So carbs, not so much, lets talk sparkys!

[J_Walker]

So.. My spark plugs, fun fun fun. Anyways. I had a question for you all. Today I did a test, I pulled my spark plugs, and switched them to the opposing side. No change in start up. Now here's my question. If you pull the right coil away from the plug, would the left side start?

Because I Pulled the right coil from the right, and tried to start it over, it wasn't firing, now than I plugged the right back in and pulled the left coil and it fired over. So coils bad? Piston Derped? Spark plug bad? could be why there's been my "popping issue" its misfiring and that's what is popping. or the reason my engine has been getting hot.. piston is stuck or something and I've been running on 1 cylinder sense I got the bike... I don't know the difference first bike I ever rode..

GStwin gods, I call forth you. Tell me whats wrong?

[BaltimoreGS]

Sounds like you may be running on one cylinder.  Start the bike and let it run.  Pull off one spark plug boot and it should run rough but continue running on the other cylinder.  Repeat for the opposite side.  If the bike dies when you pull one side's plug off, the other cylinder is not working (i.e. you are only running on the one cylinder you unplugged).  Then you have to determine if it is a spark or fuel issue.  If you have a spare good spark plug (doesn't have to be a GS plug), plug it into the boot and hold the tip up to the engine whileyou run the starter.  You should see a blue arc jump across the gap.  If you don't have a spare good plug, use the plug from the working cylinder to test.  If you don't have spark, then it may be a coil issue.  If you have good spark it is probably a fuel issue (probable clogged jet).

-Jessie

[J_Walker]

I know 1000%%%%% its not a fuel issue... I know. because I've cleaned them carbs to where they cannot be cleaned any more!!! so ima go for, its the cylinder and spark issue.. God this whole time I thought it was the carbs.. but it was my engine.. SILLY ME! okay so what baltimoreGS said sorta answered my question, IT should run only on 1 cylinder... no matter the side. so.. is the spark plug bad, or the coil.. WE shall find out.

[BaltimoreGS]

Hopefully it is something simple like a bad plug but those aren't the only possibilities.  You can have fuel and spark but the cylinder still won't do anything if it doesn't have compression.  Start by checking for spark issues since it is the most likely cause (Accom's razor).  If it isn't a spark issue, then do a compression test.  If you don't have good compression start looking at the valves.  If you do have compression, go back to the carbs.  Good luck!   

-Jessie

[J_Walker]

well, I did switch the plugs, one side from another, so that means Coils/compression? is there a fix for the coils? or do I just have to get whole new ones?

[BaltimoreGS]

You don't fix coils if they are bad, just replace them.  I'm sure adidasguy has a good used coil in his stash if that turns out to be your problem.  Your first step is to check for spark.  If you find it is a spark issue, swap the coils side to side to make sure they are the problem.  If the coil is bad your engine should now only run on the opposite side cylinder.  At that point you are safe to spend money on a coil.  If the bike still only runs on the same cylinder you have eliminated the coil as a problem.  Then you get into the pick ups and other areas that are part of spark.  Let's not get too complicated yet, just check for spark and go from there   

-Jessie

[adidasguy]

Almost like Trey - and  that was spark plug.
But try this - the side it won't start on. What about with full choke?
Try swapping coils. Check for good connections to the coils.
Sure you swapped plugs?
(Yes, I do have a pile of coils)

[J_Walker]

I'm sure I swapped plugs, one was PERFECT looking, other one was "wet" Rich looking perfect. left side, good side. Wet right side, bad side. Tried full choke, still wouldn't turn over. no choke, half, full, nadda. I'm not sure how to swap coils, gotta take the gas tank off by my view don't you? LOL... I'ma buy new spark plugs just in case anyhow.. doesn't matter wont kill me. Ill check the swapped plugs right now.. Wait for details.

[adidasguy]

With long and angle tools, you can remove the coils without removing the tank. I did that on Trey before I really got into him.
Go slow. Take your time and it can be done.

[J_Walker]

its fine, took the tank off, don't have those tools.. Better safe than sorry. Swapped the coils, Its not the coils... :/ God more and more I get into this the more and more I Think it might be serious... So. coils/spark plugs both fine.. IDk how to check compression without one of them fancy tools.. And im sure thumb over hole doesn't work.. lol

[J_Walker]

Thumb over hole, Thumb 1 hole 0, ITS COMPRESSION!!!!!!!!!!!!

okay, now how do I fix it? Lol...

