BBR 150 Big Bore w/ Cam Smokin' problem

For those who know or have installed the 150 Big bore kit, how long should the bike smoke before burning off whatever it needs to on the cylinder/piston? I just installed one in my wifes bike and it's smoking after about 5 minutes of running. Should I be investigating the cylinder for an improper bore job? Ideas/suggestions? Thanks!

- Dan


'03 YZ450F

'04 TTR 125LE (Wife's bike!!!!)

try it a few more times and get it hot. if it still smokes it should come apart again. It's really hard to be sure the oil rings are in right and if there is a problem with the way they were installed you may see what your describing. My oil rings tried to bend over when I put the cylinder on the piston. It's not common to see oil more than a minute after first start. unless some is in the exhaust ports or intake ports. I had this happen when I set valves once. I have no idea how oil got in the exhaust but it took a while to burn out.


I measured the cylinder/piston difference and got 0.017" instead of the BBR spec which indicates 0.002"... the same measurement for my stock one was 0.005", so I think I got a bad cylinder... just want a second opinion, Thanks...

ring gap must be about a centimeter!! haha ya, .006 or .008 would be extremely wore out so .017 sounds like something got missed.. are you doing the measurement with the piston in the cyl? sorry to hear but they should stand by it!

no, I was measuring the across the top of the cyclinder compared to the widest part of the piston. I did the same to my stock cylinder / piston and got 0.005", so I think it is just a bum kit.

If I remember my engine building right, shouldn't the rings be placed in the cylinder then the gap checked?

I got a BBR 150 kit cylinder that was bored at a slight angle and had a problem w/ oil leaking out between the case and cylinder right under the exhaust outlet. We sent it back initially, before cranking it up, b/c the piston just seemed real tight in the cylinder. They sent it back saying #1 we don't have a replacement for you, #2 "That's the way it's supposed to be; they wear in". It worked OK, but for the $, we shouldn't be getting such crappy equip. Never had a single problem w/ Powroll!

I haven't had any noticable smoking occuring yet. I've had my bike out for 4 fairly long riding sessions since I did the mods (did them before ever riding it stock), and it's working well. Very strong, for a small 4-stroke. It's starts right up, every time, since re-jetting.

Will let you know, if things go from good to bad.

I'm changing the oil and cleaning the air cleaner more often than I should, to get max longevity from the modified engine.

I know in the install instructions they stress the 90- degree difference in placement between the seams of the different ring-components. (ie. Don't line-up all the seams in a row.) Not sure if that could be an issue, here.

Best of luck,


Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now