New 1981 GS450L Won't Start!!!

[den151]

I just bought a nice looking 81 gs450L for 300 bucks. It has 2,200 miles on it!!! It has been sitting since around 1983 in a garage, all fluids were drained back then. Everything works on it except it won't start.. Cleaned the carbs out good, tank has zero rust inside, oil is filled, new plugs, air cleaner. Tried to start it and it backfires hard after 10 or 20 seconds of cranking[exhaust]. It seems to have a good blue spark on both sides, getting fuel. What kind of tests do i need to do? I have been working on cars for 30 years, this is my first time working on a bike. A little frustrated...
Bike still looks new, original everything!!!!

PLEASE HELP ME HELP MY BIKE

[Nessism]

If the carbs have overflow tubes on them you can blow into them to prime the carb.

The pilot jets have a tiny orifice which needs to be clear or the bike will not run properly. Hope you pulled them out when you cleaned the carbs out.

[den151]

Yes, removed everything soaked, cleaned, air pressure through everything

[chef1366]

You are sure you have fuel in the bowls? Did you prime them?

[nabrams]

Same old story. Bike has been sitting for years, now it won't start.
I've restored two non-running GS450 bikes, so take a deep breath and read this carefully (you may not have found this when you searched the forum - you did search, didn't you??).

This bike is "new to you" and you really have no firm idea of what is the current state your carbs, compression, valve adjustment, air leaks, exhaust system leaks, etc.
There are MANY posts (some by me) that detail the minimal set of items that should be verified so that you don't endlessly chase your tail (play guessing games about what's wrong) - You will need to verify these items eventually - there's just no way around it. In cases like yours it is almost always more than one issue that needs to be solved.

Here's a post I put on another forum:

The process of reviving an old neglected bike has included the following steps for the four non-running bikes I've revived (the last being a 1980 CB750). It seems (from reading other's posts to this forum) we all go through more-or-less the same steps.

The following is not meant to discourage you. Just the opposite. I want to show you that many of us have been there and with some perseverance you can have a great bike for a fraction of the cost of a new one.
It took me a long time to work out all the kinks on my CB750. This site was a huge help.

Now for the hard realities:

1. Most mechanics will do more harm to your bike than good and you'll be paying them a fortune too. Many of us have horror stories. With that money you could get all the tools you need and a spare parts bike to boot.
2. You're going to need to invest between 30 and 60 hours of time wrenching to get that bike back in decent working order.
3. Do NOT attempt to troubleshoot poor running before doing a valve clearance adjustment. No amount of carb fiddling will do any good if the valves aren't closing fully (leading to below-par compression). Unfortunately, I learned this the hard way.
4. You will certainly have to go through the carbs yourself and verify EVERYTHING is in order. I'm assuming you've got a manual (or just print out the manual on this site).
5. Carb boot air leaks and/or exhaust leaks are almost certain on your bike, or any other 20+ year old, uncared for bike.
6. Almost EVERY 20+ year old bike will have electrical issues (coils and/or electrical rotor and/or stator, etc.) if it's all original equipment. See the stator papers for info on how to verify your charging system. Bad coils could definitely be a factor in top-end performance - coil performance degrades at higher RPM.
7. Once you get the basics worked out, you're going to have annoyances pop up at least once a season (leaking fork seals and the like).
8. Using the search feature of this forum and spending some time reading (and following the advice that there's a consesus on) will save you a TON of time.

Here's some more:

If the bike has been sitting for some time you're going to have many tasks to perform before the bike runs properly.
Here's some advice I gave to somemone:
I've "restored" two GS450 bikes that had been sitting for long periods (mine and a friend's) so I've encountered almost all the typical issues.
You will almost certainly need to do a thorough carb cleaning. The fact that it started up is deceptive. It will not produce smooth, full power till you get those carbs spotless. Your air filter element, air box and all boots that connect to the carbs will have to be checked (any air leaks and all bets are off - see my other posts about this). Your regulator/rectifier and stator should be checked (as described in the garage section of this site). It is also likely that you'll have some loose and/or dirty electrical connections.
Some of the cables may need lubrication and adjustment. Of course, you will need a new battery.
If you've never done any of the above stuff then it will take you a while to learn it all and to acquire the right tools - anywhere between 25 and 60 hours of work - I'm trying to be realistic here based on my own experience. The second time I did a "restore" (on my friend's GS450) it went much, much faster. A Clymer's manual is a must.
If you're in no rush and you enjoy wrenching an hour or two a night then I'd say go for it. If not, you could take it to shop and pay an arm-and-a-leg for them to do half-baked job that you'll have to "finish up" - once again, I'm speaking from personal experience I had with a Honda many years ago.

Here's some more:
You had a running bike before the carb rebuild, so I'd guess your main problem is with the carbs. However, it is possible that other factors are just borderline enough that a slightly worse carb situation would expose those issues as well.
Before tearing the carbs down again, verify all the easy stuff first:
1. Put in brand new plugs - I can't tell you how much time I've wasted just to finally realize that my plugs were so wet and fouled that the bike had no chance of starting. This is especially common after doing carb related stuff.
2. Verify your air filter element and box and boots are all set up properly and that there are NO air leaks.
3. Using those new plugs, check that each one is sparking. If the bike is properly carbureted, even a faily weak spark should ignite the fuel/air mixture.
4. Verify that your petcock is letting fuel through to all carbs.
If all of the above checks out OK and you still can't get her started, then it's time to tear into those carbs again. Make sure your floats aren't leaking (there should be no liquid sloshing around inside of them) - I once overlooked that very important test and spent many hours fiddling with other things till I remebered to check if my floats were leaking. Sure enough, one of them was leaking like a sieve.

Also:
Your starter motor may be really dirty inside, preventing full electrical contact: been-there, done-that.

The 1980 GS450 is electronic ignition so there's no timing adjustment necessary.

Of course the gas tank must be drained.
Soaking the carbs in gas is useless, you must disassemble the carbs and clean them meticulously (especially if they've been sitting for two years).

Good Luck. Let us know how it turns out.

[den151]

Thanks all for the info, looks like i have a lot of work ahead. I'll be back later with some results.

[den151]

New old 1981 gs450L, STARTED!!!

Thanks for the help, Cleaned the carbs again, primed them by blowing in the overflow tubes and fired it up!! Now i have an oil leak.... seams to be coming from left side behind chain cover???? Runs good, eveything else works good. Could the backfiring have blown something out?

[chef1366]

Old bikes=oil leaks. Pull the sprocket cover off and see where it's coming from. Those seals are easy to replace.

[Nessism]

Clutch pushrod seal and/or shift rod seal are common leak sources. Both of them leaked on my 450. Easy to fix which is good. Hardest part is getting your hands on the parts.