no power in low revs after heating up

right well i just changed the engine in my aerox and used most of the parts from the old engine variator,clutch,carb and exhaust thing is they worked perfect on the old engine.

basically when you start it up first it goes fine until it warms up, it will hit about 10-15 mph and just sit there for ten seconds or more then all of a sudden it will just take off, its like the revs are being held back.

thing is tho is that when you lift the back wheel off the ground it will rev as it should, only seems to happen when there's a load on the engine ie' the rider.

has a technigas exhaust but im not sure if the carb was up jetted or if the roller weights were changed. was working perfect on the old slightly fucked engine lol

 

its not the roller weights before anyone mentions them as i removed two to make it lighter and its still barely revving! goes to about 10-15 mph and takes off and times it just stay at about 15mph on wide open throttle.

if you let the engine cool down a bit and go out on it it will take off perfect on the 1st twist of the throttle, after that when you come to a standstill and take off it goes back to the same old problem! really frustrated so if anyone has any ideas please post them up :good:

 

To be honist mate (dont stab me), it DOES sound like your running stupidly heavy rollers, what weight are you running? Is the engine is factory condition?

Could also be running stupidly rich, whats your carb settings and mainjet size?

Also, check your entire transmission to ensure you assembled it 100% correctly. Is the belt the wrong way round? Correct belt being used? Did you slack off the belt when tighening the variator and clutch? You dont wanna sandwitch the belt between the pulley's.

 

stock rollers and as far as i know stock main jet! just cant understand how the same setup worked 100% on the old engine, just transferred everything from the old engine to the new and all of a sudden this problem starts.

 

and yes transmission is perfect because the engine i got never had the variator cover off in its life and had the drive gear in there since factory, hence why i changed over the variator belt and clutch because i thought that the problem was the drive gear in the new engine.

 

Maybe your new engine is fucked?

Running stock rollers and mainjet with a technigas pipe will cause the problems you've said above. You need lighter rollers, stiffer clutch springs and upjet around 5-10%

Atleast try that before you go any further, remember to make sure everything is assembled correctly, look out for worn parts, take you time and dont rush!

Or why not use the brand new variator and clutch instead of your old ones?

 

hope it's not fucked lol it came from a breakers anyway with a months warranty so if it is i'll send it back, what could be fucked on it tho that would cause this problem?

dunno about up jetting etc as the same setup worked perfect on the old engine.

just seems strange that it works perfect first time its started and then the problem arises!

yea well gave most things a check over before i put the engine into the bike.

 

Last owner could of had it in pieces and put it back together incorrectly, or could just be heavily worn piston/cylinder and crank. If it were worn out, it would be very hard to start and run shit when cold, when warmed up old engines seem to run ok as the heat expands the piston rings and brings back some compression. Would smoke alot too.

But it does sound like a transmission problem, Somethings not right and not engaging properly.

 

starts first kick every time with very little effort!

funny feeling crank bearings could have a part to play in it because the engine has a slight vibration in it but then again it feels fine at about 30-40 mph

 

That could be caused by something in the transmission, the vibration. Are you sure the belt is on properly and your running the right size (not weight) rollers?

At most it'll be a bent crank causeing the vibration, or dodgy bearings. Sometimes slightly bent cranks will straighten themselfs out if your lucky

My zip has started vibrating more than normal, but thats probly because ive been running 70kits on the standard crank for the past 12,000miles lol. Im expecting it to snap soon.

 

yep everything is on fine and the rollers are the right size, as i said the stuff came straight off the old engine and was working perfect on it.

my problem shouldn't really be caused by having a bent crank tho should it?

only back in there now from trying a few things and still no joy! gave everything a quick check over and seems every thing is fine. went out started it and it went as it should then when i stopped and went to go again it was just crawling up to 15 mph as it was doing already!

 

Can you make a video? Get someone to film you riding up and down the road.

 

looks like its pulling off fine mate, so it'll pull away nice like that and just sit at 15mph? It did sound abit sputtery in the video but its hard to tell, sounds like a timing issue to me.

Perhaps someone on here who knows a little more about Aerox's can point you in the right direction?

 

yea sometimes it will just sit at about 15 mph and go no faster at all! even down a hill lol

that vid it went up quick enough but other times it would take a lot longer.

 

basically the exhaust flange on the cylinder was broke and the casing had a load of bolts broke in it and the cylinder bolts were all helicoiled then water got into the crank and fucked the bearings etc! so thought it would be better to start with a fresh un-molested engine than re building the old one.

the engine is bone stock minus the technigas pipe clutch springs variator rollers etc are all stock. jetting could have been changed but i doubt it tbh. only thing different is that the exhaust was blowing when it was on the last engine due to the flange being broken but doubt that would have made any difference.

after a lot of searching it seems a few people are having the same issue but no definitive answers yet.

 

i have taken 2 rollers out and it was no different, crawled up to 10mph then just revved it's tits off because of how light the variator was lol

And i dont know if it should be like this but the vibration seems a bit much, if i have the bike on the centre stand and me sitting on it (and i wouldn't be the lightest of lads) the vibration is enough to move the scooter around!

the breaker i got the engine from gave me a months warranty so im gonna see if he will replace it with another to see if it solves my problem! seems it only happens when the engine gets a chance to heat up. if the engine is cool it goes like it should without problem.

really appreciate the help btw guys :good:

 

Your Not supposed to run it with only 4 rollers in, your gonna fuck this engine big time, throwing everything off balance and end up bending your crank, stripping the splines and mashed up bearings...

Do it properly, get a bunch of different weight rollers, like minor and the rest of us said, Around 5g, get 4g, 4.5g, 5g, 5.5g... And use ALL the rollers not just 4!