Why did i soft seize?

So, i started my 80cc puch metrakit smallport kit for the first time today. i was riding it down the street, doing maybe 30-35. I had the throttle at maybe 1/4 full or less. I figured i soft seized because of an air leak. I got home, check, and sure enough i had an airleak i overlooked. So, i put some liquid copper gasket stuff on there to seal it u, and i'll test it for leaks tomorrow. But it something else occured to me. When youre going downhill, you want to be at WOT, so it gets enough gas/oil. Maybe becuase i was going so fast at only 1/4 throttle, i wasnt getting enough gas/oil.

What do you guys think? Either one of those, or a combo of both?

Also, i took my head off to look at the cylinder. Its get a few score marks in it where the piston gouged it. it still runs really strong though. is that scoring going to give me any problems?


Re: Why did i soft seize?

btw, im was running a 103 main jet at the time, and ive since downjetted to a 96. it still bogs a ittle bit at wot, but its pretty good. ill probably end up with like a 93 when its all said and done.

but, anyway, since this wasnt at 1/2 throttle+, from what i understand, the main jet size really doesnt have an effect. right?

Re: Why did i soft seize?

Ok, so i just looked at jessejamz photos of his cylinder. mine looks just like that, as far as the scoring goes. And everyone in that thread says that its fine, so i guess it will be ok. So disregard that question :)

Re: Why did i soft seize?

I.R.E. Mike Pee /

What kind of carb are you running? I'm assuming a 21mm dellorto PHBG on the metra 80, but telling is the only thing that is going to help you.

I wouldn't downjet on any circuit if I were you. Fix your airleaks first. If you're having issues at the same throttle point after that, then you've got tuning troubles, which are pretty easy to fix.

Re: Why did i soft seize?

Yeah, its the 21 phbg. I just made a new gasket out of liquid copper gasket, so hopefully that fixes it.

if i have an airleak at the head gasket, what can i use to fix that? im already running an aluminum head gasket, but i noticed that it lowers my idle just a touch if i spray carb cleaner on there. maybe it will go away, now that ive got everything retightened. or is such a small leak not that big of a deal?

BTW, we have the same last name, mike. lol.

Re: Why did i soft seize?

I.R.E. Mike Pee /

Jon Peters? haha I'm from the upstate NY peters, if you've got any relation there,

Anyways, I run a 65 metrakit on an e50 on my magnum. I don't have any head/base/intake leaks, but I'm running 210psi compression and I so have an exhaust leak, but no matter how I tighten it, it doesn't fix it or affect my tuning. I bumbled through my PHBG tuning,and it definitely is wrong. So take the time, read,and figure it out. If I had a metra 80 I'd tell you what jets I use, but I don't.

Good luck!

Re: Why did i soft seize?

Haha, i dont think i have any relatives from there. It wouldnt surprise if we were distantly related though. I know i have french canadian blood in me, and thats not too far from upstate NY, lol.

Well, ive asked a few people and theyve said that mid nineties are what most people are running with an 80 metra. Im going to dick with the idle mixture screw, and maybe the needle tomorrow, too.

I was just wondering if you guys thought that the soft seize was because of the throttle position not delivering enough gas, or if it was because of the airleak. im scared to go fast now, after the soft seize. (i know...i suck lol).

Re: Why did i soft seize?

if you have even the slightest air leak, use will have problems. FIX THEM BY USING NEW GASKETS AND TIGHTENING DOWN PROPERLY! it will not get better by itself, and a little leak WILL matter.

chamfer the edges or your ports and tune you carb. you can change your main jet all day long, but you need to be focusing on your idle jet, needle, and mixture. read up on some dellorto tuning guides.

Re: Why did i soft seize?

yeah, i already chamfered the ports. i guess ill be messing around with the idle mixture tomorrow, and if that doesn't work, ill have to order a leaner idle jet.

yeah, all the gaskets were brand new, thats why i dont really know why it was leaking. i guess ill find out tomorrow if i fixed it.

no one answered my original question, though. :(

Re: Why did i soft seize?

Ok, so i was doing some digging around the forums here, and i think i found out why i seized it.

