Fuel starvation problems,...HELP!!!

[bladerunner]

I'm having some fuel starvation problems on my race SV. I have been completely through the fuel system and cleaned every single component, i.e. carbs, petcock, fuel filter, vaccum lines, tank,...you name it.

My bike idles just fine and starts from dead cold without hesitation. While sitting in the garage, it will rev to redline without any problems, but once out on the bike, and with the engine under load, the bike bogs terribly and won't excellerate beyond about 50mph. I need some help.

My initial thoughts at this point is that the vaccum petcock is phuced and is not allowing enough fuel from the tank to replentish the float bowls under load/acceleration?

I figure one way to see if this is the problem would be to gut the vaccum petcock to where it is continuously feeding fuel from the tank regardless of engine vaccum? Anyone else done this??

Chime in please.............


Thanks,

Trent

[MrStinky]

Has the bike been sitting w/ race fuel, U4, in it? That stuff can really gum up the jets and make it seem likes it running on 1. Replace the fuel lines/filter, if its not that, you may be looking at electrical, but i still think its fuel since your bogging under load.

[bladerunner]

It was definately a fuel starvation problem. I pulled the plugs from both cylinders. The rear plug looked good and light-brown with an even burn pattern around the entire electrode. The front plug was light grey, almost white which indicated a lean condition/lack of fuel.

I use nothing but pump gas as I have a completely stock motor. Reliability is #1 to me!

I took the entire fuel system apart and cleaned everything including the pump and petcock, and flushed out the tank. I didn't find any crud in the float bowls and everything appeared normal and working properly upon re-assembly.

I took it for a short shakedown run (illegal as hell) and everything seems to be back to normal? Time will tell.

[secularist]

double check the little screens inside the carbs. I'm trying to remember exactly where they were, but my old team mate had a similar problem at Daytona last year...tried everything until he totally dug into the carbs.

[bladerunner]

Where are these screens inside the carbs? I have removed the float bowls, jets, needles, caps and diaphrams to clean everything. I never saw any screens? I have re-assembled everything and cleaned all. But I still have a slight hesitation upon acceleration? I'd like to get this problem completely sorted before my next trip to the track on Thursday?

More help would be appreciated.

[EvilTwin-05]

only screens I have ever seen are on the petcok stem.

[bladerunner]

I finally fixed the SV. I started by eliminating the fuel pump and just running a gravity feed directly off the petcock as I thought maybe the carbs were not being fed by a faulty pump. Not the case as it was running very rough between 7-9K rpm. Stumbling, rough, no acceleration.

Well I finally got completely fed up with chasing my tail, so this past weekend while racing at MAM, on Saturday I took my bike to the Dyno via HitManMotorSports. The run an exhaust gas annilyzer on their dyno, so I thought I'd give it a shot.

Well on the three pulls they did, none of them were good. Fat on the bottom with a very choppy pull to redline. Air-Fuel ratio from 7-10K rpm was at 17.5:1, Ouch!!! Only making 62hp with K&N filter, de-snorkeled air box and full Yosh exhaust.

HitMan suggested jumping from the 150 main jets supplied with the DynoJet Jet kit to 160's and turning in the mixture screws a full turn.

Went straight back to the pits. Pulled the 150 jets, replaced with 160's, turned the mixture screws in one turn, and whala.......I have a completely new bike that pulls like hell all the way to redline.

Best $75 I ever spent.