Airbox conversion

[motorhead13]

Hi, I've just picked up a 1978 XS1100 yesterday that needs a fair bit of work. While not really checking it out yet, one thing missing is the airbox.

Has anyone done it or is it possible to use pod filters on the carbs rather than an airbox? And are the airboxes model specific or can they be interchanged?

I used to have an XS250 and 400 as projects so they're not totally foriegn to me but this is a bigger project than I've done before so could be interesting! Any pointers or advice is much appreciated.

[oldyam80sg]

I don't know what other air boxes will fit. Most leave the airbox on for some reason-I for one remove them when I get a bike. I think it is cleaner and once you get pod filters fitted and tuned bike runs nice. My opinion only. I run APE filters on my 80 SG.

[bikerphil]

The only air box that will fit is 78-81 XS1100. The problem you will run into is that K&N no longer makes a filter for them and the cheap paper type that are available are way too restrictive IMHO.

[motorhead13]

Thanks for the replies.
I agree oldyam80sg in that pod filters look better, probably a bit lighter too? I did them on the 250 I had but can't remember much about that now and didn't use it much. Does it require much amending to other things like hoses etc fitting pods?

That's a pain about the filters for the air box.

[DiverRay]

Pod filters will work well on any bike. That said, you NEED to make sure you use good filters. The XS1100 carbs have a jet on the lip of the airbox side of the carb. A lot of filters will cover this and the bike will never run correctly. Make sure you get the filters without the lip. A search on "pod filters" on this site should help a lot.
For the rest of it, it's easy. There are TWO "T" fittings between carbs 1&2, 3&4. The BOTTOM fitting is for the fuel connection, the top is a vent for the carb float bowels. I would put a short bit of tube and a paper filter (fuel filter for small engine) on each one. Keep the bugs out and the floats working correctly.
Last is the larger tube from the engine breather to the airbox. Again, find an automotive filter/breather that will fit the tube to keep the critters out.
I would also look for the parts to put the right front brake assembly back on. When running correctly, these bike had a hard time slowing down as they WILL pull like a train! The XS1100 was the fastest production motorcycle in 1978 for the 1/4 mile, turning in a time of 11.74 seconds!

[jetmechmarty]

Uni pods work fairly well with these Mikuni carburetors. They’re popular in the XS650 community. Those bikes run very similar carburetors. Performance is superior to K&N in this application.

[DEEBS11]

https://www.ebay.com/itm/270700149239?_skw=xs1100+k%26n&itmmeta=01JWY2JVCZA34ST0PPGRZC54RD&hash=item3f06fc79f7:g:86sAAMXQY8JRgyQe&itmprp=enc%3AAQAKAAAA0FkggFvd1GGDu0w3yXCmi1ftdXt7zyHICTzEt93CfPs7bUPoQs765mFE5Jw%2BHAEr04%2FT59xaRn%2B%2BiKWJ1Edt9fG2CaO5gk2Rai7BFej7VxBsTRS1%2FaOeswkswisnimx4y2bxbGJYzt9LG7sTaOHgAYqAzxSgedcE6FUnaLE4S0pI4%2Fld%2BYu7B3kNzPpdA9q2JFPYP78Di55Y9GIrQakUzmoBso2Uw4JBPPfcuPl8zHMFDTlHgOoOb%2BSzQr4DD63Zbi9VOr9h8GdH4jnm4B%2BbFpk%3D%7Ctkp%3ABk9SR9C2y8LnZQ

