Replacing air filters, where does this line go?

[hjpaul7]

Super newb here, but learning. I have a 78 xs650 Special, all pretty stock. Stock mikuni carbs I believe.

So I'm replacing the air filters and I noticed this line that connected from the old air filter to the engine, I'm wondering with these new filters, does this line need to go any where or just leave it open? I'm assuming it recycles air or something.

Photo below (line above filter)

 

[grepper]

I take it you took off the stock air box.
Oh Boy, these cheap emgo style air filter are crap, they are known to block passage ways. You might need to re-jet your carbs to work with these too. There are much better pod filters out there, like UNI's or K&N's.

If pods is they way you want to go, people either put a filter on the end as to not suck crap back into the engine, or put a break booster valve on it to maintain vacuum in the engine case.

 

[hjpaul7]

Any tips on how to re-jet the carbs? I just rode with them on with that line open and it runs better than the air box with the old filters. The filters really weren't too bad looking

 

[itsatoy]

Scroll up and click on "Tech" in the orange bar at the top. Among other great info there is an extensive carb guide.

 

[cobrasneverdie]

http://www.amckayltd.com/carbguide.pdf

 

[gggGary]

The original "mouse hair" filters should be avoided they can look fine on the outside but the inside is often shedding fine bits of junk, not the best thing for the carbs to breathe in. but anyways rub em a little bit and they just fall apart. I will clean all old crap off the old filter frame and wrap with oiled uni filter foam, that seems to work well

 

[alwaysmonday]

Hjpaul7,

Welcome and congrats on the new bike. Are you headed out tomorrow for this? http://www.rockersreunionindy.com

Jon

 

[5twins]

Yes, re-wrap the original "cages" with UNI foam or just buy UNI pods. Whatever you do, take those cheapo cone filters off. Set one open end up on your desk. It makes a great pen/pencil holder. That's all they're good for. You'll never get it tuned correctly with those filters.

 

[hjpaul7]

I downloaded the carb guide, will try to clean the carbs out today. The air filters I bought were EMGO, and I guess they're crap? So looking into UNI pod filters but..I can't really find one for my year. It's a 78 special, stock carbs I believe. Am I missing something? Don't see anything for 78's on UNI. If I can find some, then I'll reject.

For the time being, isn't here anything to help the shit pod situation? I read the rubber seal of them EMGO pods that goes over the carb can be too..long. 3 holes inside the carb lip that needs to be open and not covered? So maybe cut the rubber on the filters.

 

[gggGary]

I bought a bunch of cheap flea bay pods a few years ago and knifed away the edge of the flange, they worked, nothing great but the motor would run fine.

 

[hjpaul7]

I bought a bunch of cheap flea bay pods a few years ago and knifed away the edge of the flange, they worked, nothing great but the motor would run fine.

Is the flange the rubber piece?

 

[gggGary]

Is the flange the rubber piece?

Yeah I knifed a bevel in the rubber carb flange so it didn't block the ports.

 

[hjpaul7]

Would the ports being blocked cause the bike to overheat and backfire?

 

[grepper]

Would the ports being blocked cause the bike to overheat and backfire?

Yup, that or not jetted/tuned properly. Read the carb guide, then read it again and again.

As for UNI Filters, any year up to 79 will fit. 1978 had the BS38 carbs, then in 1980 Yamaha went to the BS34. There are minor differences in the BS38s over the years, but the opening sizes are the same.

 

[hjpaul7]

Ordering some UNI 4200s today, hope this'll help and I'll try to rejet.