Jump to content
Sign in to follow this  

CRF 150 R Gearing and engine mods

Recommended Posts

We have a leftover 150 that we bought and are in the process of getting out of our fully modded PR2 Suzuki 85. My boy loves the stock 150R but thinks the low end could just need a little more power. The bike doesn't pull 4th with authority in the sand. It takes a while to get up to speed unless you clutch it. I have bought an R and D bowl and moded the carb, so bogging isn't a problem anymore.

I am thinking the stock gearing is a little high. What are some of the gear ratios that some of you guys have run?

Thinking of a cam also. I just bought a header pipe. Had it made by MRD, as he said the can is a very good can. Haven't tried the pipe, but wanted to know what some of you are running, as far as engine mods.

I don't want a bike that needs race gas or is unreliable, just want something that pulls down lower a little harder than we have at the moment.

Yes it pulls better than the 85, to a degree, but we are looking for a little more onph in the sand for the opening GNCC race. The advantage to the RM is it is a six speed, and the Honda is a five speed, so this seems to be critical to him.

thanks

Share this post


Link to post
Share on other sites

I think the stock gearing may be a little high. Most of my riding is on a very tight backyard MX track and I run a one tooth smaller front sprocket. You made a good decision on the MRD header as everyone seems to agree that it increases torque.

Share this post


Link to post
Share on other sites

13.1 hc piston and remove backfire screen if you haven't yet. Cams are hit and miss on these motors and I don't feel it's a good way to spend your money,,, with a stock motor. Gearing is personal preference, wheel size, track conditions, rider weight and motor mods all play huge roll in gearing. Momentum is your best friend on a track just like any super mini’s. In the woods gear low and keep the rpms in the 8-9000 rpm mimumiun. This will keep the bike moving while able to loft the wheel easily. Auto clutch keeps the bike from stalling and adds good traction on off camber rooted greasy mud.

My bike is stock w/MRD header, QS3 and runs really strong. I use a smaller pilot jet (42) with a larger main (140) with 45+/- leak jet. This seems to cover a wider temp range. This motor is very forgiving with the main jet. Pilot , leak jet and air screw make a big effect on performance. Race gas loses HP with this motor. Good gas is needed, mix with 87 for a 94-96 rating. Keep an eye on the valves if the rider hit the limiter often. Stock cam gear tends to move resulting in a slight tick at idle. This will eventually end with a damage valve and many mistake it for unreliable top end. There is no such thing as porting this head. The head flows too much for a 150cc. Angled cut to the valve seats gives good results but if cut too fast/hot will crack seats in short time. GNCC racing I would run just stock valve train as most of these east coast races are not wide open.

Share this post


Link to post
Share on other sites

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
Sign in to follow this  

×