Fuel Filter or worse? KZ650 Backfiring and will barely move.

In mid july I took my 77 KZ650 on a 200 mile ride alongside friends who were on modern bikes. I pretty much did 80-95 for about and hour.

I let the bike sit for two months, something I NEVER DO!  Went to start it up last week. It idles fine, but when I roll the throttle, it backfires and sometimes dies. It backfires A LOT. This NEVER happened until I let it sit.

Ive checked the coil. spark plugs and plug wires and did several electrical system tests. All was fine.

Im thinking, there is a barrel shaped fuel filter the OP put on the bike 3 years ago. I havent changed it since. Could this be fuel starvation due to a clogged filter? And wouldnt the filter clog up BEFORE the jets in the carb?

Im hoping I dont have to take the carbs out as everyone knows, getting them out of this bike with the aribox still on, is a NIGHTMARE.

Any advice?

Have you checked for air leaks ? Also worth a compression check (if you have a sticking valve it may be firing with it not fully closed)

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Have you checked for air leaks ? Also worth a compression check (if you have a sticking valve it may be firing with it not fully closed)

 

Thanks fro your response, but it is none of those things. Compression test was done and its fine. Also checked for air leaks and there are none. The bike ran fine for years. Ran it in july, didnt ride again until october and that somehow caused a problem. Im thinking something got gummed up while it sat. It had no issues before it sat so long. Maybe its fuel starvation.

It idles fine, but as soon as I roll the throttle it backfires. My garage is under the house and to get out from it, you have to climb a small hill. When climbing the hill, the bike backfires like crazy.

If your fuel has ethanol in it, sitting for several months may have clogged the pilot circuits with barnaclized fuel.

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If your fuel has ethanol in it, sitting for several months may have clogged the pilot circuits with barnaclized fuel.
 

I was hoping you and Wookie would chime in as you two are among the most knowledgeable. So I guess I have to take the carbs off? its such a pain on a KZ650 with the airbox in. Its times like this I wish I had airpods!!!!

I assume the airbox is clean and clear. Mice (rodents) love to make a home in those places. Just a thought.

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I assume the airbox is clean and clear. Mice (rodents) love to make a home in those places. Just a thought.
 

Thanks. My garage is heated and secure and there are no rodents in the box. The airbox is clean.

Chuck the fuel filter. Unless the filter element is cleanable then they dont last. Bike gets hard to start. They are cheap so definitely worth replacimg every few years.

may or may not be the problem but worth doing anyway

wrote:

Chuck the fuel filter. Unless the filter element is cleanable then they dont last. Bike gets hard to start. They are cheap so definitely worth replacimg every few years.

may or may not be the problem but worth doing anyway
 

I havent changed the fuel filter in three years haha and the fuel i use has ethanol in it. so yeah, thats my first test, changing the filter.

Your pilot jets/passages are clogged. You'll need to pull the carbs. Or you can run some seafoam through the carbs and hope they clear on their own. Let the bike idle with the seafoam/gas mixture and see if that works. 
From now on, I would advise using fuel stabilizer when it's going to sit, run non-ethanol fuel, or make sure to run your bike for a few minutes once a month. 

Just curious. Couldn’t this just have been in your previous thread that you started on a very similar subject but never resolved. Did you feel starting a new thread on the same subject was going to get you better answers?

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Your pilot jets/passages are clogged. You'll need to pull the carbs. Or you can run some seafoam through the carbs and hope they clear on their own. Let the bike idle with the seafoam/gas mixture and see if that works. 
From now on, I would advise using fuel stabilizer when it's going to sit, run non-ethanol fuel, or make sure to run your bike for a few minutes once a month. 
 

I REALLY hope I dont have to pull the carbs. Its a pain in the ass on that bike! First I'll change the fuel filter which I havent changed in YEARS. If that doesnt work, then seafoam, and if that doesnt work, then I'll have to pull the carbs.

thanks for your suggesstions