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Vito's 404 Monoblock Jetting


Eric Krupp

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I would think it would be in more of the range of an EEJ and a 42 or 40 pilot.

 

I ran it as I specified this morning;

 

200 Main

EEK 2nd from top

48 Pilot 1 1/2 out

 

Bogged bad at 1/4 throttle, bike would almost die if you kept it there. Brought it back and put a 52 pilot 1 1/2 turns out and bogg went away.

Would the EEJ richen it up 1/4 slightly? That damn Keihin Needle chart is easily confused in my opinion.

 

Another question; should my plug chops all look the same at the various throttle positions? 1/4, 1/2, 3/4, WOT? Or will the smoke band vary at the different positions. The way I understand it is that it should be 2mm at every position.

 

I am going to rip it back down and go with your suggestions;

 

42 Pilot

EEJ 2nd from top

200 Main

 

I am listening to your directions.

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I ran it as I specified this morning;

 

200 Main

EEK 2nd from top

48 Pilot 1 1/2 out

 

Bogged bad at 1/4 throttle, bike would almost die if you kept it there. Brought it back and put a 52 pilot 1 1/2 turns out and bogg went away.

Would the EEJ richen it up 1/4 slightly? That damn Keihin Needle chart is easily confused in my opinion.

 

Another question; should my plug chops all look the same at the various throttle positions? 1/4, 1/2, 3/4, WOT? Or will the smoke band vary at the different positions. The way I understand it is that it should be 2mm at every position.

 

I am going to rip it back down and go with your suggestions;

 

42 Pilot

EEJ 2nd from top

200 Main

 

I am listening to your directions.

 

pj_jet.jpg

Refer to chart.

 

get the settings in ballpark, then make adjustments one at a time. Start with main jet, then needle size, then clip position, then pilot jet and air screw. Dont ever change a bunch of stuff at once, you wont know what affected what that way. I dont do plug chops, I go off feel, and general look of the plugs I am running. I also use egt's in certain situations. I run alot of stuff on the dyno, so thats another way I get jetting in to the ballpark.

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pj_jet.jpg

Refer to chart.

 

get the settings in ballpark, then make adjustments one at a time. Start with main jet, then needle size, then clip position, then pilot jet and air screw. Dont ever change a bunch of stuff at once, you wont know what affected what that way. I dont do plug chops, I go off feel, and general look of the plugs I am running. I also use egt's in certain situations. I run alot of stuff on the dyno, so thats another way I get jetting in to the ballpark.

 

Okay, hold on!

 

Set Up #1

200 Main

EEK 2nd From Top

48 Pilot

Bogged bad at 1/4 throttle. Would all but die if you held it there.

 

Set Up #2

200 Main

EEK 2nd From Top

52 Pilot

Still bogged but much better.

 

Read your post suggesting an EEJ Needle and 40-42 pilot.

 

Set Up #3

200 Main

EEJ 2nd From Top

42 Pilot

Bogged slightly at 1/2 throttle but seemed much snappier.

 

Set Up #4

200 Main

EEJ 2nd From BOTTOM

42 Pilot

Ran really well. Plugs started to show color but slightly wet still.

 

Set Up #5

190 Main

EEJ 2nd From BOTTOM

42 Pilot

Runs extremly well. Plugs showing good color after a 3-4 mile hard run. Pulls hard all the way to the top.

 

That all transpired today. I may do a plug chop tomorrow on my mains to see what I'm getting to be safe.

 

Explain your "feel" theory to me. I would like to understand. It seems to me it would be real easy to get it lean since lean is usually faster. Not argueing against it just want to know different theories.

 

Also, would I be better off going to a richer needle and moving the clip to the top so I have more adjustment for temperature drops? If so which needle would I go too?

 

I am definitly much closer, bike is running good and plugs are shaping up. Thanks.

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Okay, hold on!

 

Set Up #1

200 Main

EEK 2nd From Top

48 Pilot

Bogged bad at 1/4 throttle. Would all but die if you held it there.

 

Set Up #2

200 Main

EEK 2nd From Top

52 Pilot

Still bogged but much better.

 

Read your post suggesting an EEJ Needle and 40-42 pilot.

 

Set Up #3

200 Main

EEJ 2nd From Top

42 Pilot

Bogged slightly at 1/2 throttle but seemed much snappier.

 

Set Up #4

200 Main

EEJ 2nd From BOTTOM

42 Pilot

Ran really well. Plugs started to show color but slightly wet still.

 

Set Up #5

190 Main

EEJ 2nd From BOTTOM

42 Pilot

Runs extremly well. Plugs showing good color after a 3-4 mile hard run. Pulls hard all the way to the top.

 

That all transpired today. I may do a plug chop tomorrow on my mains to see what I'm getting to be safe.

 

Explain your "feel" theory to me. I would like to understand. It seems to me it would be real easy to get it lean since lean is usually faster. Not argueing against it just want to know different theories.

