fuel starved or jets?

Hey all,

I am still having no luck richening my mixture on my 85 xj700 even after adjusting the pilot mixtures almost all the way out! I have been talking with Rick Massey and we have resolved to try larger pilot fuel jets next. Is it possible that a faulty petcock would cause a fuel starvation problem severe enough to cause such a problem? It appears to flow fine on prime and I can see fuel running through the inline filter when running. Idles well at 1000 RPM with the occasional stutter. Can an old air filter cause a lean condition?

 

Wow! I have this problem also.

 

i wouldn't see why for the life of me, an old air filter would cause a lean condition a rich condition yes not enough air more fuel yeah but cause less fuel no but i really could be wrong...does it lean out further at higher rpms?does it run better on prime or same either way (prime-on) how does the vac line to the petcock look (cracked, brittle, Collapsing), is the bike Bone Stock?

 

I agree about the filter, should run rich if dirty, but what if disintegrated? I'm going to try changing the vac line to a more ridged hose just in case it is collapsing. It seems its most lean below 6 or 7000 rpm where I can get some color upon chopping. Otherwise, they retain some tan (I assume left over from the high RPMs ) but are generally clean.

RickLees, I'm curious, are you still running the bike or are you worried about overheating. How clean are your plugs?

Thanks guys.

 

lol i'm running 4 to 1 supertrap with pods and on stock jets.......i'm lean on 2 and 3 but 1 and 4 are perfect............tan.............figure that one out :lol:

 

I wish I could.

 

mfchapman, I have only had the bike running to sync and tune it except to take it for inspection and tags, other than that have only had it running short periods of time but my exhaust at the head is turned colors.

Temp at exhaust is even but I can't get it to richen with the air mixture screws.
keep in mind I just went completely through them. Ultrasonic cleaned and cleaned more, new stock jets, float needle and seat, o-ring washer and spring for air mixture screw. throttle seals, fuel o-rings clean as a whistle and polished slide and slide bore.
Replaced vac line and fuel line to tank. boots on both sides of carb are old but look good.

I like to never got it to idle down so I could sync and tune it, not really sure what I did but it finally idled down, synced it, tried to adjust fuel mixture to fine tune it, I have colortune plug. color is blue on the whitish side can not get mixture to turn to the orange side with screw. SO why are my plugs, all of them. dark brown on the porclen and blackish on the metal but not wet nor heavy or built up. Sprayed WD40 around all joints trying to detect airleak no increase in idle speed from that.
At this point my exhaust pipes have turned blue to black 4 or so inches down the pipes indicating too hot= lean condition. exhaust is 4 to 1 don't know brand air filter is K&N in factory airbox But once upon a time this bike ran sweet on this setup. So I've stepped away from it for a few days taking a break.

Had it purring smooth onstand before riding now it ildes 900 -1100 different every time I start it and doesn't run smooth I can hear it but not sure how to discribe, just off smooth. I'm missing something just not sure what it is at this point. My first time working on motorcycles

Valves are in spec.
compression: 140, 135, 128, 138 respectively

 

If your 4-1 exhaust is only single-walled, don't assume the pipes turning color indicates an overhot or lean condition. My Norton is in perfect tune, a leetle on the rich side (on purpose) and the (single walled) pipes are blue for the first four inches or so, and always have been. Stock Yamaha pipes are double-walled, you never get to see WHAT color the actual inner pipes are.

 

Ok bigfitz52, noted

However these pipes have been on bike some 24 years and never turned this color until I decided to work on it, lol