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CXR 230
Topic Started: Mar 25 2018, 03:36 PM (609 Views)
Othen
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Knight
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Monty
Mar 25 2018, 12:17 PM
Look like its running lean judging by the colour of the header pipe, should not go blue like that if correct,

exhaust does look good, good luck with mot
You are right, the original carburetor is set up to run really lean. I did consider re-jetting it, but I thought I'd get the bike through the MoT before changing the unit for a Keihin PWK, which will fix the problem and allow some proper tuning (it came with a good range of jets).

I gave the bike a good check over this morn, let's hope all is well for the MoT test!Posted Image
Edited by Othen, Mar 25 2018, 03:38 PM.
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Othen
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Knight
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Posted Image

The Keihin PWK carburetor is fitted, it was almost a straight swap for the original CV type item (I just had to change the throttle cable for a normal bike type). The bike seems to be running pretty well, it has got rid of the popping on the overrun and is running cooler (the original was set to run very lean to comply with the emissions requirements).

I'll take the bike out for a spin at the weekend and assess whether there is a genuine improvement in power and control.

Posted Image
Edited by Othen, Mar 27 2018, 01:11 PM.
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Othen
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Knight
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... afternote: The only issue with the new carburettor is that the fine adjustment (air and slow running screws) are on the left (inboard) side, making adjustment really fiddly. I had to raise the tank up about 6" (blocking it in place with a piece of wood) in order to get just enough clearance for a small screwdriver for the air screw. Fortunately the mixture was about right (I'd replaced the main jet with a 140) at 1.5 turns out and it just had to be leaned off slightly. I could adjust the slow running jet by hand with the tank in that position, bringing the tickover down to about 600 RPM.

Even though the fine adjustment was fiddly, I can't really say it was worse than the original CV carburettor which had the slow running adjustment (a simple lifter on the external throttle assembly) inboard, and no air adjustment.
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Othen
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Knight
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... an afterthought: perhaps it would have been better for me to have put this thread in the 'Projects' rather than 'Introduction' section. If the moderator agrees perhaps it could be moved there?

On the other hand, the CXR 230 is a bit down market - so parhaps no one is really fussed - no matter, I still quite like the bike and have more or less the same thing as a Honda CRF 230L for under 1000!
Edited by Othen, Mar 28 2018, 08:13 AM.
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Monty
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Charlie Big Banana's
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Thread split, keep up the good work as I've never played with a CXR 230, all good info
If it aint sharp I can play with it
My Utube Channel, lots of bike vids here. Subscribe if you likehttp://www.youtube.com/user/choppermark?feature=watch

Posted Image
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Othen
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Knight
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Monty
Mar 28 2018, 01:12 PM
Thread split, keep up the good work as I've never played with a CXR 230, all good info
Monty,

Many thanks for moving this for me, it makes more sense in the 'Projects' section (if I'd thought about it I'd have started it there in the first place.

I'm not sure how many subscribers will be interested in the 230, but I'll paste anything I think might be useful here.

Best wishes,

Alan
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Othen
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Knight
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I'll take a few photos of the original (CV) carburettor whilst it is still on the bench to show its limitations. The flat slide Keihin should be a far superior unit for a dirt bike...
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Othen
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Knight
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Posted Image
... here you can see the butterfly valve - which is connected to the throttle cable, but there is no mechanical connection to the flat slide. Good for fuel efficiency (because the fuel:air ratio remains fairly constant) but bad for throttle response (due to the lag between the butterfly valve and slide moving) and power output (due to the obstruction caused by the valve itself)...
Edited by Othen, Mar 29 2018, 12:03 PM.
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Othen
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Knight
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Posted Image
... and here is the inlet side with the flat slide, which has no mechanical connection to the throttle cable. This arrangement is good for efficiency on road bikes and for controlling emissions, but not what is required for a dirt bike (good throttle response and power output at the expense of fuel consumption and emissions).

The Keihin PWK I have fitted should be a much better solution for the 230 (we'll see how it turns out).
Edited by Othen, Mar 29 2018, 12:44 PM.
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Othen
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Knight
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Having succeeded with my video of the Suzuki B120 running I've done the same with the CCM:

https://1drv.ms/v/s!Ask6E_1jz4xIskfv2MiRl1NPoLe3

I'm quite pleased with the way this little bike came out. My son and I will be taking it to our other house in Norfolk to try it out off-road today.
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Othen
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Knight
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I tried the CCM in the woods at West Bilney yesterday. The bike has very much better throttle response, improved torque and I've got rid of the popping on the overrun (due to the very lean standard carburettor set up). I couldn't try the top end because it was so wet, but the bike certainly feels much more powerful.

