Gs500 problem starting

[stellious]

Hi i recently got a SUZUKI gs500 2003 engine from a crashed bike. i fitted in my 2002 frame. since putting it all back togheter it turns over but wont start. There is a good spark on both spark plugs there is petrol goint to the engine i also tried startin with clutch in aswell as with the stand up and in gear none of this has worked. when trying to start also it would backfire now and again and also spit flames 2 or 3 times. please someone help pulling my hair out at this point.

[mentalshark]

Back fire from.the intake or exhaust?
Could it be a timing issue?

[stellious]

Hi its backfiring put of the exhaust spit a few flames out of the exhaust too. Checked timing and it is okay.

[chris900f]

Are you using the 2003 ECU? The timing(pulse) rotors/ECUs changed between 2002 and 2003.
If you want to use the 2002 ECU and wiring you need to swap the single lobe pulse rotor on your 2003 engine,
with the dual lobe version from your 2002 bike.

[stellious]

No I actually haven't changed that. I'll look into it and let you know how it goes thanks

[stellious]

Are you using the 2003 ECU? The timing(pulse) rotors/ECUs changed between 2002 and 2003.
If you want to use the 2002 ECU and wiring you need to swap the single lobe pulse rotor on your 2003 engine,
with the dual lobe version from your 2002 bike.

could I buy a 2003 ecu and take the 2002 cdi off? Would it work. As I don't really know the connections

[mr72]

Swapping that rotor is really easy, provided you have access to the old engine and that part is not damaged. That's the way to go. Are you using the carbs from the '02 engine?

[stellious]

Swapping that rotor is really easy, provided you have access to the old engine and that part is not damaged. That's the way to go. Are you using the carbs from the '02 engine?

yep I'm using carbs from the 02 engine. And part is easy to get at and isn't damaged

[mr72]

yeah then I'd swap that rotor so the carbs/ignition/PCM/etc. are all of the same generation.

[stellious]

yeah then I'd swap that rotor so the carbs/ignition/PCM/etc. are all of the same generation.

yep will do I'll post once I get it in and let you know what happens thanks for the help

[stellious]

yeah then I'd swap that rotor so the carbs/ignition/PCM/etc. are all of the same generation.

yep will do I'll post once I get it in and let you know what happens thanks for the help

yes finally got part. its running now onmly issue now is in 6th gear at about 90km/h there is a slight loss of power very slight but noticable any ideas?

[herennow]

is that at WOT?

[stellious]

is that at WOT?

What is wot?

[Bluesmudge]

What is wot?

Wide Open Throttle (aka full throttle)


What gear you are in shouldn't really effect anything. The carburetor doesn't know what gear you are in, only how much throttle you give it.

Slight loss of power isn't much info but its likely a carb issue. Maybe a vacuum leak that isn't noticeable until you are at WOT. Did you rebuild the carb at all? It might need new o-rings, since all the rubber is now 20 years old. Are the boots from the airbox to carb and carb to engine still pliable?

Also make sure the carb vent hoses aren't routed forwards. This can cause issues at speed if air is being forced up the vent hose. They should run down the back of the carb.

[stellious]

What is wot?

Wide Open Throttle (aka full throttle)


What gear you are in shouldn't really effect anything. The carburetor doesn't know what gear you are in, only how much throttle you give it.

Slight loss of power isn't much info but its likely a carb issue. Maybe a vacuum leak that isn't noticeable until you are at WOT. Did you rebuild the carb at all? It might need new o-rings, since all the rubber is now 20 years old. Are the boots from the airbox to carb and carb to engine still pliable?

Also make sure the carb vent hoses aren't routed forwards. This can cause issues at speed if air is being forced up the vent hose. They should run down the back of the carb.

Once I'm at about 90 to 95km/h it will start to loose slight power and get it back again. Feels like the break is being slightly pulled then released. And no it's not wot. I will have a look at the carbs just to cross it of the list of possible problems. Also there is 2 emissions tubes coming out of the head that I don't have plugged into anything could that possibly cause the problem.

[The Buddha]

That 90-95kph little hiccup if its when opening throttle, its rich. Likely a high float, but jetting is related to throttle position, not speed or rpm. So What your issue is may be in a different circuit. Maybe needle lifted too high.

If the problem is at steady throttle, you are too lean. Again, throttle position determines the circuit, not rpm.

Cool.
Buddha.

[stellious]

That 90-95kph little hiccup if its when opening throttle, its rich. Likely a high float, but jetting is related to throttle position, not speed or rpm. So What your issue is may be in a different circuit. Maybe needle lifted too high.

If the problem is at steady throttle, you are too lean. Again, throttle position determines the circuit, not rpm.

Cool.
Buddha.

Okay ye it does have a heavy smell of petrol also. I'll have a look at that aswell thanks

[The Buddha]

That 90-95kph little hiccup if its when opening throttle, its rich. Likely a high float, but jetting is related to throttle position, not speed or rpm. So What your issue is may be in a different circuit. Maybe needle lifted too high.

If the problem is at steady throttle, you are too lean. Again, throttle position determines the circuit, not rpm.

Cool.
Buddha.

Okay ye it does have a heavy smell of petrol also. I'll have a look at that aswell thanks

OK Overflowing float. Check that first, you dont want to be riding a potential grenade.
Cool.
Buddha.

[stellious]

sorted the bike out turns out the vacum tube was being pinched and not working properly thanks for the help everyone