76 XS650 won't start after carb rebuild

[5twins]

Here's the regulator adjustment info from the factory shop manual. I "doctored" the diagram and added more info .....

When I finally got around to testing the charging output on my '78, I found it a bit low, maxing out at about 13.8 volts. When I checked the regulator, I found both gaps were off. Adjusting them to spec restored the proper charging output and I didn't even need to play with the adjustment screw.

 

[Vivianthebarbarian]

How about a picture(s) of the entire bike...love me some 76 models.

Here's the regulator adjustment info from the factory shop manual. I "doctored" the diagram and added more info .....

View attachment 220759

When I finally got around to testing the charging output on my '78, I found it a bit low, maxing out at about 13.8 volts. When I checked the regulator, I found both gaps were off. Adjusting them to spec restored the proper charging output and I didn't even need to play with the adjustment screw.

Thanks for this, I was trying to figure out how to adjust them. They were quite a bit off, hopefully this will help.

 

[Kevin Werner]

Thanks for this, I was trying to figure out how to adjust them. They were quite a bit off, hopefully this will help.

After setting core and contacts loosen #9 and adjust #10 until you have good charging at 2500-3500rpm. Roughly 14-14.4 v at the battery. There are specs for this but you need to be putting as much or more into the battery as your lights and ignition are taking out.

 

[Steve Brand]

You're gain'in on it!

Hi. I've read all the info you, 5twins and others have posted on on this topic. Great stuff. Many thanks. It's now printed off and waiting for the weekend to come around.

Question.....Has anyone ever seen or created a comprehensive trouble shooting guide / flowchart or similar on the subject "My engine won't fire up"

I'm in a similar situation with a '76c standard points machine. Currently working my way through what I think is a logical progression of work....checking and replacing stuff to get good spark..... going back and checking/cleaning (again) the carbs..... fitting new points....... Engine was running fine prior to the bike being renovated (I didn't muck about with the engine!), so how much could have gone wrong???.... But a comprehensive and logical guide on what should be done first, then second, then third, etc, would be a bonus, if such a thing exist?

 

[MaxPete]

Hi. I've read all the info you, 5twins and others have posted on on this topic. Great stuff. Many thanks. It's now printed off and waiting for the weekend to come around.

Question.....Has anyone ever seen or created a comprehensive trouble shooting guide / flowchart or similar on the subject "My engine won't fire up"

I'm in a similar situation with a '76c standard points machine. Currently working my way through what I think is a logical progression of work....checking and replacing stuff to get good spark..... going back and checking/cleaning (again) the carbs..... fitting new points....... Engine was running fine prior to the bike being renovated (I didn't muck about with the engine!), so how much could have gone wrong???.... But a comprehensive and logical guide on what should be done first, then second, then third, etc, would be a bonus, if such a thing exist?

My highschool auto shop teacher always said that all an engine in decent shape needs to start are:

• Spin (it must crank over sufficiently fast)
• Spark (assuming it is not a diesel)
• Spirit (i.e. fuel or some sort of combustible stuff sprayed or sucked into the combustion chamber).

So, the first things I would do are the simple ones (and yes, I know some of these are sort of duhhhhh....):

1. Check that the kill switch is in the "RUN" position
2. Check that the fuel petcock is turned to the "ON" or "RES" position (depending on the fuel level. If the tank is very low - use "RES" or "reserve" which means the petcock lever will point straight up)
3. Check that the enricher lever on the LH carburettor is pushed down (some people call this a choke - but it isn't really a choke but rather a special fuel flow circuit that introduces extra fuel into the intake to help with cold starting)
4. Check for a spark.

Oh - and one more thing: remove the fuel tank FIRST and make sure that the connectors to the ignition coils are all secure. Those old "bullet" connectors can get loose after 30-40+ years.

To check for a spark, follow these steps:

• remove either spark plug (and do not strip the threads when re-installing);
• lay the thick metal body of the plug firmly against the cylinder head;
• turn the garage lights off (so that any spark will be more visible);
• crank the engine.

