4 mill bogging at full throttle , tried every kind of jetting .Need help!

[bluebanshee2]

Recently installed a 4 mil hotrod crank with spacer plate and wisco pistons . Had a dune port prior to 4 mill , also have T-5 pipes, new spark plug wire and caps, and new stator. Bike gets on the power band for about two minutes then loses power. I've tried every kind of main jet ,pilot jet, needle clip, and air screw and get same results. Can't figure out the problem 

[hoppedupandcutdown]

Might try cleaning the screen on your petcock. And check the vent on your gas cap.

[sleeper06]

Head gasket spacer or base plate , is it an oem stator , does it sound like an ignition break up or gurgling over

[Larry's Shee]

have you leak tested it? How long does it have to sit before it will go full throtle again?

[RadarRacing]

Coils bad. Imo

[bluebanshee2]

Coils are brand new from Yamaha dealer, stator from racetech electric, I chrcked the gas cap but haven't ckeaned the petcock. I was thinking it might be the porting. When I took it to the local machine shop he said it had more of a drag porting rather then "dune" porting but he said it would run shitty the whole time if that was the case: ill try and get a pic of the porting when I get home

[sleeper06]

It really depends how aggressive your dune port was before your timings could be through the roof

[BUILDER]

Your porting will have nothing to do with the bike running great for a min then falling on its face. Sounds like to me you are running the carb bowls dry. I would check that before you run it too hard and burn up a piston

[bluebanshee2]

It only takes a min or less for the power to come back. I've checked the carb bowls and they are full with gas, even messed with the floats so it would use more gas.We ride in glamis, CA. We went from stock main jets 200 to set us back at zero then 280,300,310,330,340. 300-310 ran perfect with pilot jet at 30, but got the same top speed results. I thought maybe it might be the CDI box but it looks to be in good shape. Ive also thought about changing the petcock to the dual one so both carbs have their own direct hose but they are full with gas when i checked the bowls. maybe bigger reeds? I have stock ones . here's a pic of some of the porting

Edited October 21, 2014 by bluebanshee2

[do-work-son]

Check the fuel cap or if ya have one of the vent hose with the cool little cap it might not be working right. Had a couple stick closed on me before going back to a full hose.

[trickedcarbine]

If you are checking it for fuel it has time to recover by the time you actually work on it. That isn't telling you anything. You need to learn if it's bogging because it's lean ( more of a hiccup ) or if it's rich ( more of a gurgle ). Not just for jetting, but if you are in the ball park for jetting those will indicate a fueling issue or an electrical issue.

 

Was the port work touched for the new stroker and plate? Even if it had high durations, it would be a bit boggy off idle but would rev to the moon easily.

[bluebanshee2]

I went back to the regular gas cap hose as well. Porting was not touched after stroker installed , I was told with the spacer plate the porting would stay the same. The spacer I have goes on the bottom of the cylinders. I'm running a stock head

[trickedcarbine]

Is the piston lower then the exhaust at BDC?

[bluebanshee2]

Yea , here's some pics of the lowest spot the piston drops to 

[trickedcarbine]

Photo is janky. Is it flush with the bottom of the exhaust port at least?