Dead Cylinder to not starting

[Owen8]

Hi Everyone,

This is my first post and my first bike so bear with me ,

I recently got a 1978 XS650 and have been slowly working on it for about 5 months now.

I've completely rewired the bike with a Wire Harness from Mikes Xs, I've got a brand new Battery (that should have plenty of power to produce a large enough spark), Complete Carb rebuild and Clean, and has recently been timed.

I recently got it running and it was running perfectly for about 3-4 days until one of the cylinders went dead at low RPM. Its worth noting that this didn't start happening until I started messing with the Spark plugs. After looking around for awhile I noticed one of my coils was cracked and was red hot. I bought a new coil and reassembled everything yet when I went to kick over the bike it still wouldn't turn over. I've read my carbs could be the issue but I recently did a full rebuild and the bike was running good until I got to fooling with the plugs.

Any advice on where to start would help loads!

Thank yall

 

[gggGary]

Welcome aboard!
Have you charged the battery?
If that does it, you need to see if the charging system is working.
On a points bike leaving the ignition on with the motor not running will burn out a coil (and drain the battery pretty good.
Drain the float bowls into a pan any dirt?

each carb should drain about an 1/8th cup into the pan.

 

[Jim]

Yes, welcome aboard!
If the problem started at the same time you started swapping plugs, try putting the originals back in? I mean, could just be a fluke that something else broke at the same time. Or it could be the plugs.... or the plugs and something else broke....

At any rate, I'd start there.

 

[cycleranger]

Recheck all the wiring connections to the coils etc.

 

[Owen8]

Yes, welcome aboard!
If the problem started at the same time you started swapping plugs, try putting the originals back in? I mean, could just be a fluke that something else broke at the same time. Or it could be the plugs.... or the plugs and something else broke....

At any rate, I'd start there.

Ya I switched back to my old plugs with the new coil. I'm pretty certain my old coil is toast because its cracked pretty bad and was red hot after a ride that I had on one cylinder. when I did switch back to my old plugs I ran into the same one cylinder firing problem.

 

[Owen8]

Recheck all the wiring connections to the coils etc.

Welcome aboard!
Have you charged the battery?
If that does it, you need to see if the charging system is working.
On a points bike leaving the ignition on with the motor not running will burn out a coil (and drain the battery pretty good.
Drain the float bowls into a pan any dirt?
View attachment 331887
each carb should drain about an 1/8th cup into the pan.

Im pretty sure Ive left the keys in the ignition once... whoops... ill start with that... also (if this helps any) my bike doesn't have points its this weird electric timing system that is extremely similar to the one that Rawhide makes for this bike. I didnt install it, it was on the bike when I bought it, so im not sure who makes it.

 

[Its been a long time]

Im pretty sure Ive left the keys in the ignition once... whoops... ill start with that... also (if this helps any) my bike doesn't have points its this weird electric timing system that is extremely similar to the one that Rawhide makes for this bike. I didnt install it, it was on the bike when I bought it, so im not sure who makes it.

If the ignition coil got hot enough to crack then you could have damaged the electronic ignition system. That would be my thinking. Going back to basics, do the plugs fire outside the cylinder? (Plugs must be grounded of course).

I seem to remember the ignition sold by Rawhide bears a resemblance to the ones sold by Tytronic. They're Chinese, I doubt you'll get any support from them? Try searching here and you'll find more information about that.

 

[Paul Sutton]

You mention "coils" so I assume it is the points ignition. It would be worth checking to see if one set of points has slipped and is permanently closed or shorted - This would kill one cylinder and overheat the coil.

Good Luck.

 

[Melnic]

78 shipped new with points (at least mine did) simply remove the side cover plate on the left side of the cylinder (middle of the 3 plates) and you will see points or a pickup. take and post pic.

Divide and conquire
Spark, Fuel, Compression

What plugs did you have before and what plugs did you put in (what is brand/number of plug?)

Find out if you have spark first.
Pull both plugs and ground them against the engine.
Look for spark while pushing starter button.
Helps to be in garage w/ lights out or at least in the shade.
You can wrap something around plug to create more shade if you are outside like using toilet paper or paper towl core or just wrap some card board and tape it up.

If you have spark, you might be able to move to fuel. but just cause you have spark does not mean the timing is not out of wack. If you move to fuel and find you have fuel then go back to look at timing. I've had bad timing cause really bad misfires.

There are ways to look to see if fuel is getting there by looking for a wet plug w/ the choke on.

 

[Adamc]

A warm welcome from Wales.
Looking forward to your bikes development.
Ads.

 

[Owen8]

Hi everyone!

Sorry for taking so long to respond I’ve been fooling with this thing for quite some time now. Long story short is it’s running! I took apart the carbs again after making sure all my electronic/spark components worked. (Fun fact that I heard from a friend, is that if you don’t have your spark plugs grounded when testing them there is a chance that signal goes back into the coil and fry’s it!) probably something you all knew but as a learning mechanic I did not. anyways I’ve run into a new problem! There is a constant ticking when riding the bike. I’ve done some research and people say it’s valve chatter. any thoughts?

