Why would a Roketta 150CC hesitate from 25-50? By methogod (Read 1,364 times)

[methogod]

Roketta 150CC MC04 long body Gy6, been though a few accidents, but all in all working. Just laying it down caused some issues...

replaced head, valves and exhust. Ran fine for a while (1000+ miles), but started to have idle issues. Where it would just cut out, without keeping idle up to 3000ish.

Turned out that the exhaust valve tighten down on it self. Set both gap's to .004 and now it was idling better.

Somewhere they replaced the stock air box for a pod, the little crappy one that fits without any extension or foam protection. This caused many issues. Went back to stock air box. Better, no more gurgling.

Carb started getting iffy again, so just replaced it - $50 bucks with new enricher with a unlocked air screw. No bogging at low end and now great acceleration with a 2000 idle, the idle is not solid, it will jump around from 1-3000 at times, which is odd, but i rather it do that then bog down on aceleration.

Now for the issues as you have my life's history.

It seems that its "hesitating", like the trotle responce is slower then ever in WOT at mid speeds. Top speed seems to be 45, when it used to be 55-60... but i rather it never cut out the go faster.

Pulled the jets out of the old carb just to see what they were at true stock - 105/H35, i don't know what is in the new Carb but it should be stock. Unless in 2009-2010 models were slightly different then what we bought new from a reputable shop locally (not ebay).

What we are trying next...

Starter fluid, checking for any vacuum leaks....

if nothing is found, i want to check the rollers, and CVT - but the belt, clutch and rollers assembly were all replace at 700 miles when we had some CVT belt issues. Bike has just under 3000 miles, prob needs an oil change. This is a daily driver for us at our work, so i need reliability over speed or power.

I will post a video of the hesitating tomorrow. but figured I would open this up for some help now.

Scooter shop, although good people will always suggest fixes that require service, like they claim this issue may be a bent valve or damaged valve seal.... any way to tell? or something to look for...

what do my symptoms suggest....

beside a sh*tty Bike...


thanks,

Mike

[Alleyoop]

Have you checked the Diaphrgam it could be sticking or the rubber diaphrgam is leaking and will not hold the needle out. But it all appears to be fuel delivery problem. If the idle bounces around your to lean and you need to richen up the FUEL RATIO MIXTURE. If it idles and the idle then drops and wants to DIE and or die it is to RICH.
Alleyoop

[methogod]

thanks, will try a minor air/screw adjustment... but i would hope the brand new carb does not have a bad valve... any chance the pedcock is failing?? or just not working correctly? I dont know the failure rate on them...

I see what they mean by hesitation, the throttle response from 3800rpm-5000 takes a few seconds to catch up. Rather then a smooth curve like it is from 0-3500 range..

I understand rich and lean, but and i think sounds ok, i dont hear anything i am worried about, the "burbing" went away 100% by going back to the stock air box, but now its this hesitation in the mid to high range.

I have more time then parts into the bike, but i do want it to run correct and as reliable as possible. Looking for reliability with the 50mph top end if possible. Not that 45 is ok, as long as its not hesitating.


Two videos hosted on my drop box, just the bike idling, and reving up and down, then up and rear break to show the bogging.

www.dropbox.com/sc/enrwvry594li9mo/c1Z1ZFWm3x


is there any good guides besides the 10-15 good manuals that is more for trouble shooting then anything else...

like if you experience this, then check A, B, C

[Alleyoop]

it is LEAN richen up the fuel mixture about a 1/2 turn on the screw.

Also if it has a stumble at mid-range raise the needle one notch. So move the CLIP down one notch and see if that takes the stumble out.
Alleyoop

[methogod]

OK, so longer story, we dont know exactly what was wrong, but we do know something was not hooked up right, the breather hose from the head some how was tied into the vacuum lines. Making it choke x 2 when high throttle.

Mech came out pulled the OEM air box for the POD air filter. Pulled the emissions except for the 1 vacuum line to the pedcock.

It runs great, starts right up, goes 55-60 downhill. and sounds good.

