Why does everyone hate 4-stroke bikes?

[noah9988]

Yup, just had to say something. The last couple times I ran it before the rebuilding of the crank and rod, it acted very strange. Everything seemed fine when I rode it for the first minute. It has plenty of power, doesn't miss or stutter or bog down. When I cruise it down a road I use here for testing it starts to act up. At the end of the road, it stalled and was smoking out of the valve cover. I started back up after several pulls and drove it back. This is when it started missing, bogging, wayyy down on power. It stalled again at the start of the road and same thing, smoke out of the valve cover. I started it after several more pulls and limped it home. In my garage I lifted up the back tire and it wouldn't rev out even without a load on the engine.

I don't have the crankcase vented, just whatever it comes with from the factory for venting. Could this be the issue? Could it be overheating? Bad cylinder? Rings? Valve train?

And yes, this is why I don't like 4 strokes and regret touching one.

 

[Chainlube]

Check your valve lash, this sounds like a cold setting that once it warms up is too tight. Start it up and get it warm in the drive, then pop off the valve cover and see if you can wiggle the rockers any or if they are super tight.

 

[DieselTech]

Yup, just had to say something. The last couple times I ran it before the rebuilding of the crank and rod, it acted very strange. Everything seemed fine when I rode it for the first minute. It has plenty of power, doesn't miss or stutter or bog down. When I cruise it down a road I use here for testing it starts to act up. At the end of the road, it stalled and was smoking out of the valve cover. I started back up after several pulls and drove it back. This is when it started missing, bogging, wayyy down on power. It stalled again at the start of the road and same thing, smoke out of the valve cover. I started it after several more pulls and limped it home. In my garage I lifted up the back tire and it wouldn't rev out even without a load on the engine.

I don't have the crankcase vented, just whatever it comes with from the factory for venting. Could this be the issue? Could it be overheating? Bad cylinder? Rings? Valve train?

And yes, this is why I don't like 4 strokes and regret touching one.

So did it start running worse after these repairs? I'd be looking at valve lash settings or cam timing. It could have a air leak also. The other thing to check, would be to make sure pushrods are straight.

 

[noah9988]

So did it start running worse after these repairs? I'd be looking at valve lash settings or cam timing. It could have a air leak also. The other thing to check, would be to make sure pushrods are straight.

Well, I have some more answers. It was running the same before the rebuild and after. But that's not entirely true, because when I started it for the first time I actually did rev it up (without a clutch on it) up to 7500 rpm by blipping the throttle. Now here's the thing: the reason I had to rebuild it was because the rod bolts came loose. Imagine my surprise when I put a wrench on the rod bots again and finding them loose. It did cause damage to the brand new crank and rod but I don't care, it's not too bad and if it blows up then whatever.

Now the torque spec is 10 ft lbs but after they came loose I torqued them to 12 with oil. This time I'm going to use some sort of threadlocker.

 

[DieselTech]

Well, I have some more answers. It was running the same before the rebuild and after. But that's not entirely true, because when I started it for the first time I actually did rev it up (without a clutch on it) up to 7500 rpm by blipping the throttle. Now here's the thing: the reason I had to rebuild it was because the rod bolts came loose. Imagine my surprise when I put a wrench on the rod bots again and finding them loose. It did cause damage to the brand new crank and rod but I don't care, it's not too bad and if it blows up then whatever.

Now the torque spec is 10 ft lbs but after they came loose I torqued them to 12 with oil. This time I'm going to use some sort of threadlocker.

You should replace the rod bolts, its what's referred to as rod bolt stretch, & could be the reason why the rod bolts are loose.

 

[noah9988]

You should replace the rod bolts, its what's referred to as rod bolt stretch, & could be the reason why the rod bolts are loose.

They were replaced with the rod during the rebuild.