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GS450 "coughs" and won't run on highway

  • Thread starter Thread starter aoywi
  • Start date Start date
A

aoywi

Guest
Hello,

I just assembled my GS450, with a programmable ignition from ignitech, the SH775 R/R and relay for ignition mod.
The engine is the new model with the new model TCI/ignitor, but the carbs (and jets etc.) are from the earlier model.

The problem is when i drive to work, i drive about 8km through the city and then i have 8km to do on the highway. While riding through the city, the bike "coughs" once or twice, it feels like it briefly turns off/misfires. When i get on the highway the first 500-1000meter are fine, but then it start coughing a lot, and won't run at all. I have to get of at the nearest exit, and the bike will only idle, as soon as i put it in gear and want to drive, it coughs and coughs. If i then put on full choke, i can run it to work but only with very little (if any) throttle or full throttle, the throttle in between just kills it completely.

Any ideas of what i could be ?
Thanks!
 
fuel starvation. Check that fuel tap....sounds like it is getting enough fuel between stoplights but not enough on a steady go.

Your symptoms decribe my bike running out of gas....try switching the tap to" prime" if you have the oem fuel tap.
 
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Wouldn't be at all surprised if the spark is weak. It often appears as a fuelling problem because you have to dump more fuel in via pulling the choke so that the pitifully weak spark can ignite something (bear in mind these engines run on the borderline of weakness most of the time) and this leads to confusion.
Might be bad connections on the 12V supply side to the ignition, or the ignitor or the triggers. Might also simply be a dodgy ignitor unit.
 
Gorminrider said:
fuel starvation. Check that fuel tap....sounds like it is getting enough fuel between stoplights but not enough on a steady go.

Your symptoms decribe my bike running out of gas....try switching the tap to" prime" if you have the oem fuel tap.
Click to expand...

Thank you very much for your fast reply! I had the tank of yesterday and rinsed out the fuel tap, found i lot of dirt but it didn't help. Is there a way of measuring the amount of "liters a minute" or something like that? I am thinking it could also be the vacuum on the tap thats a bit dodgy? :-)

Also i forgot to mention, i checked the spark plugs and black of soot and dry, the other one is very light brown nearly grey.
 
Grimly said:
Wouldn't be at all surprised if the spark is weak. It often appears as a fuelling problem because you have to dump more fuel in via pulling the choke so that the pitifully weak spark can ignite something (bear in mind these engines run on the borderline of weakness most of the time) and this leads to confusion.
Might be bad connections on the 12V supply side to the ignition, or the ignitor or the triggers. Might also simply be a dodgy ignitor unit.
Click to expand...

Thank you very much for your fast reply! I have replaced most of the wires etc that leads to the ignitor & coils. But of course i have not measured the voltage yet :redface:

Also i forgot to mention, i checked the spark plugs and black of soot and dry, the other one is very light brown nearly grey.
 
Might be an ignition advance problem, but this stuff.....
"....If i then put on full choke, i can run it to work but only with very little (if any) throttle or full throttle"

sounds like fuel level in bowl is dropping interfering with main circuit- since "choke" gets its fuel from lower in bowl, it can supply a bit more.
First check petcock, get container ,stick under fuel outlet,and switch to "PR" spot - fuel should flow good. Now get clear tubing stick on petcock vacuum fitting. With petcock in "ON" spot, no flow till you suck on tubing- watch for fuel in this clear tubing as petcock might have failed.
 
tom203 said:
Might be an ignition advance problem, but this stuff.....
"....If i then put on full choke, i can run it to work but only with very little (if any) throttle or full throttle"

sounds like fuel level in bowl is dropping interfering with main circuit- since "choke" gets its fuel from lower in bowl, it can supply a bit more.
First check petcock, get container ,stick under fuel outlet,and switch to "PR" spot - fuel should flow good. Now get clear tubing stick on petcock vacuum fitting. With petcock in "ON" spot, no flow till you suck on tubing- watch for fuel in this clear tubing as petcock might have failed.
Click to expand...

Thanks for your answer! :-) - When you write "PR" spot, what do you mean exactly? I have an ON and RESERVE, thats it.
I will try you vacuum testing later today, thanks a lot! :-)
 
cowboyup3371 - Thanks!

I tried to pull of the spark plug cap on the right cylinder(when sitting on the bike), and nothing seemed to change at all. When i then came to pull of the cap on the left cylinder, the engine stalled.

