HI New to the form and Just bought this Boulder BI for my 4 year old grandson and want to adjust the throttle so it doesn't go to fast for a month (or longer) or so until he is use to it.My problem is when I turn it down the speed is fine but it has no power to climb hills so it is useless like this. When I turn it up it has the power but goes to fast. I was wondering if anyone has solved this problem? I was thinking about a sprocket change to a larger rear sprocket so he will have the power low end but not on top end. Looking for ideas from the form. Can I even get a larger sprocket Thanks

 

The issue i found using the limiting screw is the carb/engine will load up so you have now power these little engines need a birp of the throttle once and a while .. I found it easier just to take the extra time with my little one and not use the limiting screw. you can go larger on the rear but may have to swap out chain as well. I think for what you want to accomplish you would have to go with a few sizes up to give it some grunt at a low throttle..

 

Thanks for the reply here is what I have found after hours of research. It seems like I could take the front sprocket off a ATA 125D,or 135DU which is a 13 tooth(down from current 14 tooth), I could also take the rear sprocket off a Cheetah which is a 41 tooth (up from current 37 tooth). Now will the chain fit?? I can get a Cheetah chain which is 96 links take the required links out to make it fit. (currently the boulder has a 78 link chain). Although I am hoping the original chain will fit.The bike is new so I don't know how much adjustment there is to do this. Now all of this depends what the dealer or a parts store tells me about whether the parts are interchangeable.The B1 chain is a 420 and the cheetah is a 428 not sure what the difference is. Anyone have any ideas on this conversion I would sure appreciate it

 

I guess if I am going to do this I will go with all 428 pitch I am sure the 420 chain will be to short.

 

you cannot intermix the pitch of the sprockets and chain.. They all have to match or the chain will jump... So you cannot mix 428 and 420 parts.. they all have to be one or the other.. you would be better off hitting ebay/amazon and ordering everything from their as well as a chain splitter. Chain will probably be to long and you will have to take a few links out of it.. Using a chain splitter is way easier that a hammer and punch.

 

thanks for the reply that is exactly what I did last night ordered a 13 sprocket a 41 sprocket and a new chain all 428 pitch