Bonneville America Forums Forums Technical Forums Performance Mods what did I mess up?

my 06 speedy has gutted stock pipes,122 mains and 45 pilots and the mix screws out 1.5 turns by the dealer and ran ok. Over the winter I installed a K&N filter, drilled out the airbox, changed to 130 mains with thruxton needles.tried to balance the carbs with 2 dampened vacuum gauges but couldn't get the vacuum to change at all with the right carb screw. snapping the throttle seemed ok but when I am on it the slightest throttle movement and the engine will sputter as long as I keep it there. further movement of the twister and it takes off strong. what could I have screwed up in the idle circuit on that carb?

mike

Hey Mike,

You don't balance the carb with air mixture screws. Get those set back the way they were and use the single screw/bolt in the center of the carbs. Best pic I could find is from Pat's Carb Site

Look closely at what Pat cricled here. You don't need to move it much to get results.

Well duh, I saw that pic and it must of flown over my head so fast that it didn't register. I should of read it over more than once. getting worse than my know it all yute. That is also one of the reasons pat took his tank off. I am going to try again tomorrow. my experience adjusting truck and car carbs confused the c##p outa me.

thanks

mike

It's not impossible to do it with the tank in place but it ain't easy! As you should do it warm, the friggin hot carbs add to the misery!

sounds from the jets you are probably running way lean too.

I started at this size from Dinqua's calculator.I'm going to turn the mixture screws out to 3 turns and try again tomorrow.

mike

3's a good point to work from.

I just re-read and you are using Thruxton needles? Those might just work with the rest of your mods. You don't have any TBS needles and shims, do you?

no, I told my dealer,Todd what I was trying to achieve and he suggested the thruxton over the tbs needles. but if there are problems, they are only 5 minutes away.

IIRC, several guys have found the Thrux needles to be too rich, and the TBS needles to be a good compromise. But then again, your results may vary

I jumped the gun I should have asked your altitude I was comareing to my set up.If his calculator told you to run what you have you are probably pretty close if not spot on. My mistake! With your mods it seemed to me larger would be in order but I trust that calculator having used it with several bikes and then running them on the dyno.

Ok, I'm now at 3.5 turns out and balanced the carbs with the 2 vacuum gauges and took it for a ride and it is better but still sputters at one quarter throttle. I pull the choke out and it pretty much quits sputtering but it doesn't have the pull I was expecting and there is no popping on decel. just thought of pulling a plug and checking color. Still trying

mike

Try new plugs, too. If you were running lean, it only takes a few miles to pick up metallic bits on your plugs, which will short them out, causing some stumble on the lower end of throttle range. Then, adjust your mix screws to 4 turns out, maybe?

OK I heard about Thruxton needles awhile ago and recently from you guys the TBS needles. I am not sure what I should do. My midrange dip is slight so then the TBS needles?

3.5 turns is a lot with your setup. You mentioned it ran smooth with the choke on. The choke richens up the mix, which leads me to think yours is way lean at idle. At 1/4 throttle (and this is somewhat inaccurate, as these are vacuum driven) you are engaging the pilot jet, pilot screw, and the throttle valve.

Start with the easiest then move to the most likely. Start with the mixture screws. Make sure all the little parts are in the correct order and accounted for. Should be screw/spring/washer/o-ring. Check the o-ring closely. Look up in the carb body, as the o-rings get caught up in there sideways. Replace if there are any nicks or anything.

If these are good, pull the tops and check that the diaphragms are not torn of have a hole in them and are seated correctly and the needle assemblies are installed correctly- basket (right side up)/shim (if applicable)/needle/spring/lid. Check the hole in the slide to make sure it is not blocked or clogged.

If all is good, reassemble and move to the bottom of the carb. Check the pilot jet for an obstruction in the passage of the jet.

Also check the little rubber vacuum plugs for cracks and a tight fit.

I'm guessing one or both of the diaphragms is not working right and not opening until there is a lot of vacuum.

This is almost the same setup I had prior to the ghetto freak mod. I was running TOR longs, airbox drilled with holed K&N drop-in, 132 mains and stock 42 pilots with two shims on the stock needles. I was at about 3.5 turns out with this setup and the AI removed of course.

Here's a very safe, inexpensive way of synching the carbs.

Try falling back to the stock needles with two shims (small Home Depot brass washers). This is a very inexpensive, easy test.

You may also want to fallback to the 42 pilots and bump the mains up to the 132-135 mark.

Mine ran well in the above configuration, Went to the pods and gutted airbox just to see if I could pull it off.

Regards,

Tom

Thanks for the suggestions, I did pull out and verified the pilot screw parts were all there. Initially I accidentally removed one of the pilot jets and now I will go back in there to see what junk might be in there. and did check on the diaphrams to see if they are wrinkle free. will go back to stock needles with shims to see if it changes symptoms. One more question for now, will lightly touching the floats with your knuckles while changing the jets mess up the float settings? I know I did not use any leverage on them but I did see them move a couple times.

mike

only if you pushed hard enough to bend something. just a very light bump shouldn't hurt anything but not advised.Things are easily changed so if it was me I would double check the float lever before I reinstall.

The floats move easily up and down, that's how they work- floating up and down in the fuel in the carb bowls. You do not want to force them past the point where they naturally stop.

My local shop gave me a cool trick for checking float levels with the carbs on the bike. Put one end of a clear tube on the drain nipple of the float bowl and raise the loose end above the carb height- like to the bottom of the tank. Now, with the bike level, crack the bowl drain screw open. The fuel will fill the hose and teh level of fuel should be +-6.35mm (or about 1/4" for the rest of us) of even with the float bowl gasket line. Turger pressure balances the fuel in the hose to the level it is in the bowl. Mad science...

That is a really cool trick I always removed the carbs to set float level. I'll have to remember that one.

You can't set it that way, but you can check it! I alway's took them off and flipped them over... you know the drill.

maybe can't set but good way to determine if that is a possible cause of an issue or like was asked about bumping the float during work. He can check that way if he already put the carbs back on to avoid removing for no reason!

Try the TBS needles with no shims to start, Ian. The Thruxton needles will probably be too rich and force you to rejet.

That was what I thought you told me before. Thanx

Bryan, thanks for the tip on testing float levels. Nice and simple but accurate. That one's a beauty. cheers

Well, I got out for a test ride today after putting 1 shim under each needle and it quit flubbering at 1/4 throttle. but I'm not sure if I did anything to improve the seat of the pants power. also noticed after riding around with the test rides that my pipes are starting to blue at the heads. I hope that was just from being too lean at 1/4 throttle or else I might have to go to 132 mains or even 135 if they come in that size. well I'm burning sunlight and it is 58 degrees f and I'm going ridin.

mike

Mike57, go up to the 132's then try it again........Angelis

sounds like a plan Angelis, thanks... as soon as I find some. I'll be looking after work mon.


mike

Go to Brent's website. He and Jess have the cheapest route to carb nirvana.