What else uses fuel on my 650?

[themess]

Sounds as if two cylinders were not firing, apparently due to a bad coil.

[BigD_83]

Sounds as if two cylinders were not firing, apparently due to a bad coil.

Does sound that way, but the bike never ran on the road like it was on two cylinders. I know what that felt like as I had a bad spark plug boot that would intermittently cut out spark to #1.

I am curious, but not curious enough to do the reverse swap, and see if the problems come back with the old coils.

[themess]

We almost never use all the power available. A 30 HP GS would still accelerate nicely, and hove no trouble cruising down the highway.

[BigD_83]

We almost never use all the power available. A 30 HP GS would still accelerate nicely, and hove no trouble cruising down the highway.

I agree that dropping a coil at high speed would hardly be noticeable, but I would think that at idle or accelerating hard you'd notice when you had dropped a cylinder or two, I certainly did.

You bring up an interesting point though, if one was having issues with the charging system AND had a marginally weak coil coupled with some high resistance in the coil path, then at low RPM you might not have enough driving force at the coil...

[MisterOh]

bookmarking this thread... I'm getting around 24 mpg on my 650L

I JUST replaced the petcock though. We'll see if that does anything...

[themess]

I agree that dropping a coil at high speed would hardly be noticeable, but I would think that at idle or accelerating hard you'd notice when you had dropped a cylinder or two, I certainly did.

You bring up an interesting point though, if one was having issues with the charging system AND had a marginally weak coil coupled with some high resistance in the coil path, then at low RPM you might not have enough driving force at the coil...

I like the second paragraph.

[tom203]

BigD_83 said... if one was having issues with the charging system AND had a marginally weak coil coupled with some high resistance in the coil path, then at low RPM you might not have enough driving force at the coil... "

I would think this would lead to difficult starting, when voltage drops way down due to cranking.

[BigD_83]

BigD_83 said... if one was having issues with the charging system AND had a marginally weak coil coupled with some high resistance in the coil path, then at low RPM you might not have enough driving force at the coil... "

I would think this would lead to difficult starting, when voltage drops way down due to cranking.

I was thinking more along the lines that when cold, the coils are fine (I recall reading many stories of 550 owners' woes, not so much with the 650s) when cold (starts/runs) well at the beginning, but when hot their resistance goes through the roof and stop delivering spark well enough to get complete combustion, but enough to keep the engine running.

There have been more than a few "difficult to start when hot" or complete shutdown anecdotes on the GSR.

I'm just happy the new coils have provided a solution to the low fuel mileage issues. Now I just have to keep an eye on the coils and continue revamping/cleaning/sorting out any other electrical issues that may start showing up.

The better news is that I checked out the voltage at the coils last night when I was redoing the primary leads, and I have almost no drop from the battery to the coils.

[tom203]

Yeah, lots of ignitors failing when hot stories. I can't fathom why suzuki used so many different ignitor designs- the 650 one seems durable. With my old battery, the voltage at battery would drop to 11 volts during cranking- the ignitor probably didn't see 10 volts- yet always fired right up.

[MisterOh]

wait, this might seem to be the issue i'm facing. My bike starts and runs fine, but once it gets hot enough (after about 20 minutes) the engine will die and I have extreme difficulty starting the bike again unless I have the choke and rev the engine while pressing the starter.

where exactly are the coils?? i don't have much experience at all working with cars/bikes...

[tom203]

When you removed tank for petcock, you had coils in view!
But after dying episode, if playing with choke/throttle starts bike, it's unlikely to be an electrical problem. Did you check petcock for correct operation after replacing it? make sure tank vent is clear?

[MisterOh]

the petcock seems to be operating perfectly!

um.. tank vent? man i have a lot to learn... I'll probably know what you're talking about, but I just don't know what everything is called. I just know what they look like...

edit: wait you mean that one tube leading from the petcock to the outside air? how do I test if it's clear?

[tom203]

"edit: wait you mean that one tube leading from the petcock to the outside air? how do I test if it's clear? "

Outside air?? Hopefully one tube from petcock leads to carbs to deliver fuel and another connects to #2 carb to supply vacuum to operate petcock (in "on" or "res" ).
Gas cap has small hole that lets air in so fuel can leave tank-

[MisterOh]

Yes, I have the fuel line from the petcock to the carbs, the vacuum line from the #2 carb to the petcock, and then this random line that goes nowhere in particular

Oh yes, the vent for the gas cap works fine

[BigD_83]

Yes, I have the fuel line from the petcock to the carbs, the vacuum line from the #2 carb to the petcock, and then this random line that goes nowhere in particular

Oh yes, the vent for the gas cap works fine

Can you take a picture of the random line so we can get you on track? Where is it attached? There should only be two line (vacuum and fuel) off of the petcock.

I can't remember, does the '82 have a fuel gauge? If so, there is a fuel sending unit overflow hose that attaches to the right underside of the gas tank, and is about 1.3m (4 feet) long.

There is the engine breather hose that is a little wider and routes over the carbs and back to the top front of the airbox.

Then there are two breather hoses that attach to the carbs. One is on the left between #1 & #2 carb, and the other is between #3 & 4 carbs. Those route up and out, over some grooves in the top of the airbox