fuel starvation/bad gas mileage

[davidduarte]

My 1980 GS450 seems to have a fuel starvation problem. At low revs (<4000) it seems to stumble a bit, and even over that, it will sometimes stumble, even at highway speeds. A year or 2 ago, I ran Sea Foam through the gas, and even ran the bike off of it by injecting it right into the carbs, then turning off the engine and injecting in more Sea Foam and letting it sit a few days. I took me about 20 tries before it would start properly, but it performed much better after that. It seems that I also can't get it to idle properly. Last year, I used to get around 60 mpg, lately I'm getting only around 40.

What I'm planning to do is drain the tank and remove the petcock, then blow the petcock tube out with compressed air. I'm guessing that rust from the tank, or possibly some gunk from the crappy gas we have here in Connecticut has built up on both of the screens on the petcock tube. After I do this, I'd also like to seal the tank. I've been hearing bad things about Kreem, but very good things about POR 15. Any hints or suggestions? I'm also thinking about rebuilding the carbs this winter; anyone know of a good place to get a rebuild kit?

 

[Mike Ski]

I have seen rebuild kits on e-bay.

 

[LarryA_Texas]

My 1980 GS450 seems to have a fuel starvation problem. At low revs (<4000) it seems to stumble a bit, and even over that, it will sometimes stumble, even at highway speeds. A year or 2 ago, I ran Sea Foam through the gas, and even ran the bike off of it by injecting it right into the carbs, then turning off the engine and injecting in more Sea Foam and letting it sit a few days. I took me about 20 tries before it would start properly, but it performed much better after that. It seems that I also can't get it to idle properly. Last year, I used to get around 60 mpg, lately I'm getting only around 40.

What I'm planning to do is drain the tank and remove the petcock, then blow the petcock tube out with compressed air. I'm guessing that rust from the tank, or possibly some gunk from the crappy gas we have here in Connecticut has built up on both of the screens on the petcock tube. After I do this, I'd also like to seal the tank. I've been hearing bad things about Kreem, but very good things about POR 15. Any hints or suggestions? I'm also thinking about rebuilding the carbs this winter; anyone know of a good place to get a rebuild kit?

There is a lot there. My first question is; have you ever properly cleaned the carbs?

You could accomplish a lot with a good cleaning. While in there be sure you replace the o-rings. Cycleorings.com is the place to get them.

Next...the start, idle, and gas mileage problems all point to the carbs. Sea foam probably bought you some extra time but didn't solve the problem. Clean them. The cleanup series on BikeCliff's web site tells you everything you need to know. Follow it closely and you will not go wrong.

Third...the tank. What makes you think you need to seal it? Is there rust inside? If your tank has light surface rust you can remove it electrically by following these instructions: http://www.thegsresources.com/_forum/showthread.php?t=106016

I've used POR-15 with good results several times. But I've also restored a few tanks with just the electrolisys process.

I don't know about comperssed air to clean out the petcock. Those little filter screens are very delicate. I think you'll blow them right off the tubes. Just wash them out carefully.

Lastly, a carb kit is generally a lot of money for stuff you don't need. Except for the o-rings, the carbs' parts don't need to be replaced. Why spend $25 per carb for stuff you won't use? And all of the parts you do need are available individually through many web sites.

Hope this helps.

 

[BassCliff]

Greetings and Salutations!!

Greetings and Salutations!!

Hi Mr. davidduarte,

There are a few basic tasks that should be performed. Clean the carbs, replace the petcock, etc. You'll find a list in your "mega-welcome". It's how I say "HOooooowwDY!"

Here is your very own magical, mystical, mythical, mind-expanding "mega-welcome". Please take notice of the "Top 10 Common Issues", the Carb Rebuild Series, and the Stator Papers. Now let me roll out the welcome mat for you...

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

 

[lucabond]

Check the vent in the gas cap to make sure its open and venting or it could cause a vacume in the tank and fuel line and it will act like you discribe. Don't ask me how I know... Good luck

 

[davidduarte]

Thanks for all the responses so far. It does have rust in the tank, but it doesn't look terribly bad. As far as stator/rotor/regulator rectifier, I replaced the R/R with an Electrex unit not long after I bought it in 2001. With the 850 I used to have, I ended up doing the whole works, but this bike just needed the R/R.