[shonole]

I'm having the same problem with PITA.  Although, I don't believe mine is a compression issue.

[J_Walker]

I'm having the same problem with PITA.  Although, I don't believe mine is a compression issue.

Yeah? Maybe we can work together and figure this out.. Cause Idk if when you put your thumb over the spark plug hole, if its suppose to Suck in or blow out.. cause when I did. my finger was being blown out with little pressure, but with full body weight on arm pressure it started to sorta suck in.. I figure that's compression.

[BaltimoreGS]

You need a compression gauge with a 12mm fitting to check compression.  If you felt no pressure blowing out then I would say it is compression but other than that your thumb test is fairly worthless.  If you get poor or no reading on a compression gauge, then you have to figure out why there is no compression.  Start by checking the valves.  I would expect you'd find there is insufficient clearance on one valve and the valve is hanging open.  If you can't spin the valve shim bucket, it is stuck open.  Hopefully the bike hasn't been ridden much like that or you may have burned a valve.  But that is worse case scenario, don't even worry about that until you find if it is a compression problem.

-Jessie

Edit: Text moved below....

[J_Walker]

You need a compression gauge with a 12mm fitting to check compression.  If you felt no pressure blowing out then I would say it is compression but other than that your thumb test is fairly worthless.  If you get poor or no reading on a compression gauge, then you have to figure out why there is no compression.  Start by checking the valves.  I would expect you'd find there is insufficient clearance on one valve and the valve is hanging open.  If you can't spin the valve shim bucket, it is stuck open.  Hopefully the bike hasn't been ridden much like that or you may have burned a valve.  But that is worse case scenario, don't even worry about that until you find if it is a compression problem.

-Jessie

I can 100% say, its been ridden with this problem a whole lot... sadly..... but if not spark, not coil, not carbs. WTH? Has to be compression! Not saying your wrong or anything just I really wanna go on that trip this upcoming month.. and its like frustrating to not know at lease wth is wrong.

PO left his address on some things he gave me.. might pay him a visit... maybe take him camping...?

[89500inPA]

You can borrow a compression tester from advance, auto zone or pep boys. Go and ask for one to use. You have to pay for the item in deposit, but when you take it back, they credit all the money back hoping you will now buy parts from them.

[BaltimoreGS]

Compression Test 101

Remove both spark plugs
Screw in gauge
Hold throttle wide open
Run starter motor until needle quits going up
Repeat for other side

Around 150 psi is what I would expect to see on a decent engine.  More important is balance between the cylinders.  A 10% variance is allowed between readings.

[shonole]

I'm having the same problem with PITA.  Although, I don't believe mine is a compression issue.

Yeah? Maybe we can work together and figure this out.. Cause Idk if when you put your thumb over the spark plug hole, if its suppose to Suck in or blow out.. cause when I did. my finger was being blown out with little pressure, but with full body weight on arm pressure it started to sorta suck in.. I figure that's compression.

Yeah.  Mine is on the right side.  Pull the right plug, engine dies.  Pull the left, works great.  I've swapped coils from side to side, no luck.  New spark plugs, no luck.  Cleaned carbs a dozen times, no luck.  Adjusted float height, no luck.  (Although, I will be checking this again after my new boots get here from adidas).  I don't have a compression gauge (yet), but when sticking my thumb over the empty plug cylinder, I get strong cyclical puffs of air. 

I've been posting over here:
http://gstwins.com/gsboard/index.php?topic=58643.40

[adidasguy]

Around 150 psi is what I would expect to see on a decent engine.  More important is balance between the cylinders.  A 10% variance is allowed between readings.

OEM service manual says 142-199 normal. Low minimum compression 112psi. Maximum difference between cylinders is 28psi.

Engine should be warmed up. Insure all head bolts are torqued to correct value and valves are properly adjusted (paraphrasing the manual.) Remove both spark plugs. Keep throttle grip open when doing the test.

[BaltimoreGS]

Engine should be warmed up. Insure all head bolts are torqued to correct value and valves are properly adjusted (paraphrasing the manual.) Remove both spark plugs. Keep throttle grip open when doing the test.

Thanks Adidas, that is a bigger variance than I would have expected.  I'd skip the engine warming step though since you are only seeing if there IS compression at this point.  If a valve is stuck open you don't want to run it anymore than necessary. 

-Jessie