Not Firing after rebuild on top end

[Redoingit]

Big question. I'm stuck, Read all i can and still cant figure it out. Watched videos you name it.
Problem. I just got my top end bored out 20 over to 66.5 crank and rod were good no cracks or damage to it. nice and tight. New gaskets. reassembled took my time with it made sure to oil and lube everything as i was assembling it.
Reeds are good, new Boysen carbon fibers. Carb redone with 250 main to go with my fatty gold series with powercore 2 as recommended. Spark is fat and dark blue.

Took it out to fire it up for the first time. kicked til i was tired and nothing. puff that was it. I have read somewhere god only knows were that it can be hard to start and to drag it. Tried that and puff puff bang and nothing after that. pulled the plug it's wet and black. adjusted the carb slightly. no more wet but still no firing. let it sit for a bit

Came back to it kicked it a few times and big backfires and slight starting potential, like waaammmmp.

I was thinking when i put it back together it wasnt at TDC. Is that the issue? Any help would be really really appreciated. Also is there a gapping at the top of the cylinder that it should be at?

 

[Wifesblaster]

Well first and foremost don't run it with that 250 main in there. Fmf web page recommends a 260 with premix and lid off. We found that 270 works for us at sea level. Put a 280 in and plug chop if (after leak test.)

On to no spark. Tors removed? What year is the blasty? Parking brake disconnected? Woodruff key in place? Key (is it bypasses or still there?)

 

[89blaster89]

i thought they recomend 260 with lid on?

 

[Redoingit]

2003 Tors removed, parking break removed. Still using injector pump, lid still on the airbox. I typically ride in the 750-1000 ft above sea level. the woodruff key is the one under the flywheel right?

 

[Wifesblaster]

i thought they recomend 260 with lid on?

260 main with 32:1, lid removed, 50% race fuel.


Well you might be ok with the 250 with the lid on. Your cutting it close though. I would still plug chop it with a 280. Yes the woodruff key is under the flywheel on the crank. Have you inspected reeds? Air screw 1.5 turns out? 32.5 pilot? Clean grounds? New plug? Key bypassed?

 

[Wifesblaster]

Rider Support - Jetting Center - FMF Racing

Look where it says comments.

 

[Redoingit]

Going to take it apart again on Wednesday. See what else i can do to it. I will be walking though step by step with manual again and Ken's video's
I'll take pics and videos and post soon as i get to it

 

[Blaaster]

We developed these specs with a 32:1 fuel to oil mixing ratio of a 50/50 mix of race fuel and super unleaded, 0 - 1500 ft altitude at 70 degrees outside temperature.

Main Jet 260

Comments
Remove airbox lid snorkel

Note it says snorkel removed not air box lid.

Taking off the lid can mean 2 sizes larger jet.

The best way to find out is to plug chop.

 

[Blaner]

I would put my money one two things: One, the reeds are not sealing, two, your stator plate is upside down causing your timing to be 180* off? Wild assumption, but just check it, you want the wires coming out the top. I would also suggest you check your woodruff key behind the flywheel.

You have spark, so thats good. Its obviously not a bad earth or anything like that. I think the spark is not coming at the right time.

 

[Blaner]

PS, for the record, a 250 main with the lid on and an FMF is fine. If you are not ported and do not have any other mods, you should be ok, but once its running, I would still suggest a plug chop. This however is not your primary concern. The bike will and should still be starting.

 

[Redoingit]

got to thinking before i disassemble this thing i am going to do a leak down test. Good idea?

 

[Redoingit]

Also going to do a quick compression test between the 2 it should throw out the red flags if any

 

[jus_me]

Back fire , wet plug, good spark, ...my money is on timing. That's if compression checks out and no critter nest in exhaust or air box. Check and see if your woodruf key is still there, and if it is, make sure your stator plate is on correctly. Many many times we take things apart thinking we will remember the little things like this points up by the whojawhatsit, that goes here, that's sits kind of sideways but not really,, "but I'll remember all of this little stuff,,,,im focused on my piston!!!"...

 

[Blaner]

its never a bad idea to do a leak test and comp test. Do it. But I think your problem is with timing.

 

[Blaaster]

If the Woodruff key is not sheared, the crankcase could now be flooded.

Sometimes after a rebuild, excess assembly oil can hinder starting.

Drain the carb, remove the plug, hold the throttle WOT and kick, or drag the bike a little way in gear.

 

[Redoingit]

ok so i built a leakdown tester. i got 2 psi in it and hear a big pop. Not sure what i did to it but it didnt sound good. I'm hoping the pop was a good thing lol. I think it was the gasket i made to cover the exhaust hole. What is everyone using to plug the hole? i cut up a tube. is there something else better?

 

[jus_me]

Go to auto store and get a freeze out plug.. its a rubber plug that when you tighten it expands.. perfect for leak testing.. the pop you are talking about are you sure it wasn't the fitting going into the carb mine pops out sometimes..