 

Also, would I be better off going to a richer needle and moving the clip to the top so I have more adjustment for temperature drops? If so which needle would I go too?

 

I am definitly much closer, bike is running good and plugs are shaping up. Thanks.

 

You get ballpark jetting first. Then start going up one main jet size at a time until you feel the bike slow down. Then work back to the size before the slow down. Too rich is blubbery, too lean is hesitant and non-responsive. All the time I check the plug and look for a nice dry outer ring with some color in the center on the porcelain. I peek down towards the bottom and look for the color to be darker. I typically start out the day with a new plug and keep checking it through out the day. You cant get too bent up on plug color with running race gas, it wont make color like pump gas does. So relying on the feel is more of what you have to rely on. Two other thing you can check is for oil in the silencers and the burn pattern on the top of the pistons when you look down in the spark plug holes with a borescope. That last method isn't too common for your average atv owner though.

 

I do alot of tuning, thats my advantage against most other guys with ported 350s and mini strokers. Usually I win races on the hill cause I spend hours fine tuning the bike, and they just have their jetting close enough to run well but not awesome. It pisses some guys off that a ported 350 with pro circuit pipes and twin 28mm flatslide mikuni carbs beats their 4mm stroker with cpi's and 35mm pwk's on the strip. The big torque my bike makes gets it out of the hole quick, and it peaks at about 8600 rpm with around 68 hp. So a nice 3rd gear launch puts me in front of them, and can usually hold them off until the end of the strip. I just think its funny. :biggrin: Dont get me wrong though, I have come across a few good running 350's and some arm wrenching 4mm stroker bikes. I have had my ass handed to me by them. :confused:

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So Eric your bike had a lean stumble instead of a rich bog? lifting the needle up and giving it more fuel helped?

 

snop what type of dyno do you use? dyno jet? dyno dynamics? is it a motorcycle one or a automotive one.

 

thanks, mark

 

2 different dynos. Land and Sea crank dyno, and a Rear wheel Dynojet for atv's.

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So Eric your bike had a lean stumble instead of a rich bog? lifting the needle up and giving it more fuel helped?

 

snop what type of dyno do you use? dyno jet? dyno dynamics? is it a motorcycle one or a automotive one.

 

thanks, mark

 

Mark,

 

This is something else that I find very confusing. Explain the difference, please. Can sound files be posted on this website? Maybe someone could record a sound bite of the difference for a reference. Video would be even better but I am sure we would hit a size limit.

 

Eric

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Mark,

 

This is something else that I find very confusing. Explain the difference, please. Can sound files be posted on this website? Maybe someone could record a sound bite of the difference for a reference. Video would be even better but I am sure we would hit a size limit.

 

Eric

 

It would be damn near impossible to do that, most of the time you got to be riding it, and it can easily be undetected by people watching and not riding the bike.

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It would be damn near impossible to do that, most of the time you got to be riding it, and it can easily be undetected by people watching and not riding the bike.

 

That is another hard one to explain verbally. I may try going way up and down on my jets to see if I can figure out the difference. The bike is actually running better than it ever has. I am extremely close but I want to figure this stuff out for myself so I know. It pulls hard from bottom to top with a slight hesitation in the middle but most people wouldn't notice it. It is screaming. I really appreciate the help. I noticed on your profile that you are into Wakeboarding also. If you ever get to Missouri in the summer time look me up and I'll let you ride my Air Chair. It rates right up there with wringing a Banshee out.

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a lean stumble is when the bike will surge and "hunt" under throttle because its not getting enough fuel, kinda like when you go for a ride down the road with your fuel off!

 

a rich bog is when it bogs out and dies (it wont usually die altogether) because of too much fuel. it wont be as intermittent as a lean condition and will sound different too.

 

a good way to tell is to ride along in say 3rd gear, and ride with the throttle in the position that it is bogging or stumbling in, eg 1/2 throttle etc. ride along with the engine like that consistently and then reach down and pull your choke on. if it gets better, its lean, and if it kills the engine or gets worse, its rich.

 

snop, dynojets are inertia dynos yes? when you say 68hp did you achieve that on the land and sea crank dyno? how much are they to purchase?

 

thanks, mark

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The dynojet is an inertia. I had the 68hp on the land and sea crank dyno. Thats the only dyno I trust engine numbers on. I usually use the other dyno to check run times, and break in motors while in the bike. Its alot easier to setup than the crank dyno. I dont know how much the crank dyno is, a friend of mine owns it and has had it for awhile.

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Wakeboarding? Where did it say that on my profile?

 

I haven't wakeboarded in about 8 years. I wont get on the air chair again either.

 

I was trying to figure who knew what they were talking about on here so I looked up your and other member's profiles and I think there was a Face Book link or something. Sorry for digging too deep, I just wanted to make sure who to listen too. If your not careful on here you will get a reply from someone who knows less than myself.

 

Ended up with

 

200 main

EEJ Bottom Clip

 

Bike runs great and plugs show good color. I think I finally got it.

 

Thanks.

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