If there is a visible spark, then you have a fueling problem and if there is no spark then you have an electrical problem (along, quite possibly, with a fueling problem).

You'd be amazed at how many people try to start an engine with the kill switch OFF or the fuel turned OFF - or no fuel in the tank. I've tried all of those things and I have consistently noted that the engine darned-well will NOT start - for some $%##@## reason.

Do all of that and report back - and we'll have a think about it.

Pete

 

[Jan_P]

Thinking out loud
It is not so simple make a flow chart since it is not obvious in most cases what is the cause
A weak spark can have the same symptoms as a overly rich mixture. And the ignition timing one factor.
The weak spark can have many causes charging --battery ---wiring -

The first rule is It is always the electrics .. Unless in warmer climate and parked with gas in carbs for long times.
I have had ca 5 carburetor faults in close to 40 years but virtually electric problems every year.
Perhaps my carburetors have not been adjusted perfectly but I have been able to ride every year.
More or less stock --If modified it is another situation .

So this year when I actually had a carburetor problem I was lost in space looking for electric faults as always was the
problem.before. to long.

I keep on saying this as a demented parrot Measure the charging voltage across the battery and battery Voltage Ignition off get that right ..
If that is down all kinds of problems can manifest itself. Some electronic ignitions can also be lost in space
Not because they are defective .But because the wrong Physics in.

With the right voltage there the next step is to look at the spark --plugs out and grounded
Work on that so both are the same.
If that checks out .
Try to start with the kick starter since the starter motor draws to much

Then listening for differences left right. It can start on one cylinder but keep it on a while In most cases the other cylinder will wake up And it can take 2 tanks even before it settles Running even .

If that dont happen the carburetors can need attenion but in my life a rare occasion as mentioned above

Then there is details ( again talking stock setup ) filters intake air leaks ignition timing etc etc the bike runs but not as good as it should.
Shooting in exhaust to late timing.
Kick back on kick starter to advanced.
I try to listen what it sounds like after a while one can notice the throttle response and knocking and notice when it is off
A strobe light is needed i think with points

 

[Steve Brand]

My highschool auto shop teacher always said that all an engine in decent shape needs to start are:

• Spin (it must crank over sufficiently fast)
• Spark (assuming it is not a diesel)
• Spirit (i.e. fuel or some sort of combustible stuff sprayed or sucked into the combustion chamber).

So, the first things I would do are the simple ones (and yes, I know some of these are sort of duhhhhh....):

1. Check that the kill switch is in the "RUN" position
2. Check that the fuel petcock is turned to the "ON" or "RES" position (depending on the fuel level. If the tank is very low - use "RES" or "reserve" which means the petcock lever will point straight up)
3. Check that the enricher lever on the LH carburettor is pushed down (some people call this a choke - but it isn't really a choke but rather a special fuel flow circuit that introduces extra fuel into the intake to help with cold starting)
4. Check for a spark.

Oh - and one more thing: remove the fuel tank FIRST and make sure that the connectors to the ignition coils are all secure. Those old "bullet" connectors can get loose after 30-40+ years.

To check for a spark, follow these steps:

• remove either spark plug (and do not strip the threads when re-installing);
• lay the thick metal body of the plug firmly against the cylinder head;
• turn the garage lights off (so that any spark will be more visible);
• crank the engine.

If there is a visible spark, then you have a fueling problem and if there is no spark then you have an electrical problem (along, quite possibly, with a fueling problem).

You'd be amazed at how many people try to start an engine with the kill switch OFF or the fuel turned OFF - or no fuel in the tank. I've tried all of those things and I have consistently noted that the engine darned-well will NOT start - for some $%##@## reason.

Do all of that and report back - and we'll have a think about it.

Pete

Thanks mate. Hopefully will have time to have a play with it this weekend. (Stock '76c US model with no modifications).

