Started sputtering

[pittss1c]

I have only a few rides since a series of enginge mods.

near the end of the day on my second serious ride, when I gave it power to go up a hill, it sputtered and crackeled. Next ride I experienced the same problem intermittantly.

 

When this condition occurs, if I pull in the clutch and peak the RPM, the problem goes away and it goes back to performing great, but will persist if I don't do something other than give it more throttle.

 

Background: I think I have the mains kinda rich, but it seemed to perform pretty well, so I figured I would leave it. Most of my riding is done under half throttle, so I am not sure if the main jet could be the problem anyway. Needles are in the middle clip and the machine performs great 80% of the time. (even decent low end torque on trails)

I thought maybe I was fouling plugs... They are pretty dark when I pull them, but I am not sure that means much. I don't have enough data to be precise (but do not want to burn my engine up collecting data)

[okbeast]

Can you elaborate some on the sputtering and crackling it's doin, that's kind of a broad area

[pittss1c]

I am not sure how to describe it. Normally when I give it throttle, it quickly and smoothly accellerates to the power band, where I hold on the best I can and try not to poop.

When this condition occurs, the engine doesn't sound like it is firing all the time on both cylinders or missing some strokes, and does not ever reach the power band.

If I pull the clutch in to bring the RPM up, it clears up and everything is back to normal.

I have not yet seen the problem come back yet unless I slow down and drive slow/idle or go into the trails.

[ASRBanshee]

Whats your intake mods, pipes and main jets in there now?

[pittss1c]

Hot Rods 4mil stroker 5mil long rod crank with Hot Rods pistons, noss cool head w/21cc stroker domes, cylinders have a mild port job. V Force 2 reeds, 28mm PWK carbs, DG pipes, dual carb mounted air filters with outerwears.

THe mains are 172, and I believe the pilots are 55 (I haven't verified this) and the clip is in the middle.

[okbeast]

What do your plugs look like after a ride? What about after it sits and sputters?

[pittss1c]

My plugs are pretty black after a ride...

It might not be easy to get it into the sputtering state and pulling the plugs (it is rather intermittant...)

[okbeast]

When you say it's intermittant it makes me think it might be electrical but you said pulling in the clutch and revving cleans it up good.

[pittss1c]

yep, then it seems like it runs fine for a while after that... it seems like a plug fouling maybe.

My plug chops were done while it was colder out, I will probably do new ones.

But I am concerned that is not a main jet issue. It seems to happen as a result of low power operation...

[riderofthestorm]

you gotta keep those cob-webs blown out! sounds like plugs to me, if i just putt around on mine it does it too, gotta open her up once in a while man, just my opinion tho, good luck!

[pittss1c]

Is that true? Everyone has this problem?

It seems there aught to be a jetting change that could prevent this if it is plug fouling.

[okbeast]

Not true, if you have everything running right and jetted correctly it will not have to be 'cleaned' up every time you put around and want to accelerate.

[pittss1c]

Since this seems to happen as a result of low power operation, should I assume that it is a pilot jet/needle issue, or can the main jets being too big effect the behavior at minimal throttle operation?

[okbeast]

Well if the mains are way too big then yes it could have some affect b/c that is what the needle is going into.

[pittss1c]

Well, I readjusted the air screws (they were barely 1/2 turn out) and that improved my idle and helped the sputtering problem. Except when I splashed through a mud puddle, it ran strong all day.

Adverse effects... harder to start: I actually need to start with choke, and leave it on for a minute or 2 when cold)

Maybe coincidence, but I started seeing overheating in the woods now. (damn 4 stroke friends like woods and mud too much)

My trailtech actually says it peaked at 265! it seemed to climb to 230 easily when slow in the woods.

I backed down from 2.5 turns down to 2.0 turns and didnt seem much difference in idle, but didn't help overheating much.

No problems in the hills or dunes though.