I knew something was wrong...

[craig]

Well I knew something was wrong and I should look into getting some work done. I didn't know that would jinx the bike and it would NOT RUN when on this finally sunny day I decided to go out for a ride...



So here's what's going on. Any help on diagnosis would be greatly appreciated.

Bike starts up, kind of rough idle. After warming up it will rev pretty freely, but when I put it in gear and let the clutch out and rev it up, the revs go up and then it just cuts off. Tried this for about half an hour and finally thought whatever it was got "smoothed out" and I took off. got down the huge hill of a driveway and turned onto the street and boom. same problem.

So after pushing it alllllll the way back up the slippery gravel driveway, I get it in the garage. Took off the tank to see well..whatever I could see. Noticed the clamps from the airbox to the carbs were a little loose, but that a) shouldn't be a problem (right? or maybe that's a vacuum leak?) and b) could have been from me trying to get the gas tank out.

Could this be that valve adjustment job I've been putting off finally biting me in the ass?
"car" minded people I've talked to think it's the carbs, but I have never wrenched on carbs before so I have no idea where to begin. The butterflys seem like they're opening fine when i crack the throttle, and there doesn't seem to be any dirt, etc in there.

Now before I go taking the carbs apart, knowing ABSOLUTELY NOTHING about them and with just a really worthless clymer manual to guide me, does anyone else have any ideas as to what could be wrong??

If anyone is willing to make a trip down to the south shore to help me out (or I might be able to trailer it to you...) I will definitely make it worth your while and you will be my new best friend


I really want to get this piece of shit running before the sunday ride

[Degsy]

Sounds like lack of fuel.

Try opening the gas cap when it happens. You might have a blocked vent hose in the gas cap causing a partial vacuum. If it has a fuel pump, check the pump and filter. What kind of bike?

Check for kinked fuel lines or hoses. Usually, with a vacuum leak, you will have trouble getting the bike to idle. if the bike idles for as long as you want it to without cutting out but cuts out when you bring the revs up, chances are it's fuel starvation caused by a blocked fuel filter, petcock or gas tank vent hose or vent hole in the gas cap.

derek

[Awesome]

what he said. Some kind of fuel delivery issue.

[Honclfibr]

Originally posted by craig
Noticed the clamps from the airbox to the carbs were a little loose, but that a) shouldn't be a problem (right? or maybe that's a vacuum leak?)

As long as they seal it's not a problem. If they don't seal, you will run extremely lean, due both to the extra air getting into the engine and the decrease in pressure differential across the carburetor slide..

[craig]

It's a 1992 Yamaha Seca II. It has a vacuum pump/fuel filter. I'll try buttoning it all back up, checking for kinked lines and then try opening the cap while it's running to see if it's a vent issue.

Thanks guys and I'll post back with the results.

[Degsy]

Originally posted by craig
It's a 1992 Yamaha Seca II. It has a vacuum pump/fuel filter. I'll try buttoning it all back up, checking for kinked lines and then try opening the cap while it's running to see if it's a vent issue.

Thanks guys and I'll post back with the results.

If it turns out to be the vent in the cap, run some brake cleaner through it (keep it away from any rubber seals)

derek

[craig]

Ok in the hopes that it was the cap vent, I put it all back together.

Before putting the tank back on, I hooked up the carbs and airbox and started it up, knowing there was still a limited amount of fuel in the carbs most likely.

It started with full choke and idled while leaning on the side stand.
If I straightened it out, it would sputter and die.
If I revved the engine it would die.

I put the tank back on, primed it, set the petcock to On, and started it up. This time with the choke it actually went to about 4k RPMs to idle (normal for full choke start on the bike) and I could rev it to 4500 and then it would start to die unless I let it go - this was repeatable and at half choke it revved to 3k idle, then I could rev it up to 3500 before it would start to die. Weird that with the choke out full or half I could rev it 500 rpms before it started to cut out.

With the tank on it also starts to die when leaned straight up. Weird.

