Engine revving on high, throttle handle twists very little

[asfazrq]

The issue is that engine is revvs super high on idle. I recently changed from a 44T stock sprocket to a 36T rear sprocket and immdiately the engine revved extremely high. I have played with a idle screw twisted it all the way in and the 3.5 turns outwards but that has done nothing. I checked the carburetor and ensured that the brass barrel is properly seated. along the way the throttle handle would not pull so I changed the throttle cable. the little screw (horizontal one) on top of the carb cover is screwed all the way down, lowest cable tension but still that does not cut it. top speed is 33 mph and the idle speed without touching the throttle goes up to 26mph. I have done everyhing I can, made sure there are no kinks or sharp bends in the throttle cable, but to no avail. Initially the throttle handle used to twist quite a bit but now it turns around half than it used to.

I am not sure if the throttle handle is already pulling it a bit at the rest position. I had huge issues connecting the throttle cable to the little hole in the throttle handle. after connecting th cable and then screwing the the handle to the kill switch assembly the throttle handle would not turn, but the groove in which the throttle cable goes goes stuck in the groove in the kill switch where the throttle cable passes. not sure if I am describing it properly. but it was pain to even get so far - I had to slightly twist the trottle and then close the screws on the kill switch assmebly. that was unfortunately the only way the throttle would twist.

need your help and kind advise. very much appreciated.

 

[core2kid]

Mine did this today. What I had to do was loosen the screw holding the cable by the throttle and where the cable goes into the carb. Loosen it all the way and you should see a lot of slack. You could even take apart the throttle and let the cable loose. Then tighten your idle screw all the way, start it and start unscrewing the idle screw. It should lower in idle speed.

 

[asfazrq]

I have already done that, both the ends of the throttle cable are set to loose - the end that connections to the kill switch and one that connects to the carb, still nothing.

 

[Al.Fisherman]

I have already done that, both the ends of the throttle cable are set to loose - the end that connections to the kill switch and one that connects to the carb, still nothing.

Check for a intake leak.

 

[asfazrq]

I added a boost bottle kit (useless thing) with a pre-drilled manifold (has teflon tape on the drill screw so should be airtight). i had to replace the old (non-drilled) intake manifold and it's gasket was completed super glued to it so I made my own gasket with a very think cardboard. I kept the cardboard to be slightly larger than the original gasket and made sure that hole was exactly the size as the intake manifold opening. it's a thick cardboard a few times thicker than the original gasket. could that be the culprit?

 

[motorpsycho]

I added a boost bottle kit (useless thing) with a pre-drilled manifold (has teflon tape on the drill screw so should be airtight). i had to replace the old (non-drilled) intake manifold and it's gasket was completed super glued to it so I made my own gasket with a very think cardboard. I kept the cardboard to be slightly larger than the original gasket and made sure that hole was exactly the size as the intake manifold opening. it's a thick cardboard a few times thicker than the original gasket. could that be the culprit?

a cardboard intake gasket? ummm, yeah, pretty much the same as having no gasket at all...probably has a major air leak.
since the engine is revving really high, are you positive that the slide in the carb. is not stuck wide open?

 

[AussieSteve]

If you remove the air filter, you might be able to see into the carb's inlet to see if the slide is right down. I'd do this with the idle screw loosened right off.
Otherwise, you could remove the carb with the throttle cable still connected and really see what's going on.
As motorpsycho says, it does sound like the slide is staying partly or fully open.

Even if that is the case, it would still be a good idea to replace that gasket with a decent one. You can buy them cheaply, or you could buy some 'oil jointing paper' and make your own. I use 0.8mm, but I carefully flat-filed both surfaces first, with the studs removed from the cylinder. Use thicker if you can get it.

If the slide is returning right to the bottom then, as Ron said, you most likely have an air leak. A really bad one.

If the boost bottle is useless, while you're at it you could p iss it off and fit the stock inlet.

Best way to check if there's a problem with the twist-grip is to disconnect the cable from the carb then see if you're getting full travel.

Also, I see that at the bottom of this page under 'Similar Threads' there are two that appear related. (Haven't read them myself.) Might be worth a look, but the advice will probably be the same as ours'.

 

[asfazrq]

I have a feeling it won't be all the way down. I think the issue is with the throttle cable connecting to the throttle handle. It most probably is pulling the throttle cable half way through (or possiblly more) at the rest position. I pointed out in my original post that the throttle handle doesn't turn much - which leads me to believe that the cable is not setup properly in the throttle handle! what is the correct method to setup the throttle cable in the handle? coz I tell you what, I have to partially turn the throttle handle while screwing in the handle to the kill switch assmebly housing. i had no choice, b/c at the 100% rest position it will not turn after closing the kill switch housing. please advise

 

[AussieSteve]

I have to turn mine a little, after attaching the cable, before the cover will screw on properly. Not much, though.

I just went back and re-read your first post for clues. You mentioned that you changed the throttle cable. Is the cable and the outer casing the same length as the original cable? It sounds like you've got a shorter cable or longer outer casing.

Another point, you said 'I have a feeling it won't be all the way down'.
You're probably right, but it's better to have a look than it is to have a feeling. Then we'll be sure where we stand.

 

[asfazrq]

if the outer casing is longer, how do I fix it?