Major hesitation from a dead stop

Hi guys
First let me give a little background on the bike. I bought it not running, well it ran but the carbs were leaking a bit of gas and if you hit the throttle it would stall. I took off the original carbs and checked that the rubber diaphragms where torn up and the tube between carbs was cracked. I picked up a set of carbs off Ebay from a running bike tossed them on and been riding the bike ever since living with the hesitation. I would like to fix the problem not sure where to start though.

I dont know what the jetting in the Ebay carbs is and I have Vance and Hines exhaust on my bike. Should I pull the carbs and rejet?

Should I Sync the carbs as a first step and see if that makes it better?

Any help appreciated

 

you could try to sync carbs but sounds like you need to rejet them.
keep us posted.
if the carbs have a jet kit in them already the needle will have a circlip on it that is adjustable, for 5 positions stock will not. ( you could always try a spacer under the stock needle to see if thats helps at all )

 

I guess I should sync them see if it helps out. When I get a chance I will take a look at the original carbs and see if they have an aftermarket jet in them. If the Sync doesn't work out, I well attempt to take the jets from the original carbs and put them into the set on the bike.

 

Dave Dodge recommended 132 mains w/ #40 slow jets for my 83 VF750F which has a K&N, Accel ignition, and Vance&Hines full 2-2 system. He said that would cover my future Megacycle cam install also.

 

off idle idle screw or pilot jet............................is choke off working right??

 

yeah, check ur jetting... if that doesn't do it, try adjustin' idle, may just be a hair too low...

 

Idle is up probably way to high, trying to compensate for the hesitation since it will stall if its not. I am going to take apart the original carbs and see if they have aftermarket jets in there. I need to get a set of gauges to sync the carbs before I pull the ones off the bike. Figured that would be a good first start.

Any one use a Carbtune? http://www.carbtune.com/

 

Ok heres where Im at. I took apart the original carbs that I had laying around in a box. the back two main jets are 110s and the front two main jets are 112s. The slow jets are all 38s.

Can this be right? Whats the stock jetting for a 85 VF700F? going to pull the carbs off soon, since the sync only helped a little bit.

 

You said the idle is 2000 rpm but regardless of what jets are in there the bike should idle. By raising the idle your relying on another circutin the carbs to keep the bike running. Those carbs need to be cleaned properly first. That should fix the real problem.

 

bike idles fine, with the choke off once its warm. And will rev up without a problem as long as the bikes in neutral. As soon as the bikes in gear and I try to take off from a dead stop theres a major hesitation and almost a stall if im not careful, and theres some hesitation in the throttle while riding.

As i said before the carbs that were on the bike were pretty beat up torn slides, linkage missing when i bought the bike. I put a set from a different bike on there and not sure if the previous owner jetted the carbs to match the exhaust thats on it. If that was done, then the ebay carbs i bought probably dont have the right jetting and I am trying to compare the old carbs that i kept in a box to the new set thats on the bike or at least to a set with factory jetting.

 

OK, what rpm does the hesitation occur at? Are you giving it a handful of throttle or gently rolling into it? The needles will affect running from 2000-6000rpm. The main jets kick in above that. How is it at WO throttle? I've emailed Dynojet Technical dept and asked for help with baseline settings with good response. Don't bore them with details. Just tell them it hesitates and how it's modified or if it's stock. Ask them for a print of the original jetting instructions. they'll send them via PDF.

 

hell, could be ur lettin the clutch out too fast

seriously though, I'm puttin' money on them carbs. Either jetting's off, or they need to be cleaned thoroughly.

 

I doubt I'm letting the clutch out too fast since I start to get rolling then it really hesitates. The original carbs have non adjustable needles, so it looks like either they were not changed with a jet kit, or just the main and slow jets were changed. (still looking for the stock jet sizes)

Also found out the tool I was given for syncing the carbs is pretty well shot. going to see if I can get someone to do it or order a new Carbtune.

Where can i get just float bowl gaskets, don't want to order a rebuild kit just for a cleaning.... or can I reuse them

 

Found my repair manual. The no1 and no3 carb is a 110 and the no2 and no4 carb is a 112 so looks like the original carbs I had in the box, were not jetted for the exhaust. Guess I will pull the carbs off the bike and try clean and sync (I will check the jetting on those as well)

Anyone have a good how to on the sync for the VFs

 

Ok. Got some good news. Found that I must have rushed putting the carbs back on last time, one did not seat in the boot all the way causing a vac leak. But I pulled them out anyway. Man did they need a cleaning. Since the parts (jets, float ect) from the original carbs (the ones I took off a while ago) where really clean, I did a quick clean job and started swapping them into the other set. I am going slow making sure math the carbs up from one set to another so I don't mess up the parts. I figured I would clean the other jets and parts and put them back in the spare set. Got one carb done tonight after taking the wife out for dinner. Just need to order new float bowl gaskets to put them back together.