Pointers on fine tuning after cleaning & bench sync?

I've just finished a very, very, very thorough cleaning of the carbs and then a bench sync according to the threads on this site. I made sure the ports in the float bowl, as well as everywhere else are open, the emulsion tube is clean and the main needle gives a good THUNK. The bike runs pretty good when warm but seems to bog down a touch in low RPMs even when warm. Also, it will die if given the throttle when cold, even if the choke is applied. Again, it runs pretty well after running 2 or three minutes.

I don't have a colortune plug or manometer but am hoping for a few pointers in fine tuning without them. Any hints would be appreciated.

jmd_forest

 

Really want to think about investing in a colortune plug and getting something to sync those carbs. Boths of these things needs to be done in order for your bike to run real good.

 

Did you set the floats?

 

HOW did you set the floats?

And you will need some form of manometer, homemade or bought, to vacuum sync the carbs once back on the bike. Mixture tuning can be done by ear and by reading the plugs; but vacuum synchronization requires a manometer. It can be as simple as 3 feet of clear tubing zip-tied to a yardstick.

 

Floats were set using the clear tube method. I'll look into a home mad manometer as I bought about 3 feet of clear tubing for setting the floats.

 

I agree with Bigfitz --
Yes, the sync is MUCH more critical to decent running than the colortune. If the sync is off, colortuning is a complete waste of time.

There are lots of homemade options plus good "how to" instructions if you do a forum search.

 

okay its me again stealing another thread. i'm curious what jmd_forest has done and if has had any luck because I'm having trouble with my carbs just like another thousand people or so. after rebuilding my engine practically with new rings and a piston, the last thing I wanna be frustrated with are the carbs. other than this, I should be smooth sailing so please help me out?! thanks guys

my carbs were immaculately cleaned, dipped in carb dip, rebuilt throttle shafts, cleaned emulsion tubes, and so on.. i bench synced with paperclips and then used a mercury manometer to get them balanced very nicely even with blips of throttle. 15 minutes later I moved on to colortuning and got to see all blue flames across the board and everything sounded good. being satisfied and having learned how to properly adjust the carb syncronization made me feel good so I hopped on and went for a ride around the country block. that's when trouble happened.

first off, i'm struggling to get rid of a high hanging revs throughout shifting; not terrible as I drop the clutch and go into the next gear it drops and my acceleration continues down the road. however, the acceleration sucks. i could not get beyond 4~4.5k rpms and no faster than 50mph with wide open throttle what's this mean? i'm stumped. (keep in mind the wind was not strong at all - maybe 10-15mph gusts). when I get back there is a significant amount of popping or backfiring in the exhaust and am concerned about my engine obviously from all the work I put into (check out forum post "Checking Cylinder Compression") here's a short video with some audio that may help you fellas hear what I got. photobucket video

throttle cable is loose and i've checked valve clearances. also I've checked for leaks with propane and no change. it will idle decently but it tends to hang for a few seconds and slowly drop. maybe I'm sucking in air? but the propane test should have told me so right?

 

So you had the throttle shafts out, and replaced all 8 throttle shaft seals?

When you say "immaculately cleaned" you had them COMPLETELY apart, and probed every tiny passage with a bristle from a stiff brush or the like to ensure all the tiny holes are open?

Including pulling the "forbidden" mixture screws? Did you replace the mixture screw o-rings?

NON-YICS motor, right?

"Popping" generally indicates a lean condition, so something's not right.

 

yep. replaced all eight seals.

yep, all holes are opened with a brass bristle

i pulled the mixture screws out and left the carb bodies soak for hours. the o-rings were not replaced since they looked in good shape.

non-YICS motor, and the popping was very significant after my 5 minute ride around the country block. I'm really stumped since the flame ColorTuner showed blueish ignition. I thought I was good but I'll try and fire it up again with a plug chop. what's up with the boggish acceleration though? do other people change jet sizes?

 

May want to check your colortune again and this time back them out until you see them turn orange then adjust it just to the point of when they just turn blue. This is the way I was told to do it. Fitz may be able to explain this better.

 

okay thanks OldBikerDude. I'm hesistant to do so but pulling the carbs looks like an order of business i need to do. a complete teardown was done to prevent $h*t like this so i'm stumped. new throttle shaft seals, leveled float bowls with wet method, clunk test drops 'em with a clunk.

carbs were in sync running and then the ColorTune. I'll do what you mentioned OldBikerDude but its upsetting to not even get the acceleration beyond 50mph in 5th gear. something really bogging the powerband and its gotta be the carbs

 

Do the colortune first before pulling anything. Here is one thing to note and this happen to me...
If you can't get them to turn orange then you may have a clog somewhere. For me it was in #3 carb. The rubber o-ring broke off a jet and blocked a passage so I couldn't make it rich. Also be sure you are at around 1200 rpm when you color tune. Now if you find that you had to back the screws out a lot to make it richer (turn orange) then you are going to notice the rpm's going up higher so you need to turn the idle back down to 1200 then continue. Look forward to hearing what the result was. Oh, and if you do find that you had to change the mixture then you are going to want to sync them again and color tune them once more to check them. When you can both sync and colortune with no changes then they will be set properly.

 

geez whiz now i can't even get the bike to FIRE over using starting fluid. it'll crank crank crank since I just purchased a new battery but won't fire and run. these carbs are the biggest pita

 

Just for giggles.... Have you considered your in line filter. If you have one, maybe it is clogged? Try replacing it if you have one. Also when you spray starter fluid I have found it is kind of best to burp the choke. Remove the filter spray it directly in your box then hit the starter button with the choke off for about two seconds then throw the choke on all the way. When I was having issues, this worked for me.

 

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Update: my personal problem has been moved to xjchat.

yes, air filter removed and starting fluid shot directly into airbox hole. also all spark plugs have been checked for spark. I've got air, spark, and fuel... why no fire?