81 GS450T won't idle more than a few minutes.

[sylaei]

Hey all,
I have an '81 450T. I have finally gotten it running again, sort of. It starts great. Idles at around 3000 - 3500 rpms for 3 or 4 minutes then just dies, if I don't intervene. "Newbie Note: I just figured out that Pri on the petcock meant prime." After moving the petcock to on, it will run at 3000-3500 for a few minutes then drop to around 2000-2500 for a minute or 2, but then dies anyway. After it dies it is hard to start, if I let it set for a bit then try again it starts right up. At this point I am thinking that it is flooding, especialy when I had it on Prime. Could it be a air/fuel combo causing this? If so what should I adjust to check to fix it. I feel like I am close to having the bike running again, but its to early to strike up the band.


Thanks,
Syl

[BassCliff]

Hi Mr. sylaei,

My guess would be a fuel delivery issue. Are you using an inline fuel filter (not usually recommended)? Does your tank have any gunk in it that would clog the petcock screen? Disassembled and dipped the carbs? New intake boots/O-rings? Have you adjusted the float height? Let me roll out the welcome mat for you. It's got a lot of good info...

Please click here for your mega-welcome, chock full of tips, suggestions, links to vendors, and other information. Then feel free to visit my little BikeCliff website where I've been collecting the wisdom of this generous community. Don't forget, we like pictures! Not you, your bike!

Thanks for joining us. Keep us informed.

Thank you for your indulgence,

BassCliff

[smoothbomber23]

I read a thread about the signal generator not working when the bike gets warmed up, and it just dies, then when it cools down again it will start with no problem. Idling for a few minutes at 3500 rpms would probably warm the bike up pretty quick. If this is the case you'll need a new signal generator I believe. One more thing is why is it idling so high at start up, im assuming that you have the choke on for it to spike that high, remember to take the choke off and let it idle around 1100 to 1300. I am also new to this but recently got my 450 running pretty well and this would be my guess, but before taking my advice let the experts on the forum give you more advice.

[Nessism]

Sly,
First off, welcome to the GSR. The best motorcycle community on the web!

Regarding your bike, have you done all the basic maintenance yet? Complete carburetor tear down, soak in carb dip, replace all the old hard rubber O-rings? Replace the O-rings on the intake pipe boots? Adjust the valves? Clean the air filter? Check the tank for rust and verify the petcock is functioning properly? By doing all this basic work you will have a positive foundation to build on and troubleshooting is much easier.

[Steve]

OK, first of all,


Now, time for a history lesson. Please educate us.

How long have you had the bike?
If you have just gotten it and don't know the history, you have a long list of things that should be done to ensure a well-running bike. See BassCliff's welcome page and go through some of the things to do.

How long since you know it has run well?
Again, this comes down to how long you have had it. If you just got the bike and don't know the history, that's one thing. If you have had it for some time and it has run well, but is now not running well, that's another thing.

What have you done to get it where it is now?
Have you adjusted the valves?
Have you checked the ignition timing?
Have you cleaned the carbs THOROUGHLY?
Does it have relatively new spark plugs?
Does it have a clean air filter?

Are you using the 'choke' (enrichener) to start the engine?
When everything is running properly, starting procedure involves moving the 'choke' knob about half way, pulling the clutch lever, turning the key ON, hitting the starter button and NOT touching the throttle. Modulate engine speed with the 'choke' knob. If you are able to start a cold engine without using any 'choke', you might have some jetting issues.

Does it run without the 'choke'?
You made no mention of using the 'choke' knob, so we don't know if it's running at 3000 rpm ON 'choke', or OFF 'choke'. Might require different cures for different scenarios.



Dang, Nessism, we seem to be trading off who types quicker.

.

[sylaei]

Thanks, guys for all the quick replies. Some how I hoped you'd just say, “Turn this screw left a half turn” and it would fix it all. Just kidding, but there is more to do than I had imagined. I don't know the history of the bike at all so, I'll just make a list of everything you guys have suggested, start with that and see where I wind up.


BassCliff
Inline fuel filter? No. Gunk in the tank? No I will remove the petcock and make sure it is clean. Disassembled and Dipped the carbs? No. Is the dipping something I can do? If so what should I dip them in? Meaning liquid, not container :-O. New intake boots and O-rings? No. I'm afraid to adjust the float height. I would assume I could do that on the bike. I have 'clicked here for my mega-welcome', only to find more to do. :-)

Smoothbomber23
I'm not sure what a signal generator is, but is there a way to test it or is it a matter of replacement. At this point, I'm willing to replace anything that needs it. Also I don't have the choke on at all, it just idles really high. I didn't really know where it should idle until your post.

