Stuttering - Horizons Unlimited

**cornepol** · #1 28 Apr 2003

Hi there,

A few days ago I went with my AT into the mountains of Lesotho. The higher I got, the more my AT started to stutter. It felt like sometimes some of the sparkplugs didn't spark at all. I took out the sparkplugs, which were all black with char.

I suspect the engine is not getting enough oxygin at higher altitudes, because my bike is used to Dutch altitudes (=sealevel)therefor burning too much purely petrol.

Could this be the cause? What can I do to fix it? I really need a permanemt solutiona as I plan to travel through Etheopia later on this year...

Cheers,
corne

**edseven** · #2 5 May 2003

I think your theory is correct. As far as I remember, the best solution is to retard the timing...which I do not think is possible on modern Hondas.
The problem may be worsened if you use bad quality fuel and the bike needs a service ( dirty air filter, old plugs etc ) Maybe an octane booster helps,too?
Like you, I am guessing a bit. If you don't get a good answer here, then try www.hoc.org.uk and go to the 'answers to correspondents 'page. You should get top information and help here.
Hope it works out.

**wbagwell** · #3 6 May 2003

Yes, this is a well-known phenomenon. As you gain in altitude, the bike gets less oxygen and starts to run richer. Likewise, if you bike is jetted to run well at high altitude, it will run much leaner at sea level.

The proper way to solve this is to simply swap out jets and needle position to settings approriate for your altitude.

BE SURE to put sea-level jetting back in your bike as you go down to lower altitudes. When an engine runs lean, it can get very hot and damage the engine.

Wright