Tuning for Expansion chamber

lukecanna

Member
Joined
Sep 25, 2017
Messages
79
Just recently installed my cdh66 expansion chamber exhaust and was wondering what tuning should be done for best performance
I have stock everything just a short intake.
I was thinking i may need to move the c-clip down a notch on the needle to have a richer fuel flow
This is my spark plug
E8CE99B3-7B50-4308-9A72-F9E0976ED0D8.jpeg
 


inspectorcritic

Well-Known Member
Joined
Dec 13, 2015
Messages
1,264
Almost looks alright should look like brown coco powder not black and not gray.
But, sh*t man those motors have a physics limit they ain't going to be much over 30 MPH unless its down hill & that's with wind at your back.
 

Vikingimike01

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Jul 1, 2018
Messages
1,041
I actually went 34 mph on a long stech of road (Slightly uphill, very slightly) and I'm about 240 pounds (110 kgs)

Stock :p

I was thinking I'd go less since when I bought it, they said top speed is 23mph...
 

lukecanna

Member
Joined
Sep 25, 2017
Messages
79
Almost looks alright should look like brown coco powder not black and not gray.
But, sh*t man those motors have a physics limit they ain't going to be much over 30 MPH unless its down hill & that's with wind at your back.
it’s like grey and dry so was thinking to run a richer setting on the needle
 

Tyler6357

Active Member
Joined
Sep 28, 2011
Messages
768
it’s like grey and dry so was thinking to run a richer setting on the needle
I think it's best to run it as rich as possible without compromising performance. The richer you run it the more oil your engine gets and the cooler it will run but if the engine starts to 4 stroke, losing power anywhere on the throttle range after it's warmed up you need to go leaner. If you run it too rich it will lose power and start to 4 stroke but if you run it too lean it will get too hot and cause major parts failure.
 
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Tyler6357

Active Member
Joined
Sep 28, 2011
Messages
768
I actually went 34 mph on a long stech of road (Slightly uphill, very slightly) and I'm about 240 pounds (110 kgs)

Stock :p

I was thinking I'd go less since when I bought it, they said top speed is 23mph...
Are you using a stock 44 Tooth rear sprocket or something smaller?
 
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