Flooded carb in PRI, now gs450 won't run well

[Guest]

Hi all,

after flooding the carbs I changed the oil and replaced the spark plugs. The bike will start and idle with the choke open till it warms up then the rpm's drop low and throttle response is really lagging. If I blip the throttle not much happens. If I blip the throttle successively the rpm's will climb and hold around 3k with no throttle after the blips. I had the bike for a week before I flooded it, so I only know what I've read on this site. Any ideas? Any trustworthy mechanics is Phx that someone can recommend?

thanks,
Marco

[uspsamaster]

I am not a carb guru but I suspect a float level/needle valve issue. Hopefully one of the gurus come along and can impart from their vast wisdom soon.

[cowboyup3371]

What maintenance have you done besides changing out the oil and spark plugs?

[Nessism]

Yes on the maintenance. Better get used to working on the bike yourself unless you are independently wealthy.

The Newie Mistakes will get you started on a list of things to take care of.

[MJPerez]

Thanks for the replies!

I haven't done any maintenance. I've had the bike for maybe a month. I got it with under 10k miles and all maintenance/repair receipts. I rode it home and thought I put the petcock in OFF but there is no OFF, just PRI. I've read the Newbie Mistakes and the Carb literature. I was literally reading them while my engine flooded. I don't have a problem working on the bike but my thoughts are: if the bike was in good working order and then I did one wrong thing to it, then that mistake is the place I should start. If trouble shooting for that problem doesn't resolve the issues then I move down the line. Also, I do have a little wealth and conversely have killed two motorcycles and car by trying to do work beyond my skill level; I'm just not that good at it. I will do the work I feel comfortable doing and if that doesn't fix it, send it to the mech. Ideally, a mechanic with a long history of satisfied Phoenix customers.

Thanks again!
Marco

[cowboyup3371]

There really aren't any mechanics except for yourself that will work on these old bikes as many bike shops won't want to and don't have the experience to do so.

The petcocks supply fuel to the carbs using a vacuum created by them to operate so PRI is to prime the carbs when it's sat forever. On should be where it sits even when the bike is off while Reserve is needed when the fuel reaches a point in the tank that the tube used by On doesn't supply the fuel. This gives you about (roughly) a half gallon of fuel to make it to the gas station.

If you have read through the site and the newbie mistakes, you will know that all of us try to tell everyone Previous Owners lie and do so regularly. You need to go through all of the maintenance recommended by us and make sure it's right. Go through and clean the carbs properly ensuring you bench synch them, do the valve adjustment, check your boots and air filter (I assume you have one and not pods???), and then properly synch the carbs using a Carbtune or other synch tool.

Also, it would help to know what year 450 you have so we can help you with the synch work.

[tom203]

For your own safety , do some maintenance- put little faith in previous owner's claims or receipts. As for petcock, since it has a "PR " spot, it should have a "ON " spot and "RE" spot too - does it?? The ON spot likely has lever pointing straight down. Make sure you understand how petcock is designed to work or you will keep contaminating the oil with unpleasant results.

[tkent02]

Also, I do have a little wealth and conversely have killed two motorcycles and car by trying to do work beyond my skill level; I'm just not that good at it.

This amuses me. You can obviously afford a more modern motorcycle which requires less maintenance and which probably has not been neglected for decades like one with less than 10,000 miles over thirty five or so years obviously has. The only possible reason for choosing an old GS is that you want to learn to work on things like this, or if you already know you enjoy doing the work like most of us do. The skill level matters not, there are new guys on this forum who use it to do anything from change spark plugs to complete engine rebuilds with no prior knowledge, there is always someone here to help you out if you get stuck. We occasionally get a new guy who got a free GS or a super cheap one and falsely thinks it will cost less than a modern motorcycle to ride. Some of us tell our wives this line but we all know it isn't true.
Anyway your reasons are up to you.

