82 GS450L bogs/hesitates at ~1/2 RPM range!

[Ludeykrus]

Hi, I am a new guy posting, but have been lurking for a little bit. A little while back I picked up a 1982 GS450L for very cheap from an acquaintance. The catch was it had no key and ran a bit poorly. I managed to easily hotwire it, so now I just have to get the thing running right! :-D

This is from memory, and I've never worked on bikes before, so please bear with me. The bike has been sitting for a while during bad weather and for other technical problems.

I understand these carbs are RPM-based. I can get it to warm up and idle alright (it idled a bit low, but I adjusted the throttle cable to fix the low idle). It runs decent up to roughly 1/3 or 1/2 of the RPM range...then it starts to hesitate hard. It will do it while parked on the stand or while driving under load (which is almost dangerous enough, being bucked off can't be fun!). It will usually, though, kick back in hard at the top of the RPM range and pull strong (once again, going from bucking hard to full throttle near redline is "exhilerating"!). I've tried pulling the plugs after a bucking run, yet they show a nice healthy reddish/brown hue, IMO suggesting properly rich. When bucking on the kickstand, it almost sounds like a lean popping, though. It needs new plugs, i'm sure as well.

I am used to building up fuel injected/ECU-controlled cars and carbs give me the willies! My guess is a clogged/gummed up jet or the such. I am guessing I will need to tear down, clean, and resync the carbs...... But I will be trying a new fuel filter, cleaning the petcock, and a few other small things before going through that hassle.

Anything screaming out obvious to you guys?

[earlfor]

I have had that same problem and it turned out to be nothing more than a dirty air filter element.

Earl

[Ludeykrus]

I have had that same problem and it turned out to be nothing more than a dirty air filter element.

Earl

But would it pull hard at the top-end? The bike HAS been sitting in a garage for a good little while...

[Billy Ricks]

Go ahead and bite the bullet and clean the carbs. Synching a two cylinder bike is easy and doesn't require guages. BTW, tightening the cable isn't the right way to raise the idle. The cable needs a little slack to prevent revving when the bars are turned.

For synching, let the bike run on one cylinder at a time by removing one spark plug wire at a time. You'll have to raise the idle speed with the throttle stop to get it to run on one cylinder after warming the bike up first. Start with the cylinder with no idle speed adjuster on the carb itself and adjust the mixture screw for the highest smoothest idle you can get. Pay attention to the tach reading after adjusting the mixture. Then switch to the other cylinder. Adjust it for the smoothest idle then adjust its idle speed using its individual adjuster to match the cylinder you already did. After you're done you'll need to drop the idle speed back down with the throttle stop.

[Ludeykrus]

BTW, tightening the calbe isn't the right way to raise the idle. The cable needs a little slack to prevent revving when the bars are turned.

Yeah, I know..... I only did it to keep it running enough to check on the other problems.

I'll try popping the air filter later. Am I crazy for thinking it's a blocked "mid-level" jet? I don't know which jets control what yet, so it's just a guess.

[Billy Ricks]

Yeah, I know..... I only did it to keep it running enough to check on the other problems.

I'll try popping the air filter later. Am I crazy for thinking it's a blocked "mid-level" jet? I don't know which jets control what yet, so it's just a guess.

You're on the jet needle at that point in the rpm range. At idle to about 1/4 throttle you are on the pilot. From there the needle takes over with maybe a little overlap from the pilot circuit. At full throttle you are on the main. Check your carbs and see if a jet kit is installed. If a jet kit has been installed the needle will be adjustable with 5 grooves in it where the e-clip fits for adjustment. The jet needle works in conjuction with the needle jet (emulsifier tube as some call it). The needle jet is the brass tube the needle slides up and down in. It has tiny holes in it that may be clogged. If the bike sat up for any length of time the carbs most certainly need cleaning. They are easy to work on. Just follow the carb cleaning how to found on the homepage. It's for a different model but it will help guide you.

[Ludeykrus]

Cool beans, thanks bud!

I bought this bike from a buddy's father. I remember about two years ago it ran fine. My guess is he parked it when he bought his new Harley and, from my reading here, the carbs gummed up.

I doubt it has a jet kit since it ran fine before, and everything else on the bike is bone stock.

