xbr tickover

[tommy murphy]

hi guys any tips to get my xbr to tick over and not cut out at lights  cheers yoshi

[J Hop]

I dont know  anything about xbrs, but I would suggest cleaning out your carb, especially the idle jet and/or increasing the idle speed.

[GB500nz]

The idle should be set to 1200 or above. Beneath the float bowl is the idle mixture screw. It's very hard to get at because there's so little clearance. I use a screwdriver bit jammed in a piece of rubber hose for grip. Turn this screw out 1/4 turn and see how it goes. If that's not enough, turn it out another 1/4. It also helps to get into neutral before stopping, and keeping the revs up. Once stopped, you can let off the throttle and leave it idle. The problem seems to be related to something the CV carb does by itself.

[guest7]

Early XBRs had to be modded to allow them to tickover. The factory sent out new jets and the revised tappet settings were something like 15 in, 19 ex. Apprently the bike was originally jetted lean to help with emissions tests.

The only way to tell if your bike has been modded is to look at what size main jet is fitted, the revised jet is a 158.

Strangely, not all XBRs were affected by the stalling problem. I have one here that is still running on the 152 main jet.

Another thing is that any of my XBRs that have had the valve seats recut seem to tick over happily for hours.

Cheers
GC

[Hornblower]

My XBR has developed tickover problems which my local mechanic tells me is as a result of a "pulser coil" on its last legs.

[guest7]

How did he test the pulse generator? (I'm assuming that's the bit he's on about).

All XBRs can have crap tickover, see the posts above. What are you setting the valve clearances at? The handbook (and some old manuals) has the old settings, but if the bike was retrofitted with the larger jets then Honda specified the clearances I quoted in my earlier mail.

I'd check out the jets and tappet clearances before shelling out on parts.
GC

[Hornblower]

I'm afraid I'm no mechanic so I can't tell you what the valve settings are. What I do know is that the tickover used to be OK (that's ok for a big single) and in the last couple of months it has deteriorated. The carb is clean as a whistle and the mechanic tells me that there is a problem with the pulser coil, I have used the same mechanic for many years and he has always been spot on in the past.

On  another point, I have seen a second hand 2 into 1 exhaust system on ebay, I currently have standard pipes on the bike. Would I experience any power reduction if I swapped to the 2 in 1?

[GB500nz]

There's no power loss in the 2-into-1; possibly an increase.It weighs less, too. The pulser coil either works or it doesn't; there's no halfway. A valve may have got a bit tight. They're not that hard to adjust. There's a shop manual on www.gb.zyns.com/forums/showthread.php?t=10

[Steve H]

Or leakiing inlet manifold

[Hornblower]

Thanks for all the useful advice guys. I will go back and check with the workshop about the valves.

[guest27]

Exhaust - depends how the exhaust has been designed as to whether a 2 in to 1 will make much difference.  You get more outright power with a tuned individual pipe - but can make differences low down or in the mid range with a 2 in to 1.  However most exhausts are either designed to give so-so performance over the whole range, or to make a hole in the power just where the noise tests are done - hence quieter.  So I would guess it all depends on what you want.  I have an artical written by the late great John Robinson, where they palyed about with Forsyth's Rotax racer and found that two pipes gave better power than one, two pipes gave a better spread of power than one - but not at the same time.  They also discovered that two pipes, one tuned for max power and one tuned for max spread gave nearly as much power as two for max power and nearly as much spread as two for max spread - a result.  Mind they were about 20" different in length (500mm for the metric people) so made for an interesting set of pipes.

I guess the same would be true on the XBR - but would require a day on a dyno...

R

[guest7]

XBRs are amazingly indifferent to exhaust changes, as long as you don't go mad. I've run 'em with all sorts of combinations. If the 2-1 is made for the bike then it will work and won't reduce power.

The Motad gave an extra 3hp, but it hasn't been made for over 15 years :-(

The Micron is ok albeit a little ugly.

Don't be put off by the difference in downpipe diameter between the Micron and the standard system, the standard downpipes are double skinned and actually just as skinny internally.

Cheers
GC