Nessism
Embarrassingly I must say no to all but a few of your suggestions. The air filter is new. The tank is clean, I think the petcock is functioning properly but I will check it. I'm not sure how to adjust the valves, but I do have a chilton manual on the bike, so it will probably guide me.

Steve
History 101. I have had the bike for almost 2 years. I bought two bikes from the same person, an 81 GS450T (my wife's bike), and an 80 GS550E (mine). Both bikes ran, but the 550 had been taped and bubblegummed together to run. I worked on the 550 for a while, and my wife rode the 450 around the yard. She had never had one before. My daughter tried to ride it around the yard and laid it over. It is a small yard it didn't hit hard at all, mostly from an almost stopped position. At that point the bike quit running. I'm not sure what happened but I did remove the carbs, and cleaned the tank up. I also replaced the coils, one of the spark plug wires broke where it connects to the plug. After that it has been touch and go as to whether it would start. At some point I was able to get the bike to start and idle as it does now. My guess is that this bike was also rigged to run and something failed. I have also tried to sync the carbs. I say tried because the vacuum gauge showed 2in HG on both carbs. I didn't adjust anything since they matched but I would have expected more vacuum. Not sure I'd know what more vacuum even is. It does have new plugs and a new air filter. As for cleaning the carbs, no I haven't. As to the choke, I have been able to start without using the choke. Although I do have to give it some throttle to get it started, but not much.


I have also changed the oil and filter on the bike. No apparent issues, like fuel in the oil.



Thanks again for your suggestions. I'll compile a list of things to do and see where that leaves me. If anything I've mentioned above rings any bells, please let me know.

Syl

[BassCliff]

Hi,

Yes, you too can dip your own carbs. The carburetors are the heart of your motorcycle. They must be properly maintained. Berryman's is the preferred chemical dip, but there are others that have been recommended also.

Try the Carb Rebuild Series. You'll be glad you did.


Thank you for your indulgence,

BassCliff

[LarryA_Texas]

fuel

All the suggestions above are valid and proper maint. for your bike.

I'd like to address the 450...it just fell over and quit running?...and wouldn't start after that? That's very strange. Motorcycles don't usually do that. The carb cleanup series will guide you through and it's a lot simpler than it looks. But in this case I'd look very carefully at the float needles and the needle valve seats. Those needles are almost certainly getting stuck and blocking off the fuel flow.

That is a possible culprit on the 550 also. Or a bad petcock. Fuel is leaking in slowly. Once the bowls fill up it runs, burning the gas in the bowls. When the bowls empty the bike quits, one cylinder at a time (low RPM then off) as the carbs run out of gas. The restriction to the fuel flow (if that's it) must be corrected. I'd put my money on a bad petcock.

Clean the carbs or rebuild the petcock. Or both.

A signal generator is inside the small right side cover of the engine. It decides when the sparks fly. I've never heard of one getting hot and quitting but won't say it can't happened. The SG sends it's signal to the ignitor box which sends a signal to the coils. If you have a clymers, or a shop manual, there is a simple test to see if it's working by measuring the resistance between the wire leads that connect it to the ignitor.

Keep asking questions here. It's all going to work out.

[sylaei]

Well, quit running isn't quite right. It was hard to start and wouldn't stay running. It was impossible to ride after that. That was early last fall, I have had the carbs off, maybe that had something to do with it. I was wondering if that could be cause by the boots, maybe the fall loosened one or both. I have had it running and sprayed each boot with WD40 and didn't get a rev from the engine, so that means that they aren't leaking now. Least I hope that. I could replace them, probably should, just thought there were more important things to fix or replace.

Syl

[smoothbomber23]

http://www.thegsresources.com/_forum/showthread.php?t=138123

That was the thread about the bike warming up and dying, might be worth a look. Also I recently did a valve clearance check on my gs450l and at first i was nervous to go into the motor but it is very simple just go bike bikecliffs website DIY and you'll be fine, also the zip-tye method works really well (you'll see this all on his website). Is your bike modded at all? If so you will need to mess with the jets.

[BassCliff]

Hi,

Click here for float height information.



Thank you for your indulgence,

BassCliff