Jetting

m in sc · December 09, 2020, 07:06:57 AM

sounds electrical. id try a new coil.

pdxjim · December 10, 2020, 12:10:02 AM

Quote from: m in sc on December 09, 2020, 07:06:57 AM
sounds electrical. id try a new coil.

If you were to try a new coil, which one would you try?

There are options from $20 to $120.

85RZwade · December 10, 2020, 12:14:08 AM

I'd try a known good one before buying new; maybe the TDR could help out? Swapnostics, we call it at work.

pdxjim · December 10, 2020, 12:30:22 AM

I'll be replacing the coil and CDI (with an Ignitech or Zeel) eventually, anyway.

Prob not gonna spring for a new coil right away, unless it clearly isn't the jetting.

m in sc · December 10, 2020, 10:06:30 AM

i played this game with the lightweight and pwks until i swapped the ignition. I even swapped carbs, jetted all over the place, etc, for like, a year.

Had a banhsee aftermarket ign in it, then went to an hpi (since i had the larger taper LC crank in the bike) and all of a sudden, no issues. turned out to be the box, i think.

my money is on electrical. any dual lead cdi coil with the right resistance will work.

rodneya · December 10, 2020, 11:51:54 AM

Quote from: m in sc on December 10, 2020, 10:06:30 AM
i played this game with the lightweight and pwks until i swapped the ignition. I even swapped carbs, jetted all over the place, etc, for like, a year.

Had a banhsee aftermarket ign in it, then went to an hpi (since i had the larger taper LC crank in the bike) and all of a sudden, no issues. turned out to be the box, i think.

my money is on electrical. any dual lead cdi coil with the right resistance will work.

Ignition problems with aftermarket banshee ignition stuff is very common. the only stator that actually lasts is OEM and for CDI, OEM, Zeel or Dynayek.
All the other ones will leave you chasing your tail or stranded.

Vape and HPI seem to be doing it right though as their systems work really well.

m in sc · December 10, 2020, 12:08:04 PM

agreed. it would work, but just ran like shit.

I mean, the stock stuff is now 35 years old. minimally. time to upgrade.

rd400canuck · December 10, 2020, 10:10:03 PM

I had a 1980 rd400 that was running like crap around 4000 rpm and the more throttle i gave it the worse it got. I messed around so long with jetting and looking for this that and the next thing. One day i decided to put a timing light on it and i could see the mark perfectly... then i slowly revved it and all a sudden the mark started moving and appearing all over the place and sometimes not at all. Drove me mental... just talking about the effort i put into jetting and looking for air leaks makes me mad all these years later!

Nkreig · December 13, 2020, 08:31:32 PM

Jim, does that bottom end have new seals? I had an issue with my YZ this summer where it would run great until it warmed up then run pig rich. It turned out to be the wet side crank seal. The float stuck while parked in the garage and allowed fuel down into the crank and the seal softened. It would warm up and suck gear oil causing my plugs to look like your picture. Just a thought.

Edit: just saw your build thread and you rebuilt the bottom end. Might be worth taking a look anyway.

pdxjim · January 03, 2021, 08:20:28 PM

Quote from: Nkreig on December 13, 2020, 08:31:32 PM
Jim, does that bottom end have new seals? I had an issue with my YZ this summer where it would run great until it warmed up then run pig rich. It turned out to be the wet side crank seal. The float stuck while parked in the garage and allowed fuel down into the crank and the seal softened. It would warm up and suck gear oil causing my plugs to look like your picture. Just a thought.

Edit: just saw your build thread and you rebuilt the bottom end. Might be worth taking a look anyway.

Seals are all new. Not blowing white smoke at the right side, so pretty sure the wet side isn't leaking.

I didn't pressure test, so I guess a leak at the dry side crank seal, or intake is always a possibility.

Still chasing the jetting

Current setup is 52/1.75 airscrew/N68A#4/165

Today I raided the needles up to #4, and that helped pull away, but felt fat and not so clean thru the midrange as at #3. Not sure what to try next, but might try dropping the needles all the way down to #1 to see what happens. At least that'll tell me if I'm to rich or too lean.

Also have a Dynatek Banshee mini-coil on order. Not sure if they come with resistor or non resistor caps, but I'll get that sorted as well.

m in sc · January 04, 2021, 08:41:29 AM

i also think you'll be chasing it w those needles. you say midrange. you mean 1/4-1/2 throttle or? if its fat at #4 but lean at #3, shim it @4 or try a different needle.

side note, do you have reed spacers in? might be that simple where the frequency is causing reversion at a certain rpm, and they may need to be added or adjusted.

or, drop back down to a 50 pilot set screw at 1.25 or so. the pilot may be artificially carrying the mid range up till the needle at the #4 position starts fueling, but was lacking at #3.

edgefinder · January 05, 2021, 04:55:10 PM

Jim, Out of curiousity how high are the hoods on the needle jets looking in at the cutaway on the slide? Lower, the same or do you have to open the throttle some to see the top of the hood? I got 4 PWK's from yz85's and got 3 different heights so I know they aren't all the same. On a street bike too tall can cause problems

pdxjim · January 05, 2021, 08:42:11 PM

Quote from: edgefinder on January 05, 2021, 04:55:10 PM
Jim, Out of curiousity how high are the hoods on the needle jets looking in at the cutaway on the slide? Lower, the same or do you have to open the throttle some to see the top of the hood? I got 4 PWK's from yz85's and got 3 different heights so I know they aren't all the same. On a street bike too tall can cause problems

Hoods on the needle jets?

Like the shroud that sticks up into the bore?

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Jetting