New to this, bike cut off and now wont start.

[MFJustin]

I'm still trying to add it all up as far as the bigger picture is concerned. Everything looks clean and functioning and I haven't notice anything out of place that would cause what I experienced. The fact that it ran fine and then just suddenly one day started to be a pain in the ass and just cut off while riding.

I guess I'll just clean everything up a bit more and double check everything and then move on to tuning the carbs. Like I noticed when I pulled the plugs the right cylinder (with all the crap in it) plug was black with oil/gas on it and the left plug was white. I'm hoping this is a carb tuning issue now and after I address that maybe everything will be fine.

 

[MFJustin]

Btw I just want to say thanks for everyone's help so far. This has been a great thread with some great info and I hope others in the future stumble across it and take some positive stuff away from it like I definitely have.

 

[MFJustin]

So I followed 5twins excellent advice on how to properly measure float level and determined that one float was closer 30mm and the other wasn't too bad at around 27, i corrected them to 25mm according to factory specs. 5twins thanks so much for the pictures, it really does help a lot when you can visually see something yourself instead of having to take a guess at what you're supposed to be looking at.

Anyways after that I replaced the fuel line from both petcocks, this time around I chose not to reinstall the inline fuel filters temporarily, turned the petcocks on and gas no longer is leaking out anywhere.

Fired the bike up and its definitely got a high idle. I think this may be due to the fact that one of the carb boots had a chunk missing from the bottom of it that would create an air leak, I will replace it soon.

Bike still smokes like crazy out of the right cylinder exhaust pipe and is spitting out black stuff (assuming oil) because its all over my frame (which is red). I took it for a ride and it seems to run ok, after reading the carb guide over and over I now know what it means when the bike seems to stumble a bit when you get on the throttle. 5twins I'm crossing my fingers that after riding it for a bit more the smoking goes away, it gets pretty bad when I get on the throttle and even on the night ride I just took I can turn around and still see smoke behind me. Guess we will see what comes of it, tomorrow I'm going to do another compression test just to see if I'm still back where I need to be and then I guess figure out where I'm going to go from here.

 

[5twins]

The float level spec for your '79 carb set is 24mm +/-1mm. The spec for the '76-'77 carb set is 25mm. At 25mm, you're still in the range for your carb set but if you're in there again, you might want to try 24mm. I experimented on my '78 carb set (same set as yours), trying the entire range (23, 24, and 25mm) and it ran best at 24mm.

You have to understand that this measurement is inversely related to the actual fuel level because you're taking the readings with the carbs upside down. That means a higher number gives a lower fuel level when the carbs are turned right side up. The 27 and 30mm settings you found were actually making the fuel levels too low in the bowls and should have resulted in lean running. Running lean for a short time usually doesn't hurt anything but to do so for months like you have can cause some damage. You get excess heat and accelerated wear in the cylinders when you run too lean. Hopefully you haven't hurt the motor but the way it suddenly started belching oil out that one cylinder may indicate otherwise.

 

[pamcopete]

MFJustin,

Time out...with all this talk of gas and oil mixing it might be a good idea to check the level and condition of your oil. If you were sucking in great amounts of gas, then it probably went into the crankcase. If so, it would dilute the oil and that could make it easier for the oil / gas mixture to make its way into the cylinder.

 

[MFJustin]

I'm going to do an oil change tomorrow and see what it looks like. I pulled the plugs today after riding it yesterday and the left cylinder is back to looking like normal and the right cylinder is still coated with oil though it looks to be dry now and not wet. Also the bike did not smoke at all today when I ran it in my garage for a little while.

Regardless of the outcome, I'm still planning on tearing it down and rebuilding over the winter just to give me something to do.

 

[AndreXS]

My 81 electric igniton bob will cut out. It then won't restart unless I hit the kill switch which results in a combustion explosion in the exhaust pipe. It will then restart, cam chain adjustment?

 

[XSLeo]

AndreXS, A cam chain adjustment won't hurt.
Generally when you have symptoms like yours you want to eliminate the mechanical adjustments first. Easy to do and might fix it.
Do the steps in order.
Adjust cam chain
Adjust valves
Now if you have points, set the gaps and timing
If you have a TCI, then just check timing
With both ignitions check timing at idle and at 3000 rpms.
These things should be done every oil change or at least every other oil change as part of regular maintainance.
Now if the problem still exists you need to be a bit more specific. Describe what happens when it cuts out. Does it just quit, or stumble, sputter or just what happens.
Does it start ok, run ok.
A better description of the bike will help us help you. Your description of "81 electric ignition bob" sounds like you have an 81 that was bobbed, yet still has the stock electronic ignition. But that's just guessing.
With the stock TCI it controls the spark by turning power on and off through the coil. When you turn the kill switch off you are turning the power through the coil off. If the engine was in the right place so the ignition has the power through the coil "on" when you turn the kill switch off you are turning ther power flow off causing the coil to spark. This spark will occur out of time to when the engine is running, so you get the explosion in the exhaust or a puff or cough out of the intake.
You usually won't hear the exhaust unless your carbs are running way rich and leaving excess fuel in the exhaust.
I might suggest going through your wiring harness, start at one end of the bike working toward the other and check every connection for clean and tight. A dab of dialectric grease will help keep them clean. Espeacilly the grounds. Check the engine to frame mounts. The engimne grounds through them to the frame. If you don't have at least one with clean metal to metal, no paint or powder coat, you won't have a good engine ground and this will lead to lots of problems. A dab of dialectric grease here is a good oidea too.
Leo

