Idles Smooth. Dies under throttle.

[Munzo]

I have a 1986 GS550es I am working on bringing up to working order. So far I have cleaned the carbs (fully disassembled, dipped and rebuilt), adjusted the valves, new air box and filter (old air box was busted) and changed the oil.

I got the bike running earlier this week starts right up with the choke and after a while I can bring the choke off and it idles nicely. I let it sit and idle for about 10 mins and reassemble everything and go to take it for a spin to test it out. The bike just bogs down under throttle and dies out. I pull everything off. Turns out my float needles are bad. So I order a new set. I received those today and installed them on the bike. It started right up. I took the choke off and the bike idled for a minute and died out, and I couldn't get it started again. So I am guessing the floats weren't the only problem.

I feel like I am close just one part of the puzzle is missing and I don't know what it is. I am new to all this so any help would be appreciated.

 

[BassCliff]

Hi,

How's your petcock?

(Gee, that's funny question.)

For how long did you dip the carbs? Sometimes it can take a full 24 hours. Did you reassemble with one of Robert Barr's O-ring kits? ( http://cycleorings.com ) Is all the intake/jetting/exhaust stock?

Keep us informed.

Thank you for your indulgence,

BassCliff

 

[Steve]

I know you said you got a new airbox and filter, ... did you put them back on? :-k

.

 

[Munzo]

I know you said you got a new airbox and filter, ... did you put them back on? :-k

.

I Sure did. I was getting some backfire before i replaced the filter, but it was running. Turns out the old filter was split and looked to be the wrong size. Stuck the new one on and the problem seemed to go away.

Basscliff - I was wondering if it might be a petcock issue. I haven't replaced it. It runs freely on prime, and it idles find when its set to on. It revs fine in neutral, but when I had it in gear is when it died. Except for today when it just died after idling for a bit. I didn't order the o-ring kit but replaced all the rings with ones ordered from cheapcycleparts.com, and some I was able to pull together on my own.

I didn't dip the carbs for a full 24 hours. depending on how the parts looked I dipped them from 30mins to an hour (per the instructions on the can) and then hit them with spray carb cleaner for good measure.

 

[KEITH KRAUSE]

If the bike idles fine and rev's well in neutral but stalls when you try to pull away then that's the classic sign of fuel starvation. If it appears your petcock is supplying enough fuel then you need to check the carbs for being clean/float levels correct and all parts/jets inspected for being correct.

 

[Nessism]

Did you verify the pilot jets were open? Look for light though or poke a wire through the center?

To judge fuel starvation you can remove the float bowl drain right after it stalls out so see if there is the normal amount of fuel inside.

 

[D.T.]

Did you verify the pilot jets were open? Look for light though or poke a wire through the center?

To judge fuel starvation you can remove the float bowl drain right after it stalls out so see if there is the normal amount of fuel inside.

This is the answer me thinks. I just had the same problem. I thought it was the SP caps, but that was just a part of it. #4 wasn't firing but I had good spark. Just took carbs off and found the pilot jet full of gunk. Cleaned with a wire brush. You should be able to see through the bottom of the jet into the light. It's the jet under the rubber cap in the carb bowl.

Also my 850 won't rev over 3k without the airbox. And it won't rev very well unless it's sealed EXACTLY like the orignal airbox should be.

 

[spcdolan]

where did you pick up the airbox? i'm having trbl finding one..

 

[Munzo]

Did you verify the pilot jets were open? Look for light though or poke a wire through the center?

To judge fuel starvation you can remove the float bowl drain right after it stalls out so see if there is the normal amount of fuel inside.

Yea,I just pulled the carbs off again today to double check that the jets were open. Went through and sprayed out everything again just to be sure. I had cleaned them with a wire brush when I dipped the carbs. Everything looked fine there.

I forgot to try your float bowl removal method, I will try that tomorrow. As well as double check my float heights.

I pulled the petcock apart just to double check it, since the jets appeared to be clean and everything seemed to be in working order. And it flows. Maybe its just not flowing enough?

Thanks for the help guys. I'm new to this so I figure I just need to keep going after it until I figure it out.

spcdolan - I found the airbox on ebay. When I was looking for mine there were 1 or 2 up there still. Just make sure they have the snorkel and cover it didn't appear that all of them did.

 

[D.T.]

I am unsure of how well carb dips work. Compressed air would assist it better. I just found some gunk on my needle jets today that wouldn't come off with solvent. I had to sand it off (jet was sticky in the nozzle). It was some type of varnish I assume. I didn't try acetone though.

We use an ultrasonic cleaner at work for cleaning epoxy from our solder mask spray gun. Even though they cost around $500 bucks for a small one new, a fleabay special may be had for $100 or so.

 

[Steve]

I am unsure of how well carb dips work. Compressed air would assist it better. I just found some gunk on my needle jets today that wouldn't come off with solvent. I had to sand it off (jet was sticky in the nozzle). It was some type of varnish I assume. I didn't try acetone though.

We use an ultrasonic cleaner at work for cleaning epoxy from our solder mask spray gun. Even though they cost around $500 bucks for a small one new, a fleabay special may be had for $100 or so.

