Well, just a quick easy check you have not yet mentioned.
While it is running can you check the lft cyl timing with a timing light ?
While it is running can you check the lft cyl timing with a timing light ?
-
Enjoy XS650.com? Consider making a donation to help support the site.
XS650.com receives a small share of sales from some links on this page, but direct donations have a much greater impact on keeping this site going.
Mailman’s XS2 a full on restoration
- Thread starter Mailman
- Start date
When you checked compression did you have the valve covers off?
You might want to remove the cable going to the decompressor and see if that makes a difference.
You might want to remove the cable going to the decompressor and see if that makes a difference.
I have not done that , but I sure could. Thanks
Valve covers were on, and I did think of the decompression unit, the cable is backed all the way off.
Hey, Bob!
It's times like this when I like having 2 independent carbs.
While it's running, right fingers on the right throttle, left fingers on the left throttle,
Hold enuff rpm with the right throttle,
Manipulate the left throttle, various positions, including WOT,
See if the left tries to fire.
If so, then note when/where it does and doesn't.
If not, a bit more serious...
It's times like this when I like having 2 independent carbs.
While it's running, right fingers on the right throttle, left fingers on the left throttle,
Hold enuff rpm with the right throttle,
Manipulate the left throttle, various positions, including WOT,
See if the left tries to fire.
If so, then note when/where it does and doesn't.
If not, a bit more serious...
You know you have spark. What you don't know for sure is that you have spark at the left cylinder on the compression stroke. I would
put a mark on the rotor and watch it with the timing light. It should appear at two places 180 degrees from each other.
put a mark on the rotor and watch it with the timing light. It should appear at two places 180 degrees from each other.
Ok I’ve just been running the bike some more. Checked the timing light on both cylinders. On the right cylinder it’s rock steady firing right on the F Mark. I’ve come to realize that the left cylinder will start to fire when the RPM’s start to climb, like around 1500 and above.
When the timing light is on the left cylinder wire. The spark is MOSTLY steady, sometimes however it’s jumping all over, firing way before TDC. When I see this random flashes, the bike always misses.
2M I totally forgot I could work these carbs independently, I’m gonna give that a go.
GLJ , I’ll take a look at that rotor too.
When the timing light is on the left cylinder wire. The spark is MOSTLY steady, sometimes however it’s jumping all over, firing way before TDC. When I see this random flashes, the bike always misses.
2M I totally forgot I could work these carbs independently, I’m gonna give that a go.
GLJ , I’ll take a look at that rotor too.
When I first started my engine mine acted a lot like that. After getting carbs closer in balance that seemed to calm down.
Last edited:
...so is the left plug wet?
Well this is all kinda moot now.... just read where Bob said it'll run on both above 1500. That tells us both magnets are there.
EDIT: Sorry, head was up and locked...
In the missing magnet scenario, either lead would fire the right cyl..... or left if the other magnet was missing.....'cause in a dual coil, both leads fire.
Correct. on compression stroke on one cyl.... and at valve overlap on the other.... every 360°. If one magnet was missing and it was firing every 720°, only the cyl. coming up on compression would start a fire.
EDIT: Sorry, head was up and locked...
In the missing magnet scenario, either lead would fire the right cyl..... or left if the other magnet was missing.....'cause in a dual coil, both leads fire.
Last edited:
Ok, I’m done for the day. All I know for sure is the left cylinder is still running crappy. It absolutely will not idle.
2M , I tried what you suggested about operating the two carbs independently. I had the best success with that.
Without even touching the right carb, if I hold the throttle open more on the left carb, it will more or less run steady.
But I would have to have the left carb throttle stop cranked way more open than the right in order for it to run.
Would this be an indicator that my idle circuit is not operating properly on my left carb? Perhaps a blockage?
I did not spray carb cleaner through all the passageways when I had my carbs apart, I was concentrating on my floats.
Jim, I think I will try swapping spark plug leads tomorrow just for the heck of it, to see if anything is different.
GLJ, I did put a mark on my ignition rotor as you suggested and it did just what you said it should, the timing light lit the mark up at exactly 180 degrees from each other.
Moabite, yes the left plug was wet with gas, I didn’t check it again at the end of the day , because I did get the left cylinder running somewhat.
So, I think , maybe, I’m a little further along than yesterday. I’ve checked a lot of stuff, but I’m still not sure what the problem is. The left cylinder can be made to run, just not very well. I don’t believe it is firing every time it is supposed to, and not at all at idle speed.
Also, what the heck does this tell me? I was running mostly with the petcocks shut off, I would fill the bowls up, start it up and mess with it until the bowls start to run down, then just before it really starves, the running seems to get better and the engine speeds up, I would open the petcocks and the engine slows right down and back to running crappy.
I know, lots of questions. Tuning and trouble shooting never have been my strong suit. I can be logical and work through things, but tuning is almost an art.
2M , I tried what you suggested about operating the two carbs independently. I had the best success with that.
Without even touching the right carb, if I hold the throttle open more on the left carb, it will more or less run steady.
But I would have to have the left carb throttle stop cranked way more open than the right in order for it to run.
Would this be an indicator that my idle circuit is not operating properly on my left carb? Perhaps a blockage?
I did not spray carb cleaner through all the passageways when I had my carbs apart, I was concentrating on my floats.
Jim, I think I will try swapping spark plug leads tomorrow just for the heck of it, to see if anything is different.
GLJ, I did put a mark on my ignition rotor as you suggested and it did just what you said it should, the timing light lit the mark up at exactly 180 degrees from each other.
Moabite, yes the left plug was wet with gas, I didn’t check it again at the end of the day , because I did get the left cylinder running somewhat.
So, I think , maybe, I’m a little further along than yesterday. I’ve checked a lot of stuff, but I’m still not sure what the problem is. The left cylinder can be made to run, just not very well. I don’t believe it is firing every time it is supposed to, and not at all at idle speed.
Also, what the heck does this tell me? I was running mostly with the petcocks shut off, I would fill the bowls up, start it up and mess with it until the bowls start to run down, then just before it really starves, the running seems to get better and the engine speeds up, I would open the petcocks and the engine slows right down and back to running crappy.
I know, lots of questions. Tuning and trouble shooting never have been my strong suit. I can be logical and work through things, but tuning is almost an art.
Was that at idle?
Does sound like carb problem.
Tuning is fun ! trouble shooting ? for me not so much.
You will get to the tuning ! You will enjoy it then for sure ! Till next time
So, this thread has been going on for so long, I don't even remember - you installed a Pamco? If so, it's dual output coil would (should) fire both plugs at the same time, every time. The only thing that could cause a poor or bad spark on one side would be that side's plug, plug cap, or plug wire. So yes, switch the wires side to side to see if the bad running follows. If it does then you'll need to check (test) the plug cap, the cap's connection to the plug wire, and the plug wire's connection to the coil.
Swap plug wire so you can rule that out.
Sounds like carb problem. Your homework for tonight is to read the carb guide.
Last question is the slide in the left carb bouncing more than the right carb?
Haha! You don’t remember everything that’s happened in my 13 month long thread?
Yes, new Pamco with E- Advance, new dual output coil, new wires , new NGK plug caps, and new plugs. All professionally installed ( by me) Yeah, tomorrow’s another day. More investigating to come.
