93 CB750 Air Filter Question - PROBLEM SOLVED

[Moedad]

Okay, so I've had my 93 Nighthawk for about 6 months. Tonight I checked the air filter for the first time (yeah, shouldn't've have waited for so long). As soon as I took off the cover, I smelled fuel. The latch thingie was oily. It's the stock paper filter, BTW. There's a fair amount of smelly goo in the filter, mostly on the side that faces front. The port on the top of the filter is all crusted with black crud around the edges. The walls of the filter housing is somewhat gunked up with oily/gassy residue. Looking at the goo in the filter, I'm surprised the bike has been running reasonably well. So obviously the filter hasn't been changed in a long time. My question is, is what I've described normal for an air filter that hasn't been changed in what seems to've been a long time?

[happycommuter]

I've come across the same thing.  Bit of splatter that has a fairly potent odor.  I assume this is a normal result of crankcase ventilation or something.

Edit: possibly because I am a slacker in tube draining.  See below.

[detdrbuzzard]

and you didn't sujust he start by draining his crancase breather to see if it helps HC

[Moedad]

and you didn't sujust he start by draining his crancase breather to see if it helps HC

I do that once a month or so already.

[gammer]

My question is, is what I've described normal for an air filter that hasn't been changed in what seems to've been a long time?

Yes, this is quite normal.
The drain for the crankcase breather is underneath the air filter. However, this doesn't mean that the fluid coming from the crankcase is trickling back. It might be in mist form, which would land on your filter. Also, you can get some "spray back" direct from the carbs, which could land on your filter too.

[Moedad]

Okay, that sounds better. My question has now become a problem however. I ordered a new filter last night from Service Honda but in the meantime I put the old one back in. This morning I started the bike and the idle (choke on) was rough. It has idled fine up until this morning. I let it idle for 30 seconds or so and gave it a teeny bit of throttle and it bogged right away. I let it idle some more and tried again. Same thing. Also it was making occasional small backfire type sounds, more of a SNAP than a POP. Screw it, I'll drive the car today and monkey with it when I have more time tonight. So...thoughts/guesses, anyone? Did I maybe knock some crud loose and it got into a carb or two? Reinstall the filter improperly? All of the above?

[gammer]

Lets start simple...
My guess is that even though the filter is very dirty and it was running fine up until you took it out, it is getting choked out now. Basically its running very rich. The air flow has obviously changed upon re-installing it.
Lets see what happens when you put the new filter in.

[Moedad]

Lets start simple...
My guess is that even though the filter is very dirty and it was running fine up until you took it out, it is getting choked out now. Basically its running very rich. The air flow has obviously changed upon re-installing it.
Lets see what happens when you put the new filter in.

Yeah, that's what I kinda figured. 7-9 working days to delivery from Service Honda. Maye I'll clean my chain (again) in the meantime. Do some other maintenance stuff. Yeah, yeah, that's the ticket.

[Brittles]

Might want to sniff you dipstick (that sounds kinda' dirty don't it? ). Make sure it doesn't smell like gas.

[Moedad]

Might want to sniff you dipstick (that sounds kinda' dirty don't it? ). Make sure it doesn't smell like gas.

Hypothetically speaking, if it was running good before I checked the air filter, then after checking the air filter it runs poorly, how would fuel have gotten into the oil and cause a problem during this procedure? I'm not saying I don't need to sniff my dipstick  , I'm just looking for the connection. If fuel is in the oil (bad, I know), wouldn't the bike have been running poorly before the air filter check?

[Moedad]

I checked my dipstick last night and CRAP, it DOES smell like gas. So again, my question is how simply checking the air filter would lead to gas in the oil? I guess the simple answer would be that it didn't and that there are two issues going on here--the air filter issue, and fuel in the oil. Yes? No? The bike was running fine before I checked the air filter. It did smoke (lightly enough that I couldn't say if it was blue or white smoke) just a bit when starting cold, but only for a minute. Other than that, no issues.

Mods, feel free to move this to another forum if necessary. I thought about starting a new thread in another forum, but it might be better to just move this one if need be.

[gammer]

Its normal for oil to smell a little bit like gas. Especially if its close to needing changing. If a large amount of gas was getting into your crank case, you'd notice the oil level going up. And if you were getting gas in the oil, it would be from a float in the carb sticking, and if that was the case, you'd probably notice gas leaking from the over flow lines coming from your carbs too.

Change your oil and oil filter while you are waiting for the air filter.
Try not to over think things here. Keep it simple and do the easy things first.

[Moedad]

Its normal for oil to smell a little bit like gas. Especially if its close to needing changing. If a large amount of gas was getting into your crank case, you'd notice the oil level going up. And if you were getting gas in the oil, it would be from a float in the carb sticking, and if that was the case, you'd probably notice gas leaking from the over flow lines coming from your carbs too.

Change your oil and oil filter while you are waiting for the air filter.
Try not to over think things here. Keep it simple and do the easy things first.

Thanks, Gammer. I feel a little better.

[Moedad]

Gammer, I'm such a dork.  I was at work today thinking about how you said keep it simple and something popped into my head. Where the gas tank bolts to the frame under the lip of the deat, there's a rubber fitting between the washer of the bolt and the flange on the tank. My rubber fitting was worn out and ready to split completely in two, so I ordered another one. It came in on Monday and after dinner Monday night I took out the old, worn out rubber thingie and put the new one in. Maybe you can see where this is going. To put the new one in, I had to lift the back end of the tank enough to slip it in place. It was only like 1/2 an inch, but it was enough to, yup, pop that little vacuum hose loose that connects to the side of the petcock. It didn't disconnect from the petcock, but from the other end where it connects to a nipple on something in front of the carbs. I glanced at the petcock afterward but the other end of the hose was kind of tucked in and it didn't cross my mind to look at that end, only the petcock end. It was a couple hours later when I went out and checked my air filter. In the morning when I started the bike and it was running so rough I immediately figured it was something with the air filter and totally forgot about what I'd done earlier in the evening. At work today it popped into my head--Check the hoses, stupid! So I did and sure enough found the disconnected hose right away. I hooked it back up and started the bike. It stumbled once or twice and then ran like it always had. Problemo solved! Thanks for help and encouragement, gammer and others.

I'm still going to change my oil and filter this weekend though. Yeehaw!