Novice biker on 1983 GS450 that suddeny refuses to start!

[Anonymous]

Hi,

I just bought a GS 450E from 1983 last week. It's my first real bike and I'm quite excited even though it's an old machine (just one year my junior!). I got it cheap off a friend who took well care of it and serviced it regularly. I'm absolutely no techie, so I had to take his word for it.

The bike also ran perfectly for the first 250kms, starting without too much trouble and running like a dream. I took it for a long ride on Saturday, and everything was fine. When I wanted to start it yesterday, I just got nothing.

The engine cranks, but it doesn't spark. I tried push-starting it too, without luck. It sounds like the engine isn't getting any fuel. I checked the main fuel line where the reserve/on/? switch is, and gas only flows when it's on the ? position (neither "res", nor "on"). It does flow though. I don't see gas flowing through the line connecting to the choker (neither do i know if its supposed to). I read a lot about carbs clogging up, but I don't suppose that can happen overnight (although I do have a theory that rust may have come off the tank as I refuelled it just before heading home, and it was the first time it was refuelled since I bought it. Before that it had been sitting for a couple of months. This could also explain the potentially clogged fuel-switch, which btw was working fine up until the bike stopped starting!). But still, overnight?

Oil was getting low by the time I got back on Saturday, but it wasn't below the minimum-point, and I refilled it. Could it be an electrical problem? The fuse is alright, and all lights seem to work. What else could have happened?

I guess I better get a repair manual, but i'd appreciate any input as to where I should look to restart it. It just seems weird that the bike stopped starting all of a sudden without warning.

Thanks.

Jonathan/ Denmark

[snowbeard]

hi jona,
I'll add what I have, tho it may not be much.

the fuel petcock should be vacuum operated, so the small tube coming off should not have gas in it, as it supplies the vacuum from the running engine. the petcock should only allow fuel to flow when the bike is running when in the fuel or res setting. the prime setting should allow it to flow at any time, such as to refill the carbs after removing them, etc.

if the fuel flows on either of the fuel or res settings with the bike not running, the vacuum diaphram is likely leaking.

to bypass this, try turning it to prime (don't forget to turn it back from prime when you're done or you'll fill your crankcase with gas... ask me how I know )

prime should get you gas, now try to start it. if you're turning the engine over, it's likely you have spark, but you can check by removing one of the plugs, hook it back up to the plug wire, hold it grounded to the engine and try to start it. you should see a bright blue spark on the plug. keep your fingers back and make sure it's housing is grounded to the engine or you'll get a nice poke...

on my bike, I often have to start it with ether (starter fluid) sprayed in the airbox. remove the cover and filter and shoot a quick burst into the airbox assembly. then hit the starter. sometimes this will get it started, but I hear it's not good for the engine to use this too often.

I'll get off here now so anyone who actually knows your bike can help you more. good luck with it, and have fun!!!

[Anonymous]

check your spark plugs

choke then try to start

check battery

[bgmart450]

I am not so sure about the 83 450, but the 80-82's don't have a prime position. If it doesn't as well then gas should never flow from the petcock (fuel valve). The bike is 'off' with no vaccuum as noted in an above post. You could try the starter fluid deal to see if its the petcock.

If left dry for a long period of time and then moved dry the rubber insides of a petcock can tear. Just something to be aware of.

[Anonymous]

I am not so sure about the 83 450, but the 80-82's don't have a prime position.

I don't have a prime positon on the petcock on my 81 450S, just a On and Reserve. I do have a screw that I can loosen to manually prime it though, but only 1 of the 2 petcocks I have for this bike has that. Weird.

[Anonymous]

Thanks guys!

I'll check the plugs when I get off work and see if I can get hold of some starter fluid, and try that too. My model does have a prime position, and from what you describe it does appear to be working.

And, erhm, say it was left on the prime position - crankcase filled with gas? What is that going to do ?

[Anonymous]

Good news and bad news.

The good news is the crankcase is not filled with gas despite having been left with the fuel valve in the prime positon.

The bad news is I couldn't get hold of the fuel spray where I usually go for these things, and it's raining cats and dogs so I won't be able to check the plugs today either (no garage or shelter). The battery is also starting to run low now from all the cranking, but that wasnt the root of the problems as its practically brand new and was fully charged.

The guy who sold me the bike is coming by tomorrow and has promise to fix it. He's a mechanical engineer and dedicated bike fanatic so I have high hopes.

I still really appreciate your help and suggestions though. I'll keep you informed.

Jonathan.