I've already got a shop manual for the bike and a good set of tools. So a carb sync tool isn't necessary? The "by the ear" method will get me close enough?

*reading up on DIY carb sync tools...*

[earlfor]

Yeah, it pulled hard at top end and started and idled perfectly. About 5500 rpm, it would start losing power and jerking, missing etc. If I downshifted a couple gears to put the rpm above 7K, it accelerated normally to higher rpm.
All that was wrong was an obstructed aircleaner. Your problem may not be so simple, but it wont cost you anything to clean the airfilter to check.

If the bike sat for two years, its a safe assumption the carbs are gummed up and need cleaning. (by cleaning, I mean a complete teardown, removal of all plastic and rubber parts and the carb bodies soaked overnight)



Earl

But would it pull hard at the top-end? The bike HAS been sitting in a garage for a good little while...

[Ludeykrus]

Alright, quick update:

Tore down the carbs and cleaned them. Put them back together and set everything to the settings they were before. IIRC, the air mix screws were 1.6ish turns out. While trying to resynch them, I couldn't get it to really set at a place it liked. I would set them both at about 1.5 out, pull a plug, crank it, and turn the screw to see what it did. It would almost die out if put all the way back in, and would get just a bit faster at 3-4 turns out and stay that way until it was backed all the way out. I left them both at 1.5 turns out and it runs fine.

I checked the air filter; it looks near-new. I pulled it out and let the bike run with no filter and an open lid, and it ran a bit worse. When rev'd, it would stumble harder.

I took it out for a test drive again, and it acts the same, although not as bad as it did. It is slightly better since the carb clean....it doesn't nearly buck me off, but it still bogs hard and goes nowhere. It almost seems like it bogs hard between 2-3k and 4-5k, and then it starts to accelerate slowly at 5-5.5k and takes off around 6k. It accelerates, but it feels obvious it is being held back. I noticed the pipes are bluing bout the first 8-12" from the engine. It also pops on decel. It is running lean apparently.

I pulled the plugs and checked the spark. While it's not a huge fat spark like I'm used to on my car, it's nice, blue, and consistent on both. I found out the hard way that I can get shocked through the rubber boots when pulling the plugs, so I had to grab two pairs of my mechanic's gloves!

The bogging is independent of throttle position. It will bog just as much at 1/3 throttle as it does at WOT. When on the stand, it seems like if I put the choke in a bit, it gets a little better, I can't say how much though.

When putting the carbs back in, I rubbed some grease on the inlets for the air box and the connectors to the head, in an effort to prevent any small airleaks from showing through. I haven't had a chance to properly check for any intake leaks, though.

So what do you guys think I should try next?


EDIT - I also replaced the fuel line. The one that was on there had an inline filter on it, and it looked like it may have been restricting flow a bit due to a bend right at the end of the filter. Replaced it with new line, but no change.

[tfb]

Go for all the most basic things first, and eliminate them. It's very easy to go barking up the wrong (and hideously expensive tree) because of overlooking the basics. So...

1. Hang the expense and get a new set of spark plugs; you don't know how long they've been there and the suckers can do crazy things, like sparking OK when placed against the head (as you have done) but breaking down under load, heat and higher rpm.
2. Clean out your fuel tank; it could have enough crud and water in there to be choking up the works at the nylon gauze filter that's integral to the fuel tap. (Although if that was the prob. it would run poorly at higher rpm too.)
3. Take off the carbie bowls and clean them out to ensure that there's no crud in there (found a thick layer of rusty sludge in mine, which wouldn't drain out just by opening the bowl plugs).
4. I know you've said that the air filter looks OK, but they can look OK and actually be chokkers with crud. However the fact that you've got the prob. with the filter removed tends to indicate that the filter may not be the root of the problem.
5. As already mentioned by others, give your carbies an overhaul and thorough cleaning. Check for manifold leaks.

Keep sleuthing,
Mike.

[Ludeykrus]

Check my post right above yours; I've already cleaned out my carbs. They looked really clean, too, Surprisingly!

I will try cleaning the tank, though. Probably needs to be done anyways.

[tfb]

Ah yes, you've already cleaned the carbies, then! Hmm, I must have been reading too many threads.