1983 GS450L Not Starting

[natepittiglio]

Hi all! I just picked up a GS450L project that hasn’t run in quite some time (tire date codes older than myself!). I’m in the process of getting it back to being roadworthy, however it’s giving me trouble starting up. Previous owner never had it running, but went through and invested some time and money into it before giving up on the project. It turns over when you click the starter, has spark, has compression, but refuses to fire up. Carbs have been pulled and cleaned twice, seems they’re getting fuel as they should. Something of note, the left spark plug went black today as I was attempting to fire it up, the right one stayed spotless. Could the carbs be out of sync, and could that lead to starting troubles? Any advice or quick checks I could do are appreciated! Looking forward to digging more into this bike.

[LAB3]

Everyone here including myself will tell you that the carbs need to be "hospital clean" before you can get the bike to run right. For now we'll set that aside since I'm sure we'll get back around to it.

One common issue that gets overlooked is the spark plug caps, they have resistors built in and over time they do go bad. You can pull them off the plug wires by getting a firm grip on the plug wire and rotating the cap counter clockwise while pulling on it. Inside the cap you'll see what looks like a woodscrew that the wire is "threaded' onto. You'll want to clip the wire back about 1/4" to get past the often corroded part of it that contacts the woodscrew looking thing, be sure to clean that too.

Now, take an ohm meter and test the resistance of the cap, it should be about 10k ohms. If it measures significantly greater than that then the cap needs to either be replaced or modified to get rid of the resistor. If you ditch the resistor inside the cap you'll need to replace it with resistor type spark plugs which are commonly available these days.

So for now check out those caps and let us know what you find then the rest of us can take you from there.

[natepittiglio]

Well that just may be my issue! Pulled the (clearly aftermarket NGK) plug caps and figured out they’re only rated at 5k ohms. Replacements being ordered, will keep the thread updated on how it goes.

[Nessism]

http://www.thegsresources.com/_forum/showthread.php?t=171846

[rphillips]

I've always hated just buying parts to see if that helps the problem. I'd just remove the resistors in your caps and replace the resistors with a piece of wire. You'll then have no resistance. If it doesn't run with no resistance you'd be sure the caps aren't the problem. If it does start and run with them, you can either just run it with no resistors or if you think you want resistors "then" buy new caps... but that's just me.

[LAB3]

I've always hated just buying parts to see if that helps the problem. I'd just remove the resistors in your caps and replace the resistors with a piece of wire. You'll then have no resistance. If it doesn't run with no resistance you'd be sure the caps aren't the problem. If it does start and run with them, you can either just run it with no resistors or if you think you want resistors "then" buy new caps... but that's just me.

Agreed! If you look into the end of the cap that clips onto the top of the spark plug you'll see a slot where you can put a screwdriver with a large blade in it. Put in the screwdriver and turn it counter clockwise, this will disassemble the cap and allow access to the resistor, the dimensione of it are somewhat like an old glass style fuse. Cut a piece of heavy gauge wire to replace the resistor and reassemble.

Also, be sure to follow the link to "top 20 newbie mistakes" that Nessism posted, that's invaluable info!

[Grimly]

Well that just may be my issue! Pulled the (clearly aftermarket NGK) plug caps and figured out they’re only rated at 5k ohms. Replacements being ordered, will keep the thread updated on how it goes.

They're only supposed to be 5K ohms.

[natepittiglio]

So big update, got it running!

Not well obviously, definitely needs a thorough carb clean, fresh gaskets and new o-rings on the boots. Bogs down when revved up, chokes have to be perfectly set otherwise it won't idle happily, etc etc. I'm just happy it fires up and runs. I'm fairly certain this is the first time its been fired up since someone decided it was a good candidate for a cafe-style conversion and couldn't get it to start again. Like I said previously, tire date codes from the late 90's

Credit to my roommate who traced the wiring and figured out the spark plugs, although wired correctly and "getting spark," were firing whilst exhaust valves were open and there was a lack of compression in the cylinder. Who would've thought it'd be something so simple.

Oil is in surprisingly good condition, if I had to guess, PO changed it and a few other things to try and get it running to no avail. Still going to change it, along with new tires, chain, sprocket and whatever other gremlins I uncover while digging through this bike. Currently have it set up on a spare (rough condition) stock exhaust, however I'm planning on swapping over to a aftermarket pipes off my roommates 79 GS425 (since he took my nice condition OEM ones in exchange for free labor). Bike is also running on old, worn pod filters, which work for purpose of getting it running, but I'll most likely end up buying nice new ones. Any tips on tuning the carbs with pods would be appreciated, I understand its a contentious subject, however the stock airbox will not fit back in without significant modification, plus I'm a sucker for the pod look.

Thanks for the help thus far, I'll be back asking more stupid questions soon