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Cutting out on hills at speed

2K views 11 replies 6 participants last post by  SportsterDoc 
#1 ·
Hi everybody, wondering if i can get some advice. This may have been discussed before so forgive my repeat if so.

I recently did some of the new California BDR route with my dad, mostly the areas in Mojave’s and Death Valley. Spent about a week exploring just those sections and around the region. Great riding, but the TW had a small issue I wonder if y’all could help with.

I road my crf250l and my dad rode the tw. It was basically great the whole time, except when climbing some of the larger hills in Death Valley, on pavement, at speed. It would start cutting out once the climbs got more intense and when power was most needed.

These rides took us to a variety of elevations so maybe it had to do with that? I live in San Diego and it seems to work great there. I was surprised it would be this because, while there is climbing, we were starting at basically zero (actually negative elevation).

What does the bike act like when it is being effected by changed elevation? What is the solution when riding from super low to high? Might it be something else?

The filter seemed clean and we cleaned it to make sure.

Any help would be much appreciated as I want to do another trip like this.

Thanks



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#4 ·
A 130 will be too rich above around 3,000 feet. Death Valley has some of the most brutally long steep pavement climbs anywhere, I've been there many times. Your symptoms reflect that. I use the stock 126 in my TW when I go there and it's good to around 5,000, the altitude of Towne or Daylight Pass.

If you are experiencing bad cutting out you can remove the air filter temporarily......obviously not in the dirt! Any given main jet size will have a range of about 5,000 feet, showing symptoms of too rich or too lean at the end of that range. Too lean is MUCH more dangerous than too rich...if I forgot to change back to a 126 from my usual 122 at 6,000 I would burn up the engine on either one of those passes!

Change out the JIS float bowl screws for Allen head bolts to make changing jets easier and do it before you go back to DV. Try a 126 next time. That will be a bit lean at sea level, but not enough to hurt the engine.
 
#10 · (Edited)
...Death Valley has some of the most brutally long steep pavement climbs anywhere...
Yes, but well worth it! Unusual to see a 15% grade sign.
Road Dirt road Motorcycle Vehicle Trail

Mountainous landforms Highland Sky Mountain Caldera


In addition to the good advice already given, good to check that fuel cap is venting.
 
#6 ·
If you check your carb there should be a small plastic cup type of shroud at the bottom of the main jet nozzle. I call this a splash guard which is supposedly there to keep air bubbles from entering the jet. One TW I had did not have the plastic cup when I opened the float bowl and it did cut out pretty bad when going up steep hills and in the bumpy trails. Once I put that plastic piece where it belonged the cutting out stopped. That TW ran fine out on back roads and never had any cutting out until I got off road or up steep inclines. Just a thought and something to check because it is possible the PO of your bike might have left that part out or even slipped it over the jet up side down.

GaryL
 
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#8 ·
#7 ·
Definitely sounds elevation related. On our Big Bear group ride many of the riders experienced it and a veteran TW rider said "yeah that's normal".

My bike did it with stock jetting and didnt get any worse with a 130. Since the 130 is a noticeable improvement at home I figure I'll just deal with it. I don't have time to switch jets every trip.
 
#9 ·
The bike should still run OK at high elevation, there will just be a noticeable loss of power, but not really sputtering or cutting out. I just had my Valkyrie on a trip from sea level (jetted ideal), all the way up to 11,000ft. It was clearly too rich high up and was well down on power, but ultimately it still started and ran smoothly, just not as much oomph when you hit the throttle and a decrease in fuel mileage. "too rich" generally has a very "soft" or "mushy" feeling throttle. In very extreme cases you can get spits and sputtering, in which case the exhaust will reek of fuel/ brownish smoke and often even start blowing liquid fuel out the exhaust. "too lean" will be boggy, getting that "woooooooooooooh" sucking noise from the intake and a lack of power. Extreme lean the engine just flames out resulting in a sudden, abrupt loss of power.

Cutting out/sputtering particularly at times of high fuel demand (high RPM, high throttle) is often a symptom of fuel starvation. The engine is using fuel faster than it can flow into the carb. This can be caused by kinked/pinched lines, a plugged strainer, or in-line fuel filter that's clogged or of insufficient size. It might keep up at normal riding but sustained high demand periods the bowl will slowly drain, eventually getting the main jet dry and of course then the engine will immediately start to cut out and sputter.

That little plastic shroud is mostly there for rough terrain so fuel doesn't slosh away from the jet as the bike bounces around. It's common on dirt bikes/dual sports but street motorcycles virtually never have them (just not needed)
 
#11 ·
Thanks for this. Very interesting. I’ll check these things. These were full cutouts, not loss of power. Clearly gulping for fuel and not getting it in spurts.

I have a California bike, which has the canister up front that somehow limits emissions. Has a charm and tank inlet/outlet. Was wondering if this might have something to do with the issue. Maybe clogged. The cap doesn’t have a vent hose but a locking lid.


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