Those temps and speeds shouldn't cause huge problems. As for your left foot running warm, well...get used to that. That's where the engine cooling air is exiting, I spend the whole Vintage Challenge with a sweating left foot!
I have had too much experience with sleds that run fine once they cool off. I want to say it just loaded up and died, but I know you want to be cautious, and you said the plugs looked a bit lean, and that doesn't support being too rich. Check it out.
'09 Vintage Challenge Survivor, and I wasn't late for supper!
'10, '11, '12, '13,'14,'15,'16,'17, '18, 19, 20, 21, 22 Vintage Challenge Survivor !
72 400 restored, Father bought new in '71
73 X8 restored
'74 340 green machine
'74 X8 9 time VC finisher
'78 Spitfire in progress
2 '75 340S 1 running, one on deck
'78 LF 440 future CC clone
'73 Skiroule RTX 440, 500 mi.
That makes sense... both the air moving from right to left, as the fan tower is on the right side. And the air exit point is right above the left foot on the cowling.
I will get to it this weekend with the compression tester, and see what it looks like through the ports. Report will follow. Thanks.
At the very least, right now you are getting to know the sled. It takes time to get a feel for carb tuning and such. Sound, smell, and performance all come into play. The more you ride it the more comfortable you will get.
'09 Vintage Challenge Survivor, and I wasn't late for supper!
'10, '11, '12, '13,'14,'15,'16,'17, '18, 19, 20, 21, 22 Vintage Challenge Survivor !
72 400 restored, Father bought new in '71
73 X8 restored
'74 340 green machine
'74 X8 9 time VC finisher
'78 Spitfire in progress
2 '75 340S 1 running, one on deck
'78 LF 440 future CC clone
'73 Skiroule RTX 440, 500 mi.
Ok, Here's the newest report. The following pictures are of number 1 and number 2 plugs. Top picture is #1, bottom is #2. As I stated earlier number 2 looks worse. See what you think.
Attachments
Last edited by jep_800 on Sat Jan 30, 2016 9:43 am, edited 1 time in total.
And, here is the results of the compression test. No real guess here... First picture is Number 1, and looks like about 132 lbs pressure. Number 2 is junk, and reading about 45 lbs.
We can't really see the tips of the insulators of the plugs, but what I see doesn't look extreme. But...the compression test does indeed tell the tale!
Bummer.
'09 Vintage Challenge Survivor, and I wasn't late for supper!
'10, '11, '12, '13,'14,'15,'16,'17, '18, 19, 20, 21, 22 Vintage Challenge Survivor !
72 400 restored, Father bought new in '71
73 X8 restored
'74 340 green machine
'74 X8 9 time VC finisher
'78 Spitfire in progress
2 '75 340S 1 running, one on deck
'78 LF 440 future CC clone
'73 Skiroule RTX 440, 500 mi.
I am planning on doing a top end to it with new pistons, rings, and gaskets. It should be evident what the total damage was once the cylinders come off. The only thing I'm a bit nervous of, is did number 2 have a minor air leak which caused a lean condition. All seals and gaskets were done in 2014, since that's when the major restoration/rebuild took place. So theoretically, crank seals should not need replacing.
I can tell you that, I see why guys opt for the Cyclones & Liquifires since the engine is up front. Taking apart all that's in the way of the mid-mount engine is a chore. But, if you like the mid mounts (like I do), it is worth the effort to do it right. They always seem to gather some attention when you pull it off the trailer.
You are going to have to do some investigation as to what caused this? The plug pictures are hard to tell exactly what is going on, but to me both appear to be gray. So it is a too lean condition or pre-ignition? I would start by looking at your carb settings. I think I remember reading somewhere in the manual where the high speed screw should be set to at least 1 full turn out. Any less on the 800 and JDX8 will cause a lean condition. You need to verify your carb adjustment settings with the manual. Need to check the carb mounting flange for cracks or air leaks. Were the intake gaskets sealed? Are you running the stock plastic air box or a pod filter? Something was causing a lean condition on both cylinders. If the timing is too far advanced it can cause pre-ignition. Running a too hot heat range spark plug can also cause pre-ignition. Once you get the top end rebuilt I would verify my timing. Another thought is fuel. Are running Premium gas? Did it contain Ethanol? You need to find a smoking gun or it will happen again.
Troy
'72 400
'73 400, (2)500's, 600
'74 295/S (restored) 2010 HOF poker run survivor.
'75 800, JDX8,
'75 340/S 2011 & 2012 Vintage Challenge finisher.
'76 (2)400's
'78 Liquifire 340,440
'79 Spitfire
"If it has Tits, Tires, or Tracks it's gonna cost you money!"
I'm leaning toward something with my intake manifold. I know I had new gaskets when I put the carb back on, however, I wonder if I did not do a good enough job trimming my insulation on the tapered panel between the carb flange and the heat shield. If just a piece of that is stuck between the flange and the shield, that would obviously let a little air in. Probably wouldn't take much. I make sure to run 91 Octane, no ethanol, and good quality oil (Klotz) at 40:1. I checked my high speed needle, and it was set to 1 1/4 turns out. Low speed was 1 turn out. Before I started the run, I thought I'd set it at 1 1/2 turns out, but then with the warmer temps, my logic said I'd load up and foul a plug. Never thought I'd run lean, so air is getting in somewhere.
I think once it is dismantled, I will also inspect the reed valves to ensure they look correct, and functioning properly. Other advice?? or does this sound like good starting points to finding my problem? Thanks for the help.
I'd say you're on the right track investigating the intake side. I don't know that bad reed valves would cause this. They act as a check valve to seal the on deck charge in the crank and intake ports so the pressure can't force it back out the intake and into the carb. Usually popping back though the carb and poor performance are indicators of bad reed valves. They either don't seal off or break a petal off. Now possibly the reed base gaskets? I would be looking at the sealing surfaces between the intake and carb. There is the black heat insulator that goes between the carb and intake. Over tightening the carb mounting nuts could possibly cause those mating surfaces to bow in the center and leak air. Once running, you could spray starting fluid around that mounting flange. If the engine speeds up its sucking air there.
Troy
'72 400
'73 400, (2)500's, 600
'74 295/S (restored) 2010 HOF poker run survivor.
'75 800, JDX8,
'75 340/S 2011 & 2012 Vintage Challenge finisher.
'76 (2)400's
'78 Liquifire 340,440
'79 Spitfire
"If it has Tits, Tires, or Tracks it's gonna cost you money!"
That's where the engine cooling air is exiting, I spend the whole Vintage Challenge with a sweating left foot! 
