6th February 2011

After my exciting times with the head, exhaust & mot, I decided that a more permanent remedy was required. I would definitely require a RH exhaust Which is priced @ £86.21 + delivery on CMPO. Amongst the problems I haven't resolved is the crank case pressure. This I can only presume is caused by exhaust gas passing the piston into the sump, not so good. £53.11 cylinder, £12.95 Piston & £10 for the rings, totaling just over £162 without delivery. Off to eBay to see what can be found.

I searched through & I found 150cc head with valves fitted & 150cc cylinder complete with piston & rings for £105 + delivery. I then ordered a standard CG125 exhaust (2004 onwards) which was £70 delivered with gasket, totaling £187. This must be the bargain of the year. At my next day off I started the mammoth task to change all the parts. I recommend 2 boxes. Old bits & new bits, so that you know where everything is. I studied my CG125 Haynes manual so that I had a good idea of sequence & then began. It's all quite easy really, although initially quite tight for space at the top.

Old exhausts off first, then the carb & manifold. Off with the rocker cover & then the rockers complete on mounting. Be careful not to drop the push rods. 4 largish nuts that secure the head & the smaller 1 on the outside. Lift off head. 2 smaller bolts that secure the cylinder to the crank case & lift off the cylinder. Yes it's that easy. Next the hard bit. Getting the gasket off from the crank case is a pig. This took more time than taking the engine to bits, but, start as you mean to go on & get fully prepared before re-assembly. It's probably a good idea to put a rag or something around the con rod to stop debris getting in the sump while removing the gasket.

Once ready, swop over the valve gear in the cylinder. Assemble the piston & rings. Remove the circlip from old gudgeon pin to remove the old piston & fit the new one. I generously oiled the new bore before I put it over the new piston. It went down fairly easily, just taking care that the rings went in the right place. Once down 2 bolts to hold it, add head gasket followed by the head which when bolted down, holds the whole thing together. Push rods in (careful not to drop them in the sump) followed by the rockers. Find TDC & adjust tappets. Rocker cover on. Manifold & carb on & now to the exhaust.

This bit is the tricky bit. The exhaust was never intended for this bike & some adjustments are needed to get it on. Firstly there is only 1 & it runs down the right hand side. It is very tight on the front down tube, but does go in without fouling. A bracket is needed to attach it at the rear, I made this from a piece of shelf bracket from B&Q which cost £1.50. The centre stand needs to come off. This ideally needs to be done before the exhaust is fitted, for ease of access. I did mine after the exhaust & it was a pig. I ended up cutting the end of the stand pin off with a grinder because it was so corroded, but this worked & I now have a knackered centre stand. Strike her up & tighten the exhaust down & job done. Just one point that I found. Where the new gaskets are thicker than the old, the top engine mounting hanger is about 2mm too low. I used my dremmel to grind out the hole a little in the frame hanger to allow the bolt to pass.

I've only done 8 miles so far but things are looking up. Firstly I don't think it has ever been so quiet although the carb still roars as the throttle is eased open. Secondly, I'm not happy that the exhaust is so close to the rev counter cable & the clutch cable, some mod needed to shield these a little I think. Now I need a larger main jet & some new sprocketry & chain to suit & I'll be all done.

HN150-8 Assembled

The upturned barrels.

 The upturned barrels.

Old piston in position.

Old Piston On Con Rod

New barrel & piston installed.

New Barrel & Piston In Position

The exhaust bracket I made & it's fitted position.

My Home Made Bracket

My Bracket Supporting The Exhaust
My Bracket Supporting The Exhaust

Old & new piston.

Old Piston & New Piston

Piston side view, strangely showing a nice clean section at the top of the old piston. Does this show a fault, where the piston may have been touching the barrel ??

Side View Of Both Pistons

The extra power that you get from the 150cc upgrade makes the gears quite short. To try to stop the engine over revving I've changed the sprocket ratios. The bike shipped with 15 tooth front & 42 tooth rear, ratio of 2.80:1. The new sprockets, 17 front & 38 rear give ratio of 2.24:1 which is much more relaxed. Sprocket ratio guide here . With the wheel off it's quite straight forward. The 4 nuts hold the pins to the back of the sprocket & the circlip holds the sprocket to the wheel.


Front Sprocket

17 Tooth Front Sprocket

Rear Sprocket

38 Tooth Rear Sprocket



Hub with sprocket removed

Pins In Hub

New sprocket on

New Sprocket Fitted to Hub

Old & new sprocket size comparison.

Old & new sprocket size comparison

29th May 2011


The front metal mudguard has been showing signs of fatigue for some time. Cracks have appeared where the mounts from the forks join to the guard. I have checked to see what can be done to resolve this & have found that the 'Lexmoto Arizona' carries the same front setup, forks, wheel, brakes, etc.


With this information I have ordered the front mud guard for the 'Lexmoto Arizona' which is made of plastic. No more rust then. I've put it on & it looks fine. There are 2 holes less than there are on the original, but these were soon drilled & all is good.

Arizona Plastic Front Mud Guard Fitted

28th November 2011


A quick update, but not much to say. Just that I changed job back in May & have been back in the saddle for a short daily commute which has been absolutely problem free. These bikes are cracking machines.


14th December 2011


My insurance is due. Rampdale sent the reminder for £118, as expected. On the 'Huoniao Owners Forum', there are some threads on the subject of insurance, which I'd browsed. One thread contained a link to 'NetPig.co.uk', who I'd never heard of. I tried out the website, which is easy to navigate & successfully managed to get a quote which was actually for a 'Lexmoto Vixen' as Huoniao isn't listed. I phoned NetPig to confirm the details I had submitted & the duly changed the bike to a Huoniao HN125-8 to make it correct. The new premium is £94, which gives me the same cover, but also includes road side assistance, which is nice as it's free. So, a change of broker & also the new cover is now provided by AXA instead of Equity Red Star.


18th December 2011


The recent cold weather seems to have taken its toll on my aging battery & now it is finally no longer able to turn the engine. I've received my replacement '12N9-4B-1' from CMPO via eBay @ £23 delivered which is now fitted & working normally again.






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