66cc Exhaust and Chain Tensioner Mod

[DearthVader]

All,

I've seen this idea posted a few times and thought I would write to say it definitely works. I have a stock 66cc from Thatsdax mounted on a Schwinn Jaguar. I've gone through almost three tanks of gas so the break in period is almost complete. As it gets broken in I definitely notice a power increase.

I've heard so many good things about the expansion chamber pipe and shift kit from Sick Bike Parts and plan to purchase one of each eventually. In the mean time I've been looking for some simple performance mods. The high end torque is just fine on the bike but I don't want to spend the majority of my time in the upper rpm range. With that said, I'm trying to find ways to increase my acceleration and low-end torque.

I pulled the exhaust pipe off tonight and noticed that in general the size of the pipe very closely matches the exhaust port. Not much of a performance increase could be made there so I decided to drill five holes in the end of the exhaust pipe. After the holes were drilled I slapped the pipe back on and took her for a spin. What do ya know...it definitely has more torque and acceleration!! Granted, it's a little louder now because of the holes but I think it's worth the compromise. Mission accomplished!!

On another note. When I first assembled the bike it didn't take long to notice just how flimsy the stock chain tensioner is. The chain wasn't lining up exactly between the front and rear sprockets so that caused even more of a problem. The biggest problem was that the chain coming backwards from the front sprocket wasn't lining up very well with the rear sprocket. The misalignment was causing the chain to pop off of the rear sprocket. I finally gave up on the flimsy tensioner and went to Tractor Supply and bought a 17T #40 chain idler sprocket. I was able to use the existing tensioner mount and put a bolt through the idler sprocket. I also drilled a hole and put a small bolt through the base of the chain tensioner bracket to keep if from rotating into the spokes. After that modification I have had zero problems with the chain alignment.

Some pictures of both mods are attached.

I've put about 150 miles on this bike and must say it's some of the best fun I've had in a while. I paid $80 for the Schwinn and $150 for the engine kit. I'll have to admit that I sometimes make excuses so I can ride whenever possible.

Happy Motoring!!

[BarelyAWake]

Now THERE is a good idea!

I will stealz it o.o

[terri5212]

I replaced the idler roller with a wheel from a skate board that was wide and had two bearings. It works extremely well.

[xmikex]

cant you jsut take the baffle out and not drill holes? my friends bike doesnt have his in and it sounds awesome

[DearthVader]

Originally Posted by xmikex

cant you jsut take the baffle out and not drill holes? my friends bike doesnt have his in and it sounds awesome

Unfortunately my baffle isn't removable. It's no big deal since I plan on getting a tuned exhaust at some point.

[xmikex]

after reading guess its better to gut the muffler and take the baffle out then drill some holes in the cap and put it back on

[Bikeguy Joe]

Different levels of low will effect the engine different ways.

Drill, gut, leave it alone, the choice is yours.

[hotbug1776]

I tried this sprocket on my Grubee 66cc kit and the sprocket is too big for my 415 chain. Do I have another option?

[gubba]

dearth.....

my tractor supply stoe here in jacksonville florida does NOT have that item in their store or catalog.
what city/state address/phone where you are??? i will contact them and have them ship it to me
thanks for the trouble


by the way.... 2 items

opening the baffle too much allows too fast an airflow and will change your fuel/oil ratio too lean. it will harm your motor..... i do all of my customers with three 1/4 inch holes (after a good breakin (2 gal @ 16/1)
you will see more performance and power.

item 2:
the tensioner does 2 things.....
adjusts tention to desired setting and guides the chain onto the rear sproket. you can compinsate for misalignment (minor) by guiding the chain.
too far to the rear does not allow enough time for this and too far forward and the chaid will have too much side to side slop to stay on. exactly centered is not required.
these are my findings of course. yours may vary lol....


gubba

[hotbug1776]

I just searched for idler sprocket on the TSC site and it came up with various sprockets. I'm thinking of eventually just using the pirate cycles spring loaded tensioner with the optional sprocket.

I just wished the sprocket mentioned here had been narrower so it would have worked.