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Old 08-01-2010, 07:47 AM   #1
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Thumbs up Kyosho DBX Engine transplant to OS CV-R complete!

Thanks everyone for your tips, the OS CV-R engine is now in my Kyosho DBX and I ran about 5 tanks through it and so far it works great! Also props to Tower Hobbies and O.S. engines, both were very responsive to multiple questions via email. And to amainhobbies for super prices and fast shipping. Can't wait to finish break in so I can tune it up and really let it rip. Here is what I did, in case this helps someone else wanting to do the same. First pictures, then steps and parts listing to do it:

Here's what you'll need:

A Dremmel of some sort with a good cutting disc and a grinder wheel.

Caliper (you might not need one, but it really helped me figure out what parts to get):

O.S. CV-R engine with the slide carb:

Kyosho engine mount kit:

Screw to hold clutch bearings:

New clutch shims (optional, one comes with the new clutch shoes):

Small shims (box of 10, I used 3):

4 bearings for the clutch (can use OEM bearing, but this is sooo much better):

New exhaust joining pipe:

2 small zip ties

New exhaust gasket:

Clutch shoes that don't require a groove in the flywheel nut (the new nut has a groove that is too high):

Clutch nut to fit 5mm threads. This one works, but needed to be shortened:

The original DBX engine is 7mm round. The shaft on this OS engine is a 5mm thread with 2 flat spots on the 7mm portion of the shaft. The stock DBX flywheel WILL tighten up on this shaft, but it's too long and requires the smaller clutch nut.

Using a dremmel shorten the crankshaft. I didn't write the exact number down, but I believe it was 5mm. Use the caliper to make it the same length as the standard DBX engine.

Next put one large diameter shim on the new flywheel nut and insert it into the clutch bell. You'll notice it's too long (sorry I didn't take a picture). Mark it and use the dremmel to cut it off so that it is about flush with the clutch bell.

There is one shim on the DBX motor behind the flywheel. Move that to the OS engine shaft. Bolt on the flywheel. Install the new clutch shoes on the flywheel. Install the large shim over the clutch shoes then slip the clutch bearings onto the new flywheel bolt. You might have to use the dremmel to chamfer the edges of the bolt slightly. Slide on the clutch bell.

Now install the small screw that holds the clutch bell in place. Here you will have to choose how many shims to use depending on how long or short you cut the flywheel bolt. The screw will not thread in all the way, so use shims to take up any gap. Take out any sloppiness but it still needs to be loose enough to spin freely when it heats up. Mine required 3 shims. Put a small drop of oil on the shims.

Install the engine mounting kit in the chassis. Now when you bolt in the motor, the flywheel will hit the screw that holds the brake pads in. This is because the O.S. engine is mounted so much higher than the original DBX engine (due to the very large pullstart on the O.S. engine). Use your dremmel to take away about .5mm - 1mm of the screw. Here's the screw already filed down:

Now bolt the motor into the mount. You will need the extra spacers included with the motor and everything should line up nicely:

Next install the exhaust. Then connect the control arm to the carburetor slide. Loosen the adjusting nut on the carburetor slide and swivel the fitting around to where it fits best. Also rotate the carb a bit, then tighten it all up. You'll get a nice fit:

From here just bolt it all together like normal. The biggest caveat I've found so far is the fuel mixture setting is directly behind the exhaust. You can get to it pretty easily with a very thin screw driver so get one if you don't have one. Also you'll have to poke a hole in the body for the high speed adjustment screw to stick out, otherwise it holds the body up a little on the right side.

I'm still breaking it in, but compared to the original DBX engine the OS engine is much quieter, starts very easily and makes a ticking noise while idling. It's new so I assume this is normal, it smooths right out when the revs pick up. Also this engine has significantly more engine braking, which I don't mind (I prefer a lot of engine braking on my motocross bikes too).

I hope this helps someone else, good luck!
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Old 08-01-2010, 09:41 AM   #2
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uhhm, the engine braking you are talking about must be your linkage set wrong so the brakes are constantly grabbing or the clutch being shimmed too tight.
Because you can NEVER achieve engine braking with a centrifugal clutch.....(at least not on a function rc clutch) it's different on a dirt bike where you have a direct drive from the motor by gearbox and chain...
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Old 08-01-2010, 09:50 AM   #3
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This is not true, the clutch stays locked up until the engine is near idle speed, then the car suddenly starts free rolling when the clutch releases. Your clutch may release as soon as you let off the gas, b ut the clutch in the dbx stays locked up until the revs drop.
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Old 08-01-2010, 07:17 PM   #4
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Quick report back now that I've got almost 1-quart of fuel through it. Firstly the OS engine carburets 100% better than the Kyosho did. Idle is stable, at mid-throttle openings it doesn't load up at all even with a rich break-in setting, and it transitions from part to full throttle fantastically. Throttle control is so much more precise. It has at least as much peak power as the Kyosho engine had and even when set a little rich it revs much higher than the Kyosho did. One unexpected surprise is how much quieter the OS engine is than the Kyosho was, even with the same exhaust. Maybe this is because the air filter is thicker and muffles the intake noise better? Overall my initial impression is that the OS engine is improved in every aspect over the Kyosho engine. The Kyosho was a great starter engine, but at least at this point I'm satisfied that the effort to switch to the OS was totally worth the effort!
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Old 08-04-2010, 06:23 PM   #5
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Another quick follow up. Now about 1.5-qt fuel through it and tuning it up a bit, and wow this motor is much much faster than the Kyosho motor was. Now that it's breaking in it's revving much freer and higher and it's 100% easier to tune than the Kyosho. You actually have throttle control more than on/off! It looks to be significantly faster (top speed) than the Kyosho was and it's got more power too. Time will tell if it lasts longer. I also switched from Traxxas fuel to Odonnell fuel when I put in the new motor. Bottom line, if you break your DBX engine, don't even think about paying to fix it, just get one of these OS engines, it's a big improvement in every way and well worth the effort to install it.
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Old 08-07-2010, 02:23 AM   #6
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Default awesome!

wow ! Awesome mattfl !! My kyosho engine was great, very ez as a starter engine, but recently, found out that it started to leak (rear bearing ??) .. every time i would pull start it...it would spray oil...only ran 1 qt of fuel through it ... like he said, just buy a new one (or convert to electric like i did !!) ...
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