Xbr missing

[Clubman44]

Need a bit of help my Xbr runs fine up to about 5000 rpm in the gears however above that ther is a reluctance to rev out, in top gear it gets to about 4000 and then it starts to miss now and again,I wondered if perhaps the coil might be on its way out?
Regards Rod.

[BrendanO]

With the (non-thumper) CX, that us often a sign of the stator failing.

Hope something simple with the XBR!

[Clubman44]

I going to start with the basics and change the plug,cap, and lead. And see where I go from there,I don’t think it’s fuel related.

[BrendanO]

Always a god plan - it's too easy to imagine the worst snd start ordering parts!

Even if you don't think it's fuel (ie bike is regularky used, you didn't leave it out in the rain, and it was fine until it wasn't), it may be wofth draining the float bowl into a container to see if there's water/paint flakes/ rust in there.

Hopefully someone more knowledgeble than me will have replied by then!  cheers!

[Propellor]

The way I'd look at the problem.

It may or may not be fuel related. But if is fuel, based on the described symptoms, it sounds as if it is unable to give max power. You need the most power the faster you go, generally speaking. So in top gear at a reasonable lick the engine is loaded. Max power needs max fuel flow. Assuming you've not been tinkering with jets or anything I'd consider the possibility of a partial block. Thing is, one can check this kind of thing without replacing parts in the hope that's the cure. Next thing I'd do is get the the symptom to repeat itself consistently time and again so you've a solid theoretical base. Maybe find a steep hill and then you can see if the symptom occurs in the lower gears, lending more evidence that it is power related or not.

Just throwing ideas in the pot.

Cheers.

Edit: max power also needs max air flow. The air filter would have to be in terrible state tho.

[SteveC#222]

If the electrics are OK, it might be a damaged diaphragm in the CV carb not letting the slide lift up?

[Clubman44]

Well I changed the plug and cap, the ht lead seems to be sealed into the coil. I also put a meter across the coil the resistance on the primary was 00.5 according to the manual it should be 0.18, could this be my problem, the secondary circuit was correct.

[iansoady]

0.5 what? If ohms that's a low value in my experience. Digital meters do tend to have zero errors that need to be taken into account.

[SRXpatriate]

Stuck choke plunger?

Or as per SteveC CV carb diaphragm.

[Clubman44]

Have not had a chance to test the bike yet, Iwill try over the weekend, I have checked the choke plunger. The diaphragm I will check, however the carb is a right pain,with the one piece manifold.

[Mutt]

Interesting thread. My (complete) XBR has had a similar issue recently but I've not had chance to sort it yet. Loping along in top @4000 rpm (reads 60 mph on my clock) feels like it is running out of fuel. Drop down and it will rev through 4000 but will then hesitate higher up the band, however in fist and second it can red line without noticing an effect. The carb was cleaned this summer with a full service kit installed - it is a knuckle scraping pain. The valves are spot on. The plug & cap are new. So the one item I need to pull apart is the fuel tap (and check the fuel line is clear) as I'm suspecting that it might be that that is harbouring some crud. This weekend I'm hoping to get the time and the weather to check it.

[Propellor]

Interesting thread. My (complete) XBR has had a similar issue recently but I've not had chance to sort it yet. Loping along in top @4000 rpm (reads 60 mph on my clock) feels like it is running out of fuel. Drop down and it will rev through 4000 but will then hesitate higher up the band, however in fist and second it can red line without noticing an effect. The carb was cleaned this summer with a full service kit installed - it is a knuckle scraping pain. The valves are spot on. The plug & cap are new. So the one item I need to pull apart is the fuel tap (and check the fuel line is clear) as I'm suspecting that it might be that that is harbouring some crud. This weekend I'm hoping to get the time and the weather to check it.

It's something affecting the engines ability to develop full torque and power by the sounds of it.  Same as above. Not a massive help but a clue nonetheless

[xbally]

What's the mileage?I only ask because a few years ago i ran a ratty £500 XBR with high miles and it never did pull right.I was told it could well have been due to wear in the engine. Just a thought but i hope i'm wrong!

[Rossco500]

Been following this link too. As Xbally asked, it would be interesting to know the mileage. If it does prove to be carb related and not electrical I would suggest getting the carb ultrasonically cleaned rather than treating with carb cleaner. I have done this with a couple of xbr carbs and whilst they weren't suffering as badly as yours, it definitely improved things. Not cheap, and I know the carb on an xbr is a sod to remove but probably worthwhile together with adding a fuel filter.

I think there are some previous tips on xbr carb removal on this site if you check using the search facility.


Good luck

Tony

[Clubman44]

I took the Xbr out for a test ride today, it seemed to run quite well, the missing I was experiencing at 4000rpm is still there but not so bad as it was before changing the plug and cap, which seems strange to have a partial cure. I am still thinking the I might replace the coil in the near future, the bike has 36000 miles on it. I will report on any further progress, but I would like to thank everyone for their advice.
Rod.