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Discussion Starter · #1 ·
Being the newbie that I am... When I got my 1970 CB350 I wanted to replace any old parts that looked rough or could hamper safety or performance. So after doing plugs, cables, etc. I also changed the air filters. When I ordered them through my local Honda Dealer I figured I would be getting stock ones (most parts I had them get were OEM). But they ordered me a set of UNI-Filters. So I followed the filter's directions and they went on pretty easy. The bike seamed to run fine. But I notice at higher RPMs it tends to bog down or sputter. Could that be the filters? I fortunately saved the old stock "box-style" filters. Should I throw them back on and see how it runs? I'm basically looking for any thoughts on why my bike might sputter or bog down at higher RPMs. Could it be the UNI's?

Thanks in advance!
 

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the unis flow more than OEM...you'll probably be lean on top and need to go up a jet size on the mains
the easy way to check is to reach down and give it a little choke when it sputters. if it gets better than you're lean and need bigger mains. (don't put the choke all the way on though)
 

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Just like he said with the choke. That's the easiest way to tell if it's too rich or too lean when it's sputtering.

Another thing you can do if you're somewhere safe to do so is run it at high RPM while it's sputtering and kill the ignition and coast to a stop. Then examine your spark plugs to see what color they are. If they're gray or white, it's too lean and you can damage your engine (soft or hard seize the pistons to the cylinders.)

If you're not building a race bike and it runs better with the stock filters, I'd probably stick with them so you don't have to rejet the carburetor (not that it's that difficult, mind you.)
 

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Did you oil the filters properly? I use a spray oil for motocross filters that's red or blue colored oil. It's easy to tell if you get even coverage that way. It doesn't take a lot of it to do the job. Be sure to squeeze the filters to evenly distribute the oil as well..


GB :mrgreen:
 

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Discussion Starter · #5 ·
Wow guys! Tons of great info... I think I'm going to try putting the stock filters back on first and see if things improve. If not, I'll switch back to the UNIs and go from there.
 

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Discussion Starter · #6 ·
Still haven't had a chance to swap out the UNI's with the old air boxes... But I was wondering if anyone had any good tips on cleaning those old filters. Canned air? Vacuum? Just wondering if there's any tricks before I put them on. I might do it this weekend.
 

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You can burn or rip out the old paper media. It's been done here before. Then find an air filter that the paper is the same height as the original. A round air filter for a smallblock Ford or Chevy should suffice. As long as the height is the same as the original paper. You can then silicone that new media into the old filter plates/boxes.. Or you can buy Uni Filter foam online and glue that in the same way..


GB :)
 

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Discussion Starter · #9 ·
Ok, I finally got around to putting the old air boxes back in it. Wow, it ran worse! Sputtering, backfiring and bogging down. Now it did sit for a little while before I got to do this, probably some of the rough running. I believe the next step is to put the UNI ones back in and oil them properly. Thoughts? Any good links to oiling technics?
 

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Just spray the oil on evenly, just don't get carried away with it because you're then going to squeeze the filter to distribute the oil evenly and wring out any excess. You want them evenly coated, but you don't want them soaked.
 
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