iirc I have a 93' engine in 91 frame. I have a factory pro jet kit. K&n airfilter, timing advance, and some slip on exhaust. Soon to have full header/muffler from Kerker.

I live in N. central fla so about 100' above sea level and usually humid. These pics are from cyl #1 on left to #4 on right. Obviously the #3 is running a tad richer than the rest. These were pulled after warm up and revving from idle but no riding.

Any help will be appreciated. I have mano-metered the carbs and believe they are close.





Thanks,
Adam

 

How does she ride? I would figure out why that 3rd cylinder is richer. Could be some oil leaking in from the valves which isn't a big deal. Check your carbs to make sure the jetting is all equal, sync as well, and if its still darker its probably oil and I wouldn't worry too much unless you are ****.

 

thanks for your reply.

Seems too take longer to clear out during and after being choked to start in the mornings. It will take several quick revs to make it clear up. If i'm in traffic for a while, like 30mins+ it seems to load up. once it's clear it seems to run like a bat outta hell. Every once in a while there are some small flat spots but for the most part it's ok.

The bike NEVER smokes, no black, no blue, no white.... nothing. There was evidence of oil on the threads of the #3 plug but not on the porcelain or wire boot.

I was out burning some streets and it will keep up with new cbr's and gixxer's.


Just seems like it could use that one little tuning detail to really run well.

I think the longest it's sat was 3 weeks without being run. I went through the carbs when i put the bike together 6 months ago

 

I would pop off the carbs (or use the carb wrench if you have it) and bury your idle screws (clock wise). Count the turns out that they were. See if #3 was turned out further. I prefer to do this with carbs off the bike because it just feels more precise than digging around in the tight quarters of your bike.

If #3 was turned out more, turn them all back out to where they were, matching #3 to the others. Turning them all IN, clockwise, 1/4th of a turn from where they originally were might clean up that slow start.

If #3 was equal, I would check your mains and needles to be sure they are all matching.

You mentioned flat spots sometimes. At what RPM and can you pin point whether it is with a very hot engine, cold, or normal?

 

I know all the jets are the same because I installed them. IIRC there are 2 shims and my needles are 3rd notch down. I think the idles are set at 3 turns out. I have the D tool that came with factory pro kit so I will double check and report back tomorrow.

The spot that gives me problems is cruising around 7.5k. Warmed up engine. Runs better when it's colder out so i'm guessing it's on the rich side anyhow.

The other night it was cold out 45deg and we were rolling 80-90 down the interstate when it started to feel like it was running out of fuel. I could let off and baby it a little and it would take off again.

The other day I was driving through a big neighbor hood looking at a house to do an estimate on and it started to feel like it was really loading up. bogged down a bit and then finally it cleaned and ran well for a couple mins then did it again. After it cleaned up the second time it seemed to run better the rest of the day!

I'm gonna get her warmed up tomorrow and do some full throttle pulls then cut it off and hopefully coast back to the house to pull the plugs to see what they look like at WOT so I can report back more info.

 

Sounds like you got the jist of how to tune. The easiest thing is to do WOT with a cold engine, then let her sit and heat up, and go WOT again. See which feels better, and where your hiccups are at in the RPM range. I've done the WOT pulls and engine cut and didn't notice much from my plugs. Maybe a pro could, but I couldn't.

Honestly, K&N = loss of power, stock filter is better. I had to use the smallest size main in my jet kit with my K&N (which I only run cuz I am a cheap *** and got sick of re buying the stock filters). I think it was factory pro kit. It runs a little lean and pops on decel but there is absolutely no flat spots and she pulls hard. Plugs are all a nice clean tan too so there is no sign of overheating even after a full hard track day. The power loss won't be noticeable. 1-2 HP is never noticeable except on consistent lap times with a professional rider.

A flat spot at 7.5k sucks because you don't know if it is mains or needles. Experiment a little, but you can't believe the jet kits directions. They are BS. My jetting is perfect now and it wasn't even close to the instructions. Main was off by 1, needles were off by 2 and my idle screws were off a full turn when i followed the instructions lol.

 

ok, well, first of all, HAPPY NEW year! Second, i've been busy.

I cleaned the plugs before I put them back in the bike and added some seafoam to the gas tank. Took it out for a couple hot laps around my hood..... Ran great cold and I couldn't tell a difference in performance once i was well into operating temp.

I still think that my mains might be a tad too large because of how the plugs looked when I first pulled them.

I have a full exhaust in the mail so we'll see if that might balance it out a bit. I still don't know why or if #3 is still running rich.

 

Most likely the full exhaust will throw everything out of whack. It might set your mains right, but you will most likely need more adjusting on the other circuits.

 

Thanks for the continued replies. Ever since I cleaned the plugs and put in some seafoam this thing has been running great! The new used exhaust will be here tomorrow.
When I got the bike it had a bent up and rashed yoshi pipe. I bought a parts bike with a decent looking muffler so I swapped them.... can anyone tell me what kind it is?

 

Got the new used exhaust on and WOW way better

Here's what I'm still chasing. #3 runs about 30 degrees colder measured with infrared thermometer shot on ex. manifolds. When first started #3 is cold to the touch for a good 30 seconds or so. When it does build heat it's 30 degrees colder than the rest.

What i've done:

Thought the idle circuit was clogged on #3 so I pulled the carbs, cleaned all idles, mains, bowls, etc. Didn't really help

Thought #3 might be way out of sync. So i re synced all carbs which were slightly out, smoothed out idle but didn't change temps much.

Reset idle screws to 2.5 turns out vs the 4 i found them at.

Resynced carbs.

So now: Even though #3 is colder, the bike runs the best it ever has. Smooth over entire RPM range, smoother idle, and bike feels much more responsive and faster overall!

This colder cylinder just has me stumped and I obsess over stuff that isn't right and i can't figure out!