Shops haven't worked on old stuff like this for decades, they get burned on it. They do a hundred dollar job on some old neglected bike, break off a few bolts because it's rusted in place, now it takes extra shop hours to fix, the bill goes to $1,000 or so, the bikes only worth $400, the owners says get lost, and they are stuck with the piece of crap. Never do get paid for the work, they can't sell it because it's worth nothing, the owner never told them about all of the other problems they can't afford to fix. They can't sell it as is because they can get sued and lose their whole business. This has been the case for so long the younger mechanics are not trained on the old stuff anyway. If you do find one that says they will do it chances are good they will just rip you off anyway. Even if they tried they can't put in the effort required to do it right, time is money. So yeah it really is going to be a Do It Yourself thing. Decide if you want to continue or if you want to sell it to someone like me at parts bike prices. ( I like 450s )

If you want to continue The first thing to check is that you didn't fill the crankcase with gasoline when you left the petcock on prime. The EPA in their infinite wisdom mandated the over flow tubes go away in 1980, so now if the carbs overflow it goes into the engine to ruin it rather than spill harmlessly on the road. Just check the oil, if there's more oil in it than there was and if this oil smells like gasoline you need to change it out again.

Then start on that long list of maintenance, it's really not all that long....

[MJPerez]

Hello cowboyup, thanks for the info. I learned what PRI meant when I came out to a fuel leaking bike I have only ever owned bikes that have ON, RES and OFF before this one; so now I am petcock informed! The carbs were recently seviced by a mechanic here in Phoenix. Given the receipt record I can say that there are a number of shops still willing to work on this bike in the area. However, I do want to do the work myself, I just want a back up in case I think I get in over my head. I really like the bike and I want it to live! I have ordered a number of tools to get me set up to do the maintenance. I was getting ready to do the EPA deletes but it looks like it's already been done, as I see screws and not plugs. My problem is that the bike was in great shape and the mechanic had the thing humming well, this one goof up killed its mojo, so that's why I'm so focused on trouble shooting from there. Also, the bike is a 1983

Thanks!

[MJPerez]

Hi tom203, I will do the maintenance, promise. I have never owned a petcock with PRI, just OFF. I know all about petcocks now

[cowboyup3371]

MJ, for your own sanity please go through those carbs again; the receipt means nothing in today's day and age since the shop could have just spritzed carb spray through the carbs and not properly cleaned them.

[MJPerez]

LOL! Ok, I'll do it. I was just hoping to do it later, I wanted to ride it for a bit first.

[MJPerez]

If you want to continue The first thing to check is that you didn't fill the crankcase with gasoline when you left the petcock on prime. The EPA in their infinite wisdom mandated the over flow tubes go away in 1980, so now if the carbs overflow it goes into the engine to ruin it rather than spill harmlessly on the road. Just check the oil, if there's more oil in it than there was and if this oil smells like gasoline you need to change it out again.

Then start on that long list of maintenance, it's really not all that long....

I do want to do the maintenance, I'm just getting it out there that I have failed on some of the repair work before. The mechanic is just a safety net that I can fall back on if I think I'm on the path to murdering another bike. I'm trying to rehabilitate from my past wrenching crimes.

I did fill the case up with fuel that's why I changed the oil, filter and spark plugs. Anything else I should be checking in regards to this newb mistake?

thanks!

[cowboyup3371]

Tom is saying to smell it again and change it again if necessary - read his last line in that first paragraph you quoted again

[JRHemmen]

Welcome to the forum MJ. Like everyone else, I'd recommend a full carb clean. My friend's bike's PO had the carbs "professionally rebuilt", and my friend had to rebuild them before the bike would start. One float was broken, all the gaskets were cracked, and the accelerator pump diaphragm was rock hard. Basically, (like they've all said already) take the words of a PO with a grain of salt. I have a 450 as well, and the first thing I did to the bike was a full carb clean and rebuild. There's a guide on the bikecliff website for cleaning our specific carbs, I'd suggest you do that, along with replacing the O rings. Check your boots and boot o rings as well, you'll never get it running predictably when you've got unpredictable vacuum leaks through the boots.

Also, to make it easier for everyone when you create new threads in the future, be sure to add the model of your bike to your signature.