K&N cone filters
 

Hello everyone,

I'm new to this forum, normally I would post my questions in the Yamaha section for my XT600. As well as the XT I have an old '82 CB750FB, thats the dohc version. I'm rebuilding it after at least six years that its been sat in the garage, gathering dust and mice living in the exhausts ! Everything is going fine, I don't have a lot of time free so it's a slow process, cleaning and rebuilding. My question is this, I would like to replace the air box with four individual K&N cone filters. I've seen lots of bikes of this age with this modification, and I find it looks very nice but wondered about the carburation, would I have to automatically change my jets, needles etc ? Any other helpfull sugestions you can think of would be most welcome. This isn't the bike that will be shooting off to Russia or crossing the Sahara, It's just for a round France, short weekend breaks in good weather sort of touring bike.

Thanks in advance Chris:euro:

you certainly will.main jets can be easily enough changed, though from recollection the needles do not have grooves and clips, you will have to pack small washers under the head.you will definetly need to richen up the needles and also the mains, however this is down to experimenting with needle hieght and main jet size.do this by performing a plug chop. err on the rich side to begin with.
make a rain deflector too coz when it pees down and them filters suck in that water....

CB750F Air Strainers
 

Lot's of luck geting them carbs to carburate properly with individual K&N quasi filters. Maybe they work better at sea level but at higher elevations you will get very familiar with your carbs. and then when the wind blows from one side and your carbs run funny....On another note check your valve clearances, that particular motor family tends to tighten up and burn valves. And when you put in the little bolt or screw holding the tach cable in just tighten it a tiny bit and put something like slicone goop on it to hold it in place, it will strip out the threads otherwise.

Fancy box ?
 

Thanks for the advice,

Well, now I don't really know what to do. Should I go with the K&N and struggle through with the carbs or not ? Or does anyone know of some sort of aftermarket air box to jazz the bike up a bit ? I really fancy the K&N look, has no one actually done a set up like that before that could give me some jet size advice ? Has anyone changed the air box arrangement before for this sort of bike ? I'm looking for the old style look, something with nice clean, no plastic look. Anyone who has a bike like this must have thought about this before ! Maybe I could change the side covers only, any ideas ?

Thanks Chris. :biggrin3:

Up to you mate - if you like it go for it! But...

HIGHLY unlikely. The very best airbox is a BIG one. Note all new bikes have monster airboxes compared to the older bikes. The more still air the better. (We always knew that but they've taken it to a much higher level now than we ever dreamed of waaay back in the old days.)

Probably. BUT unless K&N or your local Honda shop has some memories of doing such a thing you'll have to start from scratch. As above, start rich - cheaper than melting your engine. :oops2:

K&N's flow more air as a general rule than stock air filters, so you need to richen it up throughout the range. Do a little search on the web for basic procedures - do it right or melt it. Note that K&N's also flow more dirt...:thumbdown:

Probably have - but they've probably also had to do the work too! Sorry, there's no easy "formula" - anyone who has done it has also probably changed the exhaust - and it for sure won't be the same as yours, so his jetting info won't work for you anyway.

Suggestion - put it together stock, make it run and ride it a little :mchappy: - then if you're still inclined to change it, go for it - but don't complicate your life sooner than you have to.

Voice of reason
 

Thanks Grant,

Your probably right, at least for the time being anyway. Like you say, the exhaust won't be the same too, this ones shot so it will have to be some aftermarket thing or straight through tubes ! :ban:

Anyway, I'll carry on with the slow rebuild, get the thing going again after all the time it's sat patiently in the garage. Give it a nice lick of paint and live with the airbox as countless others will have. After all, it's only going to be the weekend, dry day runabout. Leave the messy stuff to the XT winter bike !

Thanks again for all the advice, great web site :scooter: Chris