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I put a KN filter and it backfires

French Peasant

French Peasant

Member
the bike was running fine, and I decided to change the stock air filter for a KN with open airbox. Then the bike runs lean, I guess, and backfires. Okay with me! until I stop at a red light, and the motor dies. And at the next one. And the next one too: the idle won't hold!

So I open the carb, and check it out. Turns out the mixture screw is wide open (7 turns out).

So I decide to go back to stock airbox and filter. Set the mixture screw one and a half turns out. Watch the video for a sound check now. Sorry this website won't take .MOV video!!

It idles. It backfires in the airbox. I have air leak at the manifold.

Engine too loud.

Gottogo.

Keep you posted.
 
That's too bad. Must be a vacuum leak from something that came disconnected and you didn't notice while putting on the new air filter housing.
You could try using carb cleaner with the plastic hose on the nozzle and with the engine at idle use short burst of spray around the carb mounting areas.
 
joel said:
That's too bad. Must be a vacuum leak from something that came disconnected and you didn't notice while putting on the new air filter housing.
You could try using carb cleaner with the plastic hose on the nozzle and with the engine at idle use short burst of spray around the carb mounting areas.
Click to expand...
I found the leak, Joel. I had a bunch of seals bought for 20 euros on Amazon from which I used the intake seal, because the old one was ripped (but functional). It was too flimsy! the carburetor wasn't tight. So I went to my local HD distributor, and bought the original part made in USA for 15 euros (!!!) and voilà! the bike runs fine. You can see the difference in weight of the parts on the pictures. Food for thought.
 

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I put the carb back to stock just to see. 42 slow/160 main, stock air-box, and had to turn the mixture screw 3 turns and ¼ out to be able to hold idle. Plugs are black. No more acceleration from ¾ of throttle up. Top speed down significantly. But the farts are gone and acceleration is crisp.

It sucks!

I'm going back to 45/190 as it was.

Facts of life: I go buy the jets at my local HD dealership, the "new" idle jet is ALREADY clogged. I have to clean it before mounting. Maybe should be considering another dealership lol
 
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