I need your advice on my '89 GS everyone - I have stripped and cleaned the carbs over the winter, and everything looked good, the diaphragms were not split and all the jets are clear. I put it all back together this afternoon, and tried to fire it up, but nothing. Gas is reaching the carbs (tested by opening the drain valves a turn or two), and the new plugs spark OK. I reattached the fuel lines per the manual, as well as the vacuum pipe to the left carb (standard gas tap), and I've tried it on PRI, RES and ON with fresh gas. She ran when I put her away in November!

Anyone got any suggestions?

Try starting the bike without choke but with full throttle on,see how it goes

Gotta suggest the obvious... key and kill switch on "RUN"? 

Maybe an issue with a clutch or sidestand switch?

Good luck and keep us posted. 


edit: sorry, I think you answered all of these questions by stating that there is spark at the plugs. In that case, maybe it is weak spark.  I remember Kerry once posting about a problem where he saw spark and therefore mistakenly ruled out an electrical problem.

Mount the bike  like you're going for a ride.Valve on PRI,transmission in neutral,kick stand up,clutch in,kill switch set to run,turn key to run,and press the starter button. 

Maybe something nested in your airfilter and it's restricting air supply?

Try starting the bike without choke but with full throttle on, see how it goes

I tried that, but no better.

Gotta suggest the obvious... key and kill switch on "RUN"?   

Maybe an issue with a clutch or sidestand switch?

Yup, Kill Switch is on RUN, when it's off nothing happens, so I know it is OK. Same with the side stand up. I had a Yamaha that had a flaky side stand switch, and that used to cut out all the time in the wet.....I am used to the symptoms.

Mount the bike   like you're going for a ride.Valve on PRI, transmission in neutral, kick stand up,clutch in, kill switch set to run, turn key to run, and press the starter button.

Nice thinking – but it still made no difference. I have great compression and the starter motor spins perfectly for as long as the battery is willing.

Maybe something nested in your airfilter and it's restricting air supply?

No birds nests or dead mice in there!!! LOL It's a standard air box.

Please keep the suggestions coming - thanks !!!!

Maybe the coils are weak.Check the spark.Blue it's good,orange or red is bad.Have you checked the cam tensioner?I'm wondering if some how the cam chain jumped time.Have you adjusted the vavles?May have to much play.That's all I can think of right now.

How FRESH is the gas? Old gas will NOT burn easily, if at all. Once the aromatics flash off, you might as well put cat piss in the gas tank, because it will probably burn easier. Also, did you do any valve work? If so, check the valves; if the valve timing is off, you might not get a combustible mixture into the engine when the spark arrives, and that would keep the engine from firing.

After you crank it over with clean, dry sparkplugs, pull each plug and check it. Is the plug wet or dry? If wet, you probably have an electrical problem (or the valve timing problem I've already mentioned). If the sparkplugs are dry, spray starting fluid near the air intake while you crank the engine. It is highly combustible, so you should get SOME reaction. Don't overdo it, just spray a mist near the intake so the carbs will suck it into the engine. Even with a poor spark, you will probably get the engine to fire a few times. If the spark is too weak to ignite starter fluid (or if there is NO spark at all), go back to the basics; check all the electrical connections AGAIN, and be sure the gas isn't old or contaminated.

Fuel + air + valve timing + spark = combustion; you need the right mixture of fuel and air to arrive in the combustion chamber at the right time (so it can be compressed BEFORE the spark arrives), and a good spark to ignite the high-pressure mixture. If your exhaust valves are open at the wrong time, you won't get compression, and the engine won't run.

Obviously, I'm trying to give you a lot to think about; don't rush this. Find out what is or ISN'T happening properly, or at the right point in time, and let us know what you learn. If you can't solve this alone, there's a good chance that the collective group can help you track this down.

OK, just read your last post (reply # 5); having compression isn't enough; you have to have it at the right TIME for this to work. If the engine timing (carbs, spark, valves) isn't right, you'll NEVER get it to run. Look for a fat blue spark; with fuel in the carbs and a good strong spark, the valve timing is the next major concern. If the intakes close too late, or the exhausts open too soon, you'll kill the battery before you get it running.

