odd hesitation after needle shim & TPS adjust
07-02-2008 | 10:51 AM
#1
Thread Starter
Junior Member
Squid
Joined: Mar 2007
Posts: 29
From: Columbus, OHio
odd hesitation after needle shim & TPS adjust
I have a 2004 superhawk (12000 mi) jardine high mounts. Pulled the carbs and put two washers in the slides to raise the needles also set the TPS to about 525. Starts and runs fine with no load. At crusing speed, 5k rpm, i get a stumble from the motor and an occasional backfire through the carbs, twist the throttle wide open and it stumbles and acts down on power. Question; sticking slides, vacuum leak, one washer to many, carbs out of sync, fouled plugs, what do you think, just trying to get an idea of what to check when i tear this thing back down? oh and i checked the pvlir already.
07-02-2008 | 11:29 AM
#2
SuperCock roster
Back Marker
Joined: Jun 2008
Posts: 144
From: Aurora Co
i had that happen when 1) i had bad gas or 2) the bike i have didnt come with an air lid so when i got one and put it on did the same thing. took it off and runs like a champ.
also what is the alidatude there in ohio i was told where im at leave the carbs alone the needels are for mid range gas flow medering so if it happens at WOT and just falls on it face maybe take a shim out
also what is the alidatude there in ohio i was told where im at leave the carbs alone the needels are for mid range gas flow medering so if it happens at WOT and just falls on it face maybe take a shim out
07-02-2008 | 01:41 PM
#3
Senior Member
SuperBike
SuperBike
Joined: Jun 2007
Posts: 1,031
From: Los Angeles ish
07-02-2008 | 04:17 PM
#4
Slacker
Superstock
Superstock
Joined: Jun 2005
Posts: 489
From: San Antonio, TX
If you installed 2 washers on each needle then I would imagine taking one out will help solve this problem. Also, leaning out the mixture screws will be required, if you have not already done so. You have changed 2 things that will make the engine more rich at idle~1/8 throttle opening. 1. TPS adjustment lowers the timing advance curve, less advance necessitates less fuel. 2. Raised needles (too far?) allows more fuel to enter the engine at high vacuum levels (small throttle opening). The best method for adjusting mixture screws is with the engine idling at full operating temperature. Go in as far as possible (lean) without any drop in RPM. Otherwise, just turn the screws in 1/2~3/4 turn and then test ride.
You could also throw in a high flow air filter to help lean out the mixture.
You could also throw in a high flow air filter to help lean out the mixture.
07-03-2008 | 03:59 AM
#5
Thats Mr Dill hole to you
Superstock
Joined: Aug 2007
Posts: 389
From: Sioux Falls, SD Beeeotch
If you installed 2 washers on each needle then I would imagine taking one out will help solve this problem. Also, leaning out the mixture screws will be required, if you have not already done so. You have changed 2 things that will make the engine more rich at idle~1/8 throttle opening. 1. TPS adjustment lowers the timing advance curve, less advance necessitates less fuel. 2. Raised needles (too far?) allows more fuel to enter the engine at high vacuum levels (small throttle opening). The best method for adjusting mixture screws is with the engine idling at full operating temperature. Go in as far as possible (lean) without any drop in RPM. Otherwise, just turn the screws in 1/2~3/4 turn and then test ride.
You could also throw in a high flow air filter to help lean out the mixture.
You could also throw in a high flow air filter to help lean out the mixture.
And def. sync your carbs after all that horsin round
07-03-2008 | 06:56 AM
#6
Thread Starter
Junior Member
Squid
Joined: Mar 2007
Posts: 29
From: Columbus, OHio
i'm gonna pull everything apart, double check the tps, go down to one shim on the carb needles, and try to do a carb sync. I made a homebrew carb sync tool with some tubing, yard stick and atf. I already have a "T" in the line going to the rear of the petcock and an extension tube on the front cylinder port. I'm pretty new to carb work so this is all a learning experince = I've never done any of this before. I'll post and update when i get to ride again, looks like it gonna rain for days
12-07-2008 | 07:15 PM
#8
Senior Member
SuperBike
Joined: Sep 2005
Posts: 1,572
From: Buffalo, NY
I have a k&n with shimmed needles, using a .026 thick #4 brass washer and the bike runs very well.
12-07-2008 | 09:31 PM
#9
Honducati
SuperSport
Joined: Oct 2006
Posts: 809
From: Anaheim, CA
I had the same problem the first time I pulled my carbs apart.
Pull the airbox cover off and look at the carb slides. Slide them open with your finger, then release. If they slide back slowly, they are normal. If one of them snaps closed, you probably mis-installed the diaphragm and it is leaking.
From the service manual:
"Install the diaphragm/vaccum piston into the carburetor body. Lift the bottom of the piston with your finger to set the diaphragm rib in the groove of the carburetor body and install the spring and vaccum chamber cover".
I glossed over that part...
Pull the airbox cover off and look at the carb slides. Slide them open with your finger, then release. If they slide back slowly, they are normal. If one of them snaps closed, you probably mis-installed the diaphragm and it is leaking.
From the service manual:
"Install the diaphragm/vaccum piston into the carburetor body. Lift the bottom of the piston with your finger to set the diaphragm rib in the groove of the carburetor body and install the spring and vaccum chamber cover".
I glossed over that part...
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