Not all of us have the luxury of an ultrasonic cleaner (but I could be easily convinced to get one). How well do "dips" work? GREAT. Just soak all the non-rubber parts for a while (preferred time varies) to soften or dissolve the gunk, rinse them off with warm water, use a quick blast of carb cleaner to finish taking out all the gung, blow some compressed air to verify that the passages are all clear and you are done. A can of "dip" is only $20. I have not noticed an degradation in quality in a can that I have used regularly for about 5 years, only the quantiy left in the can. Some of the liquid sticks to the parts when you take them off and are wasted down the drain when you rinse the parts, so the amount in the can steadily goes down, but it still cleans well. I have gotten a second can, so now I do the small parts in the old "dip", where they fit better, and the larger stuff in the new "dip" where there is still enough liquid to cover them.

.

 

[Munzo]

Here's the update:

Had a friend who is a bike mechanic come over and help. Apparently cylinder 3 isn't firing (whups. newbie mistake, only ever heard it run on 3 so thought it was running fine. consider me embarrassed ). Anyhow my buddy thought it was a carb problem, thought I didn't get them clean enough. He took them home and dipped them for me over night. Got them back today, got them on, and still not firing on cylinder 3, but it has a spark. I'm too tired and frustrated to mess with it anymore tonight, so I give up for today.

 

[Black711]

Same issue

Same issue

I bought a 1986 gs 550 ef two weeks ago for $300. I put a battery in it cleaned the carbs and it fired up. The motor sounds good and it rides very nice, but as soon as I hit 6500 rpm's it pops back and doesn't make any top end power at all (sounds like it's lean). I cleaned the carbs 3 times and they are clean, same issue it didn't help. This bike has been sitting for a long time and a bike mechanic freind of mine told me critters can get in the exhaust and fill it up with nut's and debree. I am taking the exhaust off tonight to make sure. I do have a K and N air filter should I jet it up fatter? This is really frustrating me. I want to put some paint on this thing and ride it.

 

[Black711]

air box

air box

I just looked at the micro fish on line for the air box, and it appears as if mine has a rectangle hole cut in the top of it right under the seat. Does yours look like that? With the seat off the bike I can see the K and N filter through the hole. Could that cause it to run lean up top? Thanks for all your help. I do have the stock jetting 90s on 1 and 4 and 97.5s on 2 and 3. Munzo make sure the fat jets are on the inside cylinders.

 

[Munzo]

I just looked at the micro fish on line for the air box, and it appears as if mine has a rectangle hole cut in the top of it right under the seat. Does yours look like that? With the seat off the bike I can see the K and N filter through the hole. Could that cause it to run lean up top? Thanks for all your help. I do have the stock jetting 90s on 1 and 4 and 97.5s on 2 and 3. Munzo make sure the fat jets are on the inside cylinders.

The hole there is where a snorkel for your air box should be. I think without it you will run lean, but I can't say for certain. I had this problem when I bought mine, not only did it have the stock hole for the snorkel but someone had cut the hole bigger. I just ended up ordering a new air box from ebay for $20

 

[DanTheMan]

The hole there is where a snorkel for your air box should be. I think without it you will run lean, but I can't say for certain. I had this problem when I bought mine, not only did it have the stock hole for the snorkel but someone had cut the hole bigger. I just ended up ordering a new air box from ebay for $20

Ding, Ding, Ding, Ding!!!!!! Correct answer, the bike will run lean without the snorkel. It's a must have item.

 

[Larry D]

Here's the update:

Had a friend who is a bike mechanic come over and help. Apparently cylinder 3 isn't firing (whups. newbie mistake, only ever heard it run on 3 so thought it was running fine. consider me embarrassed ). Anyhow my buddy thought it was a carb problem, thought I didn't get them clean enough. He took them home and dipped them for me over night. Got them back today, got them on, and still not firing on cylinder 3, but it has a spark. I'm too tired and frustrated to mess with it anymore tonight, so I give up for today.

Have you synced the carbs ? My GK had the full treatment ie. carbs dipped, airbox sealed, etc..and wasn't firing on all cylinders before we synced the carbs. I thought my bench sync was pretty close, but, it wasn't close enough.

Your buddy took them apart again before he dipped them....right ? I hope he did, otherwise those new o-rings are trashed.

 

[Munzo]

Have you synced the carbs ? My GK had the full treatment ie. carbs dipped, airbox sealed, etc..and wasn't firing on all cylinders before we synced the carbs. I thought my bench sync was pretty close, but, it wasn't close enough.

Your buddy took them apart again before he dipped them....right ? I hope he did, otherwise those new o-rings are trashed.

He sure did.

Thanks for the heads up. I'm going to run some tests tonight and see what I can come up with.

 

[Black711]

Air box

Air box

I covered 3/4's of the hole with tape to restrict the air flow, it runs like a watch now. Thanks a bunch!!!!! Good luck Munzo, these bikes are a blast to ride!!!

 

[Munzo]

Finally a break!

Finally a break!

Finally got the chance today to go play with the bike. Swapped my plug lead and ta-da!! Cylinder 3 fires. Looks like I'll be picking up some spark plug caps tomorrow.