Runs like choked all the time

[PorP]

0 degrees should be fine. Something is up with your cdi, I recall mine pulling spark through the kick. Would be nice if you could get your hands on a known good one.

Let's start checking things off the list. Did you do a leak down test? Grounds are good? Low resistance between points? Check the spark plug cap and coil.

I was out of town this week until Friday and didn't build the tester yet.

I had a no spark issue for a week that ended up being a bent pin in a plug,  because of that everything electrical has been resistance checked and checked good in accordance with the shop man.

[PorP]

p.s. Jerry,

You described what I'm seeing on both cdi boxes including the oem box which I think is sparking real late, there is a lot of kick back on it.  It's almost as a capacitor (or something) is going bad and not passing the signal right away to the coil. I'm assuming your comments on oem boxes are older boxes that have gone bad? If so,  that's my case.

Any recommendation here for cdi boxes?  I only bought the dyna tech because I couldn't find new oem and it was the more expensive option (I wrongly assumed cost = quality).

[Jerry Hall]

Jerry, 

Ya the engine is a complete rebuild including the crank,  woodruff key is installed. My problem is primarily on the main,  it seems to idle fine. I've read what you said on the dynatech cdi, the oem vdi issue is new to me though.

Ya, venturi is the air flowing from large opening to a small opening and then to a larger than small opening,  it creates the vacuum on the jets.

Fuel jets will have vacuum on then anytime air is passing over the hole that connects the jet to the airflow passageway through the carburetor.  A true venturi is a optimally shaped reducer, placed in the air flow passageway, that is used to raise the velocity where the diameter is at it's minimum.  The increase in velocity at the fuel discharge hole, places more vacuum on the jet than it would have without the venturi.  Air flow through the carburetor is always reduced even with the best designed venturi. 

If you have not removed the flywheel to check for a sheared key I would do it just to eliminate that one possible cause of the timing being severely advanced.  The spark being delayed after the engine is coming to a rest is not uncommon.  The capacitor in the  CDI box was charged on the previous engine revolution, but was slowing down as the piston approaching TDC and the trigger bump on the flywheel is approaching the pickup.  The crankshaft may not have had enough momentum to make  the leading and trailing edge of the trigger bump completely pass by the pickup coil.  The crankshaft rotates enough to pass the leading edge of the trigger bump and then the compression slowly pushes the crankshaft backwards so that the leading edge of the trigger bump passes the pickup again triggering the spark.  The spark is normally triggered when the trailing edge of the trigger bump passes by the pickup. 

If the flywheel key is good, borrow a CDI box off of a good running bike and see if it rums correctly.

[Tbone07]

I'm sure someone on this site can ship you a known working OEM CDI so you can test that.

[PorP]

I'm sure someone on this site can ship you a known working OEM CDI so you can test that.

That would be awesome.... willing to pay all shipping and rent. 

[PorP]

I stripped the cylinder off it today,  no oil in the base.  Just anti freeze (cylinder still had some in it after i drained) and a little gas mix, just enough to smell.

I think the base is sealed good. 

I did have a little gas mix on the gakets to the intake and base gasket.... not sure if that's normal.... i think maybe running this rich?

I found 2 more cylinders for it though while I was rummaging through parts... i found a heavily ported and bored pro works 88 cylinder and a what I think could be an untouched 85 cylinder with original paint,  sleeve,  no porting and the original inspectors mark in the intake. Pretty excited about that later one.

Also found a stache of old race parts i had,  asv levers, quick release tank fittings, sparks full exhausts, lots of other stuff and a complete sparks 485r (450r bored) motor. That motor has one of John Natalie's sparks heads on it from his championship 2005 year.  I forgot I had it and it ended up being too much to race with.

Sorry about all that... got excited I found so many memories.

[2ndmoto]

Nice to find old parts. Sounds like you have a good stash.

You are narrowing down possible issues. Seems like it is pointing towards ignition

[PorP]

Nice to find old parts. Sounds like you have a good stash.

You are narrowing down possible issues. Seems like it is pointing towards ignition

I think so,  I just popped the flywheel like Jerry said to make sure the key wasn't broken or I didn't goon-up when I installed it.  Everything was fine.

CDI is the only thing left that I can think of.

[PorP]

Also,  on another note... and probably wrong section but I already got this one going.

I'm want to replace the piston,  my calipers are telling me 67.75mm ish. Is this a 68mm?


And also,  just noticed my rear shock bumper dry rotted, is there some you recommend for rebuild? I haven't had shocks built/ rebuilt since Laz passed away,  looking for someone as reputable.

[2ndmoto]

Pistons typically go by .010" bore sizes. .010" = 0.25mm. so it is a 67.75mm piston

[2ndmoto]

I have been out of there suspension side of things for a while. Norm had a guy do a rebuild for him recently. I have not heard the race report on it. Check out Derisi Racing. I dealt with Santo many years ago and he was a stand up guy

[PorP]

I have been out of there suspension side of things for a while. Norm had a guy do a rebuild for him recently. I have not heard the race report on it. Check out Derisi Racing. I dealt with Santo many years ago and he was a stand up guy

Right,  I totally forgot about Santo.

And thanks on the piston.  I did a quick search and couldn't find one.  I'll be more dedicated now that I know what I need.

[PorP]

Update,  I cannot find a 67.75mm piston.  Prox and wiesco do not make them.

Is this a "some' year cr piston?

[2ndmoto]

They might have phased out the .010" bore sizes. You can still find rings for the 67.75, but it doesn't look like piston kits are available

[PorP]

They might have phased out the .010" bore sizes. You can still find rings for the 67.75, but it doesn't look like piston kits are available

That piston is garbage. Top ring broke and overlapped in the same ring groove. Also looks like the top of the piston was starting to melt.

Thanks 2ndmoto.i wasted your time,  apologies.  I cleaned the top of the piston and found the part #. It's a 68mm wiesco.

Maybe I should have paid more than $50 for digital calipers?