85 GS450L Dies - Timing issue?

[jbayreaux]

Got an 85 Suzuki GS450L. The guy who sold it to me told me it had a bad clutch. He advised that it was sitting for a while so he changed the oil, battery, gas, and sparkplugs. And she fired right up. I was a little leary of buying her but I was looking for a project. Looks like I found one.

I took it home in a truck and fired it up. She ran, but had little power when I took her around the block. Then she died. I then let her cool down and she ran fine, but died again. So, I took the carbs off and found that one had a clogged jet and the other was similar but not as bad and passed some fuel. I cleaned them both with carb cleaner, reassembled and put them right back on. I turned her over and she fired right up again. This time she was running smoother, though idleing a little high so I adjusted that (continues to be erratic -suspect vacume issue). I took her around the block again and WHOA!!! She gets up and gets!!! Plenty of power; there was not a problem with the clutch, just a dirty carb!

Now, for the problem... When she gets up to normal operating temp, the motor runs real 'slow' and eventually dies. This occures a little after 10mins of running. Will not start up again until she cools down.

I let it cool down and road it around the block again. It ran fine then I let it sit until normal operating temp. Like clock work the engine got weak and eventually died (even if I twisted the throttle). Right when it died I took the plugs out and did a compression check, no problem there. The spark plugs are black, but do not have oil. The plugs are new.

Something is telling me,... timing. Is it pretty tough to set timeing on these type of bike? I notice that it does not have points, but some type of electronic ignition.

[Nessism]

Not timing. Most likely is a carb issue. My guess is that you have a float issue of some sort causing the carbs to starve for fuel.

[earlfor]

My suspicion is that if the plugs are black, its not a fuel availability problem, its weak ignition. On my 1150, I had the same symptoms. the bike would run fine until it reached operating temp, then would die out. It was fine again once cooled off. My problem was the ignitor box quit working once it warmed up to a certain point. My plugs were black also. I had to replace the ignition system.

Earl

Got an 85 Suzuki GS450L. The guy who sold it to me told me it had a bad clutch. He advised that it was sitting for a while so he changed the oil, battery, gas, and sparkplugs. And she fired right up. I was a little leary of buying her but I was looking for a project. Looks like I found one.

I took it home in a truck and fired it up. She ran, but had little power when I took her around the block. Then she died. I then let her cool down and she ran fine, but died again. So, I took the carbs off and found that one had a clogged jet and the other was similar but not as bad and passed some fuel. I cleaned them both with carb cleaner, reassembled and put them right back on. I turned her over and she fired right up again. This time she was running smoother, though idleing a little high so I adjusted that (continues to be erratic -suspect vacume issue). I took her around the block again and WHOA!!! She gets up and gets!!! Plenty of power; there was not a problem with the clutch, just a dirty carb!

Now, for the problem... When she gets up to normal operating temp, the motor runs real 'slow' and eventually dies. This occures a little after 10mins of running. Will not start up again until she cools down.

I let it cool down and road it around the block again. It ran fine then I let it sit until normal operating temp. Like clock work the engine got weak and eventually died (even if I twisted the throttle). Right when it died I took the plugs out and did a compression check, no problem there. The spark plugs are black, but do not have oil. The plugs are new.

Something is telling me,... timing. Is it pretty tough to set timeing on these type of bike? I notice that it does not have points, but some type of electronic ignition.

[bwringer]

Intake leaks also get worse as the engine warms and cause overheating -- make sure you check all that stuff.

You might check compression if you can get access to a compression tester. At least crank it over cold with a finger in the spark plug hole to see if you get a nice "whoosh". Burned valves can also cause the bike to run sorta OK at first then worse as it heats up (don't ask why I know this -- it's still too painful 6 years later).

How's the air filter? Clogged air filter or exhaust could cause rich running.

How's the petcock? Not leaking gas via the vacuum diaphragm, right?

It might also be worth verifying the jetting -- did any of the brass in the carb look new-ish or are you pretty sure it's original and not drilled out?

The black plugs could also simply be deposits from the PO horsing around with who-knows-what to get it started, and then leaving it running on the choke. If a new set of plugs also fouls, then you know you have a problem.

