Venture 500 cannot hold rpm at a slightly higher altitude?

norwegian

norwegian

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My problem is that the venture 500 cannot hold the same rpm on top of a hill that is only 200-300 meters above the river, where it absolutely rips. Is it that sensitive to elevation changes? If not, what's wrong with it?
The temp is about 0 C.
 
There are figures that say approx. 3-4% power loss for each 1000 ft. above sea level, don't know how accurate they are though. Could it be altitude AND temp? My Vmax is jetted for 0* C and colder from factory and I can tell you that already at +3 it's noticeable weaker and at +7-8 it starts to backfire due to running rich.
 
Really? Well yes, it has stock jetting I guess and it is very mild here now. How did your sled come jetted to 0c? I can't see that in the jetting charts. They go like +4c then -7c and then -18c
 
The drop is significant, from 7750 at the river, to only 7000 on the hill.
 
norwegian said:
Really? Well yes, it has stock jetting I guess and it is very mild here now. How did your sled come jetted to 0c? I can't see that in the jetting charts. They go like +4c then -7c and then -18c
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I seem to recall the owners manual mentioned it, it might be that 0 C is some kind of reference value but I'm not really sure. It's never been re-jetted though so what's there is what it was from factory. The season here is almost over, another week or two at most. But I'm in the middle of northern Sweden. In the mountains it's rideble far into may but I guess I don't need to tell you that.
 
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Yeah, I'm in northern norway, still rideable for 3 weeks I think, 5-6 weeks in the mountains.
 
I have no idea. I checked the jets, they are just 147,5. Seems to be no water in the gas either. Too heavy of a clutching?
Checked the reeds, they have 11000 km on them, seemed like new. Any ideas?
 
If they are black, your to rich. You should go down 1 size main jets or you could try lowering your needle 1 slot.
 
I have to check, they shouldn't be too rich, the jetting is too lean according to the book
 
norwegian said:
I have to check, they shouldn't be too rich, the jetting is too lean according to the book
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What ever the book says may not apply to your situation.
If your sled runs good at one elevation and runs bad at a higher elevation, most likely you are too rich. As you know the air is a bit thinner (less density) So you will have less oxygen molecules vs fuel molecules at your current jetting.
 
Yes, the combination of warmer temps and increased elevation are making the sled run richer. Always check the plugs, black=rich, brown=good, white=lean.
 
I see your point, but the difference between running like a champ and losing 1000 rpm is only 600 ft. So what's up with that?
 
That does seem odd, but if your on the edge of flooding and then go up 600 ft, it could make the difference. If the plugs are black, I would just drop the needle 1 slot and try it. Doesn't cost anything and then you know.
 
At colder temps I tried again at the higher altitude. Now it was able to pull, I got 68 mph before I had to let off, compared to 56 on the warm day. Even with 147,5 mains it was just a little lean, but sure, if I had held it for longer, the plugs would have been white. I have to lighten the HC weighs a little, so it will be able to pull the rpm on warmer days also.
 
If your riding in a wide range of temps and altitudes, a Holtzman ATACC would be a good investment.
 
I already have the tempaflow, I just need an optional air filter for it and the re-install kit.
 
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