Jetting Question--Stock Engine @ Sea Level

Vmaxattacks · May 5, 2011

Hi, folks,
I've read the numerous posts about individual owners' settings and the overall jetting questions in general but I want to get a general "consensus" about my setup. I have to split the rack,.....again... because I have peashot, shotgunned, and Sea Foamed myself to the brink of insanity to cure a bad low-end stumble which, have rendered useless results, so consequently I have to delve into this P.O.S. once again:bang head: So, whilst it is apart I want to pick some brains.

My, Cali '94 currently has 49-state carbs on it and it ran "okay" before but it always had too much lean throttle "tip-in" for my taste. I have stock, drilled cans (3/8" holes where the rivets used to reside) and everything else is bone-stock with the exception of a T-boost which, I rarely use, if at all. I am in southern California at about 1000' above sea level and I rarely see any other terrain other than here. I don't like the fact that I have backed out my mixture screws to damn near the limit to attain a half-decent idle (when it was running "half-decent") so I was thinking of swapping out the pilot jets since it is apart to get some more control on the mixture screws. I want to put in #40 or #42.5 PJ's and maybe go a bit leaner on the mains to #150's. My wet float levels are spot on 17MM.
It always was a non-smooth-transitioning engine from idle to +- 1/8 throttle....ALWAYS...and I have read that leaning out the mains can be beneficial for near sea level machines.
What do y'all think??

Thanx,
Bud

What do you folks think about thi

gamorg02 · May 5, 2011

i'm not great with carbs but i had to fiddle with mine enough (luckily with a sniffer), but what about a larger idle jet?

i think it was dave (vmax626) had a good response to bigger idle jets...

KJShover · May 5, 2011

When I was running trapps (not a whole bunch different than what your running) and everything else stock. I dropped my mains to 147.5, with a single .020 shim on the needle. I'm at 440' elev.

This chart and this testing method helped me dial the bike in.
http://www.factorypro.com/tech/carbtun.html

Also here is a great carb article:
http://users.telenet.be/pianne/technical/carb101/index.htm

Vmaxattacks · May 5, 2011

Nice! I was digging through my box of spare parts and I found a set of DJ160's which is equivalent (by Lvlheads's chart) to Mikuni 150's so this might be a good compromise. I see by your combo you left the PJ's alone and just shimmed the needle. How many twists on the mixture screws did you end up with?

Thanx,
Bud

Rhoy Carter · May 5, 2011

Make absolutely sure that your pilot jets are clear, if they are not clear you will never get it to run right.

Vmaxattacks · May 5, 2011

Rhoy Carter said:
Make absolutely sure that your pilot jets are clear, if they are not clear you will never get it to run right.

Yep!!

I found the culprit that as causing the bad running and it was the pilot jet:bang head::bang head:
I first quickly deduced that it was the #1 cylinder because I pulled off the vacuum nipple plug on each cylinder one at a time until the engine made no change in idle quality and I found the offending cylinder. I first checked the spark plug and it was good as was the spark. It seems that the Sea Foam dislodged a teeny tiny piece of varnish and it got stuck in the pilot jet! So much for that attempt. So now I get to put it back together again.

Once I make some jetting changes I'll be good to go.

Thanx,
Bud