Yamaha Rhino runs bad at altitude.

[DaveB]

I have a 2008 450 Rhino that I got from my in-laws. It was parked for several years down at their cabin in Boulder after my FIL passed. The rodents turned it into a hotel and plugged things up and chewed up wiring. I got it all fixed up and it runs good at lower elevations but misses badly at elevations above 7000 feet. I probably need to re-jet it but have also read that people increase the air flow to compensate. I have seen people cut holes in the air box to get more air. I have measured the diameter of the carb intake vs the air box intake. The air box intake is bigger than the carb intake so I don't see how drilling holes in the air box would help. The stock air filter is foam and gets dirty quickly. I could see how a higher flow air cleaner could help but I don't want dust getting past the filter. I'm sure some of you have re-jetted your carbs and wondered how much smaller have you gone with the jets ?

 

[gary78bronco]

Make sure the choke cable is functioning correctly. I had a Rhino that would run horrible at altitude, it was the choke cable. I can't remember what the cable was doing that was making it run crappy. A new one fixed it.

 

[DaveB]

The choke cable seems to be working correctly but I'll measure it to make sure it is closing off correctly.

 

[Gravy]

Throw the carb in the ultrasonic cleaner again before you do anything.

 

[DaveB]

Wish I had an ultrasonic cleaner, just used carb cleaner

 

[anderson750]

Take it apart and soak it all in ammonia.

 

[85CUCVKRAWLER]

This is going to be a jetting issue.

But it doesnt hurt to clean the filter and re-oil correctly. Then open the carb up and clean everything real good. More than likely there is gummy old ethanol in there and it all needs to come out. Opening the air box up doesnt open the carb up.

My KTM when winter jetted for 2000-4000 feet, if i take it up to 7000 it gets really angry, looses power, over heats and misses. Same with my DRZ400 which i keep jetted for 4000 feet all the time cant go much more past 7000 before it begins to overheat,

 

[DaveB]

I have re-jetted the carb, cleaned and oiled the filter, now i just need to go test it at altitude. I bought a range of jets so I should be able to dial it in.

 

[DaveB]

I took it up to Soapstone and ran a few trails ranging from 7600-9800 feet. The only time it would sputter a bit was above 9500 feet with full throttle and just shy of hitting the rev limit. Still have one more leaner jet but it worked so much better that I think I'll see what the elevation is for our next trip before doing anything.

 

[Rot Box]

Glad to hear you’re getting it sorted. That’s a big elevation swing—and 9500
is up there for a carburetor. I think you’re on the right track 😎

Tell me about soapstone? Was it a good time? I need to expand my horizons beyond southern Idaho haha.

 

[DaveB]

It is a fun area to ride, nothing too challenging but scenic.