 

[AndreXS]

Thanks XSLeo. My bike is a 81 bobber with electric TCI stock ignition. I have adjusted the valves but not the cam chain, do xs650s have adjustable cam chains. The bike is running rich and there is some residue in the pipes. Sometimes the bike runs fine, and the other times both just after starting and often untill warm, but sometimes anytime, the engine just cuts out suddenly without any stumble or sputter, and the other times, but less often, I'll get the combustion in the exhaust pipe while it's running, at which time it may cut out after the loud pop(while running) or sometimes it may not cut out after that pop and continue to run fine. What seems consistent though is that my bike, which is kick only, will not start again after the engine cuts out (suddenly) unless I push the kill switch and get the load pop in the exhaust pipe, I know because I tried to kick it many times in similar situations and found that it only starts up, and right away, after the exhaust pipe seems cleared by hitting the kill switch and getting pop.
I have discover the brush problems, and I used to get the cutting out more often before I changed the alt. brushes.
Thanks AC

 

[XSLeo]

Yes, the cam chain is adjustable. Your repair manual tells how.
Being bobbed it may have had the wiring harness modified. This may be part of the problem. I might suggest going through your harness, start at one end of the bike and work toward the other and check each and every connection for clean and tight, especially the grounds.
The TCI has a protective circuit that under certain circumstances it shuts the TCI box off the protect it. When this happens you need to reset the box by turning it off and back on. Low or intermittenet voltage is one of these.
You mentioned replacing the brushes. I assume you had charging issues. What is your battery voltage at idle, 2500 rpms and 5000 rpms?
If you voltage is low the TCI won't like it much. One of the many sysmtoms of low voltage is the TCI acting up. One cylinder cuts out, no timing advance are common along with just quitting.
Leo

 

[MFJustin]

Well unfortunately it looks like I'm back to square one, or at least a little further along the line with a plan of attack this time.

After riding the bike for awhile the smoke from the right side tail pipe finally went away, bike felt good....noticed that a lot of the smaller issues that I had before the original incident of the bike cutting off and the installation of the Pamco went away. No more popping from the exhaust when off the throttle, etc. etc.

Anyways I was riding to work one day and going up a slight incline and for whatever reason I felt like the bike just didn't have as much punch as it normally would have even when I gave it some more throttle. Next thing I know it started doing the same exact thing it did when it cut off before, started lurching like it was going to stall out almost as though it was running out of juice. I managed to get it to the side of the road and it just died right there.

I'm going to go through all of the usual suspects again this time from scratch. I pulled the plugs and the right cylinder plug was fouled but there was not liquid oil on it as there was before when it was still smoking. I'm going to drain the oil later, I did an oil change recently and I have a feeling I'm going to discover a very low amount of oil, possibly showing that this entire time it was burning the oil up even with fresh oil in it.

I know a lot of people will say that I should check this and that before I pull the motor but for those of you that have viewed this thread from the beginning and have provided me with excellent advice, we've pretty much already been over all of the known suspects that can be checked without pulling the motor. I'm actually looking forward to getting this thing opened up and taking a look, I plan on a few upgrades here and there to keep me busy over the winter....still toying with the idea of a big bore kit or not.

Anyways just wanted to update this thread........I'll post up some more info once I get it taken apart and can really get a look inside.

 

[pamcopete]

MFJustin,

Well, I understand your thoughts and perhaps tearing the engine down will be the answer, but you would not be the first person to tear down and rebuild an engine and end up with the same problem because they did not identify the problem before the tear down so the rebuild included the offending part.

 

[MFJustin]

MFJustin,

Well, I understand your thoughts and perhaps tearing the engine down will be the answer, but you would not be the first person to tear down and rebuild an engine and end up with the same problem because they did not identify the problem before the tear down so the rebuild included the offending part.

Pete I definitely understand the logic behind that, I suppose I'm just looking for something to do or rather something that jumps out and says "I'm the problem! Fix me!".

