Why wont this stupid thing start

[edfmaniac]

Check this thread for the tools needed to pull the flywheel if/when you decide you need to. viewtopic.php?f=3&t=6655&p=34655&hilit=flywheel+puller#p34655

[Srinath]

I have pulled and installed the fly wheel earlier, and I verified spark again, I verified timing - the marks on the rotor to the piston to valves closing and opening right. I also checked the clearances on the valves.

Carbs are off the other bike which ran great. So is coil, blackbox etc. I have spark, bright as day, I dont think its electrical.

I may not have suction or compression - due to a motor problem and if so I cant imagine what it may be. I will look into it with a borescope - mind you this bike ran with plenty of power and did not make any un toward noises as it stalled at the exit ramp the last time it ran in 2012 october.

I have got misfire in the exhaust once in a while. Else I cant even get it to fire on starting fluid.
I will look at the carbs again and see if I have suction, I may try testing the vacuum on it if my mechanic friend has the equipment.
Cool.
Srinath.

[basser23]

Got to be no compression...head gasket maybe..tho it would bubble the coolant....hope piston isn't holed...

[Srinath]

Hole in piston would make a lot of metal shrapnel and lots of clanging and banging when run ... it also wont puff enough mixture and pop in the exhaust ...

So - I have a theory ...

What can cause it to stall seconds after startup for months, and when started and revved and finagled to the highway - run with decent power for 5-6 miles but shut down as soon as throttle is shut ...

My theory is that the centrifugal decompressor was stuck/partially sticking in the on position. So I was running it all the while with the exhaust valves cracked open in the middle of the compression cycle. That made it burn.

Can any one refute/confirm this theory.

I will be pulling the headers off and shining a light in the spark plug hole and look for light in the exhaust port with piston @ tdc. Intake too for good measure. And the drain bolt ... would it light up if there was a hole in the piston ? I've stick wood dowels in the thing, no hole has grabbed it ... I need to find my usb cable camera.

Cool.
Srinath.

[Srinath]

The decompressor on this is accessible via the right side top end bolt on the valve cover ?
Cool.
Srinath.

[edfmaniac]

You'll have to pull the valve cover off to get to the decomp system. The only way to bypass it is to pull the weights off of the cam drive gear, but that leaves the decomp cam to either fall out or get pushed out by oil pressure. Modifying it is easy enough though. I have a short thread on it if you want to go that route. viewtopic.php?f=3&t=6620&p=34442&hilit=decomp#p34442

Bill J. used to modify them as one of his services but I haven't seen him around here in a while.

[Srinath]

Ok nothing burnt in the exhaust and the intake either. valves open and close nice and good, I ran out of battery before I cooked up some method of testing the spark ...
Anyway its nicely puffing out the exhaust though the left port seems to be pushing out more than the right (why might that be ?), and its taking in a puff in the intake again to ge really checked via a repeat tomorow due to battery issues.

I need to get spark at the spot where compression stroke is near the top. I suspect it may be retarded. Its misfired in the exhaust, never in the intake. Something I should check with a horrible freight inductive timing light soon.

Cool.
Srinath.

[basser23]

Just a thought...have you read the post..bike wont start ...listed under your post...,but you say you have spark..etc.. check side stand switch? diode issue...? grabbing at straws I am..

[Srinath]

Just a thought...have you read the post..bike wont start ...listed under your post...,but you say you have spark..etc.. check side stand switch? diode issue...? grabbing at straws I am..

I am not sure if those will affect spark. I have spark. I am thinking I may not have compression.
I am going to try draining the oil via drain bolt. Then put in gas in the spark plug hole. See if it runs into the case and out the drain.

Sadly I think It will hold it, have good ring seal and completely shaft me ...

Today I am thinkking I'll go try it, tomorow I'll get the timing light and find out timing is perfect.

Very frustrating ...

Cool.
Srinath.

[Srinath]

OK turned it to TDC, pulled the spark plug out, pulled the drain bolt and put a cup of fuel in the spark plug hole and it ran out like a tap from the drain.'
Its either got a hole in the piston or its worn to not make contact with the cylinder wall.
Anyway I'll pull the thing apart in the next few months and post how it goes.

Cool.
Srinath.

[basser23]

Ok, seems no compression to speak of......

[Srinath]

I still cant imagine how it got from running 70 mph working perfectly fine to dead with no compression with no weird noises, no hail of metal, no hand grenading of any kind ... in just about 5 seconds.
I am getting a borescope today. I will know soon.

Cool.
Srinath.

[Srinath]

And borescope says ... ding ding ding ... nothing, in fact the piston looks nice and clean now that I doused it with gas.

No hole, no obvious marks on top. I may just have stuck rings. I have to pull the thing apart. Can I free the rings by spraying penetrating oil. Looks bloody good other than the obvious fact that it has no squeeze squeezy. OK my bore scope is a POS, everything looks beautiful through it.

Cool.
Srinath.

[Srinath]

So why did this thing eat its rings.
So, It was geting hard and harder to start over the 6 months before it finally died. Even the day it died it stalled and then started back 20 min later.
I need to get to the bottom of this, cos in a few days I am getting the other skorpion I got back into service. I dont want to make the mistake on it too.
This bike on its last ride had sucked the foam sheet through the hole in the mesh and sucked it cross the carb bell mouth. That sheet of foam was 90% intact, not much foam went in the motor I am sure.

The other bike - It has a super trapp pipe, just as this one did, I have a paper filter from a john deere in the original filter frame. I believe I have it jetted right, but I will make sure of that. Stock + 1 is enough for a pipe and the stock filter ?

Thanks.
Srinath.

[samandkimberly]

A little bit of melted plastic might wreak havoc on the rings, effectively gluing them down. You could try finding something that dissolves that foam and pouring it in there, but whatever it is probably won't help seals and the such.

Sam