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Got a 2010 Yamaha Aerox as a project and had to completely rebuild the engine. Fitted a full circle crank shaft, 70cc Airsal Kit, 17.5mm Carb with 90 jet, 5 gram rollers, 30% spring (not sure if thats correct for what I'm running), Uprated crankshaft bearings, Lighter Clutch, Vented performance clutch bell, Double layer Polini air filter, Kevlar belt, new reed valves.

It feels like it is lacking power from watching videos where people have the same cylinder kit but not full circle crank they seem to have better acceleration. I'm going a bit easy on it because I gotta heat cycle the engine so im not going over 35 and im accelerating slower but when i do try it seems to have nothing. Also if im at about 20mph and accelerate it takes years to get to 30.

If anyone knows anything that could help please reply.

Forgot to add to the list I have a Technigas Q-Tre exhaust too.

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Does it feel like it's lacking power, or does it feel like something is holding it back?

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I think you need to get it on a dyno just to check fuelling and see the power curve. will save a lotto time in the long run
Run it in first though as dyne's are brutal

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how long would you say would be good to run it in? ive been told you should go 30-35 for 300 miles

I have a Sym Jet Euro X 2004 too with tecnigas exhaust on and acceleration on that feels alot better than my Aerox.

 

Put my hand over the exhaust for about 1 to 2 seconds to check if it was blowing and its very very oily wasnt sure if this is correct. after about 1 second i have a thick black circle on my hand.

When it gets to about 8mph it revs really loud then calms down and accelerates. It sorta has the feeling that something is holding it back. If i slowly turn the throttle while accelerating it doesnt make the loud revving noise but accelerates about the same. 

 

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Is it the iron or ally kit? 

Tbh the stock spring and variator work fine to 50 odd. You only need messing with either when your looking at adjusting the rpm sweet spot. Or you change the gearbox ratio's. Your clutch is good I assume? 

Again with the belt. Stock is fine. If you have the air seal ally kit that should be run with premix as the pump won't be able to give enough oil. You could maybe add a little to the tank to save having to carry premix. 

Jet sounds about right. My daughters bike had an air seal 2 kit with a technigas pipe and with all stock transmission and an 85 main would max out at around 55mph with my fat arse on it in a high viz coat. Wheelie'd nicely too. 

Felt criminal turning it back into a learner legal(ish) 50cc again. 

Oh as for running it in.. 

5 miles to make sure nothing falls off or boils up then nail the fkr.

Long story short. Try your stock rollers and springs. 

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A 500cc race bike, a v8 muscle car with a charger maybe. 

A scoot. No. Unless you have built a 98cc 25hp racer it won't need all that guff. 

Get it hot a couple of times. Ride it 5 or 10 miles to make sure nothing leaks or boils up and your good. 

All I have ever done in (shit) 35 years of riding 2 strokes. 

That single ring bigbore may only have  6 thousand miles in it if you work it hard. 

Maybe stay away from long stretches of wide open throttle. 

Also if it's anything like my daughters bike use spring washers on anything related to the exhaust. Keep an eye on the brackets too they break. 

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its 4 stroking lower down, if you've pushed the power further up the rev range, that's where you need to stay.

 

You can't have more power and expect it to perform all throughout the rev range, its a compromise.

 

have you tuned your power band into when the rollers bite?

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I set it up similar to how I’ve seen others set up I was going to check all the rollers and spring and everything at the weekend

It’s got no centre stand so it’s quite hard to work on the bracket for the side stand has been bent too so don’t have that either just have a jackstand under a bit of frame to hold it up

Was riding it today and it would get to about 30 (very slowly) then wouldn’t want to go much faster. If I got down over the handlebars (to reduce air resistance) it would gain a bit of power and slowly crawl it’s way to about 40 then I think the power band would start kicking in a bit so I’d sit up again and it would go past 50 but by that time I’d run out of road

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The uprated spring that ive been using is a bit taller than the stock one could it be preventing the clutch to open? https://gyazo.com/426f853db86bdec341ef80b2590d3761

 

Heard running too rich can cause power loss could it be running too rich? I put a 90 jet in because that’s what I’ve seen people use the most. Any way to stop it or is that just something you live with?

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I will say it again. 

Fit stock rollers and spring. The fancy ones make little difference overall bar fine tuning. 

Sounds like the bike is pulling way too high a ratio. 

As said my daughters bike with the 70 kit was a weapon ON STOCK TRANSMISION. A wheelie monster that rocketed away from the lights. 

 

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Okay

do you know what rollers aerox has stock? It has some 5 gram ones in but I think old owner put them in

Also ive looked everywhere and cant find it. Does the fuel/air mixture screw mix it throughout the whole time or just at low revs? I somewhere that it just does it at low revs and now not sure

 

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10 hours ago, Paul1574 said:

Okay

do you know what rollers aerox has stock? It has some 5 gram ones in but I think old owner put them in

Also ive looked everywhere and cant find it. Does the fuel/air mixture screw mix it throughout the whole time or just at low revs? I somewhere that it just does it at low revs and now not sure

 

Pedpartz can sort you out. I have found them really knowledgeable. For once the people on the phone really know their stock and what it does. 

Have to order online. Del is quick too. 

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Put 4.5 gram rollers in instead of the 5 grams I had before and it’s all a lot faster I think I got about 60mph out of it. It dies a bit from 33-38 but I can live with that for a little bit. Getting a new air filter for it so going to get it all setup perfect then

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