I have zero experience with a Mikuni, except on my dirt bike back in the 80's, so bear with me. I am getting ready for the Colorado trip next weekend and I was wondering if I might need to take some jets. I don't have a clue what jets/needle combois installed, but I might do some investigative work this weekend....

 

I suppose it depends on what altitude your bike is tuned for (hopefully that's the altitude where you reside) and what altitude you'll be going to and also how long you'll be sustaining the higher altitudes.

If you only experience a 4000 vertical foot gain for a mountain pass I don't think you'll have a lot to worry about. Now if you experience that same altitude gain but you'll be doing a bunch of riding while at that altitude, you should probably rejet.

 

For the SW Mini Rally, I will be traveling from almost 600 ft up as high as Mt Evans, over 14,000'! We're doing all the paved mountain passes in Colorado over 10,000'. I'll only be gone 9 days, with 4 of them going to and from, but I am a little concerned. I went to Ruidoso last year on my FXRS with a CV and had no problems up to 11,000', but the Mikuni is a different animal...

 

Spending that much time up there, I'd think it would be good to rejet.

I don't have experience in altitude changing rides, but that change seems significant. How's that go? You're bike will run richer when you increase in altitude?

Is that an HSR carb?

 

You may or may not have to rejet the carb, just depends on the current setup like is it running on the rich side now?
It's easy to drop the main jet size on the Mikuni if you need too. Also minimize the use of the choke. And carry some extra plugs.
I made quiet a few trips to CO on a 1975 Honda 750SS and never had to rejet the flat side carbs (but I didn't use the choke either).

MikeyB

 

It's an HSR42. It will definitely get richer with altitude, but it also depends on temperature and humidity. I've already got extra plugs. I guess I'll figure out what's in there now and carry some along just to be on the safe side...

 

I've ridden my FLHT with Mik 42 all over CO, WY, MT....up and down passes, hot & cold, raining & snowing and then back to almost sea level hot and humid Texas and have never even thought about changing jets. I didset mine up leaner than what it was out of the box just because bike ran stronger and got better mileage, and that's at sea level. After that, never touched it. As I recall: 50 acc.pump jet, 98 needle with clip in center or maybe the notch above (can't recall), 165 main, 20 pilot. Do a search on HTT and you should be able to get more info, including adjusting the accelerator pump andaiming the nozzle.Point is, once it's set up right you don't have to mess with it.

Headed to up to that country myself Saturday morning...maybe see you on the road, or chugging up Mt. Evans with black smoke billowing from your exhaust LOL

 

Monty ~

I had an HSR42 on my 02RG & we road in Colorado many times. You'll be fine for the week. You will notice that it will be sluggish up near the peaks and fuel mileage will in in the crapper, but it's not worth jacking with just for the week.

I remember getting nervous, looking for a gas station @ 100 miles one time, in higher elevation.

 

Thanks, I needed that!

Phil, I know you told me that before. I am just trying to be prepared. I guess that comes from my boy scout days. I would rather have the stuff I might need and not use it than not have it and need it. I have fixed several of my buddies bikes that would have need a tow, if I hadn't had a small tool kit. They thought they didn't need anything cause they were just tooling around town. It's amazing the piddly little crap that will leave you stranded, if you don't have a screwdriver and a pair of pliers.