[jbayreaux]

I checked compression with a tester. I checked it when the engine was cold AND when the engine was at operating temp. It held fine both times (ouch, hot sparkplugs). I am suspecting two things now.
One: an intake leak as the idle can be so erratic. I ordered some intake boots.
Two: the igniter, as Eral stated. Same exact symptoms. I did some searching and found people are replacing their ignition systems with Dyna S systems. I researching that. I also found that the regulator gets somewhat hot, dont know if that is normal or not.

As far as the jets go, they do not look drilled out. At any rate, I am still going to order carb rebuild kits that are within stock specs.

[GS550joe]

Hot coils??

take some air spray cleaner for computers and spray the coils when hot to cool them down.. if it fires back up it is the coils.. if not you have cleaned them off so they will run cooler anyway


Joe

[sf-nathan]

Got an 85 Suzuki GS450L. The guy who sold it to me told me it had a bad clutch. He advised that it was sitting for a while so he changed the oil, battery, gas, and sparkplugs. And she fired right up. I was a little leary of buying her but I was looking for a project. Looks like I found one.

I took it home in a truck and fired it up. She ran, but had little power when I took her around the block. Then she died. I then let her cool down and she ran fine, but died again. So, I took the carbs off and found that one had a clogged jet and the other was similar but not as bad and passed some fuel. I cleaned them both with carb cleaner, reassembled and put them right back on. I turned her over and she fired right up again. This time she was running smoother, though idleing a little high so I adjusted that (continues to be erratic -suspect vacume issue). I took her around the block again and WHOA!!! She gets up and gets!!! Plenty of power; there was not a problem with the clutch, just a dirty carb!

Now, for the problem... When she gets up to normal operating temp, the motor runs real 'slow' and eventually dies. This occures a little after 10mins of running. Will not start up again until she cools down.

I let it cool down and road it around the block again. It ran fine then I let it sit until normal operating temp. Like clock work the engine got weak and eventually died (even if I twisted the throttle). Right when it died I took the plugs out and did a compression check, no problem there. The spark plugs are black, but do not have oil. The plugs are new.

Something is telling me,... timing. Is it pretty tough to set timeing on these type of bike? I notice that it does not have points, but some type of electronic ignition.

I agree, those 450's have plenty of get up and go. Reliable and fun as heck too.

You may want to lube the clutch cable, and do the clutch adjustment as described in the book, for good measure. And just in case the other guy knew something.

You don't mention the choke? If I remember correctly, its the lever on the left carb. How much choke and for how long?
If you are not ussing the choke at all to start the engine, and you have new spark plugs that are already black (black means rich mixture, I think, grey = lean) then I would think the bike is running rich. This would help it start right up, but will stall it out once warm.

When you did the hot compresion test did you smell gas?



Do you have the original airbox or pods? Pods run rich. The original air box will develop leaks at the boots that connect it to the carbs.

On the ignition; I've had three of these 450's and never had an ignition problem, so I'm doubtful that's it. Make sure the ingnition pick-up is on rt. Where the points would be there is a sender unit that is mounted to a metal plate with a notch tapped into it. That should line up with a notch on the bike. A previous owner may not have put that on exactly right which would slightly retard or advance the ignition.

Good that you went ahead and ordered the carb holder boots. Those aren't cheap. So you must be commited. Buy new o'rings too. They may even be included. Make sure you have ones made for hot temps.


Ok, thats enough for now. You may also check to see if someone adjusted the pilot air screws on the carbs too.

[jbayreaux]

Well it has nothing to do with the timing. I found that there is almost no adjustment to my type of ign system, as stated in my shop manual. THe only adjustment I did was backing out the skrews on the sender plate and barely moving it. After I did that, it did not want to start. More tinkering brought some backfireing, then finally I got it where the bike started up with no problem... Never messing with that again.

So, with the bike running fine, I took it around the block. Ran fine, but of course it died; far from my house. So I activated the choke fully, and she fired up! It was idleing high so I lowered the choke a little bit. The bike was running fine like this through out, I just had to keep playing with the throttle. I notice that when I throttle hard, it might hesitate but the it gets a whoosh of power. SO, the bike is running fine at normal operating temp. The ignition system is fine. Somthing tells me it is either the carbs, or the petcock. I feel that I am getting closer.

Notable points: I do not have pods, plugs are black. I dnt smell gas, maybe burnt gas. There is no oil on the plugs. Something tells me this bike is burning rich, but my manual states that there is no mixture settings on my type of bike.