8p and Metra 80 tuning

okay everyone......so i took my 8p off of my bike and replaced it with a just a magnum header. and the bike starting running pretty damn well....and loud as fuck.

i know a lot of people run 8ps with 80cc kits....so what im wondering is....are there anything tricks i need to know about getting this thing tuned right. like i said im running 50 idle jet and 87 main jet in a PHBG. do i need to do some kinda crazy jetting. should i pull some of the stuffing out of the silencer? im open to any suggestions here. thanks everyone.


Re: 8p and Metra 80 tuning

so i also just threw the baffle part of the magnum exhaust onto the header and then my bike stared acting really shitty again.

it seems like my bike isnt handling back pressure to well. could this have anything to do with my porting or my case matching work?

Re: 8p and Metra 80 tuning

87 sounds way lean.

Re: 8p and Metra 80 tuning

Keep the header on there and say good by to your 80 kit and your ear drums.

Metra's take time and patience to run at there best. Timing idle jet needle position and main jet are what you need to concentrate on. When I was tuning my 80 an 50 idle made the bike run like shit on the low end, a 45 made it run like a champ. Also if you are running an big port metra you might want to tune the bike without an airfilter there low end really suffers with a filter installed for some reason.

Take your time and keep a record of every setting you tried and what it dose till you get familiar with what dose what in regards to tuning.

Re: 8p and Metra 80 tuning

yeah i definitely don't plan on keeping the header on there. i want it running properly with my 8p on it. i have a small port metra.

maybe my problem is that i need a Rafter pipe.

Re: 8p and Metra 80 tuning

my thoughts.

1). Is your piston upside down?

2). What's clutch set-up? Two shoe three shoe? Springs? 8ps have terrible low end. Might just not be able to get it going.

3). Timing.

Re: 8p and Metra 80 tuning

i installed the piston with the arrow on it facing down....so im pretty sure thats right.

i have the Super Super 3 shoe clutch from treats....with paz springs 2 full turns out

timing looks good as well as points....i have played with pretty much every position of timing.

i know the 8p isnt great for low end...but it should still be able to run decent...right?

Re: 8p and Metra 80 tuning

Hmm all sounds about eight. I don't know. Where's your stator set? I always just fully advance mine. Checked for air leaks?

I never ran a dellorto on my metra so I can help much with jetting.

Describe exactly what happens when you try to run the bike with the 8p on.

Re: 8p and Metra 80 tuning

Did you see this post? Might help with tuning.


Re: 8p and Metra 80 tuning

Pablo Puchasso /

Re: 8p and Metra 80 tuning

okay so heres what happens with the 8p on

i take off and its going okay....at the very beginning of the throttle it acts weird and boggy but once i get past the very very beginning of throttle its riding okay....then if i go to accelerate more...its starts bogging or sputtering, im not sure which one, and then i have to let back down to the idle jet to start going again. if i accelerate super super slowly i will eventually be able to get to the main jet.

im thinking of getting a bigger idle jet...maybe a 55 and possible throwing a bigger main in there. im pretty sure there are no air leaks. so im thinking it has to come down to how my jetting is.

ive ran the bike with my stator in pretty much almost every position... i forgot where its at right now...but that doesnt seem to be the problem.

i did match the case and transfer ports myself, so i dont know if there is anyway that i could have fucked that up and thats why my bike is running weird.

im just trying to think of everything, cause i feel like ive been over everything and i cant figure out the problem

once again here is my setup


dmp stuffed crank

super super 3 shoe clutch with paz springs, 2 full turns out

80 small port metra

21 racing PHBG 50 idle jet, 87 main


Re: 8p and Metra 80 tuning

ive got the same problem. right now my setup is

big port metra

21mm phbg

i dunno what idle jet but ive got a 96 main jet in there.

no filter just the velocity stack that came with it


it bogs off the line and WICKED slow up hills. when i had the same jetting but with a biturbo the thing could have towed boats but it was rich on the topend and topped at 35 4 stroking.

oh yeah my bike runs better at night when its cooler. hmm

it tops at 40 now with the stock magnum mkII gearing. i want my lowend back!

Re: 8p and Metra 80 tuning

Joe -

I dropped to an 89 in my Metra and it is way, way better. I was even able to raise my needle one step. I might drop it back.

Still...the 92 was too big. Plain and simple.

Re: 8p and Metra 80 tuning

there's gotta be a way to make bikes perform well with homoets......right?

Re: 8p and Metra 80 tuning

i had an 8p on my gila for a while and it blasted into the sixties with decent low end. check for air leaks, don't just assume you don't have them.


