Hola!… I’m riding an 87’ XL 600V TransAlp in good condition, compression (same as new) , carburettors original (32mm Mikuni’s, I believe), I’m running an original Honda paper filter and Laser ProDuro exhaust. These only things I can think of that might effect answers to this post.

I live in South America at 3.400 meters where the bike runs fairly well. There is a noticeable difference in power at sea level, although this is limited to horsepower and nothing more. At around 4.000 meters the bike starts to run quite rich and poorly above 4.000 RPM. This degrades rapidly as you gain any altitude, to a point where it’s really very difficult, especially loaded and/or climbing.

Over the next four months I will be riding almost exclusively between 4.000 and 5.300 meters in southern Peru, northern Chile and Bolivia. Because I do not want to deal with this issue full time, I want to do everything I can improve the high altitude performance. I’ll start by ditching the filter for a larger dual layer foam filter, dropping the snorkel, drilling the box and checking for any air leaks in the intake. Aside from this and unless I see a noticeable performance improvement, I want to go ahead and re-jet / re-sync the carburettors.

This is where the questions start coming in… I’m familiar with the jetting process. However I’m not familiar with the dual Mikuni’s (with the exception of this article, Mikuni Motorcycle Carburetor Theory 101)

I’m wondering if anyone else has had experience with these carburettors and knows more about the availability of the jets. For instance, how likely is it that these jets are interchangeable, with any other carburettors, etc. I’m in Bolivia at the moment and trying to order these internationally and have them shipped will be very difficult. I’m hoping I will find an alternative to this locally, particularly as I can reach La Paz / El Alto (which is between 3.600 and 4.000 meters) and Santa Cruse, the largest city for 2.000 kms.

I need to get this pretty much right the first time, particularly if it involves shipping or bussing the jets from anywhere else. From what I can gather so far (I’ll list some sources below), I’m probably looking at 100 mains and 35 pilots.

Anything else to consider? Any other thoughts? Any information anyone can provide would be greatly appreciated! Thank you in advance! JC


Altitude Sick Transalp

Transalp Carb Jetting for Altitude