Looking for carb opinions on a 550...

Hey guys,

First off, my valves are all in spec, and the carbs were church cleaned and rebuilt this winter with fresh seals, gaskets, and everything.

I put about 1400 uneventful kms on the bike already this year. My carbtune arrived last week, so I did a sync, colortune, and resync. Holy cripes the difference, that engine is ridiculously smooth now! But the problem I'm having now is that her warm idle is all kinds of erratic. It will default to 4000rpm, though I can slow it with the clutch/brake trick, and she'll hold a 1200rpm idle for about 5 secs, and then die. I took an unlit propane torch to everywhere when she was at 4k, the idle didn't change at all.

I rechecked the bowls, they are all spotless, and the enrichment plungers close fully, fuel levels are all correct. Slides all clunk, and the needles move around like they should. I thought maybe a butterfly was sticking, and I didn't notice any light getting by them at first, but when I got my 20LED worklight, I could see some light coming around the edges of the butterflies (yes, the sync screws were backed off). I adjusted #2, 3, and 4 just fine, but #1 still left about a hair width of light around the upper edge only. It wouldn't adjust so I pulled the butterfly out and noticed a bit of a burr on one edge.

I didn't notice it before, I almost didnt notice it this time but it luckily snagged on my work glove. I took a fine file to it, and readjusted, but there is still the tiniest sliver of light coming through for about 25°, just above the shaft. What kind of tolerances are on the butterflies?

Any other ideas? I heard that our bikes don't work with some inline fuel filters, I'm using a new filter of the same type I've always used with no issues. If this doesn't fix it, that will probably be my next troubleshot unless you guys come up with any recommendations.

 

it all started after you color tuned to a nice bunsen blue?

is the throttle linkage fully returning to the end of the idle adjuster rod end? if it is
did you try backing off the Idle adjustment screw if you do this
you may need to adjust the throttle at the grip.
is your inline filter paper if so go to sintered brass one napa has them take a day to get in part number 740-1158. its rated for 4 cylinder MC
I had to push the filter cone back into the cup inside the filter allen wrench or flat end of drill bit. bought more than 1 all were like this 3$

 

The throttle linkage is good, think I might try the fuel filter next.

 

And yeah, bunsen blue on all 4, and now this haha.

 

Did you wet-set your float levels? What level did you set them at for your initial dry-set?

 

fuel filter is not going to change a high Idle .you mentioned new filter so it was just a question on paper or brass

 

Floats were wet set after the rebuild, 2mm on all of them, I re-verified those levels last night, all still at 2mm.

It's currently a paper filter.

 

how can you adjust 2,3,4 then 1, there are only three adjustment screws. As you close 1, you open 2 and visa versa.
Don't worry about the light, the running sync is going to take care of that

 

I meant the actual butterflies, so that they are all closing completely and properly on their own. I understand the sync will only adjust 1, 2, and 4 to number 3, but my concern was that one (or more) of the actual butterflies was out of whack and binding somewhere.

 

Have you rebuilt the petcock and gas cap? Problems will occur if fuel is being sucked through the petcock diaphragm. After you change to a sintered filter and check the float levels warm it up, shut it off and pull the vac line @ the petcock. There should be no fuel there. Hope this helps.

Gary H.

 

Both were rebuilt recently, all the bike shops are closed (presumably to spent Sunday in the Church of Clean), but in the meantime I switched fuel lines to one without a filter for now. Test ride!

 

Well it's better! Mostly. I got her idle down to about 2000rpm. If I set it any lower, she will want to die. I have the YICS tool but no seals. Waiting for my silicone tubing to arrive, hopefully I will be able to sync her better then.

Thanks for all the help everyone!

 

Bench synching should put them within a inch across the board. That and having the mix screws @ 2.5 out should make her idle without the choke (use the choke to start it tho). If that's not the case two or more carbs may be working against each other. Imo using the tool to isolate each carb will help.

Gary H.

 

I don't use the YICS tool. I have one though..... It's in a bag somewhere.

 

You know enough not to have to use it. Imo if it doesn't synch with the carbs isolated he'll have to find out why.

Gary H.

 

you do mean minus 2 mm correct?

loose the paper filter

 

I think I figured it out! When checking the fuel levels, the carbs were always cold, and always gave me a (minus) 2mm level. I noticed her sputtering a bit when she warmed up, #2 was waaaaay rich (+1mm) when the carbs were warm. I gotta help a buddy move, but when I get back, I'll adjust the tang and report back

 

And then be a good sport, right, and re-synch and re-colortune the thing and report back!

 

Adjustment, sync, colortune, sync, that must have been it. She's got a 1400rpm idle now. Thanks to everyone for the input!

 

There ya go!!!