Misfiring loss of power....help please .

[carlm]

My 1983 XS special completely lost its spark after winter layover. Replaced ignition unit with an old ebay original. Bike ran great for about 30 miles. Then started missing losing power.etc... This was quite gradual and intermittent.Got home and noticed right side air filter had worked loose. Tightened it back up. Now bike starts but runs horribly backfires etc..,. Am wondering if the ignition unit is faulty. Carbs have just been cleaned, plugs replaced.
Any input gratefully received.
many thanks

 

[xjwmx]

The gradually happening part could be fouling plugs which could be from a coil that has an internal low resistance path to high voltage. See if new plugs fixes it temporarily. You could measure the coil w/ a meter but if it reads good it could still be bad. A lot of us use used Honda MP08 coils from ebay on TCI bikes. Keep the ignition you replaced, and all parts you replace really

 

[carlm]

Sounds like a plan.Will give it a try. Thank you.

 

[xjwmx]

Another thing on these is the connectors can develop resistance at the crimp. You can find that measuring from wire end to wire end -- through the crimp. It can also be intermittent. Re-crimping will fix them. There are special tools for fiddling the connector out of the molded housing.

 

[carlm]

Liked the first solution best>>> But will add to list. thanks again.

 

[xjwmx]

^Try the easiest stuff first That is the more likely solution really though. Thought I'd toss another common gremlin in, just in case. Let us know what happens

 

[RustiePyles]

What kind of air filters are you running, some of the pod filters block the air ports in the throat of the carbs.

 

[wesleyonoel]

Don't completely discount the carburetors. A little squirt of starting fluid (ether) here-n'-there with engine running will identify an air leak which can lead to a lean condition and backfiring. My '73 TX has a habit of occasionally "sneezing" the right carburetor out of it's connection to the head.............and it's darned hard to see!....

 

[carlm]

Liked the first solution best>>> But will add to list. thanks again.

 

[carlm]

What kind of air filters are you running, some of the pod filters block the air ports in the throat of the carbs.

They are K&N which i have recently cleaned and re-oiled. Today i changed the plugs and checked that fuel running from tank OK. Carbs were sonic cleaned recently. Still wondering if there is some crud in carbs. Still popping and with hardly any power??

 

[xjwmx]

Still wondering if there is some crud in carbs. Still popping and with hardly any power??

If it's a carb, it's likely just one. Pay attention to the exhaust of each cylinder to find the one. If both cyls acting crazy, probably electrical, although both carbs could have same bad adjustment because they're just back

 

[carlm]

will put that on my list too.thanks

 

[carlm]

I found a similar thread with more or less exactly the same problems i am having. The chap sent his ignition unit for a refurb and cured the problem. As i have just replaced my unit with another (old) one i am wondering if that could be the cause??

 

[xjwmx]

No, you have two unrelated ones doing the same thing so unlikely. However -- what they have in common could be a problem -- connector on harness side, the Pickup, etc. Don't know if intermittent pickup would misfire or just turn the TCI off. Test pickup with a meter, wiggle the wires around to try to find intermittent open

Another thing that could be the "gradual" effect you mentioned could be battery not charging. Running at 3000 RPM you should see a little over 14V across the battery. I assume the easy stuff has been checked already? I'm also assuming everything is basically stock. If it turns out to be carbs, if the problem is only at low RPM it points to the pilot system, only at high RPM means problem w/ main system

 

[carlm]

No, you have two unrelated ones doing the same thing so unlikely. However -- what they have in common could be a problem -- connector on harness side, the Pickup, etc. Don't know if intermittent pickup would misfire or just turn the TCI off. Test pickup with a meter, wiggle the wires around to try to find intermittent open

thanks that sounds like good sense.Will try