maybe a cafe build.....

[bcware]

I don't see anything obvious in the photos, but do you have any performance upgrades? Any popping or backfiring? Such a sign can be really ambiguous in and of itself; rpms can hang when you're rich or lean. It has been much warmer out recently and gas vaporizes easier at higher temperatures. So, you could be dirty and running lean, or simply running rich in the pilot circuit now that it's warmer out; it is hard to say. Pull the plugs and take a look at them. Check for leaks too (blind plugs, carb boots, air intake).

Since I have been messing with tuning a lot on my bike I am actually going to suspect that you are running too lean for some reason. Upon dropping down a pilot jet size I started having this exact same problem; idle not wanting to drop below 3 grand. I was able to idle fine with the larger pilot.

 

[cafedan]

thanks for the reply bcware, the weather hasnt changed much here in texas and has been running fine until this morning. im afraid my tank is to blame. im not much on ragging on po's but this time i feel justified he lined the tank over the top of rust. so every hundred miles ive been changing my inline fuel filter instead of getting a new tank. im thinking junk got past the filter and is now clogging up my carbs. ill take your advice and check leaks tonight after bike night. sure wish i was riding there haha

 

[bcware]

That would do it too; In fact, I am not sure I can completely rule that out as the source of my high rpm. Right after I changed the jets I added more fuel than I had ever done before and noticed my in-line filter was yellow. Previously I had only put very little fuel in the tank. The high fuel level probably freed a bunch of junk up. Even if large particles were blocked by the filter a high rust content would definitely do some funny things to your A/F mixture.

 

[cafedan]

well i went and looked at the plugs this morning and they are both blacker than normal. i usually run a tan color. ive been running a clean gas through it without the tank. im going to check for air leaks in a little bit.

 

[cafedan]

well i sprayed starting fluid and wd-40 at the boots with no change. i did however readjust the air/mixture screw and that helped for about a minute but then started getting the rising idle again. oh the joys...

this is a carb issue, right?

 

[Requiem]

im curious! mine suddenly starts reving up to 4-5k rpm and has a slowly rising idle :/
Happened after swapping the tank, filters, and jets

 

[HoughMade]

A "hanging idle", that is when you rev the engine and it won't come down or does so very slowly is a classic sign of a lean condition. if it was running fine before and this developed suddenly with no adjustments beforehand, sounds like dirty carb passages to me, particularly in the idle circuit....which are the most like passages to get dirty anyway.

 

[cafedan]

well im tearing into her then. i have a seat coming anyway. i wanted something to ride this summer. but just to much of a headache with my dirty tank. perfect time to do my 2-1 carb conversion.

 

[hardtailed77]

Speaking of the 2-1 conversion, have you received the carb yet?

 

[cafedan]

Speaking of the 2-1 conversion, have you received the carb yet?

not yet hardtail, i honestly haven't checked the mail since saturday though. ill check it tonight. looks like it will be here in perfect time!

 

[hardtailed77]

Ok, let me know when it gets there, and if you need anything else. Good luck with the bike!

 

[frwinks]

well im tearing into her then.

That's the spirit
Mine had the "hanging idle once warm" issue before I tore into 'er

 

[Requiem]

my bike would be idling happily around 1200 rpm, and then slowly but surely start climbing, once above 2000rpm it'd quickly rev up to around 5000... it did that while running very rich, but the jet seems about right atm, doesn't do so as often anymore...
would it be due to dirty carbs, or still being too rich/lean?

 

[cafedan]

sounds like it could be either. if i was in your shoes, id clean the carbs. if that doesnt do it, youll know its the jets. either way your carbs will be clean.

 

[cafedan]

WOW lesson learned. so my tank has been lined on top of rust. i thought well for the summer ill deal with changing my inline filter alot. all the filter did was let the small particles through ive been riding it like this for 200 miles now, you guys thing i did any damage to the motor? my tank is going to a radiator shop this morning.

 

[ahale2772]

bleckkkk..... thats not so purdy, I hope yar pistoni rings didnt take a hit...

only way to tell is to check for the old blue exhaust when you get her running again, i'd bet there is noting wrong if its only been around 200miles

 

[bcware]

I bet that stuff will burn off in the engine, but you certainly don't want to breath it in (as if normal exhaust fumes are fine, haha). What's funny is that I bet mine are going to look similar when I get around to taking them off again... stupid rust!

Oh, right; Since I am studying my butt off for the MCAT this Friday I should be able to explain exactly why rusty gas causes a lean condition. Rust is a non-volatile solute and simply takes up space. The rust effectively "blocks" or gets in the way of fuel molecules that would otherwise vaporize thereby lowering the vapor pressure. Some rust is, of course, going to vaporize and it will foul the plugs and weaken the spark.

New plugs and maybe some sea foam (I knew there was a reason to buy it) should help clean things out.

 

[cafedan]

thanks for the replys! i took my tank off this morning and found a radiator shop to clean it. they also line the tank then pressurize it to check for leaks after they are done. not bad really for $80 U.S. wish i would have done that in the first place. looks like the tank is going to need repainting too as the process is wicked on paint.

@hardtail-got the carb set up, looks bitchen! thanks dude!
@bcware- good luck on your test brother!

 

[hardtailed77]

No problem man, like I said, I tried to clean it up the best I could, and I hit it with a little Mother's as well. Let me know if you need anything else.

Also, when you get around to building your manifold, do document the process with pictures please. I'm sure there are many people who would benefit from a write-up of that. Good luck man!

 

[new kid on the brat]

i just spent the evening cleaning the carbs on my 83 shadow and they looked a lot like that!!!! the crap that is on the intake side of your carbs is not coming from your fuel tank!!!! that is either dirt from an incorrectly installed filter and or filter boot!! or in my case a horribly rotten air filter that was crumbling and had plugged my air jet's!!!