Re: 8p and Metra 80 tuning

That sounds exactly how my bike was acting during tuning. Classic overjetting of your main jet. I kept thinking that I couldn't possibly need a smaller main jet. Eventually I said fuck it I'm going to keep dropping my jet until it either stops sputtering or blows up. Well it finally stopped sputtering and started running really nicely 13 jet sizes smaller.

Just keep dropping your jet one or two sizes at a time and I promise you you'll figure it out.

Re: 8p and Metra 80 tuning

What needle size are you running? The needle may be too lean/rich.

Re: 8p and Metra 80 tuning

w7 needle 2nd from the top......tried a way smaller main jet...i think 78 and that didnt fix the problem tim

Re: 8p and Metra 80 tuning

my 80cc wouldnt run right untile i went with a hotter plug now it runs like a top.

try open your point gap

Re: 8p and Metra 80 tuning

) Cupermcnewbster ( /

you shouldn't be running 18x36. You have to go 70 to get through your full power band. Put on a 14 front and tune that sucker, then switch the gearing. I'm not sure why everyone is putting on super tall gearing, but with it low end is going to suck balls, and you likely won't get your shit tuned right. You gotta tune before you go fast.

Re: 8p and Metra 80 tuning

Low end doesnt have to suck with big gearing. I feel fairly confident i can pull most non-variated bikes with giant 18x36 gearing.........but you have to go through a clutch a month to do that.

I do think you should put on a 15 fron sprocket though. See if you can rev through the problem areas and get to your main jet.

If i were you I would start all over. go back to all the stock carb settings, but put atleast a 90 in the main. go back to a two shoe clutch. Fully advance your timing. get a b8hs plus. See what happens.

Change one thing at a time. keep track. i think you are trying too many things at once.

I dont know. thats just where i would start.

Re: 8p and Metra 80 tuning

lotsof people run 18x36

Re: 8p and Metra 80 tuning

hmm that is an interesting suggestion tommy. i suppose i could do that. i think one thing i am going to definitely try is running a hotter plug....and running through the most jetting variations as possible. maybe ill tighten the springs on my clutch too

Re: 8p and Metra 80 tuning

) Cupermcnewbster ( /

I know a lot of people run 18x36, but I just don't think you are going to get the bike dialed in with that on there. I've tried tuning an e50 with it and it was impossible. My clutch was slipping till like 35. Power sucked. I know each setup is different, but I just don't think its a good way to start.

Tommy is an exception. His bike is nuts and does have the power to pull the gearing. He's been around the guru and others so he knows his stuff and it works. I'm just saying you can get a lot more out just regearing. People think if you simply put the gearing on you will utilize it. This is not true. Tune it with short gearing then go crazy. I'm just trying to help you save some time. I do agree, make one change at a time.

Re: 8p and Metra 80 tuning

well i will take that into consideration, maybe ill throw a smaller front sprocket on there and see what happens.....haha ill pretty much try anything at this point

Re: 8p and Metra 80 tuning

ben you soft seized with a 93 didnt you? that 93 i borrowed from you didnt make my bike run any better i dont think then i threw on the malossi 90 degree filter and it still ran like shit. i cant believe youve got a 89 in there and arent worried about soft seizing. on some real shit i needa buy jets from the mid 80s all the way up the mid 90s but i plan on moving soon

Re: 8p and Metra 80 tuning

I would really throw a smalled sprocket on front. You already have enough bogging being caused by other factors. I wouldnt add another one that is easily fixed to the equation. Change it after you have it tuned.

This way maybe you can rev through the boggyness and get to the main jet.

Re: 8p and Metra 80 tuning

jesse, if im not mistake wouldn't you want to run a cooler plug not a hotter plug? i remember you having a b6hs- heat phase after warm up? b8hs-b9hs

but regardless i would upjet both idle and main a bit anyway for breakin. Boggy take off and boggy top speed sounds lean to me. im at the garage all saturday from 3 on if you want to bring it by. If you have bigger jets bring em- i think scootopia sells dellorto jets but they are $$$.

Re: 8p and Metra 80 tuning

still have yet to change the front sprocket.

but i did put in a 45 idle and 75 main....just to see what happenes. and it was by far the best my bike has run with the 8p on it. but then why i took the plug out....it was way lean..... i really dont fuckin get it.

is anyone else having this problem? what should i do? get a different pipe? i mean i dont changing the front sprocket is going to solve this problem. something seems seriously wrong here...and im super confused

Re: 8p and Metra 80 tuning

) Cupermcnewbster ( /

changing the sprocket is going to be crazy.

idle isn't going to make a big difference, at least not like the main.

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