zx50 build, tuning issues.

[mantrans]

Hi guys, first post. Ok I bought a non running zx50 2 stroke. Installed a malossi 72cc big bore, head, v8s race pipe, pollini 19mm carb,stage 6 intake with V force reeds and polline air filter. Also has naruku unrestricted cdi. I am running 110 with klotz. has var,iator with 7.5 rollers,pollini race clutch with 3k rpm springs, 1k rpm contra (big spring)

PROBLEM: Starts fine, revs fine, drives fine but lets say from a stop it will shoot up past 9,000rpms (all tach reads sorry) then at about 30mph it chokes and rpms drop to about 8,200 and will stay there for second then go again the when it hits 50mph it will drop back down and stay the entire time, wont move at all! Sometimes it will push through at after playing with the throttle and continue to accelerate, when I first got it done it would go 0 to 60 like that now it wants to quit during wide open throttle all the time, its not like a  bog, it doesnt slow down, feels like a rev limiter of sorts.Tried 90,100.110, and 118 main jet, made sure carb is working, plug looks good although it is not the right plug which I will replace. Re routed fuel hose, throttle cable is incorrect and just rigged on there for now. Tried everything with the air fuel mixture screw. Please help! its driving me crazy, I feel like the bike has so much more in it. I weigh 160lbs im 5'10". Please feel free to recommend the correct roller weights and such.

[mantrans]

My buddy has a 4 stroke, 100cc big bore, head and cam. Exhaust, intake and cvt mods and it will put close to 200 feet on him from 10 to 50mph then it will just drop rpm a little and stay right there until he eventually passes me.Seems fully capable of 60+ this is on stock gearing also. I do have up gears, just not installed yet.

[oldgeek]

WoW! You have a lot of new parts there. It sounds like a carb tuning issue, is that 19mm polini carb like the Dellorto PHBG?
What jets do you have in it?

[mantrans]

Nov 28, 2015 6:46:55 GMT -5 oldgeek said:

WoW! You have a lot of new parts there. It sounds like a carb tuning issue, is that 19mm polini carb like the Dellorto PHBG?
What jets do you have in it?

------Thank you. Yeah they are similiar, I have a 90 jet in there now.

[spaz12]

Open air filter? Or air box?

[90GTVert]

You are making big jumps in jet size. I'd recommend starting on the biggest jet that allows it to run and taking smaller steps down, going through a tuning process and taking notes. You can find a tuning process in great detail in the link below :

www.49ccscoot.com/faq/carbtune.html

Some of your issues may be related to or accentuated by the CVT tuning or setup.

[derbiman]

Try dropping the variator weights down a little. 7.5 sounds heavy to me. That may be causing your variator to open up prematurely taking your engine out of it's power band. Try something around 5.5-6 grams to see how it responds.

[mantrans]

Nov 29, 2015 12:18:41 GMT -5 derbiman said:

Try dropping the variator weights down a little. 7.5 sounds heavy to me. That may be causing your variator to open up prematurely taking your engine out of it's power band. Try something around 5.5-6 grams to see how it responds.

Thanks, I did try 6 I believe and It still did it, I will try lower thank you.
Also stupid question, I am away from the bike at the moment and the factory plug does not fit in the head, plug width is too small, for the moment I put some one off plug in there to get it running but I need a good plug, its the malossi 72cc sport kit. Thanks!

[mantrans]

Nov 29, 2015 7:59:09 GMT -5 90GTVert said:

You are making big jumps in jet size. I'd recommend starting on the biggest jet that allows it to run and taking smaller steps down, going through a tuning process and taking notes. You can find a tuning process in great detail in the link below :

www.49ccscoot.com/faq/carbtune.html

Some of your issues may be related to or accentuated by the CVT tuning or setup.

Thanks! I will try, I just received more jets in the mail, I tried 90,100,102,110 and 118. Float hight??

[mantrans]

Nov 29, 2015 0:57:37 GMT -5 spaz12 said:

Open air filter? Or air box?

Open Filer, Polini evo to be ecxact.

[mantrans]

Gave my friend a 400' head start from a dig (stop) on a 1 mile long road, I close the gap to about 100 feet by the time we hit the half mile, then at 45-50 rpms dropped too 8,200 and speed was barely climbing, went from 50 to 52 from the half mile to the mile which was barely enough to catch him. I should have easily passed him at the half mile had it not acted up. Its so weird, a couple times It went all the way to 60+ without a problem but 90% of the time it just quits accelerating at 50 amd I might gain a mph or two.

Also I hear of people having the front tire try and come up during acceleration with similiar build to mine, I mean the bike is quick but nothing like that, I feel like the bike is only running 80% of its potential the entire time not just at the 50mph mark. Thanks for all the help

[spaz12]

I'm not too familiar with the V8 pipe, although I have seen them. It's not an expansion pipe. Anyway, I would normally say that with your open air filter that you'd be in the low 100's on your main, but I don't know with that pipe. 
But I read your first post again and you mentioned that it was going just fine and then started acting weird... How long was it running okay? If it'd been a while then I would suggest tearing your torque driver apart and servicing it. Torque drivers that are bad or need servicing will act the way you described; taking off okay and then like bog down/ stop accelerating and then accelerate again. It's worth a try and never hurts to service something.

And you should be careful just throwing any ol plug that "fits" in your cylinder. You could end up throwing a hot plug in there and burn that cylinder up. 

Another thing about open filters... You should have a really big collection of mains, because they can be quite hard to tune. Don't forget about needle settings either.

[90GTVert]

Nov 30, 2015 1:57:08 GMT -5 mantrans said:

Float hight??

Explained in the link I provided.

[mantrans]

Nov 30, 2015 2:26:46 GMT -5 spaz12 said:

I'm not too familiar with the V8 pipe, although I have seen them. It's not an expansion pipe. Anyway, I would normally say that with your open air filter that you'd be in the low 100's on your main, but I don't know with that pipe. 
But I read your first post again and you mentioned that it was going just fine and then started acting weird... How long was it running okay? If it'd been a while then I would suggest tearing your torque driver apart and servicing it. Torque drivers that are bad or need servicing will act the way you described; taking off okay and then like bog down/ stop accelerating and then accelerate again. It's worth a try and never hurts to service something.

And you should be careful just throwing any ol plug that "fits" in your cylinder. You could end up throwing a hot plug in there and burn that cylinder up. 

Another thing about open filters... You should have a really big collection of mains, because they can be quite hard to tune. Don't forget about needle settings either.

Thank you, 10 4 on the plug, I understand it was a risk. I have main jet kit randing from 75 to 138 in increments of 2. Good catch on the torque driver...I pulled it apart when it first started acting up and noticed the spring was bound up meaning when I removed the Main nut from the clutch the spring did not release like normal, very scary as I had to tap it aggesively to get it to come lose, so when I did I took fine sand paper and cleaned around the base and cleaned some of the paint off the bottom of the spring to free up. I will take another look at it, thanks. I wouldnt say it worked every time at first, it would work on and off however. I made multiple test passes and 2 times out of 10 it would be fine, other times it would do as described.

[triesandluth]

That zx50 should take an ngk br8hsa. I've been running with br8hs with no problems.