Just read the cam chain tensioner remarks by ben2go (reply # 6); that would affect both sets of valves, and ruin the timing, which would cause this type of problem. Take this by the numbers (fuel, air, spark, valve timing), and let us know what you find.

Good luck; I hope you can nail this down quickly.

Thanks everyone, what a wealth of great suggestions.

I put in fresh gas that I purchased about 3 days ago, and I did check the plugs for a nice big blue spark. The bike has only done 3,000 miles so it can't be worn out yet, and nobody has had the head off it since it was at the factory in Japan.

I did try the starting fluid trick, a squirt down each plug hole made it fire for a few seconds.

I'll do some more poking about - thanks for all the encouragement ! 

Any news about this problem? Still not starting, or is it fixed now?

Thanks for checking back on me - no, it's still the same.

But I was wondering - I have attached the fuel feed hose to the lower of the two fuel intakes on the carbs, should it be on the upper one? If so, I will change it. And then if that's right, what goes on the lower one?

Quote from: simoniz on April 29, 2008, 05:31:10 PM
Thanks for checking back on me - no, it's still the same.

But I was wondering - I have attached the fuel feed hose to the lower of the two fuel intakes on the carbs, should it be on the upper one? If so, I will change it. And then if that's right, what goes on the lower one?

The upper hose is the vent, the lower hose is the fuel inlet.

If some starting fluid down the plug hole fixed your problem for a second, you have spark. That only leads me to the carbs. After you cleaned the carbs did it work fine, or is this the first time you have started since you have cleaned the carbs?

This is the first time I have tried it since the carb rebuild (not my first carb rebuild though, by the way, I have done lots of 'em). Maybe I put something on backwards? It has been known!

Well, it's definitely worth a recheck 

Good luck!

I got her running last night, finally. Someone suggested sticking floats, so I dropped the float bowls and they were OK. I refitted the carbs, and double checked the fuel line routing and remembered the vacuum hose to the fuel tap from the left carb. I tried it first with an auxiliary gas tank and it fired right up, so I knew the carbs had been rebuilt correctly after all. You know how you begin to doubt yourself sometimes? Yeah, I did that. Duh!!

Anyway, with the GS tank on and a few seconds on Prime, she fired up and ran. Right now the air box is off, so I wonder if the air box was pinching the fuel supply lines? You know how tight the clearance is there, between the air box and the frame. I might switch to Uni filters and rejet instead.

Quote from: simoniz on June 22, 2008, 08:02:41 AM
I got her running last night, finally. Someone suggested sticking floats, so I dropped the float bowls and they were OK. I refitted the carbs, and double checked the fuel line routing and remembered the vacuum hose to the fuel tap from the left carb. I tried it first with an auxiliary gas tank and it fired right up, so I knew the carbs had been rebuilt correctly after all. You know how you begin to doubt yourself sometimes? Yeah, I did that. Duh!!

Anyway, with the GS tank on and a few seconds on Prime, she fired up and ran. Right now the air box is off, so I wonder if the air box was pinching the fuel supply lines? You know how tight the clearance is there, between the air box and the frame. I might switch to Uni filters and rejet instead.

I'm a bit confused... your original post says there was no influence from PRI, ON, or RES. You also mentioned that fuel was confirmed to be in the float bowls. Now the problem was fixed by running on PRI, and the problem may have been a pinched fuel line? 

Either way, I'm glad it works now! 

I think I may have routed the fuel lines in the wrong places, too ! Taking it all apart for the 3rd time and carefully reattaching everything slowly did the trick. Thanks for the encouragement......You guys are a big help.

If my recent similar experience is any help, there was probably not enough gas in the float bowls.   I had a trickle from the drains, but not a stream.   I filled 'em up by pouring gas down the inlet tube, then re-attached my tank/hoses.   She fired right up.