Thank you all for the comments and support!

Owen

 

[Owen8]

Also I have to mention this as well. My bike when I bought it didn’t come with the original points ignition system! It’s an electric ignition system very similar to the one rawhide makes.

This is the exact name for anyone that’s wondering. (Mine is very similar but not the same)

ELECTRONIC IGNITION FOR 1970-1984 YAMAHA XS650 - DUAL PICKUP​

it’s my first bike and my first Facebook marketplace vehicle purchase and there are many mistakes I have learned to never make again when buying a bike.

 

[nj1639]

Ticking could be a valve, could be the cam chain tensioner......could be a washer on a loose bolt somewhere.
I used a mechanics stethoscope (screwdriver) on a tick I had and narrowed it down to the cam chain tensioner.
A mild adjustment and then a revisit to the valves to check their gap and alls good.
Good luck on your search.

 

[Its been a long time]

Also I have to mention this as well. My bike when I bought it didn’t come with the original points ignition system! It’s an electric ignition system very similar to the one rawhide makes.

This is the exact name for anyone that’s wondering. (Mine is very similar but not the same)

ELECTRONIC IGNITION FOR 1970-1984 YAMAHA XS650 - DUAL PICKUP​

it’s my first bike and my first Facebook marketplace vehicle purchase and there are many mistakes I have learned to never make again when buying a bike.

Does it look like one of these?

http://www.tytronic.com/tytronic/products/7797124.html

 

[Owen8]

Does it look like one of these?

http://www.tytronic.com/tytronic/products/7797124.html

Yes it does! Thank you for finding that!

 

[Owen8]

Ticking could be a valve, could be the cam chain tensioner......could be a washer on a loose bolt somewhere.
I used a mechanics stethoscope (screwdriver) on a tick I had and narrowed it down to the cam chain tensioner.
A mild adjustment and then a revisit to the valves to check their gap and alls good.
Good luck on your search.

I’m certain it’s a valve now! A quick favor to ask, say you were trying to teach an elementary school kid how to adjust valves how would you go about it? I’ve looked online and I’ve seen a couple of videos but just want to hear from others on possibly an easier way to adjust them. I know I’m supposed to rotate the crank shaft in various positions and check with a feeler gauge but this is all very new to me. Any help/insight is much appreciated!

 

[nj1639]

There are some that will swear it one way and others that will curse it. A veritable can of worms.
With the valve covers off, plugs out and the round charging rotor cover off, I rotate the crank counterclockwise until it comes off a compression stroke and then feel for which valve and adjuster is loose enough to wiggle a smidge. I’ll insert the feeler for that valve, either exhaust or intake and see what it reads. If I’m on an exhaust I’ll try the .006. If it goes in I’ll try the next one of .007. If six fits and seven doesn’t then I’m done on that one. For intake I go with the .003. If 3 fits and 4 doesn’t then I’m done on that one too.
If adjustments have to be made it’s a matter of loosening the lock nut, turning the adjuster to the desired setting and then locking it down. Best to have a proper adjusting tool and three hands, one to hold the feeler, one to hold the adjuster and one to lock it down. You can cycle the engine again until that valve shows loose again and then recheck the gap.
Sometimes these two contact points, adjuster and valve stem, will wear over time and not hold the precise setting. See elephant foot adjusters, Virago adjusters, Porsche (?) adjusters
Turning the crank counter clockwise I use a breaker bar to attempt to slow the rollover after the compression stroke. I believe that is what and where the purists want for the adjusting, but I find it an almost impossibility to hold that spot.
Other opinions may vary and are welcome.
Some terminology may be off.
I’ll say when I do the valves I give myself plenty of time……
Oh, watch your torque specs when putting the covers back on. I’ve come across a couple over the years that the threaded studs have been stripped.

 

[gggGary]

With the spark plugs out or loose, remove the alternator cover at the left end of the crankshaft. Rotate the crank with a wrench, when you get to the TDC mark, the valve overlap on the cylinder not on compression will stop the cam and crank basically at TDC, fully on the cam base circle, perfect for valve setting work (what I do) the compression cylinder will have both valves loose, (you can wiggle them a bit. The valves on the other cylinder will feel tight. Check and set that loose pair as needed. Put the wrench on the crank nut, rotate crank one full turn to TDC again, the cam/valves that you just set will once again make a natural stop point, now check the second set of valves, done.

 

[Owen8]

Ok so I’ve adjusted them 3 times now. Will I always hear the valves just a little, is that normal? I’ve tried both .004 and .003 on the intakes and the .004 sounds loose and the .003 makes my bike rev super high. Any thoughts or comments?

 

[Kevin Werner]

2.8 mm will quiet it down. 4 mm and you will have that tick, tick, tick. I just purchased a feeler set with 2.5mm and 3 mm. 3mm not quite going in is quiet.