So close to running!

[Rein]

Hi guys, I have an 81 GS 650L, which I picked up for $400. The bike itself has been sitting for about a year, and recently the carbs were rebuilt and cleaned, new spark plugs, new fuel were added.

At first the bike would catch, but it took 5-7 seconds of cranking. The bike would then idle for no longer than 10-15 seconds. Giving it any throttle would rev and then die immediately.

I first noticed that we had accidentally left the fuel cock on prime, so we drained out the gas and started it again. Now the bike idles for about two minutes. We can keep it revved now, but upon releasing the throttle the bike would die.

I'm going to check the following, and hopefully I'm on the right track: Airbox filter needs to be cleaned, Petcock needs to be cleaned, and the gas tank screen. Is it possible that I just need the carbs synched too?

Thanks!

[waterman]

Welcome to the GSR, hopefully we can help you here. Mostly I have some questions. You stated that the carbs were rebuilt and cleaned, did you do this or have someone else that you trust clean them?

When starting bike, it may take 5 to 10 seconds to fire up. When you start this bike, do you pull the choke cable? If you do, let it run on choke and then after 30 seconds or so try giving throttle. These bikes, if not in good mechanical tune tend to be cold blooded.

You state that you drained out the gas, where did you drain gas from? Hopefully from fuel bowls. You should check the oil for gasoline also. On my 650, the gasoline flooded both the airbox and the cylinders. If this has happened, drain and change oil, mixed gas with oil will destroy engine seals and if ran destroy crank bearings.

As for right track, these things are worth looking into. I would check valve clearance, replace intake boot orings, and then look into carb sync.

[Big T]

When you say the carbs were cleaned and rebuilt, what exactly does that mean?

[Rein]

When you say the carbs were cleaned and rebuilt, what exactly does that mean?

Previous owner says he did it, following the chilton's manual to disassemble, and dunk in carb cleaner. I don't mind getting someone to do it again, like at a local dealership, but can that really be the main problem?

[chef1366]

Could be alot of things. Do a search for
Valve adjustment
carb cleaning
compression
igniter/ignition
coil relay mod
BassCliff has all you need to know on his website.
Do you have a manual?

[Rein]

Could be alot of things. Do a search for
Valve adjustment
carb cleaning
compression
igniter/ignition
coil relay mod
BassCliff has all you need to know on his website.
Do you have a manual?

I have actually been messaging between basscliff for a couple days.

If there's no compression, then wouldn't it refuse to fire?

[chef1366]

Put your finger over the spark plug hole ane hit the starter. Your finger should get blown off the hole.
Yes you need compression for it to run but low compression due to out of adjusted valves, bad rings or bad valves can cause hard starting and poor performance.

[Rein]

Put your finger over the spark plug hole ane hit the starter. Your finger should get blown off the hole.
Yes you need compression for it to run but low compression due to out of adjusted valves, bad rings or bad valves can cause hard starting and poor performance.

Hmm, I see, so possibly the bike has only minimal compression? If my finger gets blown off the hole, is there enough compression? I just need to remove one spark plug, and not all of them?

[BassCliff]

Hi Mr. Rein,

Ideally you will check compression on all cylinders. But I wouldn't worry about that too much right now. Go through the "top ten" list of common issues in the mega-welcome. I know, it seems daunting, tedious, inconvenient, etc, because you just want to push the button and ride. But it is much, much better in the long run if you bite the bullet and get everything in order right up front; clean carbs, valve adjustments, new plugs and caps, fresh fluids and filters, petcock, etc, etc. After all of this is in order, then you'll probably have a pretty decent running bike and can work on the fine tuning and cosmetics. You've got a 28 year old motorcycle that has been neglected for a while and has a virtually unknown history. It will take some effort to restore it to its former glory. Once you're there you will have a very reliable motorcycle, but you have to put in the effort up front. If you don't, you'll be chasing one pesky problem after another and eventually give up because "this #$%@ thing just won't run right". I'd hate to see that happen.

I would recommend doing all the work yourself rather than let some duffer hack up your bike. If you hang around here any length of time you will hear many horror stories of "professional" mechanics having their way with these classic machines. It ain't pretty. If I can learn to work on these machines, anybody can.

Did you download the manual from my website? Have you looked at the guides for carb rebuilding, valve adjustments, stator replacement, regulator/rectifier replacement, brake pad replacement, fork seal replacement, etc? Keep us informed. There's lots of help here.

Thank you for your indulgence,

BassCliff

[Rein]

UPDATE:

So, fuel bowls were a little gummes up in those little holes that provide gas for idling, so we cleaned those out. Found the floaters were stuck because the needle valves were a tiny bit gummed up. Now she idles without throttle at 900-1000 rpm, and she purrs like a lion.

However, there is hesitation, until we choke the carbs manually, because my choke line is stuck inside the housing. If I pun my hand over the intake hole a little bit to create more suction, she'll rev with perfect throttle response. She ROARS!!!

My mechanic, who's a very helpful guy, and had me work on it with him so I could learn about carbs, told me that the last thing to check is the emulsion valve and pilot jets. If they're gummed up, then that would be the reason for slow throttle response.

[Steve]

However, there is hesitation, until we choke the carbs manually, because my choke line is stuck inside the housing. If I pun [put?] my hand over the intake hole a little bit to create more suction, she'll rev with perfect throttle response. She ROARS!!!

If you can put your hand over a carb intake, that means you don't have any filter on there. IT WILL NOT RUN WELL WITHOUT A FILTER.

As a quick test, take a shop rag, fold it in half, drape it over the carb intakes. If you have a helper, great, otherwise use nylon zip-ties to hold the rag to the outer two carbs so it's taut over the inner two. Now you can check throttle response. This will even work for a quick ride around the block, but is not accurate enough for jetting checks.

.

[Rein]

If you can put your hand over a carb intake, that means you don't have any filter on there. IT WILL NOT RUN WELL WITHOUT A FILTER.

As a quick test, take a shop rag, fold it in half, drape it over the carb intakes. If you have a helper, great, otherwise use nylon zip-ties to hold the rag to the outer two carbs so it's taut over the inner two. Now you can check throttle response. This will even work for a quick ride around the block, but is not accurate enough for jetting checks.

.

It does the same with the filter on, but I have to block the intake holes in the back. And also, I didn't put my hand on a carb intake, I just took the cover off the airbox and used a rag to choke it. Sorry I wasn't clear enough.