XBR carb

[guest1230]

Hi all.

Have been re-building an XBR 500 from almost basket case status.

Have got to the point where I can start it and indeed ride it.

Had to do some work on engine:

two new rocker arms and a stator. No spark before stator fitted.

Problem I have now is engine will not rev past about 4000 under load.

I am trying to run it without original airbox, using a K&N type filter.

Is this where the problem is.  Have a got to put that 'orrible black box back on?

Diaphragm / Needle valve assy does not appear to be moving.

Any thoughts would be appreciated.

Richard.

[guest295]

I keep hearing from people who are confused because the carby doesn't work properly when the original intake is removed. Well duuh, what do you expect? The carb is vacuum operated and there's not enough vacuum to lift the slide. You've got an oil tank in there, so the airbox just nestles in next to it neatly. The stock filter has plenty of area and doesn't clog up when it rains (K&Ns don't work in the rain). If it ain't broke, don't fix it.

[tj63]

Here endeth the lesson 

[guest1230]

Oil tank!

What oil tank?  Maybe that's why it's seized?

Seriously though. I did say I thought that was the issue but I wondered if anyone had found a way round it. Cafe racer types anall. I think Mr Honda decided the airbox was the first thing to go in the frame on assembly. I'm not saying I forgot to put it in but really . . .

[Dick Scratcher]

In all the years I've been riding (48 of 'em) all I've ever heard about K & N filters is that their fitting is usually accompanied by b******d-up carburation and a reduction in performance. Stick with the standard stuff, it works and your engine will thank you for it !. If on the other hand your engine is much modified and 'tuned' out of it's mind K & N's are probably the way to go.

[guest1230]

Well . .  I've put the airbox on and "duuh", exactly the same!  Will strip carb and check jets etc as its been upside down in a box for years.

[SteveC#222]

Have you checked the diaphragm? They have been known to split on XBR's especially if it has been in box for a few years....bloody expensive to replace

[guest1230]

Yes, I've had a look at it. It appears to be ok. I can't seem to get my head around how it works though, as there is no vacuum connection ABOVE the diaphragm how is it supposed to pull up?
All the airways are below it suggesting it is "blown" up!
I have a second xbr that runs perfectly. This was my "spares" bike. Will have to look at the carb on that and see what's diferent. Don't want to mess that up tho!

[guest1230]

Problem now solved.

Not quite sure how but think it was inlet tract seal. Remembered to put jubilee clip thingy on this time! plus cleaned jets etc.

R.