New head, but less power?

NutrientR46

New Member
Nov 25, 2015
5
0
0
Colorado Springs, CO
So I recently had to replace my carb since it started to leak fuel, I decided to get one of those performance carbs and I saw the High Compression Billet Head in the recommended section.

I used to be able to go 25~28 MPH on my bike before I had to get new parts. I put the new carb on first and rode it, and still kept the same speeds with the stock head.

However, after I put on the Billet Head, my bike struggles to get above 20 MPH. Is there something I've done wrong?

:-||
 

crassius

Well-Known Member
Sep 30, 2012
4,032
155
63
USA
I'm in the minority here, as I try to get good longevity and reliable transportation out of these motors for my customers. I don't believe any 'performance' parts will improve these things, and most parts will just cause more problems. I've seen folks put hundreds of dollars into these and get only 3 or 4 mph diff out of them after weeks of tuning and adjusting.

Were I you, I'd do the simple fix on the leaky original carb and return the motor to stock.
 

allen standley

Well-Known Member
Oct 22, 2011
1,115
213
63
Bangor, Maine
I'm in the minority here, as I try to get good longevity and reliable transportation out of these motors for my customers. I don't believe any 'performance' parts will improve these things, and most parts will just cause more problems. I've seen folks put hundreds of dollars into these and get only 3 or 4 mph diff out of them after weeks of tuning and adjusting.

Were I you, I'd do the simple fix on the leaky original carb and return the motor to stock.
They are what they are. I too may be in the minority. I concur. crassius
longevity and reliable transportation. That should be the objective. Loud pipes save lives and speed kills.
 

Legwon

Member
Mar 2, 2013
248
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16
Van bc Canada
put the stock head back on and live with it.
these chinadoll engines DO NOT like to have parts changed out once broken in.
if your gonna be putting on aftermarket parts (head, exhaust etc.) do it from the get go, or towards the end of break-in.
the only thing they do accept (after break-in) is porting, and my recommendation is THAT is probably your best bet for performance increase anyhow.
 

Nashville Kat

Well-Known Member
Apr 20, 2009
1,497
48
48
Jacksonville, Florida
Billet intakes are the exception though- billet intakes WORK, though I imagine that you could have some "mating" problems with the wrong carbs- a standard port billet intake with a regular NT carb did wonders for me-


It runs well and I don't care to play around with it- they are small motors and can only get so much power without trading some reliability or break downs

I'd probably run a 40mm billet intake with a 40 mm port jug and a larger type carb
if I was younger and wanted more speed


Any rear sprock over 36 T is a slow dog as far as I'm concerned, for fairly flat street riding at least


I just got a nice alloy one on ebay for the 50 cc. The 66 build has an alloy 34 from Kings Sprockets

http://www.ebay.com/itm/282035056125?_trksid=p2060353.m2749.l2649&ssPageName=STRK:MEBIDX:IT

Drill a smooth large flange fixie hub and use 6 titanium bolts, or get a rear disk brake freewheel hub and it's an ultra light set up.
 

Nashville Kat

Well-Known Member
Apr 20, 2009
1,497
48
48
Jacksonville, Florida
I am a little bit sorry to hear of your troubles- tho not entirely surprised.

While they look great- but always out of the anno colors it seems- the prices have kept me away, and the realization that the head is really just something that everything else pushes against.

Unless the dimensions that contact the cylinder are smaller in proportion, to raise compression- I don't see what performance they'd increase. The cooling fins I think are supposed to dissipate more heat, but I've never had any overheating problems with the bikes.

Although I tried to use every practical advantage on the bike that the old 14 years of road cycling gave me, I still think of the bike in terms of being like a Chinese Junk boat- a thing of practicality and use and not something designed for speed. That might help.
xct2
 

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Tyler6357

Well-Known Member
Mar 15, 2012
1,142
170
63
Santa Barbara, CA
A high compression head works best with a squish gap of .025"-.035" You don't get the benefit of the high compression head if your squish gap is over .06". There are several ways to reduce your squish gap but it would be useful to know exactly what kind of high compression head you have. Here is a video of different kinds of heads.

https://www.youtube.com/watch?v=x8OgOjltnqE&list=PLu0jJKmeTV1t_QVveXgE4-EI_FIwKNPYA



brnot
 

salorr33cc

Member
Apr 30, 2016
49
0
6
pennsylvania
high compression heads give you a little more low end , but you do lose top end speed in my opinion and experience with them,, sounds like you got the RSE 6cc round billet head,,, i lost top speed 3 mph using this head,, and squish bands dont really come into play until 9,000 rpms,,, just use a good stock head and double base gasket for more power and speed..