Gents,
I restored my RZ350 last summer with about 900 miles on it so far and wanted to check the experts here on ideal jetting for 7,000 feet above sea level. It never really ran the way it should but looking at the plugs (BR8ES) it seem to run quite rich.
I did go down from 420 to 250 based on some advice from a local mechanic but it hasn't really helped much. I believe it has to do more with Pilot jet at this point.
Mods:
Spec II F1 Expansion Chambers
UNI POD Filters
Carburetor:
Mikuni VM26SS
Main Jet - #250
Pilot Jet - #20
Oil pump set per manual with Carbs synced & Cables adjusted.
Any advice is highly appreciated as I plan to daily it this summer.
Many Thanks!
Cool bike! It looks like it's itching to be ridden.
Hopefully someone's got the right info for you to get it running better.
Since nobody responded, I gave my google skills a try.
Going by the general rule of decreasing one jet size for every 2,000 feet of altitude increase my calculations are with BR9ES Spark plugs Main jet size of 210/220 with 15/17.5 Pilots. (Standard per manual is 230/20)
So over the next weekend I'm gonna take a stab by jetting down at 220/17.5 although this may be still a bit rich but rich is better as they say.
if you had a 420 main jet in it, thats indicative of a toomey jet kit. reason it was so big was the needle in this kit protruded into the main even at wot.
take a look at the carb internals and verify what you have there.. jet tube and needle, before going too far.
Quote from: m in sc on April 07, 2025, 07:23:19 AMif you had a 420 main jet in it, thats indicative of a toomey jet kit. reason it was so big was the needle in this kit protruded into the main even at wot.
take a look at the carb internals and verify what you have there.. jet tube and needle, before going too far.
I did check, it is stock 5CK needle with the black plastic washer on it. The jet tube too seems stock. Over the weekend I did go to 220 main and 17.5 pilot. It flooded the first time (ID-10T error) and after second attempt runs like never before. I see no glitches upto the redline and throttle is crisp.
I might run this setup this season and see how it goes but eventually would want to get on individual carbs perhaps TM34 which I have a pair of or TM28 which are flat slides and much easy to work on. Those stocks are a pain to deal.
Thanks for the advice.
maybe somebody in the past read 'my rz has 420s' and copied .. regardless, the bikes going to tell you what it wants, seems like you're on the right path though
Here's the instructions from a Dynojet kit that I bought for my RZ several years ago. 420 main is for aftermarket chambers and air filter.
yup. see the needle series?
Instructions from 1989 .... I think these remain relevant even today.
Anyways, I do have the Dynojet needles that I'll play around with and report back.
Some things I noticed about the Dynojet kit are the needles they give you are close to the dimensions of the stock ones but have the grooves for the clip to adjust them, the stock ones don't. I have mine set on full lean and it still has a rich spot show up at about 5000 rpm. Maybe that is like a stammer caused by the pipes and not the jetting?? Then I looked into getting new needle jet tubes and the stock one seems to be a one of a kind 357 0-8. It looks like a 28mm carb RD jet but is an odd length. I have the 420 mains in mine with Factory Pipes and a K&N Y-boot type of air filter (boy that filter is noisy, honks as loud as the exhaust pipes). It seems good at WOT but maybe I'll try the 340 main to see what happens. It is a real chore to remove and tear down the carbs on these bikes.
Yep the EPA carbs suck to work on. That's why I put VM30s on my White RZ. Not saying they is anything wrong with them but I don't have the patience to go through all that. If you like the stock carbs the non EPA 26s that everybody in the world who aren't us got they come up on Ebay regularly and they are much easier to deal with in my opinion.