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After hitting a nasty bump on the road a month ago, which stalled my bike immediately, the engine will occasionally go from providing normal amounts of power to about 25% of that power, and it will stay in that low power state for a seemingly random amount of time, could be 30 seconds could be 10 minutes. The engine will make a deeper noise when it knocks into that state, and it will have to rev to 4-5k RPM to get moving to 10 mph, normally something it could do with 1-2k rpm. Basically making it slow as hell and unridable when it gets like this. It used to happen once a week, then once a day, now the bike cannot even get down the street without running into this low power state. It consistently happens when stopped at a light or going down a steep hill.

I know the problem was caused by the bump but I don't know what it did. I replaced the spark plugs, recently cleaned out the air filter, exhaust is coming from both pipes when it's like this so both cylinders should be firing. My bike is carbureted and google searches are leading me to believe there might be a problem there, but I have never pulled carbs before and am not sure what mess I'd be getting into. A couple days ago I sat on my bike to try to figure this out and the headlight and taillight wouldn't turn on, so there is probably a wiring issue somewhere. Could that be related to this low power problem?

Looking for guidance on what part / area of the bike I should be troubleshooting to narrow it down. Does it sound like a carb problem? Electrical? What can I do to eliminate some potential causes?

thanks
1980 gs250t
 

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Welcome.
The problems with the lights might be an important clue.
First, check the connections at the battery and get the battery tested.
Having a multi-meter might help.
 

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Discussion Starter #3
Thanks, you might be right because after looking at it again today the Neutral light is going off and on as the bike is moved. That has never happened before, so something is definitely messed up with that. I do have a multimeter so I can check that soon
 

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There may be two problems.
Your comment about having to rev the engine to a high speed just to get going sounds like a slipping clutch.
Electrical problems and a slipping clutch usually are not related to each other.
 

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your neutral light going on and off is result of three possible issues: 1. the neutral switch is being moved to ground and then off ( being activated). 2. a bad connection between Neutral indicator and switch including the ground. 3. The indicator light itself is going bad ( unlikely if LED). As for your running condition, sounds like a cylinder ingnition drop out which could also be the result of a bad ground and not necessarily at the battery or frame eng heavy ground. Also check for a loose connection and fuzes at the fuze box since all these systems get power (pos +) from there.
 

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Discussion Starter #6
Yep VFR you were correct - took off the tank and indeed there was a loose connection - one of my ignition coils had wiggled loose and was completely unplugged. Plugged it back in and the bike has been good ever since. The neutral / headlight is probably going to take a similar fix. But at least it runs great now. Thanks for the help on this one guys.
 

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After hitting a nasty bump on the road a month ago, which stalled my bike immediately, the engine will occasionally go from providing normal amounts of power to about 25% of that power, and it will stay in that low power state for a seemingly random amount of time, could be 30 seconds could be 10 minutes. The engine will make a deeper noise when it knocks into that state, and it will have to rev to 4-5k RPM to get moving to 10 mph, normally something it could do with 1-2k rpm. Basically making it slow as hell and unridable when it gets like this. It used to happen once a week, then once a day, now the bike cannot even get down the street without running into this low power state. It consistently happens when stopped at a light or going down a steep hill.

I know the problem was caused by the bump but I don't know what it did. I replaced the spark plugs, recently cleaned out the air filter, exhaust is coming from both pipes when it's like this so both cylinders should be firing. My bike is carbureted and google searches are leading me to believe there might be a problem there, but I have never pulled carbs before and am not sure what mess I'd be getting into. A couple days ago I sat on my bike to try to figure this out and the headlight and taillight wouldn't turn on, so there is probably a wiring issue somewhere. Could that be related to this low power problem?

Looking for guidance on what part / area of the bike I should be troubleshooting to narrow it down. Does it sound like a carb problem? Electrical? What can I do to eliminate some potential causes?

thanks
1980 gs250t
I think some residue got dislodged in a carb jet. Put some seafoam in the tank and run it till it's empty. Then fill her up with ethanol free gas and more seafoam.

If the jet is completely clogged, the bike won't start. But if the jet isn't clogged, the seafoam will eat away at the residue and clean the jets after a few tanks with a high concentration of seafoam.

Don't try to run it on seafoam alone because if the residue is removed too quickly, it can clog the jet.
 

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Then fill her up with ethanol free gas and more seafoam.
Welcome to the fourms.
The "ethanol free" isn't really important.
And despite their glowing marketing claims, SeaFoam is NOT a good heavy duty cleaner.
Berrymans B12 Chemtool or Gumout are much better when a problem actually exists.
 

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When it comes to this, I personally would not go with a higher strength cleaner. You want it to clean the jet, and if the jet is clogged, cleaner will not flow. If it's a strong cleaner, it might dislodge a bigger chunk and block the jet.

And for the ethanol free gas, it's good practice to fill up only on Ethanol free. Ethanol gums up carbs. You don't want to add to the problem.
 

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If it's a strong cleaner, it might dislodge a bigger chunk and block the jet.

And for the ethanol free gas, it's good practice to fill up only on Ethanol free. Ethanol gums up carbs. You don't want to add to the problem.
If you have "chunks" of stuff stuck in there, likely that no amount of solvent in the gas will do the trick.
And a good cleaner is always better than a barely adequate one.

Then.....the myth about ethanol that you are perpetuating is doing nobody any favors.
When used in an engine that is designed for it.......and is used on a regular basis.......an ethanol blend fuel is no more likely to "gum up" a carb than any other formulation of fuel.

It does tend to go bad over the long term a bit quicker than pure gas but even that depends on some other factors too.

Ethanol is NOT the work of the devil.
In most normal circumstances, there is NO good reason to avoid it.
 
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