Topic: Please help a newbie regarding a weird sound

[Jamil20]

I'm going to say check that nothing is obstructing your intake. I used to keep an oil rag under my seat that would block my intake on my 400 twin. I'm not sure how the fours are set up, but that could be an issue too.

[FLo]

Okay guys here's some pics.  Sorry it took so long.  Been busy at work.
The plugs are NGK iridiums DR7eix.  I was planning to replace them with just regular NGK D7EA's.  What model of plugs should I replace these with in the future?

Thanks to all!

[Gordon]

Thanks for the follow-up pictures.

So we've determined you definitely have a Dyna-S ignition, so the problem obviously wouldn't be the points or condenser.  It's possible that it could be a problem with the Dyna unit, but that's less likely than some of the other possibilities, so I wouldn't worry about it too much right now. 

It's difficult to tell for sure from the pictures of the spark plugs, but #3 and #4 look to me like they could easily be causing the symptoms you described.  They may be only firing intermittently or not at all.  Replace the plugs, then check to make sure they're all getting a spark.  You do this by hooking each spark plug into its lead but without screwing it into the engine.  Hold the metal nut part of the plug against the side of the engine and crank the engine over with the starter, making sure the kill switch is in the "Run" position.  Verify you have spark on all plugs and then install them. 

[FLo]

Thanks Gordon for the instructions re: checking spark.  Followed your instructions and checked old and new plugs.  All were sparking, so I left the new ones in.  Ran a little bit better but still didn't sound right.

Checked the air box, and noticed that the housing was dangling on one bolt so the filter was tilted.  Took out the filter and filthy as hell.  tons of oil too.  Went to a gas station and cleaned the filter with the air hose, made a cheap homemade clip to bolt the airbox so it's straight.  Now runs good, but I reckon I need to get a new air filter.  Been doing some preliminary searches but can't find a K & N filter yet.  I'll keep looking, but if anyone can point me in the right direction, it would be greatly appreciated.

Thanks to all for helping this newb.

-FLo from Vancouver

[OldSchool_IsCool]

Hey Flo,

Here is a recent thread about 550 air filters. 

http://forums.sohc4.net/index.php?topic=46979.0

[FLo]

Hey Flo,

Here is a recent thread about 550 air filters. 

http://forums.sohc4.net/index.php?topic=46979.0

Thanks Oldie,  that's a thread I started.  Ha!

[OldSchool_IsCool]

DOH!

[FLo]

Okay so I ordered a uni foam filter, put it on, and performance got worse.  Acceleration was really slow.  Fearing that re-jetting was needed, I opted to order an OEM paper filter since that what the bike had before and no problems.  Installed the paper filter, acceleration is better but still slow, and when I rev over 6000 rpm, I get a sudden drop in hp, and the engine makes a deep weird sound.  Acceleration is extremely week and slow.  I'm stuck on what to do.  Thinking about hitting up a mechanic, but your tips are greatly appreciated.

Thanks

[Gordon]

Don't give up.  We'll figure this out.