Plagued by this '83 GS450L - won't start AGAIN!

[incarceration]

I just swapped my pilot jets back from #47.5 to stock #45 a few days ago, week at the a most, and it was running just fine; maybe acting a little rich.

Well today, I wanted to take it for a ride and verify everything was good, before taking it to work tomorrow. So i tweaked the pilot screw\fuel and air mixture screw by putting them all the way in and backing them out 1.5 turns, on each. I then let it warm up and took it up the straight away by my apartment complex and ran it hard up to 60MPH then turned around and did the same thing up to 60MPH. After I got up to speed I let off the gas and started slowing down to ~50MPH as I went to ride around town a bit. After I rode around for a bit, and sat at the red lights, it started idling weird again, acting like it was running rich and about to die. So I went back to the road near my apartment and ran up the road again hard then turning around and coming back toward my apartment and I hit the kill switch and then rolled to a stop on the side of the road to check my spark plugs, to see if the engine is running rich, lean, or just right. So I pulled out my socket wrench and checked them both, and both of them seemed ok except the left was kind of rich IIRC and I adjusted the pilot screw in a little bit then put them both back in and started it up again. Well now the bike has not run normal AT ALL since. It sputters really bad, doesn't get even fast enough to switch into 2nd gear, so I practically push it back home. Once I get home I pull the plugs again, and I had found some extra plugs I had and put them in because I remember I dropped one while sitting on the side of the road 20minutes prior. Now the bike doesn't even start up, it just cranks and cranks, but never starts up.

I have checked both plugs to spark next to the engine head
I checked both plug wires to be within spec of OHM resistance with volt meter from battery to inside the plug boot
I checked both cylinders for compression, LEFT is ~90PSI and RIGHT is about 118PSI

I don't get it. Not even an hour prior, the bike was running fine, but idling weird at a red light.

How could killing the engine when running, pulling spark plugs and putting them back as usual, and adjusting the pilot screws make the engine not start AT ALL now?

Please help!

 

[chuck hahn]

But did you regap them after dropping them???? May still be a faint spark..but a wider gap will give a better spark. regap them and set everything back to when it was known to run ....

 

[incarceration]

Hey! Thanks for the reply.

I dropped them on their side. Do you think this is a spark plug issue?

I tried another pair of plugs I had that were for this bike and it did the same thing. It'll crank and crank and sometimes just sputter but never actually start up

 

[chuck hahn]

got a plug cleaner? Take some wire ( like welding wire) and some carb spray and scrub around the center electrode and the threads and loosen any carbon deposited there that could cause fouling. Got me one of these from Harbor Freight and it makes them look like out of the box new again.


http://www.ebay.com/itm/like/290633842701?lpid=82

 

[incarceration]

What about a wire brush?

One of them has soot on it, the other looks like it's burning rather normal.

The 2nd pair of plugs I put in them were brand spankin new and shiny.

You think this would happen all of a sudden after it had just been running earlier today?

EDIT: I just checked compression again because I remembered that I didn't roll the throttle wide open; both cylinders are damn near exactly the same at 152PSI

 

[chuck hahn]

Could. You adjusted the screws and maybe you could have dislodged some crap..who knows. Thats why i suggested regapping / cleaning the plugs and resetting them back to the last "known" running settings and see what happens.

If it wont run where it was last good..then maybe the carbs got gunk loose in them?????/ Just a wild guess, but the 3 things you need are fuel, air, and spark. Too much fuel will make sooty plugs quickly. Stuck needles and such can be a problem.

 

[incarceration]

Actually I just checked the plugs and one is bent, so bent it's pretty much touching the electrode. I put in some plugs I had here, the new ones I tried earlier and now it's running fine again. Started right up.

I'm gonna go run around town again like I did earlier and see how it runs.

I'll get back to you about 30min - 1hr

 

[incarceration]

It runs like a dream now! I don't know what happened or why it was acting that way but the same plugs (that appear to be new) are in it now and it's running great.

One thing, when I sit idle at a stop light, it'll idle around 1.5-2k RPMs, is that normal for the 1983 GS450L? I thought it was supposed to be around 1.2k?

How do I adjust this and what can I adjust to fix this? Pilot screws and idle screw?

I turned the idle screw a tiny bit when sitting at a light and it seemed to help a bit but I don't know how far I can adjust that.

Thanks for your advice on checking the gapping!

 

[chuck hahn]

The big knob between 2 and 3 is the idle and can be set so low it will stall and not restart..or can be set so its at 4 grand!! Warm the bike up well and adjust back to around 1200 or so. It will start better and should idle consitantly. Bad idle fluxuations can be from air leaks in the intake manifold orings ( carb holders)

 

[Nessism]

Did you replace the carb boot O-rings yet? Very common to get air leaks (and erratic idle) if you haven't.

Pilot screws should be open about 2.5 - 3 turns.

Vacuum sync is critical for a smooth idle.

Lastly, please tell us you have adjusted the valves. That low compression suggests otherwise. You will burn the valves if you don't adjust them properly. This is not optional maintenance.

 

[gustovh]

Make sure that your throttle cable is tight at the carbs. A loose cable can also give the symptoms that you describe, went through that with my Rebel.
V

 

[chuck hahn]

That..and be sure there is just a tad of slack when the grip has returned to its neutral position. Its a fine balance between good grip response and too tightly adjusted cables. AND tight cables may not allow you to idle it down well enough either.

 

[incarceration]

Sorry, I measured the compression wrong, I forgot to hold the throttle open.

My compression for each cylinder is at 150PSI

Both intake boot o-rings are replaced with new o-rings

No I didn't adjust the valves, how do I do that? I didn't know I needed to do that :\

I would like to vacuum sync the carbs but I can't because I don't have a vacuum sync tool. Do you know of any relatively cheap ones I could use?

chuck, one time when I adjusted the idle screw too low\lean it was making the bike run too lean which made one side of the bike knock every now and then or jump during idle, it was weird, but when i opened the idle screw some it fixed that


BUT, good news, I got the bike up and running again. I swapped out the plugs with the same plugs I tried earlier today (new Autolite 4054 type) and everything is running good. I don't know WHY it is working now but not earlier. I think I did change the mixture screws one more time, so that's all I can think of that could've fixed it from when I tried the same spark plugs earlier today after it wasn't working anymore

Thanks for all the advice guys!

 

[ron bayless]

question for Nessism- I know the valve adjustment as well as rings can cause low compression readings. With these bikes the valves are the usual suspects. But i have always wondered how much would one expect the compression readings to rise once the valves are adjusted properly. I also read one time if the motor doesnt have at least 100 psi it should be rebuilt.

 

[chuck hahn]

It wasnt knocking because the idle was too low so much as it was knocking because the valves need adjusted and the carbs need synced right. Knocking because the cylinders are fighting each other for fuel and proper ignition at the same time. Adjust the valves FIRST and then sync the carbs.

Ask for some help from someone relatively close to you with gauges and experience with the valves. Youll need a new gasket on hand when you do them. For a service manual check here....there are other manuals at the bottom link. If not there, you need to find one for that year and model bike. Maybe an aftermarket Clymer manual from a dealer or online venue.


http://members.dslextreme.com/users/bikecliff/