BUT NOW and only when you ride for 20 minutes of so at 30-40, comming to a stop the bike sometimes dies, and its not a slow cut off like when your idleing too low, its just a complete cut off. Then you would think hot engine should start right back up some times it does, other times it takes 2-3 tries...

Theory's ---

1. FAILING PETCOCK or gas line issue.
2. Hot Engine ? overheating? Noise from the muffler that we think is just the heat sheild coming lose from the real pipe, but that wouldn't cause this... or would it?
3. CDI
4. something i am missing...

Even if there was some bad wiring, some where in the bike, ie. the rectifier was not working all the time, so the lights and electrics cut out, the motor should still run even at idle (everything is mechanical).

thanks, for all your help getting there...

[Alleyoop]

That is a Classic case of tight valves, tight valves will not hold idle after getting really hot and stay open and the motor looses compression. Adjust both Valves to .004 inchs.
Alleyoop

[methogod]

just set them both at .004, part of what was preventing the idle and some other stuff...

Mech, adjusted everything except the gap, as its was already at .004 top and bottom.

Will check them on Monday if they tightened up...

1st - if they are self tightening (does that means i need new head?) or just need some better torque?

2nd if they are still at .004, what else would cause the cut off and make it hard to restart when running hot?


Seems like more then 10 minutes of steady ridding, its starts to act up. Could it be a short? or faulty DCI?



thanks,

[Alleyoop]

It takes a few minutes for the valves and rockers to cool off and then they retract and seal, then you have good compression back again.
When the valves are adjusted the motor has to be stone cold, if you adjusted them when warm then they would be to tight again when it gets hot.

Also make sure the piston is at Top Dead Center when you adjust them. In that position you should be able to grab the ROCKERS and wiggle them.
Alleyoop

[tvnacman]

if your valves are adjusted within spec . I would look at ignition CDI's and coils are cheap and an extra never hurt .

John

[methogod]

Was the coil, got a replacement, and of course its shorter by 2" or so, but was able to make it work, just had to remount the connectors with zip ties instead of the factory screw post.

Ran great for 2 days, then yesterday wouldn't start. Gas was flowing but not getting into carb. Clogged main jet. Dont ask me how - well we did pull the fuel filter off while testing everything.

ordered 5 of the clear ones off ebay. Any one suggest a really good fuel filter, not sure what clogged the main jet, but something did..

[kz1000st]

Try running Seafoam in your tank. You could be picking up bad gas. Seafoam will help keep your system from gumming up.

[methogod]

is this it? marine product?

www.ebay.com/itm/NEW-Sea-Foam-SF-16-Motor-Treatment-16-oz-/151123370110?pt=LH_DefaultDomain_0&hash=item232fa7a07e

[kz1000st]

Yes. Most auto parts stores have it for under $10. NAPA is selling it for $6.99 this month. It's good stuff.

www.napacircular.com/

Last page,

[methogod]

Seafoam and fuel filters did the trick, was running great for 4 days...

My brother was about to ride off and we noticed the swing arm was bent away from the rear wheel.

So now out of nowhere the rear wheel nut must have come off at speed, causing the rear tire to sway, pushing the swing plate/arm (where the muffler is mounted) to walk itself out on the threads of the rear axle. Oddest thing I have ever seen.

The rear wheel had some wobble always thought it was off a bit, but not enough to do this.

So we took it apart, bent the swing arm back into shape, cleaned the bearings out all on the exhaust side. nothing inside transmission, except to check the belt and clutch was intact.

Took off the wheel checked the splines. Everything looked ok, so we...

Got a new rear axle nut, tightened as specified.

Tested on stand, and it did the same thing. Walked right off bending the swing arm again.

I am a little weary about replacing everything to find out it’s a bent wheel.
Have you ever seen or heard of this…

This is really the bike that just doesn't want to run well...


How can i tell if its the wheel pushing out, bearings, or the final drive axle. I feel less then happy about taking apart the transmission but not that treads are shot.

Suggestions, need pictures? i can get some video in the AM.

Was going to start to pull it apart later this week. To make sure we dont get any wrong parts online or locally.

[shop242]

Hmmm.. Get another BIKE! Dont let it work ya..