Jetting time

[Striker1423]

I highly doubt a half size will cause that bad of an issue. One half size up from a good jet might make you foul a plug or two but it's safe. It won't cause an issue usually.

I'd take a step back and a deep breath. Make sure you're cutting the throttle at a good WOT run and cut the threads off to be sure you are seeing the base of the porcelain correctly.

It sucks but unless you stick to a fat main and a burbly inefficient top end you have to be able to see the porcelain correctly. A handful of 3 dollar plugs is a lot cheaper than a mistake in jetting.

[1976RD400C]

Quote: I looked in the mirror and the entire stretch of hwy, and the cars on it, were completely smothered in smoke... looked like the fog had rolled in on them. I wish I had a picture... when I saw what I had done I started laughing. Everyone must have thought there was a car on fire up ahead but no... was just me.

The carb jet wasn't causing that. Something else must be going on. There must of been oil pooled in the crankcase or something with it getting too much oil. Did the smoke clear or keep coming?

[rd400canuck]

nope... it was just rich as hell with the 150's.... i could tell on my way to the hwy that it was smoking more than normal when i would goose the throttle a little on the way to the on ramp and on the hwy it didnt clear up at all as I went tearing up it.

What I am doing is warming the bike up and riding about 5 to 10 mins before pulling over... putting the new plug in right near the hwy on ramp. Then I start it up and go up through the gears and hold it wide open in 6th as long as I can. It usually makes it to 8000 rpm before I hit the kill switch, chop the throttle and pull in the clutch to pull over and have a look at the plug.

Is that long enough at wot to get the plug insulator hot enough to show a ring or coloration at all? I think im getting to about .7 of a mile before having to chop it. The bike is going way too fast at that point and I am sort of forced to let off.

Something is going on... I aint doing something right. Today I will put the 150's back in just to make sure I'm not nuts and it is indeed rich as hell.

[rd400canuck]

ok, 150's back in... checked everything over and went for a ride and hit the hwy... I dont know what the eff I did the other day but the 150's aint smoking now like they did. no clue... maybe the float was stuck and the bowl was over filling and i didnt notice it. I have no clue but now its running fine. Beats me!

So.. i need more new plugs but if I had to guess the 150's are too lean. I'll order some 155's up to 170's. The bike pulls smoothly with them as I twist the throttle to wide open and back at different rpms... I cant really detect any dips in power delivery like I could when the jets were 120 and 130 so it seems this bike really wants a lot more fuel. Im going by the fact that it doesnt seem to pull into a wheelie when i am fuel throttle like it would if I hold it at 3/4 or a bit less. Also, no I'm certain the needle needs to lean out to the stock middle position. The fatter mains are richening up the needle a lot.

I know I keep saying this but... is anyone surprised a stock bike will go from 115's to possible 170's or so?

[SUPERTUNE]

150's mains are way too rich for your stock setup... 130-135 I  would think is would be max.
Chuck

[rd400canuck]

I'm completely confused then.. plug chops were coning out bone white with the 130's and even the 140's.  But another weird thing... I was able to get to nearly 100 mph with the 150's. Would it be able to do that if it were really rich?

I'm getting new plugs today... am gonna plug chop the 150's just to see. I'll wait till this evening though... it's hot and humid here like crazy.

[Czakky]

How long are you on the throttle when doing a plug chop? It's supposed to be between 20-30 seconds... if I remember correct?

I try to short shift a bit, still hairy though.

[rd400canuck]

I hold it for 20 seconds at the most I think. After a good warm up I put in new plug...  I short shift right into 6th asap then hold it wide open till it pretty much almost stops pulling and im near 100mph. Hit the kill switch, close the throttle and pull in the clutch and brake to a stop. If it needs to be longer than that I'll have to come to a near stop then repeat it... I'm just going too fast and the bike is screaming near 8000 rpm. This bike could definitely use a tooth on the front sprocket if you ask me.

I have 8 new plugs... gonna plug chop the 150's this aft and see what comes out.

[rd400canuck]

Plug chopped both sides with the 150's. No rings at bottom of insulators and electrodes are white. The first two pics are the right side.

I guess.... just keep going up sizes and see what happens or could there be something else causing this?

[Jspooner]

I don't know if this is good advice or not but I jet my bikes for the type of riding I do most, which is back and forth to work and the occasional rip thru the gears on a back road and I run the same jetting all the time, I don't change it based on weather or temp or whatever. I don't worry about if it's going to last at WFO in 6th gear for XX minutes or seconds or whatever because that's NOT normal riding. Unless you plan on using it to outrun the cops everyday or its going to be a track bike or something like that just get it so it runs good where you are comfortable riding it 90% of the time. My trip to work includes about 5 miles of freeway and I usually will ride about 80mph or so on that stretch maybe occasionally taking it up to 100 or so where I know it's safe to. I haven't had a problem yet. Don't get me wrong, I do go out and do a plug check after doing a top ender but I don't place all of my time and effort on that..................I would if I was jetting a race bike tho.   

[rd400canuck]

Hey JSspooner... is true.. I could get by with the seemingly way too lean 130's I had in it for the longest time since I rarely went past 1/2 throttle and even more rarely past 3/4.. spend most of my time at 1/4 or less where the bike runs like a champ. But... I want all the power this thing has to offer even if I dont use it all the time. If i open it to 100% then I want it to make 100% power that it can make. Right now its way too lean and dangerous 

[Jspooner]

Are you sure everything else is correct, timing, no air leaks, etc.? Like Chuck said, 150 should be way too rich on a stock bike.

[1976RD400C]

Me too about the timing. Are you sure that isn't advanced too much? Here's a pic of the ring.

[m in sc]

are you sure the uni filter is sealing all the way around?

[murphywv]

Just an idea...What % of ethanol is in your gas? If it is way up there it may explain the big jetting.