The bike is a bit high geared (13/39) for off road work at the moment, so I've ordered a 50t rear (only a tenner delivered direct from a Chinese supplier), which I think will give it the same ratio as a standard CRF 230. That will take a couple of weeks to get here, so I may try a 12t drive sprocket first.
Edited by Othen, Apr 3 2018, 07:26 AM.
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Othen
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Knight
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The bike is bogging down at the top end, although low end and middle range performance are excellent, it just will not exceed 60MPH. I think I've fitted too large a main jet with the #140 and will have to go down to a #120 (I just pulled out the original from the CV carburettor and have found it is a #106 (with a #31 pilot) - but that was with the more restrictive exhaust).
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Othen
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Knight
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I fitted a #120 main jet today and all is well: top end power has returned and the bike is now capable of 70+ MPH (my nerve gave out at 70 with knobbly tyres on a country lane). Top is still quite a tall gear, so I suspect lowing the gearing with a 50t sprocket will not change top speed very much.

Adjusting the air mixture is still very difficult so I've ordered a DAB Products replacement screw (only a tenner - what a bargain) with a nice knurled grip so I'll be able to adjust it easier by hand. The bottom end feels a bit lean (with a #38 jet), I'll see if it can tune that out with the new air screw when it arrives.
Edited by Othen, Apr 11 2018, 05:20 AM.
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Othen
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Knight
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I'm quite enjoying fiddling about with the small CCM, this morn I dropped the needle down a couple of notches in the Keihin carburettor (now on #5). The leanness in the mid-range has disappeared, as has the popping on the overrun. There might have been a slight hesitation at the top end, so I'll probably put the needle back to notch #4and see if that is a better compromise.

I have added some generic hand guards, which needed a bit of persuasion, but work pretty well (for about a tenner from some seller in China). All the bike really needs to be a pretty useful green laner is the 50t rear sprocket I have ordered (again for a tenner from some retailer in China).

Posted Image

The advangage of a bike like the CXR 230- being a copy of a common user item - is that so many parts fit, and they are so cheap. The project has been a bit of fun and only cost:

Purchase price: 850
Battery: 20
Exhaust: 89
Keihin carburettor: 35 ($49)
Alloy gear shifter: 14 (vanity)
Hand guards: 11
50t sprocket: 10
520 chain: 13
Air screw: 10
MoT: 29
Total: 1081

I think a grand for a lot of fun is good value - with the added bonus that my 13 year old son learned to ride a bike on it last weekend.
Edited by Othen, Apr 11 2018, 09:20 AM.
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Othen
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Knight
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The CCM is now taxed and insured - I'll give it a proper test on the road in the morn ...
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Othen
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Knight
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... I've just tried the CCM on the road and is quite civilised; it generally keeps up with traffic and managed an indicated 72 MPH on the dual carriageway (I'm 6'2" and 100kg). I think that is plenty for the tyres fitted, so it will probably be worth changing to the 50t rear sprocket when it arrives - if it can then achieve a 65 MPH top speed I'll be quite happy.
Edited by Othen, Apr 17 2018, 02:37 PM.
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Othen
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Knight
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I'm pretty pleased with my modifications to the small CCM. I took it out for a green lane ride from Geddington to Brigstock today - a muddy track (just) passable to tractors - and it generally kept up with my mate's 310cc Husqvarna both on and off off road.
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Othen
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Knight
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Posted Image

About 10km on the Peddars Way in Norfolk exposed some serious limitations in the original (Chinese CST) knobblies today - it had rained heavily overnight and grip was very poor off road. The tyres have lasted 3,800 km (the speedo is switchable between MPH/KPH, but the odometer is in km) and hardly look worn at all, so they mist be a really hard compound for off road tyres. The CST tyres are pretty good on the road (the bike hit 70 MPH briefly on the dual carriageway near Swaffham on the way home and things were more or less under control, which was nice), but I think I'm going to have to fork out a little more for some proper tyres.
Michelin AC10 looks like the best choice and are only 75/pair delivered - I suppose that still makes it a cheap bike for what it is.
Edited by Othen, Apr 26 2018, 06:06 PM.
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Othen
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Knight
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The latest carburettor settings are:
pilot: #38
main: #120
needle: notch #4

The bike seems just about right now: easy to start (with the electric boot), good mid-range and top end. A couple of spare pilot jets I'd ordered (#42 and #48) arrived in the mail the other day. I think I'll swap out the #38 for the #42 and so get the air screw in the middle of the optimum adjustment range (it is 3 turns out at the moment - which is fine and the bike runs well, but the #42 should bring that inside the 1-2 turns range where it is supposed to be). I know, this is a bit obsessive.

The 50t rear sprocket arrived in today's mail - I'll put it on tomorrow and see how that suits the bike. I think I'll probably use the CCM mostly off road, so it should be an improvement. As long as it can maintain 60MPH on the road that will be acceptable (70 is a bit fast with knobblies).
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Othen
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Knight
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I fitted the 50t rear sprocket (from a CRF 230 - all the parts seem to fit exactly), plus a new chain of course (needs 112 links with the new sprocket).
Posted Image

Off road the bike is far better, first to third are really good ratios for woodland trails. I gave it a brief spin along the country road close to the cabin and it still does just over 60MPH (it was a wet day), which is perfectly acceptable. All in all a good result.

Posted Image

All the bike needs now is some proper knobblies (arriving next Tuesday) and the project will be complete (well, it might never be complete ...).
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