So because of the leaning over vs standing up issue I'm thinking that the fuel pump and/or filter are the culprits. Is that a fair assessment, or could the carbs still be to blame?

[Stoneman]

Pull the fuel tank off and see if you have little flakes of rust sitting in the bottom of it...

[Degsy]

Put the petcock to reserve. You might have a bad filter on the 'full' tube inside the tank.

[craig]

put the petcock to reserve, same deal.

Also cracked the drain screws on the carb float bowls and fuel did flow out. Was recommended by someone else to see if fuel was at least getting to that point and that wasn't a problem it seems...not sure where that leaves me though. Does that mean it's not the fuel pump/filter?

[craig]

Originally posted by Stoneman
Pull the fuel tank off and see if you have little flakes of rust sitting in the bottom of it...

Inside the tank? I shined a flashlight in there and could not see any rust...it's been resealed though apparently.

[oreo_n2]

sounds like fuel delivery to me too... but along with not enough fuel... could convesely be too much air... perhaps a vaccuum leak between the carbs and the head perhaps? Are your carbs mounted to rubber boots... which could be cracked with age and leaking air?

[craig]

They do use rubber boots, but I inspected them inside and out and they look fine. I also made sure to double check all hoses/clamps for the system when putting it back together, thinking initially like you that a leak might be the problem. I'm going to have a car mechanic friend of mine take a look at it. At this point I'm trying to determine if it's the fuel pump and/or filter ($$ i'm sure) that needs replacing or if the carb jets/needles are clogged.


Thanks for all of the help/advice/tips so far.

[TheIglu]

Has the bike been sitting all winter? If so, it sounds like you may have gummed up jets. It'll run way lean normally but running on the choke circuit will allow more fuel in. Drop a bowl and pull one of the main jets out. Give it a look in the light first, then blast it out with carb cleaner. Give it another look. If the hole got bigger, I'd recommend you do the same to the rest of the carbs.


To test the theory of the fuel filter/pump, drain the bowls. Turn the bike on (don't start it though) to let the fuel pump run. I'd say about 10 seconds, no longer. Shut it off, drain the bowls again. You should have a good amount in each carb. If you do, then it's 'probably' not the fuel delivery to the carbs but the carbs themselves.

It could also be timing that is WAY off. Or, a camshaft timing off a tooth. I've seen both create similar situations.

[TheIglu]

And I'll be in Waltham possibly friday night looking at an apartment. If you are around and I go, I can stop in and help you troubleshoot. Got tools and a garage to work on it?

If so, then your my new best friend. Garages are hard to come by with an apartment and I'll need a place to stash my bike

[RandyO]

I'll expand on Iglu's post....... Is the fuel stale?

[craig]

Originally posted by TheIglu
And I'll be in Waltham possibly friday night looking at an apartment. If you are around and I go, I can stop in and help you troubleshoot. Got tools and a garage to work on it?

If so, then your my new best friend. Garages are hard to come by with an apartment and I'll need a place to stash my bike

I'm actually down in Pembroke for the summer...gotta update that location. No more Bentley/Waltham for me *sniff sniff* - ahh the post-graduation blues.
Looking at apartments in that area too though.

Well I do feel a bit embarassed. Sometimes it's the simple things I don't even think about.

Stale gas was pretty close -- the final diagnosis was water in the gas. I guess leaving it out uncovered during this 12" of rain was probably a "bad idea".

Siphoned it all out, put in some fresh gas w/ conditioner, let it run for a while and boom - revs freely, took it for a 15 minute ride around the hood and had a few sputters around 5k rpms at first but it eventually cleaned out.

Stupid problem, easy solution, stupid craig. Thank you all for helping me through this and dealing with my dooms day attitude to the whole thing. Definitely glad it wasn't anything serious, but I do feel a bit like the boy who cried wolf now Oh well lesson learned. Now I have Sunday's ride to look forward to.

Thank you all again!

[OreoGaborio]

hey, ya got it solved, that's all that matters we've all had our share of those moments, & this one isn't even that bad compared to some of the ones other members have had.... *COUGHhonkleCOUGH*