Maybe instead of compressed air, I have some dust-off type stuff for cleaning out the computer, maybe that would work ok? At any rate, I just ordered a new petcock gasket and some other parts from Bikebandit. I'm hoping to drain the tank and get it off the bike sometime this week (not sure when as I am a Mr Mom, and I work at night). Once I do that, I'll have a better idea of what the inside of the tank looks like.

Anyway, so if I don't need a carb kit, where can I get all the stuff that I need to replace in the carbs?

 

[BassCliff]

Anyway, so if I don't need a carb kit, where can I get all the stuff that I need to replace in the carbs?

Feel free to read your "mega-welcome". There actually is a lot of good information in there. I've worked very hard to collect the best, most often used, tried and true tips and suggestions. You'll find links and everything.



Thank you for your induglence,

BassCliff

 

[davidduarte]

alright, so I ordered the O-ring kit for the 450, saw the page about JIS philips screwdrivers. Anyone have experience with them? I'm just wondering what length screwdrivers I should buy for this application. It also seems that I should replace the intake boots while I'm at it. Looked on Bikebandit, it wasn't immediately apparent that they have them. I'll have to check some of the other sources listed.

 

[fenderfreek]

FWIW, I didn't use any special screwdrivers. All but one of mine came right out without any trouble, but the last one was an epic battle of physics. I put about half a can of penetrating oil on it and tried everything under the sun to budge it loose.

Ended up dremeling a notch and using a 4lb mallet and a big screwdriver. It even took 3 or 4 swings with that to move it, but it came out. You should really get the allen-head bolt kit from cycleorings.com. If I didn't have it, I would have been stuck one bolt short.

Not only will you probably destroy one, they look and work nicer too.

 

[Clone]

If you have enough rust in the tank to block the petcock screens which are huge by the way. You will also need to pull the float valves and clean the screens above the float valves.

 

[davidduarte]

I drained the tank out as much as I could, then flipped it over and took off the petcock. There was some gunk on the screens that I sprayed off with WD40. There's still gas in the tank, but it seemed that no matter how I turn the tank, I can't get the remaining gas out. My next step will be to remove the carbs.

 

[lucabond]

You could leave the tank out in the sun and the gas will evaporate. Then put a smaller tube like an old hose in you vacume hose tape it or stuff a rag to seal the connection now you can get the smaller hose into the tank to suck up all the loose rust. Make sure the tank is bone dry before you use the vac or some fumes could hit a spark from the vac and Boom. Good luck

 

[Clone]

I would suggest compressed air instead of the vacuum, vapours are seriously explosive.

 

[davidduarte]

I finally got the carbs off yesterday. Much easier than I thought it would be. Being a Mr Mom with 2 boys I don't often have opportunities to work on it. After disconnecting the throttle cable and removing the screws holding the airbox in, I put the handle of my mallet down through the frame and used it as leverage to push the airbox back. It was pretty easy then to remove the carbs. Now I just have to meet up with my buddy and his parts cleaner.

 

[BassCliff]

Hi,

I kind of know what you mean. My schedule has not allowed me to work on my bike as much as I would want. But I'm very close now. I've been seriously working on it since about October. I hope your work progresses faster than mine has. Let's get to riding!

Thank you for your indulgence,

BassCliff

 

[teddux]

If your 450 is consuming more fuel, then you are looking in the wrong area.

 

[davidduarte]

If your 450 is consuming more fuel, then you are looking in the wrong area.

I was also experiencing fuel starvation, and the bike wouldn't idle properly. These are problems I need to straighten out anyway. It's long overdue to have the valves adjusted. I'm also thinking of sealing up the airbox; any recommendations on what I should use? I think the megawelcome mentions weatherstripping, but I'm not really sure what I should seal up or what I should use to seal it.

 

[BassCliff]

Hi,

Here's what we do on an 850....

Airbox Sealing
(by Mr. Roostabunny)

Air Intake Repair:
Airbox removal, intake boots and O-ring replacement​

Thank you for your indulgence,

BassCliff

 

[davidduarte]

I just ordered new boots for the intake and the airbox. Should be a bit easier with a twin vs the 4. I'm a little leary about the screws holding the intake boots on; I'm sure they've never been off the bike in 30 years so I pray that they're not frozen.

 

[terrylee]

Soak them for a day or two with deep creep (made by seafoam people). I couldn't get an impact driver in there, so took small visegrips and got them loose enough to move with a screw driver. Or you can try a small chisel to break them loose.(just don't hit anything but the screws.) terrylee