85 250R carb issue & possible engine sound

[Drama]

OK,

Finished my top end rebuild on Friday. Upgrades: Fresh bore, Wiseco 66.5 piston, mx woods porting, 38mm PWK.

Engine Stuff

So I warmed it up for about 10 minutes at very rpm's, tightened some bolts, and then let it cool down. I did that 3 times. Let it sit all day Saturday (was out of town) and then today I started it up again and let it warm up for about 10 minutes at low rpm's before I took it for a light ride. The engine sounds fine at this point by the way.

Then when I'm riding it, I start hearing this sort of crackle. I can't be sure, but it seems to be coming from the engine. I realize it makes the most sense that it would be coming from the piston, but I honestly cannot be 100% certain that it is. It happens around half throttle. But also, when the bike is parked I don't seem to hear it.

I'm not sure if I'm hearing things, or what. This is the first time I have a wiseco, and I've heard they are noisier than the cast honda pistons. (I had a cast honda piston in it before). Plus I'm so paranoid that I did something wrong cuz this is my first top end rebuild, I think I'm looking for something to be wrong. The engine feels wonderful when I'm riding it though.

What do you guys think?


Carb stuff

The bike will idle but I think it's running lean during it. Right now, the air screw is completely closed and if I put the choke on, the engine picks up RPM's. So it seems to me that I need a bigger slow jet? Is that right? The slow jet in it right now is a 45 or a 48, I can't remember at the moment. Right now the idle screw is 4 1/2 turns out. The carb I have on it is a stock CR 250 carb which is a 38MM PWK.


Also, could the crakle/tick/odd sound that may or may not exist, possibly be a jetting issue? Is it the sound of the engine missing? I have a 175 main in right now. Prior to this rebuild/porting, I had a 145 in it. The jet needle is in the 3rd position.

[3 or die]

It sounds like you havent done jetting before. You have money and time invested in that build. I recomend finding somone who can jet that carb properly and you watch for your next build. Always start to rich and work your way down. Remember you wont hurt it running to fatt, but lean will kill it......good luck

[Drama]

I know lean will kill it. I put in the largest slow jet I thought I could possibly need, and have a few other smaller ones. I plan on getting larger slow jets tomorrow, and go from there.

I have jetted my bike before, but this is a fresh bored/ported engine with a new carburetor. I didn't know where to start, so I decided to start big. I just don't think I started big enough. I thought a 48 (I went and looked a few minutes ago) in the slow and a 175 in the main was big enough. The thing does idle, but it seems odd to me that the air screw needs to be all the way in. From what I do know about jetting, that seems that I have too much air/not enough fuel. So I thought I should get a bigger slow jet.

Is that reasoning correct, or not? That's what I'm asking.

[jenndnn3]

No air leaks?

Double check that..

[MagicJames]

I have the same problem with my 38 pwk, when i pull the choke up it idles HIGH. Really high. I just turn the choke off after i get it started. Maybe not the right thing to do.
As far as the piston noise goes, I've had the same noise, ticking while mid throttle, with my R and it has been doing it for almost a year now, and still no blown piston/cylinder.

[Dammit!]

Could be detonation maybe? Impossible to say without hearing it but something to keep in mind.

[Drama]

I thought about detonation possibly. I'm running 93 octane in it. It's the highest pump octane I can find around here. I do have a CR head gasket on it which increases the compression, and I did port it. The guy who did the porting/boring for me said pump gas would be fine for the engine. I'm gonna buy a gallon or two of 100 octane today and see what happens.

The local bike shop doesn't open until 1pm (eastern time), so I'm gonna go up there later and buy some more slow jets, and then double check for air leaks. I'd sooner have a bigger slow jet in than necessary than run the engine more with one that is too small.

I'll check back in here later today.

[Drama]

Ok,

Well I have good news and bad news.

Good News

My bike seems to be running well by replacing the slow jet with a 52 (was a 48 before), but...

Bad News

I think my engine noise went away due to race gas. Which is sort of good, but do I really want to spend $7 a gallon on gas? The one atv shop wanted $12 a gallon. What is that crap???

We'll see.