off idle - too rich or too lean?

[psycoreefer]

the latest theory...

Well I left the larger idle jets in and balanced the carbs this morning so I could ride it to work and see how things were working. The bike is now ridable but still sucks between idle and 2.5k. After that it's a rocket. Also the problem is noticably better once the bike is hot - indicates still to lean.

I tried pulling the choke but that doesn't really tell me much because the idle jumps to about 3k and thats above the problem area.

some history....
They guy I got the bike from and the guy he got it from had been riding with no 1st and 2nd gear. The first thing he said when I went to look at it was "It'll do 130 pretty easy".

Based on those two things I think the bike spent a lot of time at WFO and not much time at 1/8th take of.

Now when I was cleaning I noticed that the needles have a very slight yellow tint on the top 1/3rd closest to the slides. I'm thinking this is maybe a very thin layer of varnish?
Is it likely that that thin layer of varnish in combination with the new "tighter" emulsion tubes is preventing the flow of fuel at 1/8th throttle that would normally come from them and thus causing the need for larger idle jets to balance the mixture?
Anyone have a good solvent for quickly removing varnish? I've sprayed them liberally with carb cleaner and it doesn't take it off, neither did the sea-foam I ran through the tank. I suppose I could let them soak... but I'm impatient and I want to ride now!

[petejw]

i read in an early post u bought k&l jet needles,
that u hadnt tried because of the difference,
is it worth giving them a try and c how they go?
the straight part of the needle effects off idle as well
as the needle jet diameter and pilot jet,
your symptoms do sound lean tho,
wat have u set the jet needles at?
good luck and stick with it. :-)

[boyat68]

psycoreefer:

I assume that your carb cleaning and needle replacement means that you went into the diaphragm region. One thought comes to mind. If by chance the diaphragm was not replaced correctly in its rim edge and allowed to buckle up, then one or more carbs might be leaking air, which would affect the mid range of the bike.

Short of removing the pistons and polishing them, I don't think that varnish would come off with carb cleaner.

[psycoreefer]

petejw: Yeah I've got K&L needles but they are different, I did try them and went back to the stock needles, but that was before the new emulsion tubes. If I can't get the "yellow" off my stock needles or I haven't figured this problem out by the end of the week I'll give them a try and see what happens. I'm just afraid that the lean miss at higher RPM will come back, I got rid of it by going back to the stock needles so I have to conclude that the K&L needles are leaner then stock.

The needles are set on the "center"/#3/stock clip position. I hadn't considered raising them because up until now I've been focused on this being an idle circuit problem when I suppose it could be in the overlap between idle and needle jets.

Boyat - Yes I was into the "tops" of the carbs but if the diaphragm was not seated wouldn't I be able to tell by how fast the slides drop when I lift them and cover the hole in the front of the carbs? All four drop very very slowly and evenly so I think I'm good. I'll double check next time I have the carbs off anyways because I'll have to remove the tops to get the needles out to clean them.

[psycoreefer]

main's

Well I rode the bike to work again today and on the way there is a big hill, great for WOT plug chops so I gave it a try. Plugs were all white as new.

So when I got home I pulled the carbs again and took a needle out. I couldn't measure the difference between the "yellowed" part of the needle and the section immediately below it using my dial calipers so I'm not going to waste any time polishing them. I put the 140 mains back in it. I had tried them before I got the new emulsion tubes and they seemed to big - I had more power with the 137.5's so I went back.

This seems to have further improved the problem to the point where it runs very good when warm but still hesitates and lacks power when cold so still a bit lean. I didn't think the main jet size had much effect below 3k but my experience here seems to indicate different. I plan to do another plug chop tomorrow and see what that indicates.

I'm also going to try going back down to the stock 43.5 idle jets and see if the main jet was possible the cause of the problem the whole time. If the problem comes back with the smaller idle jets then I'm going to try shimming the needle up 1/2 of a clip position. I figure if it needs more gas at WOT it probably needs more gas at part throttle as well.

I probably won't get to all that this week but next week is my B-day so I should have a bit of "me" time to tinker with the bike.

[petejw]

hey psycoreefer,
i found that out 2 b the case also,
i was running rich with the mains,
once i lowered that my problems of off idle have all but gone,
hoping the new idle jets will solve it completely.
good luck with it.

[oseaghdha]

Throttle shaft seals?
Maybe the carbs were dunked in cleaner.