I've followed all of the excellent advice in this thread and got the bike back up and running again after it cut off on me the last time. After going through all of the recommendations in this thread, it seemed everything was back up and operational, I rode the bike all over the place with no major hiccups. Then all of a sudden out of nowhere it cuts off on me again and refuses to start. It's almost as if I've done a complete loop and I'm back at the start with the same problem.

I suppose I have no qualms with working backwards, I've got the time to take it apart and poke around inside for a bit even if I dont see anything glaringly wrong. Being the bike is still relatively new to me, I'm tempted to crack it open just to see the condition of everything inside just because I can. Tomorrow though I will retrace all of the information in this thread from start to finish to see if this time around I can in fact isolate a problem.

 

[peanut]

After going through all of the recommendations in this thread, it seemed everything was back up and operational, I rode the bike all over the place with no major hiccups. Then all of a sudden out of nowhere it cuts off on me again and refuses to start. It's almost as if I've done a complete loop and I'm back at the start with the same problem.

.

if there was anything seriously wrong with the engine I doubt that it would have run as well as you state it did .

As far as I recall the previous problem was a leaking head gasket with oil leaking from the crankcase to one cylinder

The HG leak may have occurred again but this is very easily checked by doing a compression test. A compression test will tell you everything about the health of your engine provided you know how to conduct it properly and to read the results. If the engine has a fault the compression test will tell you what it is without stripping it

If you strip the engine and do not find a fault what are you going to do then?

You need to test everything and establish that the fuel delivery and ignition system is not at fault first

 

[pamcopete]

MFJustin,

I would agree with peanut except I would suggest that you do a cylinder leak down test which is more revealing. Harbor Freight just happens to have a sale on their leak down tester for $39.99. Although you may have read unfavorable reviews of this tool, I have one and it is a very good tool, so I think that the negative reports are due to operator error. You don't need a big compressor if your technique is right.

http://www.harborfreight.com/catalogsearch/result?q=cylinder leak down test

 

[peanut]

thats a real bargain Pete. I hadn't realised that portable leakdown test equipment was available to the diy'er so cheaply nowadays !

On my Christmas list for sure....together with a vacuum smoke tester for my car and a new set of ratchet wrenches and ....................

 

[pamcopete]

OK. Here is a technique to do a leak down test without a leak down tester...

1. You will need a compressor with a built in adjustable regulator.

2. Allow the compressor to run until it has reached its maximum pressure, typically 100 PSI.
3. Adjust the regulator for a pressure of 50 PSI.
4. Get an adapter hose that will fit into a spark plug hole on one end and your compressor hose coupler on the other.

5. Warm up the engine, shut it off and remove a spark plug.
6. Rotate the engine to TDC on the compression stroke.
7. Screw the adapter hose into the spark plug hole.
8. With the compressor adjusted regulator adjusted for 50 PSI, quickly connect the adapter hose to the hose coupler from the compressor.
9. Note the pressure reading on the regulator gage.

Note: You must record the regulator pressure before the air tank pressure goes below 50 PSI.
In the example shown, the regulator pressure is 35 PSI, so the percent leak down is 50-35 = 15 / 50 = 30%. Generally, a leak down percentage up to 40% is acceptable. I did this test again with a warmed up engine and got a regulator pressure of 40 PSI for a leak down % of 20%, so warming up the engine is important. However, doing a cold leak down followed by a warm leak down can provide a better picture of the cylinders condition.

 

[peanut]

Well unfortunately it looks like I'm back to square one,

I was riding to work one day and going up a slight incline and for whatever reason I felt like the bike just didn't have as much punch as it normally would have even when I gave it some more throttle. Next thing I know it started doing the same exact thing it did when it cut off before, started lurching like it was going to stall out almost as though it was running out of juice. I managed to get it to the side of the road and it just died right there.
.

I think there is clue here . The bike was running fine until you started riding uphill ! then you apparently got all the same old symptoms back again.

I've reread the whole thread again to build up a complete picture and it would seem that you have several issues here perhaps unrelated.

We assume that the loss of compression issue is solved with the head retorque and you have confirmed with a compression test ?

We assume that you have solved the leaky petcock and filter issues you were having yes ?

What do the new plug electodes look like now ? they should a nice medium honey colour if the air/fuel mix is about right. To use the plugs to diagnose properly you should clean the plugs then run the bike somewhere at wide open throttle then cut the motor and coast to a stop so that a possible faulty idle mixture does not contaminate the electodes.
A picture of your plugs would be usefull

Does it still backfire ? if so inlet or exhaust .

Incidentally does your bike have the vacuum petcocks fitted ?

 

[MFJustin]

Unfortunately I do not have a compressor (yet anyways) so I cannot do a leak down test myself.

