Engine stumble at cruise.
 

Howdy folks,

Okay, so I neglected my poor '01 SV650S (stock everything except K&N air filter) for about 8 months, with fuel in it. Finally fired it up a few days ago, and it was only running on 1 cylinder (rear). I figured the old fuel was gummed up, so I:

• Put fresh fuel in the tank
• Cleaned and gapped the spark plugs (HATE doing front cylinder, btw)
• Cleaned the air filter
• Removed the carbs, took them both apart and cleaned everything, reassembled
• Replaced the little fuel lines between the carbs since I messed them up bad during the disassemble (yay)

It started right up, ran and idled pretty smoothly, so I took it for a ride... It pulls really strong during hard acceleration and runs smooth while decelerating, but it stumbles pretty bad during light acceleration and constant-throttle cruising. I often suck at forum searching, so I only found a couple potential hits, and wanted to ask you folks for anything else I should check "while I'm at it..."

Possibilities my search turned up:

• Choke plunger stuck open?
• Idle mixture too rich?
• Missed some gunky fuel somewhere?

More ideas?

Cheers!
-Troy

Re: Engine stumble at cruise.
 

Idle mixture too lean, check what you set pilot screws to.

Re: Engine stumble at cruise.
 

The pilot screw is the one originally covered by a plug on some models, right? When I took the carb apart, they were about 3 full turns out from fully seated. Sound reasonable, or give 'em another half turn or so? Most of what I read about them sounds like they're usually about 2.5 or 2.75 turns out when new...

-Troy

Re: Engine stumble at cruise.
 

HAHA im currently strippin n workin on the sv when i get the chance, jus routine stuff and freeing a jammed choke plunger and i have had a socket and extension bar stuck in my front sparkplug well for the last 3 days as i havnt got to fix it, got the radiator forwards and got the socket in then the extension, didnt realise when they where together ther was not enough room to pull the extension and socket back out! my radiator hoses just arnt long enough so now tmoro after work gotta unplumb radiator n remove that haha! gona do a compression test too so may as well have it outta the way and change coolant! kill several birds in one afternoon! still cant believe i have a socket lodged in the front head tho, such a silly problem :rolleyes:

Re: Engine stumble at cruise.
 

:p Awesome, nice work. ;) I managed to do mine without pulling the radiator by removing the horn, just in case, loosening the top 2 bolts, removing the bottom 1 and then gently pulling the radiator forward and jamming some cardboard folded or a piece of wood between the edge of the radiator (not on the fins!) and the valve cover.

That gave me JUST enough room to drop my socket in and wiggle it around to get it to drop on the plug, then finagle my extension in there, then just barely clear the socket wrench itself.

To get it out, I took out the wrench and extension, leaving the socket and plug behind... Then I jammed a piece of 3/8 inch rubber hose down into the socket. It gribbed enough to pull the socket and plug, and was bendy enough to get it all done without removing the radiator.

Mind you, there was a LOT of automotive-induced Turret's Syndrome going on.

I'm itching to get out of work and go home to try making my idle mixture richer, see if it fixes my problem...

-Troy

Re: Engine stumble at cruise.
 

congrats for the smooth job, i detest working on my front cylinder haha too much hassle in too small a space! as for the tourettes all i could do was laugh and shake my head when i got the socket jammed hahaha... if u cant laugh at yourself...

Re: Engine stumble at cruise.
 

I never had problem with front cylinder like that? Remove horn and it is easy

Re: Engine stumble at cruise.
 

My radiator hoses won't stretch very far at all, can't move the radiator forward more than an inch or two at the bottom.

Re: Engine stumble at cruise.
 

The horn is off including it's bracket and the radiator Is completely unbolted but there is no way the hoses are long enough to move it more than an inch, I reckon the hoses where replaced as a botch job a few years bk!!!

Re: Engine stumble at cruise.
 

If hoses have been shortened it might be different. In that case I'd probably fire in and check the valve clearances too. Good a time as any if you are draining the coolant anyway.