1428 stage 7 jetting

[dodgediesel59]

Well guys I am waiting on carb parts to do a rebuild here. Just curious if anybody has any experience with jetting on a big bore. I am running high comp pistons in a 1428 chain drive but everything else on the top end is stock other than some mild head porting. It will have a marks 4 into 1 and I have a stage 7 kit from Sean ready to put in. Just curious on any pointers or jet size recommendations you guys might have. Thanks for the help,
Robert

 

[PATMAX]

Depends on the elevation of Marshall Wisconsin.

 

[one2dmax]

See if Jim Rogers can help us out on his 1428 setup?

Sean

 

[dodgediesel59]

Elevation around her is between 950 and 1000 above.

 

[Rusty McNeil]

I ended up a few jet (like 175 Mikunis I believe) sizes bigger on the mains and a clip or two position out from what was working with stage 7.
Also went with one size bigger on pilot fuel jet but the way I've hot my needles adjusted at around 2 1/2 turns out don't think it was needed and could have stayed with the 37.5

PAJ 2 I played with but ended up back with the stock 170's

I think my floats were set just slightly higher than what most recommend but don't remember the numbers

Similar build, 1540, 13:1 with mildly self ported heads and .380 cams.

Tried a lot of other stuff but found it wasn't really necessary. Mostly your after feeding it at WOT and a good cruise a/f

My elevation is 25'-50'

 

[dodgediesel59]

Hey guys, Got the monster up and running over the weekend and got to get close to 100 miles on it finally. I put in 165 main jets and the 40 pilots, shimmed the needles to the 4th clip down from the bottom and set the float levels a touch higher than recommended for stock as well as 2.5 turns on the pilot screws. It almost acts like its a bit lean on the top end yet though. When you crack her open for a few and then back off and get back into it, it almost acts like there is a bit of hesitation like I sucked most all the fuel out. Any thoughts on what I should do ?

 

[tugla]

How's the plugs read.....wide open cut.......

 

[Rusty McNeil]

165 Mikunis or 165 dynojets.

If DJ's I would say they are way too small for that motor.

If Mikunis then not as bad but in my opinion still too small.

My 1540 has Mikuni 182.5's in it ( I'm home now and looked in my carb journal) at this point I actually think I could ease back down on the size and run a 177.5 and be good. With these mains and WOT over 7000 rpm its running slightly rich at around 12:1 a/f

Considering how much money you've got in that motor I would consider a WideBand setup so there's no guessing here.

 

[dodgediesel59]

I have a nice wideband sitting around from the turbo setup so maybe I will get that all wired in there. The jets are mikuni jets from sean. The next size I have are 175s. I guess I should get the af gauge in there and tune off that. How much does needle height effect mixture? Also, where would be the best place to put the bung for the af gauge?

 

[dodgediesel59]

Any thoughts guys?

Sent from my SCH-R530U using Tapatalk 2

 

[gamorg02]

Any thoughts guys?

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I have 6 for dyno tuning. 4 equidistance from each exhaust port and 2 after each Y. I have a 4-2 system

 

[dodgediesel59]

I am running a 4 into 1, but for me six sensors might be a bit overboard! So it would probably be best to run mine in the collector or close to the end of it near the muffler?

 

[gamorg02]

I am running a 4 into 1, but for me six sensors might be a bit overboard! So it would probably be best to run mine in the collector or close to the end of it near the muffler?

That would be fine. I did the individual 4 for af screws

 

[Rusty McNeil]

I run one bung in the pipe right after the 2-1 collector on. 4-2 system.
Its not ideal but there is no ideal spot on these exhaust systems that would be aesthetic and street able.

And more than one sensor I think is just overkill unless you have tons if money. High dollar turbo cars often only run a WideBand on only one bank of cylinders.

Kind gotta take it on faith that if two cylinders are running right, and the carbs are all set up the same, then you should be good.

 

[dodgediesel59]

Well This weekend I got all the water leaks fixed up and got the a/f gauge all setup on the bike and took it for a brief ride in the cold gusty winds. At idle I am running about 14.5-15. I put in the bigger pilot jets, so on these carbs does the air fuel screw adjust for idle circuit or all around? Midrange and up was a bit harder to tell, it seemed like the longer the pull was the lower the number I was getting. I would say 10 to 12 was common. I am running 165 mikuni mains and have the needles set up to what the stage 7 kit reccomended. Would dropping the needles a slot or 2 lean up the mixture enough or Do I have to go back to the tedious task of switching the mains?

 

[tugla]

You can lower the needle and it would lean it out in cruise/wide open. What clip setting are u on now. You can also add a shim to be in the middle of a needle clip position if need be.

Air screw is mostly effect the idle. If you are too many turns out,about 4 or more chg
The pilot fuel jet in metering block,stock is 37.5 or something,go up that will help that.

Have to ask Sean or Garrett but they ( motor)do like to run on lean side, but they would know what number best. I've only used plug read not a/f gauge to set up jet on bike,got gauge for my sled.....awesome tool to have

What's your numbers at wide open in forth gear lets say......

How is it starting and idling....if u already went up on pilot jets but also u are running a big beast of a motor. Must pull like a freight train

 

[Rusty McNeil]

Not really sure what the WOT good numbers are according to the gurus but ill venture to say that anything under 12 WOT is rich. I've set mine up as close as I can get to 12.8-13:1 WOT

Too get true "off the needle" and only on mains WOT you gotta really wail on it, I don't think the needles leave the picture until WOT, a decent load, and past around 7500 rpm or so?

Idle and cruise are not too big a deal in my mind, you're not asking much of the engine, load is light, and detonation pre-ignition hazards are low here.
I'm not sure I even believe my WideBand at idle. I thinks it's a flow issue??? I use a DJ WideBand Commander with one sensor looking at two cylinders.
Idling at 17-18 oughtta be just fine as long as its not popping I think. As long as it passes the idle blip test.

Part throttle steady state cruise I shoot for around 14.5-15.0:1

 

[Rusty McNeil]

Just curious, are you running vboost or the eliminators?

I couldn't get mine to idle worth a damn with the vboost open, fought it for a while. Gave up and called Jon Gainey, he said these motors do that and to put the vboost back in. Or get flatslides. Something to do with the cams, compression and whatnot I think?

It solved the problem.

I was kinda disappointed, I was looking forward to that nasty vboost open idle.

It sounded meaner stock with the vboost open than it does now with the vboost operational.

 

[tugla]

Should be able to getting to work with eliminator s installed or vboost wired open....

 

[dodgediesel59]

Yea I have the v boost cable locked open. Idle is very lumpy but no misses and when ya grab the throttle it responds right away. The wide open throttle has been tested extensively :biglaugh: On a good long wide open pull in fourth or fifth it starts around 12.5 and steadly drops to 11 and I might have even seen it dip into the high 10s on ocasion. So do you think the needles will drop enough fuel here or do I need to drop the mains down a size or even 2? cruise is around 12:1 average. My sensor is reading in the pipe that comes across from the 2 left cylinders into the collector so im getting 2 cylinders worth at least.