube. I'm guessing the backfire was caused by leaving it run on prime, it was dumping too much gas directly into the induction tube.

I am going to remove the petcock and clean this before I run the comb. test on all cylinders. This might just be my problem.
Click to expand...
 
earlfor said:
All the prime setting on the petcock does is fill the float bowls without the need of vacuum to allow fuel flow. Prime is nothing more than a gravity feed bypass to fill the float bowls. There is no line dumping fuel directly into the induction tubes.

Earl
Click to expand...


Thats what I thought, but then I noticed the two gas lines. If what you said is true (not doubting you) then what is the gas line that runs right to the number 3 induction tube for? The other gas line runs to the carbs. and both come from the petcock.

Is the one running to the induction just a vaccuum line?
 
The large diameter line on the petcock goes to a fuel fitting between #2 and #3 carb. This fuel fitting is aaprox level with the top of the float bowl.
The hose on the petcock that goes to the fitting on the side of #3 carb is a vacum line to operate the petcock diaphram.

Earl


JGonier said:
earlfor said:
All the prime setting on the petcock does is fill the float bowls without the need of vacuum to allow fuel flow. Prime is nothing more than a gravity feed bypass to fill the float bowls. There is no line dumping fuel directly into the induction tubes.

Earl
Click to expand...


Thats what I thought, but then I noticed the two gas lines. If what you said is true (not doubting you) then what is the gas line that runs right to the number 3 induction tube for? The other gas line runs to the carbs. and both come from the petcock.

Is the one running to the induction just a vaccuum line?
Click to expand...
 
earlfor said:
The large diameter line on the petcock goes to a fuel fitting between #2 and #3 carb. This fuel fitting is aaprox level with the top of the float bowl.
The hose on the petcock that goes to the fitting on the side of #3 carb is a vacum line to operate the petcock diaphram.

Earl
Click to expand...

Got it. Learn something new every day, right?
 
Ok earl, new question.

I got the piece I needed for my compression tester and I have started checking the compression on cylinders 1 & 2 however, I think I might be doing this wrong. Tell me if this is right.

I took out plug #1 and screwed in the tester into the #1 cylinder. I then started the bike. Now here are the results. The needle on my gauge hardly moved unless I rev the motor. I get the same results on cylinder #2 also.

The 120 compression mentioned earlier, is that when the bike is idling or at a higher rpm.? I have it set to idle with the choke off at 1500 rpm's. At what rpm's should I be checking compression at?

Thanks.

P.S. The plug in cylinder #1 is still fouling up with black soot, but only on cylinder #1. The others still look new.
 
Compression should be check on a warm engine at wide open throttle.

It should not be check running.

Start the bike take it for a ride.
Now disable the ignition (pulling the positive wires off the ignition coils should do it).
Remove the plug you want to test. Screw in the gauge. Crank the engine over a maximum of 4 times with the choke off and the throttle held wide open.
Repeat this for the other cylinder.
You should have less than 10% difference between cylinder.
If you have money start looking for problems.

Thanks,
Gavin
 
What condition is the battery in? How new are the spark plugs? Electrical problems are often diagnosed as carb problems. IMHO, Yamahas are designed by engineers from hell.
 
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