My New Project (MC-54-250) - not the "B" Variant

Ebuddy · 05-18-2015, 08:35 PM

Hey guys!
Well, while my 150cc is still a project, I went out and bought a 2008 Roketa (Jonway) MC-54-250 (CF Moto clone). It runs like a top and can carry my fat rear end up to (so far) 64.3mph (GPS verified).

My perplexing issue is that the bike has stripped 2 variator covers (the part with the fan louvers) at the drive shaft. The teeth on the drive shaft don’t seem to be worn but the cover (I actually purchased an entire assembly) went from brand new to completely smooth in about 350 miles. When I replaced the variator assembly, I also replaced the entire clutch assembly with new units from ScrappyDog.

The belt seems large at a 918/22.5, but seems to be correct given that the bike has 13” wheels.

Any thoughts of why this might be happening?

bull · 05-18-2015, 08:44 PM

My first thought would be that it is not locking tight against the variator sleeve. IOW, the total variator length is not as long as the crank on that side.

To test my theory, remove the belt and properly retighten the variator, then check if it has clearance between the outer pulley and the sleeve with a feeler gauge. There should be none.

Ebuddy · 05-19-2015, 11:58 AM

I can’t test the theory just yet as the outside of the variator was so stripped it wobbled a bit. The nut could have come loose, but I thought it seemed pretty tight when I removed it.

There isn’t supposed to be something (e.g. a washer) behind the assembly, is there? I didn’t think so, but I figured I’d ask.

So I’ve ordered a new assembly (and nut). I’ll put it on and test your theory then and report back. My worst fear is that the spleens on the crank are too worn as I’ve no desire to replace the whole crank.

Ebuddy · 05-27-2015, 01:31 PM

So after removing the variator assembly, I carefully cleaned out all of the components and purchased an outside pulley (until my new assembly arrives as it is on backorder). I took some pictures of the splines and showed them to a local guy who owns a scoot sales/service shop. He indicated that they didn’t look too badly worn but did notice that perhaps a thread or two was a bit stripped (which might have caused the nut to loosen).

I also noted that the idle had been set by the previous owner seemingly too fast. The manual says the bike should idle at about 1,600 RPM +/- 100 RPM, which is where it sits when warm (according to the tach). When cold however, it’s at 2,000 RPM. I do recall when riding it that even when warmed up, it seemed to run a bit fast and I could feel the belt gripping the clutch, pushing the bike forward slightly. On the center stand, the wheel spun pretty fast as well. I wonder if the constant braking at idle, combined with not moving, with the idle set too high didn’t cause the belt to work the outside pulley and nut loose, thereby shortening the life of the pulley.

So I put it all back together with a generous amount of Loctite and put a lock washer between the nut and the pulley. I know it’s not necessary, but my hope was to get the nut on the better threads. I verified no gap between the outside pulley and the bushing/hub/thingy. I also lowered the idle speed quite a bit. Cold or warm, the tach reads about 1,100-1,400 but the engine doesn’t seem to be struggling to stay running (though I think I’ll tweak the mixture just a hair).

We’ll see how this goes. The last one failed at about 400 miles, so I’ll look at this one at about 200 and see what it looks like.

05-18-2015, 08:44 PM	#2
bull Join Date: Feb 2015 Posts: 257	My first thought would be that it is not locking tight against the variator sleeve. IOW, the total variator length is not as long as the crank on that side. To test my theory, remove the belt and properly retighten the variator, then check if it has clearance between the outer pulley and the sleeve with a feeler gauge. There should be none.
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05-27-2015, 01:31 PM	#4
Ebuddy Join Date: Jun 2013 Location: Minnesota Posts: 73	So after removing the variator assembly, I carefully cleaned out all of the components and purchased an outside pulley (until my new assembly arrives as it is on backorder). I took some pictures of the splines and showed them to a local guy who owns a scoot sales/service shop. He indicated that they didn’t look too badly worn but did notice that perhaps a thread or two was a bit stripped (which might have caused the nut to loosen). I also noted that the idle had been set by the previous owner seemingly too fast. The manual says the bike should idle at about 1,600 RPM +/- 100 RPM, which is where it sits when warm (according to the tach). When cold however, it’s at 2,000 RPM. I do recall when riding it that even when warmed up, it seemed to run a bit fast and I could feel the belt gripping the clutch, pushing the bike forward slightly. On the center stand, the wheel spun pretty fast as well. I wonder if the constant braking at idle, combined with not moving, with the idle set too high didn’t cause the belt to work the outside pulley and nut loose, thereby shortening the life of the pulley. So I put it all back together with a generous amount of Loctite and put a lock washer between the nut and the pulley. I know it’s not necessary, but my hope was to get the nut on the better threads. I verified no gap between the outside pulley and the bushing/hub/thingy. I also lowered the idle speed quite a bit. Cold or warm, the tach reads about 1,100-1,400 but the engine doesn’t seem to be struggling to stay running (though I think I’ll tweak the mixture just a hair). We’ll see how this goes. The last one failed at about 400 miles, so I’ll look at this one at about 200 and see what it looks like.
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