When I first got the bike back up and running and after the Pamco installation I took it to a friend of mine who is a mechanic so he could help me time it since I couldn't find my timing light at the time. This was all towards the start of this thread after I finally got the bike fired up. Anyways we did a compression test and determined that the left cylinder was reading around 150 and the right cylinder was reading around 90. He hooked it up to a leak down tester and after playing with it for a few minutes we determined that there was a small amount of air leaking out of the right cylinder exhaust pipe. At the time the bike was also smoking pretty badly from the right exhaust pipe. Following the excellent advice in this thread I went through all the motions and tightened the head bolts up as 5twins recommended and the smoke from the exhaust eventually went away. Also around this time I did a compression test again and it seemed as though the compression was back up to normal on the right cylinder.

I just want to throw this out there to see what you guys might think considering that this is new to me. The first time the bike died out on me weeks ago, I drained the oil and barely any oil drained out from both plugs. I figured that low oil level had caused something internally to overheat and fail. Then we went through the steps listed in this thread already and I got the bike back up and running again. Last night when I was in the garage working on it I drained the oil once again and again barely any oil drained out. I mean if this bike is supposed to take 2 quarts of oil, I understand not all of it will come out if the bike is cold but this just seemed significantly low for what I was expecting. Is it entirely possible that a bad piston ring caused that much oil to leak by and all of that smoking was a result. Running low on oil means no more blow-by which makes me think I corrected the problem when theres no more smoke coming from the tailpipe?

Blahhh its just so confusing and I feel like I've gone over all of the usual suspects with no real solution. Valve clearance was within spec, took the carbs apart and they were squeaky clean...nothing that I noticed being wrong or out of place. Ignition system is a brand new Pamco as detailed at the start of this thread. When the bike died on me just recently once I got it home I pulled the plugs. The right cylinder plug was most definitely fouled and the left cylinder plug looked ok. I replaced both plugs with brand spanking new spares I had laying around and there was zero change.

 

[MFJustin]

I think there is clue here . The bike was running fine until you started riding uphill ! then you apparently got all the same old symptoms back again.

I couldn't say it was solely based on riding uphill. I couldn't even say where it ended up dying on me was really a hill, it was just more of an incline than a regular flat highway. Only reason that I bring that up is because right around my house is VERY hilly and the bike would shoot up and down it no problems after I got it fixed again. The only reason the incline had any significance was just because I noticed it seemed like I was losing power and I went "oh crap" and next thing you know its cutting off on me.

I've reread the whole thread again to build up a complete picture and it would seem that you have several issues here perhaps unrelated.

We assume that the loss of compression issue is solved with the head retorque and you have confirmed with a compression test ?

After the bike cut off on me the first time, left cylinder compression read about 150; right cylinder compression read about 90. After torquing the head down and riding it for a bit, I rechecked the compression and it did seem as though numbers were back to normal. Both cylinders read, from what I recall, roughly the same.

We assume that you have solved the leaky petcock and filter issues you were having yes ?

I put in brand new fuel line from both carbs to petcocks and did not put inline fuel filters back in just because. Before though, I put in new fuel line with brand new inline fuel filters and it would still leak out of the left side fuel line when the right side petcock was the only one open. This is something that I never noticed before the bike cut off the first time. It was almost as if the carbs were overflowing with fuel and it was coming out the higher side. This is another one of those random symptoms that came up that had me scratching me had because it had never done that before the bike had cut off the first time.

What do the new plug electodes look like now ? they should a nice medium honey colour if the air/fuel mix is about right. To use the plugs to diagnose properly you should clean the plugs then run the bike somewhere at wide open throttle then cut the motor and coast to a stop so that a possible faulty idle mixture does not contaminate the electodes.
A picture of your plugs would be usefull

When it died the second time I pulled the plugs when I got it home. Left side plugged looked ok, the right cylinder plug had deposits on it and looked like it had fouled out. The difference though was that now there was no liquid oil on it as there was before, and I pulled the right cylinder exhaust pipe to look inside and it no longer was coated in oil. I will take a picture of my plugs and post it up.


Does it still backfire ? if so inlet or exhaust .

When I first got it running again it ran great minus the extreme smoking. There was no backfiring or popping from the exhaust at all. Towards the end of its run though before it died again I noticed that the popping was back, mostly on deceleration or when I would be riding down a hill and was not on the throttle at all.

Incidentally does your bike have the vacuum petcocks fitted ?
No vacuum petcocks. Gravity fed.

Peanut I see what you are saying though, its like I do have multiple problems going on at once that are hopefully unrelated. Its just rather fishy to me because I noticed none of these problems before the bike cut off on me the first time and then afterwards they all pop up. Leaking from the left side fuel filter, oil on the plugs and it smoking from the right cylinder exhaust pretty bad. Unfortunately though, when the bike died the first time I assumed it was spark related and ran out and bought the Pamco and installed it. It seems that now considering that the bike died on me again that the ignition/spark wasn't actually the problem and that its something else.

10--char