https://www.ebay.com/itm/256592992131?_skw=xs1100+airbox&epid=1823353933&itmmeta=01JWY2P1DDME926K1YB9ZNF0N5&hash=item3bbe225783:g:~gsAAOSw~vNmQpC1&itmprp=enc%3AAQAKAAAA0FkggFvd1GGDu0w3yXCmi1cEOT8K7DRAE5dj6DOyo6FHPcbZ0UofFl985GQUo9GK%2B6RIgHemkvS4wakKuZBVMFbZFklwp%2BpwXXkANW%2Bd7uh5hhOPHfAIm%2BgQyBH0w7YXbOfOqubFNyN%2F65ucje2%2FChxhYU9wuh3NgUrkejbpAL0cYoK9V18cNUFhRLUQ7CIDfYfBL9v6zPm45DBr32j3zV46eJ%2FAFVUIUQJc2qvQTnK7qoCc1iOhB6KUyiqEFnZQaqJG4OOU6mf%2BQaV1U2ppC6U%3D%7Ctkp%3ABk9SR_qW2MLnZQ

[motorhead13]

That's awesome, thanks for the advice and info will be so helpful. Definitely will go with pods then.

Thanks DiverRay. That's how the bike came with the brakes off so will look to rebuild them if they're ok if not replace the calipers. The rear brake needs sorting to, possibly the master cylinder. The carbs were off the bike when it came Tuesday and started looking at them yesterday, so will aim to get it running then look at sorting everything else.

[DiverRay]

Pour some ATF (auto trans fluid) into each spark plug hole as you are working on the carbs if it's not been started for a while. This will free up the rings and help the process on down the road. DO check the valve clearance and cham chain tension before your first start.I know, valves should be hot to check, but just add about 0.002 thou to what they should be. These bikes have the clearance REDUCE as they wear, so you need to make sure you don't have a valve not opening when you try to start.
Good luck, and you WILL be happy with it once sorted. You can put this bike in high gear at 35mph and it will just pull from there if it's set up like stock.

[motorhead13]

Thanks for the tips. I've not checked a cam chain before and not done valve clearences for a long time so will try and find out all I can. . Excuse my ignorance but is ATF gear oil or could you use engine oil? I think its hardly been riddn in at least 10 yrs and the throttle lever was initially stuck on the carbs as the butterfly's weren't opning but now they're opening fine with a bit of lubrication. Would you think it best to clean and rebuild all the parts in the carbs or try just cleaning first? I was thinking maybe just go ahead and replace the parts as the carbs are off.

Thanks for the support. I wasn't looking to buy another bike (don't go on ebay when you're bored!!) but looking forward to getting this back on the road now and the cahllenge of trying to do it.

[DiverRay]

ATF is Automatic Transmission Fluid, or oil. It has a high content of anti-oxy in it that helps break down rust in small amounts, and will lube the rings so they will "float" as they need to on the piston.
For the carbs, just clean everything. DO NOT replace the jets UNLESS you have Mikuni jets. ALL the aftermarket kits with jets are junk, and will cause nothing but problems if you install them. You may want to look at the jets that are installed and verify they are Mikuni jets.

[jkorn]

Years ago when I took off the stock air box I lost all kinds of low end. I believe the bike needs that bit of restriction first the carbs to work properly. Vacum is needed for the carb slides. Also someone years ago said to open up large holes on the bottom of the air box. Same issue, bike ran not near as well.

maybe high end will be better but lots all kinds of low end torque which the XS has so much of.

just my 2 cents.

Unfortunately, these days mine sits too long between drives. I spend more time these days in my 4 wheel R8 instead of 2 to keep wife happy.

good luck with your project. My clutch slips slightly under hard acceleration, but engine has never been open so I’m tempted to leave it that way.

jeff

[jetmechmarty]

It's my belief that the best way to run this bike is with the stock airbox. It works fine, makes HP and helps scavenge the crankcase. The stock bike also looks better with an airbox on it.

[DiverRay]

Look at the photo he posted. No airbox on the bike. Sometimes we need to make do with what we have, and in this case pod filters make more sense.

[motorhead13]

Thanks for all the replies and info, I appreciate it. Will definitely add some ATF like you say DiverRay. Will have a look at the jets to check them as it all needs a big clean anyway as the throttle lever was stuck and 3 of the 4 floats weren't moving either but now all are.