Carbs or Ignition??

[PRoberts317]

Im pretty new to this forum and motorcycling in general. Got my first bike this year, an 83 XS650 Heritage Special. When I got the bike everything was stock and I havent done much to it.

The bike wouldnt run when I bought it, then I had the carbs cleaned and rebuilt it ran wonderfully. At this point the bike wouldnt hold a charge, I thought I needed to replace the regulator/rectifier, then found out I actually needed to replace the charging rotor, so I changed them both at the same time.

*Now on to the real problem*

So at this point the bike is running around town pretty good for about 10 miles, then I decide to take her out on the highway for the first time. I run on the highway for about 10 miles, then about a mile after I get off the highway the engine starts to misfire a bit. At first it only misfires between 2500-3500 rpm (in all gears, including Neutral), but if I keep it about 3500 or so I can ride fine, up through all the gears. This continues until eventually I cant get the bike to revany higher than 2500 or 3000 rpm (top speed is about 35 or 40mph at 3000 rpm in 5th gear). The decline in performance was gradual although very quick, but not immediate (maybe a connection shook loose or something??)

My first thought was that maybe some crap from the old (original) air cleaners got stuck in the carbs, so i take the carbs off, clean them out (nothing in there I dont think... I'm sure there was nothing in the main fuel jet, pilot fuel jet or the tube with all the holes) and finally replaced the airbox with pod filters. NO CHANGE.

I talk to a few old gear-heads, mechanics, and the usual lot... Most advice pointed to my ignition coils. I ordered performance coils from Mikes XS, and to help add to my peace of mind I also ordered new NGK performance plugs, plug caps, and plug wires... Hooked everything up, still no change... Sputtering and puffing sound from the left cylinder and out the back end of the carb.

Checked out the resistance on the pickup coil (both wires are the same at about 770 ohms) I grab a timing light (I did mess with the timing plate a bit while I was exploring and replacing the alternator rotor), and when I hook the timing light up to the left-side spark plug wire the light fires sporratically and rarely, and furthermore I cant get the timing mark to come to where it's supposed to be. Then I hook the timing light up on the right-side plug wire and the light is firing away like its supposed to, but I still can't set the timing and I still cant figure out why my left side isn't firing correctly..

Today I switched the plug wires to see if the problem moved to the right side.. Still sounds like its comming from the left. NOW THE KICKER... I bypass everthing by wiring the ignition coil directly to the battery and its STILL THE SAME!!

It has to be my carbs right??? Someone give me some advice.. I feel like I've done everything

(Also checked the cam chain and it's fine)

 

[PRoberts317]

The tank is pretty damn clean inside and before I bought the bike (should I still clean and Kreem it? I've heard Kreem is a BS product) and the guy I bought it from put a new petcock in it, the kind with the screen I'm pretty sure.

 

[XSLeo]

I think I responed on your other thread. From what you said there I would think the carbs are a bit plugged up. Remove them and clean them well. There are very small passages that can plug easily.

 

[tx650]

I don't know if this will solve your prob,so here's the deal.
You can static time the points or use a timing light,the latter will assist with diagnosing the advance system as well.
It might pay to set up your points gaps and then do a static test and that will most probably tell you where you are going wrong,start right at the begining and try to eliminate all possible scenarios.
I had a bike with points once and whenever I set the timing I would remove my test light after ligning up the marks and tighten the screw!!.....So what you might say?Well the only thing that was wrong was the screws over the years had indented onto the plates and whenever I tightened them down the plates would shift and the timing would be thrown off to buggery.So what I ended up doing was double check the timing AFTER I tightened the screws.

 

[pamcopete]

PRobert..,

Try unplugging the reg/rect. Sometimes the magnetic field from the rotor will interfere with the pickup for the TCI.

 

[PRoberts317]

Ill try unplugging the regulator/rectifier tomorrow.... How about this though: Today I switched the carbs out for a set that I KNOWW is in perfect working order and it didn't change a damn thing!!! Could this be an engine problem? Valves? A loose gasket somewhere?

 

[nj1639]

Add where you're from, up there near your screen name, might be somebody close by.
I'd be checking voltage @ 3500 to 5000 rpm too. Should be 14 +/- @ 5 grand IIRC.

Thinking, 'then theres the carb diaphrams'.

How far did you run it before the rotor and reg were changed? Did it act up then (if any distance running).

 

[cooltouch]

Have you checked your valve settings yet? They need to be correct and the cam chain adjusted properly before you time the motor.