Move to lower elevation

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greimers

greimers

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Jan 19, 2015
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I moved from Calgary AB (1000m) to Winnipeg MB area (200m) and my bike is running really poorly - puffing and popping. Plugs are light and it runs better on 1/2 choke. Seems to be ok from 3/4 to WOT

I wasn't expecting the elevation change to make that much of a difference (what do people do on long trips?)

Anyway, I'm looking for suggestions from people at similar elevations. Should I be looking for jets, needles, both?
 
First thing to consider......are you running aftermarket exhaust? Are you still running stock jetting, or have you gone to stage 1/stage jet kits? Sill running the stock airbox?
 
Everything is stock as far as I know. I haven't had the carbs apart but the air box is definitely stock.
 
Then there isnt be that much of a difference. Yamaha did a very good job of setting the bikes up from the factory to go pretty much everywhere.

The choke, is actually an enrichener. I wonder if you have an idle circuit plugged?

Read this.

http://vmax.lvlhead.com/tips/shotgun.htm
 
3/4 -WOT is the main jet. If that part of the throttle feels OK then you shouldn't have to adjust the main.

Being in Canada, I assume you have a Canadian vmax which has adjustable needles. If you know your carbs are clean and this issue came about directly after moving elevation my first reaction would be to lower the clip on the needles 1 position. Lower the clip will raise the needle and allow more fuel flow.

Start with 1 change at a time and track your changes.
 
I just started doing exactly this as I was cleaning them and discovered the needles were adjustable. The clips were in the middle and I moved them 2 notches. I might back them down one
 
I also discovered one of the idle air screws was bottomed out so I've turned that out about 1.5 turns. I have a carb sync tool so I will probably do that as well once I'm done this bit.
 
greimers said:
I also discovered one of the idle air screws was bottomed out so I've turned that out about 1.5 turns. I have a carb sync tool so I will probably do that as well once I'm done this bit.
Click to expand...

The A/F screws cover 0-4000 rpm, and 0-1/8th...maybe 1/4 of a throttle.

A good place to start on the A/F screws number of turns out is 2.5. Most people start there and adjust.
 
Tuners going around the country on a circuit would know the difference between sea level and 6500 ft. Not the same. Air density and altitude make all the difference. Especially if there is 1000 ft difference.
 
I have it back together after doing the shotgun clean procedure and lifting the needles one notch. It's idling a lot better and revs up to 4500-5000 ok, but hesitates after that point.

I still have the airbox off. I know with some engines that makes a difference with air flow. Prior to this it ran terribly without the airbox.

What's the recommendation at this point?
 
You need to put the airbox on and make sure the vent hoses are properly routed for it to run correctly. Do a test run and report back.

Sent from my SM-G930V using Tapatalk
 
[email protected] said:
You need to put the airbox on and make sure the vent hoses are properly routed for it to run correctly. Do a test run and report back.

Sent from my SM-G930V using Tapatalk
Click to expand...

+1. The stock carbs are not set up to run without the airbox being on.
 
Does anyone have a trick for getting​ the vent hose back on the air box?

Sent from my A0001 using Tapatalk
 
Ok got that. Now to get the air box down on the carbs

Sent from my A0001 using Tapatalk
 
Just loosen up the clamps, you can also spray WD-40 around the bottoms of the boots.
 
Got her all back together and she's running much better. It idles much better and acceleration is smooth.

I still feel really minor hesitations when holding it steady between 4000-5000 rpm though. I still need to put in the new plugs.
 
greimers said:
Got her all back together and she's running much better. It idles much better and acceleration is smooth.

I still feel really minor hesitations when holding it steady between 4000-5000 rpm though. I still need to put in the new plugs.
Click to expand...

Be sure those vent hoses from the carbs are routed correctly.
 
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