Install a 16 Tooth Front Sprocket

[bmw633]

Without a tachometer, how does one know whether the engine is redlining at WOT. This bike is for my 130 pound daughter to learn to ride. I am also considering a 16 tooth front sprocket to keep the revs down. I just tore down the engine to the cylinder because of low compression, the bike topped out at 50 mph. This is an E-Bay engine I got from Pin Worms (sp.) Motorcycle recycling. They would not even give me a partial credit because it was past 30 days since I got it. It took the shop a couple of weeks to swap motors, then the weather prevented a trip for another couple of weeks. It ran ok for about 50-75 miles, then it started losing power. By the time we got it to the shop it took another week or two for them to find out what was wrong with it. 110 psi compression.

I copied the shop manual and went to work tearing the motor down. I am taking the parts to a machine shop so they can hone/overbore the cylinder walls and new rings, and possibly an overize piston. I noticed while removing the carburetor the black plastic top had a loose screw, which caused the top to wiggle around. Could that be the cause of low power? I am also taking the head and camshaft for a valve job and to check for wear.

[jonathan180iq]

The lose carb top would definitely cause some mixture issues. Underneath that top is the needle diaphragm. If it's not sealed, you're first letting in too much air. And secondly, I don't know that they needle will operate properly, as the top is also what compresses the spring to hold the slide in place... So that's a big leak right there.

I once cracked the black plastic cover removing a stuck screw with some vice grips. Some Epoxy solved that problem once and for all. was the other screw stripped? That tends to happen when people take their carbs apart for the first time. I'll be previous owner, or an overzealous shop mechanic bunged it up and didn't take the time to fix it.

[Fawlty]

Great Howto, but I cannot open the images in the first post. Any advice would be appreciated.

[jonathan180iq]

Uh, oh.... That's a new problem.
We'll look into it.

[dhamby]

Ive had mine for 2 weeks yea 1st gear is short.but im concerned about doing this mod im a bigger guy about 235 and worried i will loose more bottom end than what its worth ??

[jonathan180iq]

Your gears actually last a little longer. 235 isn't too heavy. Make sure your tires are aired up and give it a shot. It's only a $16 investment if you hate it. But I don't think you will unless you live in a very hilly region. It makes the biggest difference in 5th gear. The lower gears become more usable, IMHO.

[dhamby]

Thanks could u post the part number and a link where i can buy it at again so i order the correct part. Thanks gonna do it like ya said if i dont like it im out 20 bucks max .

[jonathan180iq]

Pretty sure all of that information is back on the first page. If not there, it's the second.

Lots of places should carry it.

bikebandit.com was the big one at one time

[anruari]

great how jonathan

i have my gz just 3 days,love except for onething

on long, 2-3 mileinclined i cant hold the speed much over 50, there is just nothing left inthe throttle

does this mod make it possible to keep the bike at around 60 and keep with traffic flow on the long inclines?


thanks

[JWR]

A 16t will lose top end and have very little pulling power going uphill.
You must down shift to 4th if you want to keep your speed going up a hill.