Skip to main content

Engine revs up externally high when I let off of brake

Hello.

I am working on a friends bike and I replaced his drive belt. Variator and put a new carburetor on it. I’m new to working on scooters. I got the new carb hooked up and I can start the bike and it seems to idle near normal levels. However, when I let off of the brake, the bike starts revving really high and the rear wheel starts spinning really fast. If I had to guess I’d say it goes to around 3000-5000rpm (no tac on this bike). Since I’m new to this I took pictures of my work so far from multiple angles. I haven’t removed the old air box in case we end up having to put the old carb back on. I also confirmed that the belt was attached properly with the previous carb and test drove it.

Block Image

Block Image

Block Image

Block Image

Answer this question I have this problem too

Is this a good question?

Score 0
2 Comments

Not sure why but Ifixit won’t let me upload images.

by

@oldturkey03 sorry for the late reply. Thank you for your help. I updated the post with the image from that angle

by

Add a comment

1 Answer

Most Helpful Answer

@jeremyickes all of this sounds like you have some linkage issues. Releasing the brakes will not increase the power it only lets it being transferred to the drive. Double, no triple check your work. That includes the linkage on the carb as well as the accelerator cable etc. You can always post images with your Question buy using this guide Adding images to an existing question

You just have to edit your Question, open teh media manager and pull your images into that one. Then place them in your Question. Just like the guide says :-)

Update (09/19/23)

@jeremyickes take a picture from the side of the pointing arrows. Let's see what it looks like when you have the cable on the carb. Your throttle handle on the low gas position when you attach the throttle cable?

Block Image

Was this answer helpful?

Score 1

7 Comments:

@oldturkey03 thanks for the help. I just uploaded pictures of what I’ve got so far. I tried following some tutorials online but the hosing on this bike is a bit different from those videos. I’m totally stumped here.

by

@jeremyickes look s pretty good and it appears as if it sits right at the idle screw. Does it bind when you move the accelerator? When you start it up just like this, is the idle high or low?

by

@oldturkey03 it's not even starting at this point. I think the only reason it started at all was because I used starter fluid so I'm pretty stumped as to what's going on. I might just put the original carb back on.

by

@jeremyickes did you change like for like? Same carb etc? Have you checked if you get fuel to the carb? Check the fuel bowl and see if you may have a stuck float or valve. Do you have a make and model for the carb? Something looks odd on this. What make/model bike is this? Any info on the motor? Are all the vacuum lines etc. reconnected? You finished the routing of the throttle cable? In our picture it still looks a bit loose....

Like its just hanging there (2nd Picture)

by

@oldturkey03 it's not exactly the same as it's been a huge ordeal. I know for a fact fuel is getting to the carb but it was originally going to this metal thing with 3 hoses coming out. I've got the factory carb on and I still can't get it to run! Not sure what I messed up at this point. I kept the throttle cable loose on purpose because I keep having to take this thing off. However it won't even start. I have no clue what it could be. The original carb had two vacuum lines one running to the engine and one to that strange metal circle thing.

by

Show 2 more comments

Add a comment

Add your answer

Jeremy Ickes will be eternally grateful.
View Statistics:

Past 24 Hours: 0

Past 7 Days: 0

Past 30 Days: 3

All Time: 54