Trouble shooting help please.

1982 seca 650 RJ.

Prior to carb clean. Hard starting, wouldn't hold idle, okay constitant power.

Cleaned carbs, clunk test and spray out of enrichment jets, set floats for fuel within 3mm of bowl lip, bench synched, synched on bike with sticks. Started up nicely on first go round. Idled, etc. Color tune seemed to have no real effect when turning idle mixture screw until well out. (like take the screw out out). Color was blue. Screwing in to less then 2 turns out lugged motor. All set to orginal precleaning settings of 3 1/4 to 3/12 out.

Valve clearances adjusted to with in specs (three were out (2 and 4 intake and 3 exhaust) and are now in)

Went for a test run and seemed okay.

Now has the following problems: Stumbles at the line. Power is intermittent (like some one occasionally kicks me in the butt as I ride at constant throttle (say at 50 MPH). Won't keep idle and/or hangs idle high. So when it won't hold idle I turn the idle screw to make it idle faster, then when that is better, some time later it will idle at a to high speed after a run down the road.

Bike seems to have little change (some) when I pull the lead to plug 1 or 4, but I can feel them shock me. Pulling 2 or 3 and the bike dies immediately.

The last part says to me that I may have an ignition problem, but don't know where to start with that one.

Is there an easy way to confirm weak or intermittent spark. Can I simply switch coils some how to see if one of them is on the fritz. Where else might I be looking.

I believe 1 and 4 and 2 and 3 essentially fire by the same circuits, but not sure I have those numbers correct.

Hopefully, there is enough here for someone to say, "oh I had that problem check the spitzer valve and all will be good" but if not, fire away questions.

Thanks,

Ken

 

You have to eliminate any AIR Leaks spoiling the Combustion Mixtures.
The Manifolds have to be Air Tight at:
Where they connect to the Head
Where they connect to the Carbs.

No Change in ColorTuning indicates too much Air is happening.
Find and Plug the Leaks.
Re-Colortune:
Turn the Mixture Screw OUT s-l-o-w-l-y ...
Get it to become Blue.
Keep turning it Out ... micro-adjusting ... like moving to the next second indicator on a watch ... a few seconds until you find the Back-side of where its Blue.
That's where it needs to be.

 

You are correct: 2&3 fire together from one coil, and 1&4 fire together from the other coil.

Since you have a Colortune plug, you can certainly use it to verify whether 1&4 are getting good spark.

 

I agree with Rick. You should be able to get a nice yellow flame and work back toward blue. It's one of 3 things:

1 - air leak
2 - carbs not fully clean (or floats too low!).
3 - cylinder(s) misfiring so you've got the throttle too far open to get the yellow flame.

As SQLguy pointed out, you should be able to see with your colortune plug if they're firing.

 

Okay, I went out and played with it some. I tried the propane torch trick around the boots (between carbs and cylinders) and got no reaction any where.

Checked with the color tune an was getting spark in 1 and 4. 4 gave no combustion. 1 gave combustion in blue, and on reving a little, I got some exhaust poping (back fire). Nothing I did to four gave me anything with the color tune. When I pulled the plug on 4 after having the color tune in 1, I found it black. Cleaned it up and lowered the mixture. It is still not fireing and I smell raw gas smell in the right side exhaust not the left (smells like combustion products the entire time.).

I believe the problem is in four, but don't understand why spark + fuel isn't equaling bang...

Didn't recheck float hight, but will tomorrow.

 

Until you get #4 firing you won't be able to colortune the others.

Probably going to need to re-sync it too.

If you haven't done a compression test that might be in order too.

 

Next step should be a compression check. If you've got valve or ring problems you can waste a lot of time chasing your tail with the carburetors.

 

Compression check, followed by being sure you don't have an igniton problem. (Maybe swap coils) THEN mess with the carbs.

 

If the number 4 plug is wet, and low or no compression, I would think a valve. Sometimes they get carboned up, or a small piece of dirt in the seat and won't allow enough compression to fire the air/fuel mixture.

I would defiantly do a compression test - only takes a few minutes. Then do a leak down on any low cylinders. (anything below 100)

 

you may have already checked but, if the end of your
plug wire is loose in the cap, you'll still get some spark and will
definitly get a shock.

i over trimmed my# 1 wire and can tell when it pulls out a bit-poor performance and a small shock as i reach down and push/twist it
back in. also cracks it the coil bodies or wires can cause spark to
leap out to the nearet ground-like your hand if you touch it.

as for the rest +1 from everyones advice.

good luck

ron

 

Okay, I checked the fuel levels again and 2 and 4 are a bit high and 1 and 3 a bit low. I will correct them first and try and borrow a compression tester from a friend just incase.

Can I change the levels with the cars on the bike? I adjusted them on the bench, but I guess there was a problem since they are now not in specs. If I can get a driver in there (I have an angled one) is there an issue with dropping the bowls with the carbs on the bike?)

Thanks,

 

I don't think that its possible.
Never thought about doing it like that.

I think you should pull them and adjust all four until you have them perfect.

 

After reading this, you might have a bad coil, my opinion.
Just swing by my house and I'll hook you up !!

 

"When I pulled the plug on 4 after having the color tune in 1, I found it black."
so it is firing a little, that's why it black
is the enrichment plunger ALL the way down ?
did you have the plunger out, is the spring any good ?
swap the plugs around, maybe you have a bad plug
i kind of doubt your going to adjust the floats on the bike

 

I've done this, and I prefer it since, IMO, the service fuel method is the best way to know that your floats are set correctly.

It's a real pain to get those Phillips screws out (and also back in) with the rack on the bike, though. For mine, I replaced the bowl screws with stainless Allen screws. That makes it, not easy, but at least easier. Especially if you only need to adjust one float, being able to drop the bowl on the bike is much faster than pulling and reinstalling the whole rack.

 

I had a problem with my 83 xj 750 jerking and hesitating. Cleaned carbs with no change. Noticed plugs were carbonized(black) and wet from fuel. I had to keep the throttle open to keep an idle and ride the bike. I changed the plugs, but instead of just popping them in I first gapped the plugs according to specs. This gap is a lot closer(.23) Now she runs like a champ.

 

Okay, I finally found some time to pull the carbs again. Spent quite a bit of time adjusting the levels again so that all are right about where the head of the bowl screws meet the bowl. Seemed like they would be good, then I'd adjust the ones out of spec and the "good ones" would be off. Also noticed that they were very sensitive to adjustments like the smallest changes I could do seemed to send them from barely any gas to overflowing. Started tapping them all upon refill and this seemed to help.

Reinstalled on the bike an she started and raced toward the red line. Shut her down and slapped my forehead and remembered that I had adjusted them all the last time on the bike and did not reset them.

So pulled them again and bench synced them again and reset all of the idle mixture screws to 2 1/2 out.

Loaded her up again and fired her up with full enrichment. Ran her for about two minutes and adjusted the idle and was able to lower off full enrich. Checked the pipes an 1 - 3 were hot, but 4 was stone cold...

Tomorrow, I will check the level in 4 (again) on the bike (and the rest while I'm at it) and replace the plugs (just in case).

I knew there was a reason I put off cleaning the carbs, even though I knew they needed it...

 

The Bike cannot be Fine-Tuned until the Carbs are perfectly clean.
The Diaphragm Piston Bores de-oxidized and polished.
Emulsion Tubes removed, cleaned and port-checked.

Minimum.

 

Did that, been there. I pulled them completely apart, etc. Rick, this has just been a frustration (and really the first one in all that I have done). I will eventually beat this problem.