Post by niz76 on Feb 27, 2015 14:41:24 GMT -5
Ya fellas when I grenade 'em I do it good! lol. Quite honestly the plug doesn't look lean-
but I've had the same plug in for a while now- before I installed this 24mm carb even. I haven't even gotten the MJ tuned close enough to start doing plug chops yet but I'm thinking that even this biggest MJ I have at the moment (150) is still lean because like I mention when my pilot jet fell out (I wasn't surprised because I installed it on-the-fly with a screwdriver that was too large and I kinda suspected I didn't get it snugly screwed in) the fuel was flowing unrestricted through tha passage and my scoot had great WOT power and temps were staying just above 300. That's when I realized I needed to go way up in jetting. I had a 90 MJ in when that happened. I'm running stupid high compression (like 190+) with a tight squish at .6mm. No advance at all and stock CDI!
I thought maybe the rod stretched and smashed the piston against the head and spark plug but the plug isn't smashed at all. Still gapped correctly haha. Of course now I'm back to using that modified 50cc squish head I was using back in the beginning of the 90cc install. Basically a combo of running too lean- running the wrong head that I'm sure isn't enough cc's- my scoot would never rev over 7200 RPM's before with the stock carb and exhaust though- now I'm hitting 9k which is the most I've seen from this engine. Normally I'd back off way before 400 degrees but I got caught up in the moment as I was about to break 60mph which I've never done before. Funny thing is during all this tuning I've never heard any signs of detonation. Except for the huge hole in it, the underside of the piston looks pretty healthy- no "death ash".
Oh yes- another huge contributer I was going to mention is my home-made exhaust. I'm just not that good at welding yet and I don't know if you can tell from the pics but there's about four or five different "wet spots" on it where my welds are leaking.
Normally I'd obsess over even the tiniest drool at the manifold and now I'm running around with like 5 exhaust leaks- another one seems to appear every day- which all combined for the perfect storm and one heck of a piston hanging up my wall!
I guess it was fate that I accidentally purchased that Technigas 100cc because I've hung up this home-made exhaust. It's retired until someday I get a hair up my butt and decide to strip it down and fix all the leaks.
but I've had the same plug in for a while now- before I installed this 24mm carb even. I haven't even gotten the MJ tuned close enough to start doing plug chops yet but I'm thinking that even this biggest MJ I have at the moment (150) is still lean because like I mention when my pilot jet fell out (I wasn't surprised because I installed it on-the-fly with a screwdriver that was too large and I kinda suspected I didn't get it snugly screwed in) the fuel was flowing unrestricted through tha passage and my scoot had great WOT power and temps were staying just above 300. That's when I realized I needed to go way up in jetting. I had a 90 MJ in when that happened. I'm running stupid high compression (like 190+) with a tight squish at .6mm. No advance at all and stock CDI!
I thought maybe the rod stretched and smashed the piston against the head and spark plug but the plug isn't smashed at all. Still gapped correctly haha. Of course now I'm back to using that modified 50cc squish head I was using back in the beginning of the 90cc install. Basically a combo of running too lean- running the wrong head that I'm sure isn't enough cc's- my scoot would never rev over 7200 RPM's before with the stock carb and exhaust though- now I'm hitting 9k which is the most I've seen from this engine. Normally I'd back off way before 400 degrees but I got caught up in the moment as I was about to break 60mph which I've never done before. Funny thing is during all this tuning I've never heard any signs of detonation. Except for the huge hole in it, the underside of the piston looks pretty healthy- no "death ash".
Oh yes- another huge contributer I was going to mention is my home-made exhaust. I'm just not that good at welding yet and I don't know if you can tell from the pics but there's about four or five different "wet spots" on it where my welds are leaking.
Normally I'd obsess over even the tiniest drool at the manifold and now I'm running around with like 5 exhaust leaks- another one seems to appear every day- which all combined for the perfect storm and one heck of a piston hanging up my wall!
I guess it was fate that I accidentally purchased that Technigas 100cc because I've hung up this home-made exhaust. It's retired until someday I get a hair up my butt and decide to strip it down and fix all the leaks.