Carburators

[Conquistador]

Carburetors

I have a 2004 XL650V and recently rode at very high altitude here in Chile, up to 4700m. I would barely run over about 3500m. The symptoms were lots of bogging, loading up with gas, black smoke, almost zero power. It ran a little better at very low throttle position under 3000 rpm. As soon I descended, all symptoms returned to normal. Later in the trip I checked the needle valves to see if they could be adjusted, - no go –they are in a fixed position.

So the questions are:

What carburetors does this bike have, I think I remember reading about Keihin CVK 34.
Has anybody done any jetting modification for altitude? I‘d like an adjustable needle and smaller main and pilot jets – any ideas as to sizes I should try?

What is an easy way to sync these carbs after I’ve monkeyed with them. Do I need any tools?

Nice site you have here – it’s great to find support for a good bike. Check out my trip at ADV rider http://www.advrider.com/forums/showthread.php?t=188978


Saludos,

[Dilbert]

Welcome to the site, it's always nice to hear from members in far flung locations.

I think the first question you need to ask yourself is "do I need to do anything" and only you can answer that, almost certainly the problem you have is with the mixture becoming too rich at altitude because the air is too thin.
If you intend riding a lot at high altitude then yes you may want to rejet for a smaller main jet, if it's just occaisional use then this would not suit your everyday use.
Generally most Hondas seem to run a little rich so a small change in jet size could be benificial at high altitude, but still allow good running in normal situations, sorry, but you're just gonna have to try it and let us know how it pans out.
Good Luck

[LazyRider]

Re-jetting a carburetor is not easily done on a trip. What would be easier, is to remove the air filter at altitude, this would weaken the mixture. It could be worth a try.

For many years we ran our bikes without any air filters at all.

[piguglyshandydrinker]

Carburetors

I have a 2004 XL650V and recently rode at very high altitude here in Chile, up to 4700m. I would barely run over about 3500m. The symptoms were lots of bogging, loading up with gas, black smoke, almost zero power. It ran a little better at very low throttle position under 3000 rpm. As soon I descended, all symptoms returned to normal. Later in the trip I checked the needle valves to see if they could be adjusted, - no go –they are in a fixed position.

So the questions are:

What carburetors does this bike have, I think I remember reading about Keihin CVK 34.
Has anybody done any jetting modification for altitude? I‘d like an adjustable needle and smaller main and pilot jets – any ideas as to sizes I should try?

What is an easy way to sync these carbs after I’ve monkeyed with them. Do I need any tools?

Nice site you have here – it’s great to find support for a good bike. Check out my trip at ADV rider http://www.advrider.com/forums/showthread.php?t=188978


Saludos,

Hi, Saludos and welcome.

Sorry to hear the bike is running poorly at altitude, have a look at the post on air intake, drilling the airbox may help a little, otherwise rejetting is the answer, I fitted smaller mains to help with fuel consumption, I have yet to have it dyno'd to check on fuelling, bike still runs fine at sea level, jets are #125's (stock are 132).
As for adjustable needles???maybe fitting carbs from an older 600 Alp as I think they have adjustable needles and are still 34mm.

Phil

[Dessert Storm]

Hi, and Welcome.

A friendly and helpful group of folk on here.

Great report over on Adv riders, if slightly embarrassing from a TA owners point of view!

I think a big part of the problem may have been identified in the ride report: the fact that the TA has CV carbs, that rely on vacuum to raise and lower the slide. At high altitude, the much smaller difference (when compared with low altitude) between engine vacuum and ambient air pressure may well cause the problems you have described. The measures that people have described above may well help, but IMO a change to 'normal' carbs would make the biggest difference, but I've not heard of anyone doing such a conversion and you'd likely still need to change jetting and/or needle position when riding at the edge of space!

Good luck: it would be great to hear how you get on.