I have a 1997 YZF 750 street Bike will adding some Vp race fuel clear my carb problem there not that bad i?

Question

already had them cleaned

Answer 1

race fuel is not going to fix the problem.

Answer 2

If the carbs have already been cleaned, then maybe they need adjusted. Maybe it isn't even the carbs, is the air filter dirty?

When is the last time you adjusted the exup valve? does the bike have a jet kit or stock jets? If they are stock...pull the exup cover off (its right under/behind the left footpeg..held on by 3 bolts) you will see what looks like a fork...when you turn the ignition on that fork should be positioned perfectly over the tuning hole behind it, if it isn't then it needs adjusted. An out of adjustment exup valve will simulate carb problems, and it is operated by cables, they stretch over time.  I check mine atleast once a year.

Have you added an after market exhaust or slip on? K & N filter? did you richen the mixture slightly after you did?  A lot of people add end cans because they like the sound, but don't know they just leaned out their mixture slightly..and don't adjust the carbs to richen them back up... this will also make a bike run slightly off of expectations.

Back to the exup for mods.. I have a jet kit, kept the factory stagger on the mid two carbs..the stagger is 1.5 on the jets... I recommend anyone who adds a jet kit keep that stagger because Yamaha did it for a reason. The two inside jets are 1.5 smaller than the outside jets..because the two inside carbs are subject to more heat and the air going in is hotter...so you need to put in less fuel.  I also have a D & D end can which I shortened by 5 inches to reduce even more restriction and increase air flow... added a K & N filter, and set the Exup fork mid ways on the tuning hole so that it is slightly more open than stock.

Adding an end can on a Exup bike ONLY reduces restriction from the exup valve out...you will maintain the same restriction from the head to the exup..so when you increase fuel the only way to increase air is to adjust the exup to allow a little more flow.

That is a touchy bike you own due to the exup..if you have made any mods what so ever, it will simulate carb problems.

If the carbs have been cleaned and the bike is still showing problems...I would have them adjusted, if you dont have a vacuum gauge then take the bike to yamaha and let them do it. If the problem still exists check the air filter, and exup valve.

If they cleaned the carbs then they had your bread box off , or air box which ever you know it by. Pull your tank, MAKE SURE they got all four boots completely on the carbs and that all four clamps are tight... a loose boot will make a bike run bad.

Wish you had included a desciption of what the bike is doing so I could help you better... but if the carbs are clean, then it is something else, its just hard to say what without knowing what the bike is doing.

Good luck!!!

Answer 3

High octane does burn clean enough to have a small cleaning factor but since you already had them cleaned, it would be a waste of money in this case.

If they are clean but still troublesome, they need adjusting. Something isn't set right. I stay away from carb work so i can't offer any experiential help. I like the other suggestions though. Have carbs readjusted and look at the exup.

Answer 4

it might help but adgusting it would help

Answer 5

I'd try Sea Foam.  Usually available at your local autoparts place.

This is a great solvent, and you can run it straight(ie 100%, just pour it in), or  mix it in your fuel.  It is also a fuel preservative or stabilizer.  When I was refurbishing my Honda, I put some of this in the tank and only ran it occaisionlly for a year and a half.  Seemed like a pretty darned good solution.