Commando Brando (some thread about polinis seizing up): "i seized once from running too large of main jet, i had to stay off the throttle so the needle taper/idle kept it to lean, overheated back of piston seized on 2 sides on the mk.80."

I did the exact same thing. When i pulled the head, i could see i seized it on the back side.

I had too large of a main jet, so i was only running 1/4 throttle, and riding the needle. My needle is probably too lean (set at 2nd to top notch). So i guess ill drop the needle one more notch. My idle seems really rich, so i dont think that had an effect on it.

Does that sound about right?

Re: Why did i soft seize?

) Cupermcnewbster ( /

I always start with the needle in the richest possible position just to make sure I avoid a seize like that. You can always lean it out, but its better to start rich for sure.

What kind of gearing are you running to tune the beast? I'd reccomend something short like 14x40 or 14x36 so you can really get the RPMs for proper plug chops and readings.

If you were only riding 1/4 throttle you weren't riding the main jet so thats not what caused your seize. Main jet is 2/3 or 3/4 to WOT only. I guess it would have some effect on how it was running at 1/4, but not much. What needle are you running?

Re: Why did i soft seize?

Yeah, i actually have it geared 14 by 40.

Its a w7 needle.

Re: Why did i soft seize?

You can get a broad range of low rpm mixture ratios just with the idle mixture screw especially if you put in a large idle jet

Re: Why did i soft seize?

Oh yea, It's always good to blip the throttle as you descend a hill to maintain lubrication

Re: Why did i soft seize?

Dont use permatex copper high temp rtv, it disintegrates when exposed to gasoline.

Permatex black is OK, permatex grey is the best, they have it at autozone and such. Get it, use it, love it.

Also....let it cure first, otherwise you get air bubbles and leaks and such.


Re: Why did i soft seize?

well, that must be why i still have an airleak. i'll get some of the grey kind tomorrow. and clean it all up and re seal it.

What do you guys do about heak leaks tho? ive already got an aluminum head gasket on there, but there seems to still be a SLIGHT leak, as the idle slow just a little bit.


Re: Why did i soft seize?

ok, so i just sealed up the base with that grey parmatex.

still wondering what you guys would do in the event that i have a leak at the head gasket after i start it up tomorrow?

Re: Why did i soft seize?

Perfekt Timing Angel /

I don't think you want to be at WOT on the downhill...I thought you want to blip it every now and again as SteveW said?

Also, your main jet controls 4/4 throttle, not 1/4 throttle. You might have seized because of a lean condition caused by a combination of the leak and your needle/idle jet setting(s), not your main jet setting. I'd check your jet numbers with those on the shreadsheet to get an idea of where you might need to be. They won't be %100 accurate because of altitudes differences and such, but should get you on the right track.

Get that tharr cylinder stud fixed first before ya start messing with the tuning ritual.

Re: Why did i soft seize?

Thanks Angel. Yeah, i know that the main jet is 3.4 throttle and up. I dropped the needle earlier (raised the clip up a notch).

I wasnt going downhill when it happened, i was just making a comparison, as i was nearly coasting (less than 1/4 throttle)when it happened. i kinda assumed maybe i was going too fast for the amount of gas i was giving it, and having a lean needle and an airleak didnt help im sure, lol.

hopefully that gasket maker stuff takes care of the leak. we'll find out tomorrow, i guess.

Re: Why did i soft seize?

You do not want to drop the needle, you want to raise it such that it passes more fuel when the throttle in only part way open.

Re: Why did i soft seize?

Yeah, i realized that today before i started it up, thank god lol. i was just like "wait, that doesnt make sense". and checked the tuning guide.

but yeah, i still have a slight leak at the base of the cylinder. im going to redo the liquid gasket shit. it worked great on one side, but i dont think i layed out a thick enough bead on the bottom side of the cylinder.

i ran it today with the needle raised and even with an airleak, it was bog city. i couldnt get above 15 mph for like 3 blocks, lol.

so i guess i just wasnt giving it enough gas when i soft seized it.

im going to redo the liquid gasket tomorrow. it has a leak at the head gasket, too. it already has a head gasket on there, so what should i do to fix that leak?

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