 

[jpdevol]

General troubleshooting thread started by INXS:

https://www.xs650.com/threads/troubleshooting.2736/

If specific sticking points or questions arise, ask away.....

 

[Steve Brand]

Thinking out loud
It is not so simple make a flow chart since it is not obvious in most cases what is the cause
A weak spark can have the same symptoms as a overly rich mixture. And the ignition timing one factor.
The weak spark can have many causes charging --battery ---wiring -

The first rule is It is always the electrics .. Unless in warmer climate and parked with gas in carbs for long times.
I have had ca 5 carburetor faults in close to 40 years but virtually electric problems every year.
Perhaps my carburetors have not been adjusted perfectly but I have been able to ride every year.
More or less stock --If modified it is another situation .

So this year when I actually had a carburetor problem I was lost in space looking for electric faults as always was the
problem.before. to long.

I keep on saying this as a demented parrot Measure the charging voltage across the battery and battery Voltage Ignition off get that right ..
If that is down all kinds of problems can manifest itself. Some electronic ignitions can also be lost in space
Not because they are defective .But because the wrong Physics in.

With the right voltage there the next step is to look at the spark --plugs out and grounded
Work on that so both are the same.
If that checks out .
Try to start with the kick starter since the starter motor draws to much

Then listening for differences left right. It can start on one cylinder but keep it on a while In most cases the other cylinder will wake up And it can take 2 tanks even before it settles Running even .

If that dont happen the carburetors can need attenion but in my life a rare occasion as mentioned above

Then there is details ( again talking stock setup ) filters intake air leaks ignition timing etc etc the bike runs but not as good as it should.
Shooting in exhaust to late timing.
Kick back on kick starter to advanced.
I try to listen what it sounds like after a while one can notice the throttle response and knocking and notice when it is off
A strobe light is needed i think with points

Thanks buddy. Yes, appreciate the difficulty of an all encompassing trouble shooting guide.....I was just hopeful....... Gonna play with it this weekend and follow logical steps - spark first, then fuel. After all, all it takes is spark, fuel and air.....don't it????... LOL

 

[Steve Brand]

General troubleshooting thread started by INXS:

https://www.xs650.com/threads/troubleshooting.2736/

If specific sticking points or questions arise, ask away.....

Thanks buddy. That's just the ticket! Gonna give it a bash this weekend.

By the way, just found (what I have now figured out to be) a PAMCO electronic ignition unit in a bag of assorted motorcycle bits I bought recently.....I think it is all present.....just three parts...the plate with the circuit board and connecing wires (red, black, green) attached...the magnetic rotor thing...and a large flat washer. Any ideas on where to find a detailed installation guide...nothing found on google so far :-(

 

[jpdevol]

Any ideas on where to find a detailed installation guide...nothing found on google so far :-(

How about a couple links with words from the man himself (PamcoPete)?
https://www.xs650.com/threads/boyer-and-pamco-ignition.46859/
https://www.xs650.com/threads/pamco-electronic-ignition-vs-high-output.749/

 

[Kevin Werner]

As mentioned above, electrics. You stated that the engine was not touched. Is that to say gas sat in the carbs the whole time? Was any wiring moved or "adjusted"? Did you change handlebars or headlight shell or play with either? These are things you need to review. At some point you will come to an "ah ha" moment. Good luck.

 

[Steve Brand]

As mentioned above, electrics. You stated that the engine was not touched. Is that to say gas sat in the carbs the whole time? Was any wiring moved or "adjusted"? Did you change handlebars or headlight shell or play with either? These are things you need to review. At some point you will come to an "ah ha" moment. Good luck.

LOL....Yes, all of the above (except retaining the fuel in carbs....). Engine out and bike stripped down to the bare frame, cleaned up/repainted and put back together again over the past 6 months. Got myself a good handle on a great range of troubleshooting tips now (thanks to all!). Hopefully she 'll be firing all cylinders again shortly