Qingqi QM125/200 upgrades

[Ed209]

Hi Everyone, I have a Superbyke RMR 125, which is a variant of the Qingqi QM125. I have made a number of upgrades to it which have much improved it, so I though I would share......
Firstly, I should point out that my bike started life as a QM200, but I managed to kill the engine through my own stupidity - it only had 300Km when I got it but I rode it at sustained high revs/max speed, and also I had put high performance semi-synthetic oil in (I found out too late that being an old engine design, it actually runs best on low-tech 10w40 mineral oil).The whole point of the bike purchase was to run as a economical commuter, as I have a Honda VFR800 for speed thrills and touring. The VFR was costing me way too much in petrol/tyres/servicing, so by sharing the workload with the Qimqi I wanted to reduce these costs. But this also meant that once I broke it, I couldn't justify spending a lot on new parts and labour for an engine rebuild. I lucked upon a used Sinnis Apache 125 ( also a Qingqi QM125)engine on ebay, which I haggled down from £175 to £100. Being basically the same bike chassis wise, it bolted straight in with no dramas ( in the unlikely event that anyone else wants to do the same!).
The engine came with the 125cc carb, but no airbox, so I bought a Pod filter from Xian racing, which together with a Xian Racing P&P exhaust I already had on the bike should have been a good setup. However, after a number of test runs and endless fiddling, I could not get the fuelling right. The bike was guttless off the line, had some brief areas of peaky power bewteen 3 and 5K and woudl only spluuter its way to a max of 55mph, with little power to get past anything going faster than 40mph. Whilst this still fullfilled the cheap transport mandate, it was not ideal, and borderline dangerous due to the need to maintain forward momentum.i.e I was taking risks to keep moving!
So.....my mind wandered to the Mikuni 28mm CV carb and airbox from the original 200cc engine. The only obstacle was the manifold adapter (goes between the carb and engine head). The 125 item was much smaller, both in bore and distance between the mounting bolts.
Then came some very dodgy 'custom engineering...I managed to sleeve down the 28mm carb adapter using a chopped down conical bottle top ( which was snug push fit), some 22mm brass tubing and some araldite.I then widened the mounting holes so I could bolt it to the cylinder head.
Anyway, I mounted the adapter, CV carb and airbox, started her up and waited for disaster....mircaulously, there wasn't one! She fired uo fine, and after some minor adjustments to the idle speed and air/fuel mix, everything ran perfectly. The bike now has a lot more pep from pulling away, and briskly makes it way to 60mph, with 70mph possible in the right conditions. More importantly, there is now a lot more oomph in the 20-50mph range, which means I can easily stay ahead of 4 wheeled traffic on my 20 mile backroad commute.I haven't dyno'd the bike, and don't intend to, but I reckon it has added 4-5 bhp to the standard 9.6bhp output of the 125, and a dollup of torque.It really doesn't feel any slower to 60mph than the 200 did, if any thing,it feels better!
So to anyone with a 125 considering a Molkt carb or similar, see if you can get hold of the Mikuni CV 28mm carb and airbox for the 200, it may be a better bet.

I would also reccomend the following cosmetic upgrades for both models:

- Renthal MX bars to replace the heavy and too narrow originals
-Thicker grips
-Mirror extenders

I did the above for under £50 and it has made a big improvement in how the bike feels to ride.

[CrazyCarl]

Ed,

That's really fantastic news! It's nice to have an experiment work IN your favor evey now and then ain't it?

So what you're saying is the Qingqi 200cc carb and airbox works wonders on their 125 engine? I think they make the 200 run WAAAY lean in order to satisfy envorinmental regulations so this makes sense. So much of the engines (125 and 200) are similar and the 200 seems to be less than optimized in terms of output.

The 125 version of the bike is all over the world and I"m sure someone out there will find this useful.

Happen to have a pic or two of the final set-up?

Cheers,
CC

[forchetto]

You learn something everyday. Thanks for the info.
To save the trouble making the carb adaptor, doesn't the 200 cc engine adaptor fit? I thought the distance between the holes in the head would be the same for the 125 and 200 cc.
I'm intrigued by the bottle top/brass pipe/araldite mod. You haven't got any pictures or rough sketches, have you?.

The BS28 carburettor, genuine MIKUNI, costs about 193 inc.VAT here in Spain, about £163 or USD273, so it's not cheap.

[Ed209]

Hi Guys
Yeah it does seem that the CV carb setup is big improvement over stock, although to be fair I haven't ridden a standard 125 in stock trim. However, all the reviews I have read describe it as incapable of going over 55mph, and also the stock bikes I have seen ridden in my area (there are a couple) do seem very choked.
Blimey Forchetto, that is a bit steep, I didn't realise the carb was that expensive new...I guess you get what you pay for though. I have read 3 or 4 posts on various forums from people who have bought bigger Molkt or similar carbs for £30 , and they all go along the lines of 'gives more power but it runs like crap'.Whether that's down to poor setup, the carb itself or the pod filter which they all seem to fit it with is open to debate.Maybe if anyone reading this has a successful Molkt setup on the 125 they could put post up?
I didn't ake any photos of the sleeve down work I did on the adapter at the time,mainly because i didn't think it would work! I will try and take some photos of the components I used though and of the bike as it now looks and put them on here when I get the chance.
And yes, I can confirm that the distance between the mounting holes is shorter on the 125 than on the 200.

[Ed209]

Here is a pic of the bike now, the side view shows the bigger carb in place. I have also put up a pic of the cockpit which has been improved by Renthal bars, mirror extenders and a cable tie holding the brake hose out of the way of the clocks (so you can actually see the speedo!).Finally there is a pic of the remaining bottle top and brass tubing which I have arranged in a way which approximates what it looks like.

[Ed209]

On a whim last weekend, I took the bike on some gentle local dirt tracks, and was struck by three things:
1) How much fun 40mph off road is !
2) That the geometry, power,suspension and weight of the bike are ideal for off road riding ( particularly an offroad novice like me)
3) That the limiting factor is the 17 inch wheels and road tyres (especially in sand!)

so I had an idea - get some 18 and 21 inch offroad spare wheels!I know some people have done this buy buying pare wheels for the dirt version of the QM125, but this looked a littel steep to me. Luckliy, the Ebay Gods have been good to me again - I saw a pair of 1991 Suzuki DR125 wheels with motocross tyres going for £80. Looking at the pictures, the hubs look exactly the same as the road wheels, and seeing as the QM125/200 is basically a DR125/200 copy, I took the plunge and bought them.
When they arrived, it was good news/bad news time.
Good News - the back wheel bolts straight in. The axle, hub and drum brake on the RMR are exactly the same size so it is very simple job to swap it in - 10 mins if that.It also means that if you have a later model QM125/200 with the rear disc, then this swap won't work - so low tech is actually an advantage for a change!
Bad News - The front hub on the DR wheel uses a thinnner spindle (although this is better than it having a bgger spindle).I have also checked that it isn't just smaller internal diameter bearings, but sadly the bearing seats are also slightly smaller.Also the speedo drive is slightly different. On the plus side, the hub is the same width, and the brake disc bolts are in the same place, so it will only need some spacers making up to get it to fit.I have sourced a 1991 DR 125 speedo drive (from the same seller as it happens), so it shoudn't be too much drama to come up with a plan.I will of course update this post with progress reports:-)
In the meantime, I have taken some pictures of the bike with the rear wheel fully fitted and the front wheel in place but not in a ridable state. I'm quite pleased with how it looks, particularly the asthetics of the gold rims matching the gold forks.