Won't start and has black fuel in exhaust pipe...

[dinkyguitar]

So I lowered the bike a little over an in.

This time without the stand, no choke, piston at TDC, kick starter up high, kicked it and started again on the first kick  .

Forgot to mention I had a new spark plug when I got it started the 1st and 2nd time. It had the old one when I couldn't start it.

Idled for about 3-4 minutes...took a compression test after about 25 kicks and still came up 140 psi.

The dirt bike shop honed the cylinder and it looked pretty....now I could see marks up and down the cylinder when I look inside. Not scratches I can feel, but those marks are not even...just streaks.

After honing:



This is before honing....but it looks like this now:





Should I have bored it out to make sure the cylinder was perfectly round throughout the whole barrel?

And I'll try that leak down too....

dinky,

[sandblaster]

Hey Dinky.
I know you spent some dough on that piston but I would bore it to the next size up which would mean getting a new piston.
140 psi after several kicks isn't the greatest.
On the flip side, more displacement means more go power 

[Foxx4Beaver]

140 psi after several kicks isn't the greatest.

+1...that's a bit weak....or weaker than I'd want to see it if it were mine.

[dinkyguitar]

Hey Dinky.
I know you spent some dough on that piston but I would bore it to the next size up which would mean getting a new piston.
140 psi after several kicks isn't the greatest.
On the flip side, more displacement means more go power 

I was thinking the same thing when I was rebuilding it, but decided to get it honed based on what the guy at the shop said....

If I get it bored, does it have to be plated or anything?

This site, http://www.rpjperformance.com/ could bore, hone and chamfer the ports for $45 per hole.

Is this about right?

dinky,

[sandblaster]

Since you have a sleeved cylinder you do not need to get it plated.
45 bucks is about what some of the local shops want.
What kind of piston are you going to buy?
Regardless of what you get you want to be sure that the company that is going to bore it has the specs from that piston manufacture.
Then, before you install everything you want to measure the ring end gap and the cylinder to piston clearance.
Make sure it's in spec BEFORE you put it together.
Also, check to see if you need to drill any oiling holes in the piston.

[dinkyguitar]

Since you have a sleeved cylinder you do not need to get it plated.
45 bucks is about what some of the local shops want.
What kind of piston are you going to buy?
Regardless of what you get you want to be sure that the company that is going to bore it has the specs from that piston manufacture.
Then, before you install everything you want to measure the ring end gap and the cylinder to piston clearance.
Make sure it's in spec BEFORE you put it together.
Also, check to see if you need to drill any oiling holes in the piston.

The piston that was originally in the bike was a wiesco std bore. So I got the same for the rebuilt.

That shop I noted will take your "supplied" piston and measure it, then bore the hole to match. I would probably include the rings too for them to check the fit...I should be good after all this....

Might not happen till next year though...

Also, I never heard of drilling any oiling holes....at least the instruction I had with the wiesco piston didn't say I needed any.

dinky,

[sandblaster]

I don't see that you have an exhaust bridge so you should be ok without the holes.
However, if your piston does not have any oil holes in the wrist pin area I would seriously consider adding some like this.
Note the holes on the left but none on the right:

[dinkyguitar]

I don't see that you have an exhaust bridge so you should be ok without the holes.
However, if your piston does not have any oil holes in the wrist pin area I would seriously consider adding some like this.
Note the holes on the left but none on the right:

I'll check my original wiseco piston...I'm curious now.

Don't you have to chamfer the hole where the wrist pin is, to avoid any sharp edges?

Is it like a DIY thing? And how large of a hole?

dinky,

[Foxx4Beaver]

Don't you have to chamfer the hole where the wrist pin is, to avoid any sharp edges?

Is it like a DIY thing? And how large of a hole?

dinky,

it's ALWAYS a good idea to thoroughly check any part that's going into your motor for burrs and abnormal edges...yes, it is a DIY thing.

1/8" would be suffice.

[motopunk]

OK so something magical just happened....maybe divine intervention...

I put the bike up on the stand (something I never do when I try to start it) climbed up on the bike, gas on, choke on, felt the kick starter and put the piston at TDC raised the kick starter....kicked it solid and she started right up   1st kick (double   )

She has NEVER started 1st kick....

Moved the bike off the stand and out the garage since the fumes were killing me.

Let her run about 10 minutes or so...blurping the throttle (neighbors must have loved me at 8pm).

Messed with the idle and air screw and got a smooth idle. Not sure if a dirt bike should have a lumpy or smooth idle.

Yeah, the idle went up and down a few times...but hey it started....

Not sure what to do now  . Maybe I wasn't kicking it hard enough trying to start it??

I usually find TDC on the kick starter and kick from there...the lever is 1/2 way down at that point.

Usually when I find TDC and bring the lever up, I can kick it but 1/2 down the lever stops on me like I don't have enough power in my leg to follow through...

I'm scratching my head and wondering if it was my wimpy kicking that prevented it from starting.

dinky,

the describe of your starting sounds a little bit like to much compression now after the rebuild...  you can try a second base-gasket to see if it would be better...   
but its nice to hear, that the bike was running now... ;O)

[Candyman]

I like to use 500 grit sand paper and just lightly clean up any sharp edges.
its not that the piston will scratch the cylinder wall but it can act like a wiper and wipe the oil off your cylinder.
the key it to LIGHTLY smooth the edges.
kinda like what Foxy was talking about.

[dinkyguitar]

Sandblaster,

The original piston has those holes....and although I don't remember them on the new piston, it's the same make and model, so I would "assume" the holes are there too.


motopunk,

I wish my problem was too much compression. I've measured it with the engine clod and after running it, and both times it was a sad 140psi  

Thanks for your help!!! I probably wouldn't have tries those bigger jets. The true test will be if it starts again. But since I really don't have a place to ride, I don't want to keep idling the bike all the time.

dinky,

[sandblaster]

Don't assume.... Wiseco has really cut back on their machine steps to save all they can on production.

[dinkyguitar]

Since you have a sleeved cylinder you do not need to get it plated.
45 bucks is about what some of the local shops want.
What kind of piston are you going to buy?
Regardless of what you get you want to be sure that the company that is going to bore it has the specs from that piston manufacture.
Then, before you install everything you want to measure the ring end gap and the cylinder to piston clearance.
Make sure it's in spec BEFORE you put it together.
Also, check to see if you need to drill any oiling holes in the piston.

Just for ha-ha's I called a shop to see how much it would be to bore out the cylinder and he said ballpark about $700.

He said after boring you would need to:

Port the cylinder to match all the ports since it's a bigger bore now
Do something with the power valves, I guess port or match them
New piston, gasket, clean power vales

Is all this really necessary?

They did however say to get a quality pressure gauge as my new harbor freight might not be accurate...could an inexpensive gauge be 30psi off?

dinky,

[motopunk]

dinky put your bike on a trailer and take it to a place, where you can test it and ride it with the jetting , that i spoke off and maybe you need a little bit practice how to kickstart the 250 in the right way...