idling low then high please someone help

osiris10

New Member
May 16, 2011
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philadelphia
ok i just got a 2002 blaster its bin bored with wisco piston and rings i have a fmf phatty with the powercore2 silencer brand new vforce3 reeds new aftermarket air filter stock carb with new dynojet kit now this is the first time starting the bike with all new parts started first kick but it would idle low wanting to shut off hit the gas just slitly and it stays at idle, push the choke in and it wants to stall give it a little gas and it idles now after warm, it will idle but high low high low hit the gas fast and it starts to bog hit the gas soft and it revs but then stays at a high idle turn of the engine start back up and it idles but hit gas and the same thing stays at a high idle dont understand now i tried to find some info on the jetting and evryone is talking about a 270 280 main jet well my kit has neither of thoughs the dyno jet kit i got has 200 210 220 340 350 360 all of them have dxp in front of the#now i fallowed all instructions with jet kit and to me this is were i think my problem is i checked the intake boot no cracks all gaskets are new so there cant be no leaks the top end is fresh was told it was broken in but not sure im treating it like its not the carb is 100% clean the air screw is 2 turns out as the jet direction suggested the needle i replaced with the jet kit one as suggested its down 3 grooves for my elevation is less then 5000 now i messed with the idle but it made no diffrense made sure the throttle is not sticking nope thats not it can someone please help this is getting aggravating
 
Sounds like idle is lean. Have you ever done a leak down test? With changes to the intake track such as reeds can introduce leaks. So until thats done you don't know if there is a air leak. Air screw should be close 1 1/2 turns from bottom as a starting point. If that improves the idle you were running lean, More turns out the leaner the idle jet. More turns in and your richening the idle jet. The idle or slow jet effects the first 1/4 throttle on the carb. Mikuni jets would be easier to give you base line starting point. As I'm not familiar with dyno jets #s.
 
go ahead and get a leak tester. they are not to complicated to make and a dude on here sells em i believe.
do not run it like this until you know you dont have a leak.
i had put a new gasket on my reed cage and it leaed......BRAND new yamaha gasket too
dont just assume there is no leak. test it and be confident
 
definate leak at the intake, use some rtv on the gaskets, the vf3's are prone to not sealing good, but some hi-temp copper rtv sealed both my sets, just a thin layer on all sides of all gaskets will do it

as for the jet kit....welcome to the sore ass club, they are complete garbage

ditch that needle, put the stock one back in (middle clip position)
same for the pilot jet if you changed it, airscrew... start at 1.5 turns and adjust at 1/8 turn increments in/out till it idles the highest (give it 10/20 seconds to catch up to the adjustment) and revs clean to 1/2 throttle
and i always like to start big, i'd go to the local dealers and grab a 300/290/270 jets and throw the 300 in, and work down, doing plug chops with each one
search button up top for "plug chop"

then list that jet kit on ebay and try to recoupe some of your loot
 
ok i am upset with the jet kit what a waist of money will try to get rid of asap thanks to all for info i will start all test later after work thanks again if theres anything else i could try please list and will do thanks will post after my test
 
ok so i was about to do a leak down test when i saw a oil trail under the exhaust from were the cylender meets the bottom end now i know i would need a new gasket but its a oil gasket correct?so cant i use gasket sealer you now the high heat copper gasket sealer in the squeeze tube or the rubber gasket the kind you buy from autozone that you cut out im really onley asking because i have these in hand
 
are you sure it's not just from a slight exhaust leak, as most of us with A/M pipes are accustomed too, or are you seeing a base gasket leak ??? < which will show up during a leakdown test, pump it up to 7 lbs. and spray the soapy water to it, if its a base gasket leak, it'll bubble up there

and if it is a base gasket, you'll need a new base and head gasket, and we all highly recommend using a stock yamaha or cometic gaskets only, the green paper ones will eventually leak