carb help!!!!!

[yamahablaster4]

now I know that there are so many jetting guides out there on this subject all ready and I have checked them all and still have same results. so the problem is that last summer I rebuilt my blaster with a vitos 240 kit it was all ready starting to get cooled off out side I had broken the motor in to specs in 4 different heat cycles. I replaced the main jet with the one supplied it is a 340 main jet and with the supplied pilot jet and put the new needle in the bike set on the middle setting my air screw was about 1 and 3/4 turn out to were it ran the best then.

the mods to the motor are the vitos 240 kit a moose 3/4 inch reed spacer v force 4 reed cage and a uni air filter on stock carb the pipe is a rdz left hand pipe

I have already ran the bike in the local sand drags it runs 6.551 is my fastest time in 300 feet at 46 mph the bike has run great on that day it was about 75 degrees out but now that it has made its way in to the 90s the bike has no power it acts like it is running rich it spits and sputters at high rpms in 1st gear threw 3 but then it seems to clear up a little in higher gears but still isn't all there.

I have tried every setting I could think of as far as main jet and air screw and the needle the bike gets extremely hot and leaves wet plugs but it starts really easy one kick it is ready to run I also did a compression check it is caring around 140 psi so all of that is ok the reeds are also closing

any help or advice on what I should try next would be a big help thank you

 

[Blaaster]

Did you use a jet kit and the needle that was supplied with the kit?

Have you tested for air leaks?

Did you re tension after heat cycling?

Did you plug chop to confirm jetting.

Did you check the float level and set the idle as per specs?

What oil do you use pre mix ratio or injection?

 

[yamahablaster4]

yes I used the vitos blue needle it is about a 1/4 inch longer than stock

I have not tested for air leaks

yes I retightened evry thing to correct tork

plug chopped when it was running good and it was a light brown all most like cardboard

I have not checked float

I pre mix 50 to 1 klotz benol

like I was saying in my recent post the bike ran great until this warm weather came and now it just acts like it is to rich and I tried choking to see if it improved but it kills the motor

 

[Blaaster]

I find that needles from any kit are only good for cleaning wax out of your ears.

I am concerned about 50:1, not enough oil for this old fella.

With temperature changes, jetting needs to be changed. Warmer weather needs less fuel.

Increase the pre mix ratio to 32:1, that will simulate one size down on the main jet, it will run leaner.

You need to do another plug chop.

Set the float, adjust the idle, leak test, calculate jetting and plug chop to confirm.

Try the stock needle , clip in middle slot.

 

[Larry's Shee]

Problem I see is conflicting symptoms.
Mikuni pocket tuner https://www.google.com/search?q=mik...biuoDoDw&ved=0CCUQsAQ&biw=1440&bih=721#imgdii=_ would indicate a smaller main for temp change. One maybe two.

As to the overheating. Is your fuel fresh? sealed container? What octain? What is your timing at? What plug you using?
When you do your leakdown, flex the carb boot to ensure it's not cracked .

Here is where I strongly disagree with Blaaster. I have a Vito's jet kit that came with the Fat Bastard pipe, Mikuni jets, no idea who made the BLUE needle. Works perfectly fine with my set-up, and I'm on and off the throttle way more than you. As long as you aren't having a bog when you launch, or returning to pits, DON"T change it. Your air screw setting indicates that your pilot jet is good.
I presume this set-up was recomended by RDZ? BTW, is it a regular or big bore pipe?

List what jets you tried.
Very important that you check/set your float height.
When tuning only change one thing at a time.
Wholesale changes only when major changes to your set-up (motor wise)

BTW, 340 main doesn't seem excessive for a full on drag pipe.

 

[yamahablaster4]

ok thanks blaaaaaaster for your help and advice I will wait until all this rain passes and mix some gas and give it a shot

 

[yamahablaster4]

ok and for larrys shee I run a liberty gas its 87 octane 100 percent gas says it has no ethanol

I have tried jets from 290 to the larger 340 and as far as you saying that 340 is not a large jet that in my opinion is a very large jet for something that small lol

to step from a stock 230 to jump a hole 110 up to 340 is amazing haha

but im not entirely Shure on how to set the float can u guys help me out on that as well I have never done it

I run a ngk br9es plug

and I noticed earlier that on my exhaust right next to the head at full rpm it shoots a little smoke out will pulling the pipe and stuffing it with rpv copper that could also be some of my problem

 

[Blaaster]

 

[yamahablaster4]

were can I fine one of those fuel gauges is that like a ebay item and thanks for the chart very helpful

 

[Larry's Shee]

Have to think that's a Genuine Yammy part #.
I use either a small machinist type scale or calipers.

 

[Blaaster]

Why for you use a br9es it is the wrong heat range, too hot.

You should use a br8es or a b8es!

 

[yamahablaster4]

I use to used to the br8es but the kit says it recommends the br9es

 

[yamahablaster4]

Have to think that's a Genuine Yammy part #.
I use either a small machinist type scale or calipers.

and yes good point

 

[Blaaster]

I fear that the 9 heat range will be too hot for the combustion temperatures and may lead to pre-ignition due to the electrode overheating.

I would've very inclined to revert back to the 8 range,the worst you can do is foul a plug.

If the carb is jetted correctly, there is no reason that a plug should fail.

I run Bean oil at 25:1, and jet on the rich side and I have never ever fouled a b8es.

Have you fixed the pipe leak yet it will stuff up the jetting.

Are you able to get some higher octane fuel, the overheating could be coming from slight detonation.

 

[yamahablaster4]

I have fixed the the pipe and the bike runs 20 times better I think if I move my needle to the leaner side and a

little more air screw than it will straighten out thank you blaaaaster for all your help I would probly still be cussing

the thing if it want for you lol

 

[Blaaster]

Before you lean out the needle try a little experiment.

Mix up a little fuel at 32:1, rather than the 50:1, it will effectively lean out the AFR by about 1/2 a jet size.

See if that helps fine tune and plug chop to confirm the main.

Messing with the air screw will only affect the mix up to 1/4 throttle.

 

[yamahablaster4]

Before you lean out the needle try a little experiment.

Mix up a little fuel at 32:1, rather than the 50:1, it will effectively lean out the AFR by about 1/2 a jet size.

See if that helps fine tune and plug chop to confirm the main.

Messing with the air screw will only affect the mix up to 1/4 throttle.

ok thanks I will give it a shot and get back with you

 

[Larry's Shee]

Jet size has really nothing to do with cyl displacement, it's all about set-up and tuning. not really surprising with a full-on drag pipe. I run a 320 main on SS, home port and Fat Bastard pipe.

Just think of how much faster you'll be able to make yours

 

[yamahablaster4]

Jet size has really nothing to do with cyl displacement, it's all about set-up and tuning. not really surprising with a full-on drag pipe. I run a 320 main on SS, home port and Fat Bastard pipe.

Just think of how much faster you'll be able to make yours

yea ik after this season im shipping my head and jug of to have stage 5 porting done and 15 mm domes its going to be turned in to a stick drag bike

 

[yamahablaster4]

ok guys I have checked float it is perfect

I have settled on a 310 jet it runs the best but it still spits and sputters a little bit 4th threw 6th is this

air skrew or needle I think its air but im not shur