I have now done the following:

Measured the coils -
Coil 1 secondary - 3,9Ω
Coil 1 primary - 11,6kΩ
Coil 1 voltage - 12.9V - 14V when running

Coil 2 secondary - 3,9Ω
Coil 2 primary - 11,6kΩ
Coil 2 voltage - 12.9V - 14V when running

Measured the pickups:
Pickup 1 - 0,35kΩ
Pickup 2 - 0,35kΩ
Between pickups - 0,7kΩ

When i measure directly on the pickups between each pickups points, i am not able to measure anything, i dont know why?
When i do the same on an older engine i have, i can measure 65Ω.

Tested the vacuum with a clear tube, a nice stream of fuel came out.
 
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You need to determine why right cylinder is not working- either no spark or no fuel mixture. Rule out former first. Remove spark plug, put plug back in plug cap, crank engine while holding plug against engine. If weak or poor spark, remove plug cap and trim 6 mm off plug wire (this exposes fresh copper to cap) , then crank again.
Does this ignitech system use the stock suzuki signal generator coils?

your ignition coils test good- but you've mixed up primary and resistance readings. The 3.9 ohm is the primary.
 
tom203 said:
You need to determine why right cylinder is not working- either no spark or no fuel mixture. Rule out former first. Remove spark plug, put plug back in plug cap, crank engine while holding plug against engine. If weak or poor spark, remove plug cap and trim 6 mm off plug wire (this exposes fresh copper to cap) , then crank again.
Does this ignitech system use the stock suzuki signal generator coils?

your ignition coils test good- but you've mixed up primary and resistance readings. The 3.9 ohm is the primary.
Click to expand...

I tested the sparkplug against the cylinder on both sides to compare the spark, and they seem the same.
I took apart the carbs and found out that the float hight was all wrong, so i corrected this and cleaned the carbs real good. This seems to have solved the highway problem (i haven't had a good long run at around 100km/h yet, but a few kilometers), but the sudden cough while riding through the city still exists.

It seems like the right cylinder only runs sometimes, at some lights the idle speed is very low and other times its normal. If i pull off the right cap when the idle is low, i can definitely tell that this cylinder is not running.

The ignitech system uses all stock signal generator coils & ignition coils. Its just a custom TCU/ignitor/CDI.

Okay, that you for that :)
 
Progress is always good! In the city, the carbs spend lots of time on low speed circuits- these get gummed up easily, so your right carb might not be delivering fuel consistently to its cylinder during low loads. The passages are tiny, hard to clean without immersion - spraying might work if you get lucky. Or try some fuel cleaner for a couple of tank fills.
 
tom203 said:
Progress is always good! In the city, the carbs spend lots of time on low speed circuits- these get gummed up easily, so your right carb might not be delivering fuel consistently to its cylinder during low loads. The passages are tiny, hard to clean without immersion - spraying might work if you get lucky. Or try some fuel cleaner for a couple of tank fills.
Click to expand...

It is always good! :)
I cleaned it with air today, but maybe i wasn't thorough enough.
Is there something i can soak the carb in to get them real clean? a tub of petrol?
I have a set of spare carb laying around, so i could soak and clean those and see if that makes a difference :)

Does that fuel cleaner stuff work ? :)
 
aoywi said:
It is always good! :)
I cleaned it with air today, but maybe i wasn't thorough enough.
Is there something i can soak the carb in to get them real clean? a tub of petrol?
I have a set of spare carb laying around, so i could soak and clean those and see if that makes a difference :)

Does that fuel cleaner stuff work ? :)
Click to expand...


What country are you in?
If in the USA,you can get Chem-Dip at wal-mart that works really well.
If you are in a place you can't get this,sometimes boiling them with a degreaser might work,or you can use laquer thinner,but it is toxic,and very flammable.
 
megatwin said:
What country are you in?
If in the USA,you can get Chem-Dip at wal-mart that works really well.
If you are in a place you can't get this,sometimes boiling them with a degreaser might work,or you can use laquer thinner,but it is toxic,and very flammable.
Click to expand...

I am from Denmark, so wal-mart isn't an option ;-)
But thanks a lot! Now I have something to go for :-)
 
No walmart ! I thought we were sending them everywhere !
look for a good household degreaser/cleaner - over here we have Pine-Sol, nasty smelly stuff . As mentioned , heat speeds the attack on deposits. Or visit some repair shops and see who has done some ultrasonic carb cleaning.
I would avoid anything flammable.
 
Haha, apparently not - but probably close ;-)

I will see if i can find an ultra sonic place, or some nasty degreaser.
 
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